its British Gas (BG) Standard - for - Fabrication of Equipment and Piping...
BG Standard Materials Engineering
Fabrication of Structures, Equipment, Piping & Pipelines
BGA-ENG-MATL-TS-0007
Value Assurance Framework (VAF)
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
DOCUMENT INFORMATION SHEET Title: Fabrication of Structures, Equipment, Piping & Pipelines Purpose and Scope: This Standard defines minimum Company requirements for the fabrication, joining, inspection and testing of metallic and non-metallic structures (including offshore jackets, trestles etc.), static equipment (including pressure vessels, tanks, boilers, furnaces, sub-sea manifolds, machinery and valve casings), piping systems and pipelines (including flow lines, trunk lines and risers) In addition, it defines the minimum Company requirements for in-service modifications and repairs to operating facilities (to follow)
Document Verification: Responsible: Author Signature:
Position: Group Technical Authority (Materials Engineering)
Name:
Date: July 09
[email protected]
Approval: Head of Function Signature:
Position: Head of Engineering
Name:
Date: July 09
S Iveson
Consulted: Name:
Position:
Mark Nishapati
Head of Safety Engineering
Informed: Name:
BGA-ENG-MATL-TS-0007 Issue 03
Position:
July 2009
2 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Approval and Issue record: Issue No.
Description (see Revision Record for details)
Date
Author (name)
Approved (name)
01
Aug 2006
Issued for use
R Carroll
M Freeman
02
April 2008
Revised and re-issued
R Carroll
A Smith
02a
Nov 2008
Approvers changed
W Dunning
A Smith
03
July 2009
Revised and re-issued
R Carroll
A Smith
Revision Record: Issue No.
Description of Revision
01
Original issue
02
Revised and re-issued
02a
Name of Head of Safety changed
03
Major revisions: Standard re-formatted and revised to address comments and outcome from Standard’s Gap Analysis – no revision markers shown Document re-titled to include fabrication of structures and pipelines Requirements for fabrication of components exposed to sour environments added New section on in-service modifications and repairs added
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
3 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Contents 1.0 1.1 1.2 1.3 1.4 1.5 1.6 2.0 2.1 2.2 2.3 2.4 2.5 2.6 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 4.0 4.1 4.2 4.3 4.4 4.5 5.0 5.1 5.2 5.3 6.0 6.1 6.2 6.3 6.4 7.0 7.1 7.2
Introduction Purpose and Scope Responsibilities Definitions Acronyms Units Referenced/Associated Documents General Fabrication Requirements Design Health and Safety Materials of Construction Forming Joint Preparation Handling, Storage and Transport Welding Requirements General Welding Processes Welding Consumables Shielding and Purging Gases Pre-heating Post Weld Heat Treatment Special Procedure Qualification Requirements/Testing Weld Overlay/Clad Restoration and Metallic Hard-facing Non Destructive Examination Positive Materials Identification Production Tests Baseline Surveys Repairs Non-Metallic Materials Fabrication General Fibre Reinforced Plastic Materials Thermoplastic Materials Inspection and Testing Repairs Additional Fabrication Requirements for Sour Environments Fabrication Requirements Welding Requirements Specific Equipment Requirements In-service Modifications and Repairs General Welding to In-service Components Hot Tapping Temporary Wraps Quality Assurance General Quality Records
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
6 6 7 7 9 10 11 12 12 13 13 13 14 16 17 17 17 17 19 19 20 21 23 24 27 28 29 30 31 31 31 32 34 34 35 35 35 37 38 38 38 38 38 39 39 39
4 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
8.0 Feedback Appendix A: References Appendix B: Feedback Form
BGA-ENG-MATL-TS-0007 Issue 03
40 41 44
July 2009
5 of 44
Value Assurance Framework (VAF)
1.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Introduction This Standard should be read in conjunction with BGA-BGA-GEN-OS-0001. It is essential that everyone is aware that compliance with this, or any other BG Standard, is mandatory and failure to comply may constitute serious misconduct and disciplinary action may be taken against the employee(s). Although BG Standards are mandatory, dispensations may be granted in exceptional cases by the relevant Group Technical Authority - BGA-BGA-GEN-OS-0004 sets out the procedure in full. Please note that dispensations need to be granted before any BG Standard is deviated from. In all instances, legally required National codes and standards of the country where the equipment is to be operated shall be complied with, together with any other applicable legal requirements. Where BG Standards are more stringent, then the BG requirements shall take precedence. Where a BG Standard appears to be less stringent, then the applicable legal requirements shall be followed and it shall be brought to the attention of the appropriate Group Technical Authority. All applicable International Codes and Standards shall be complied with. If you are reading a hard copy of this Standard, you should consider it uncontrolled and refer instead to the version currently on the Portal.
1.1
Purpose and Scope The purpose of this Standard is to specify minimum Company requirements for the fabrication of metallic and non-metallic structures, equipment, piping and pipelines. Commentary: The intent in specifying minimum requirements is to supplement the appropriate design code requirements with lessons learned from both Company and relevant industry experience; improve consistency in the fabrication of structures, equipment, piping and pipelines and quality control across Company assets; ensure that materials are fabricated with fewer fabrication-related problems; ensure that fabricated components provide the specified mechanical properties and corrosion resistance to specified environments and provide long term operational performance
This Standard supports the principal Materials Engineering Standard, BGA-ENG-MATL-TS-0001, and shall be read in conjunction with that Standard. This Standard includes the welding, fabrication and inspection requirements originally specified in BGAENG-MATL-TS-0003 (which is now withdrawn). The scope of this Standard applies to the range of facilities referenced in BGA-ENG-MATL-TS-0001 and includes, but is not limited to, the following: Structures including offshore jacket structures, sub-sea manifold protective structures, jetty trestles, equipment supports and miscellaneous structures such as pipe racks, walkways etc. Static equipment including pressure vessels, heat exchangers, atmospheric and pressurised storage tanks In-plant process and utility piping including in-line valves, special piping items Fabricated rotating machinery casings, including associated piping systems and static equipment Fabricated valve casings Steam generating boilers and associated piping Fired heaters and furnaces and associated piping Sub-sea systems and offshore pipelines flow lines, trunk lines and risers Onshore pipelines, flow lines and trunk lines, transmission pipelines including pressure let-down stations Package units.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
6 of 44
Value Assurance Framework (VAF)
1.2
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Responsibilities To support the fabrication of metallic and non-metallic structures, equipment, piping and pipelines, it will be the responsibility of the User to specify the relevant requirements of this Standard in purchase order, contract and sub-contract documentation as appropriate during the ‘Assess’ through ‘Operate’ stages. Where the project execution strategy for a development is split into discrete contracts (e.g. offshore platform, interconnecting pipeline and onshore processing facility), the User of this Standard shall ensure that the fabrication requirements for each of these contracts fully meets the requirements of this Standard and that each of these discrete contracts is fully aligned with one another in order to ensure consistency in material procurement. This Standard shall not be construed as covering all requirements that may be necessary to address potential fabrication issues applicable to a specific development. Where additional fabrication requirements are identified as applicable to a specific facility or development, the User is responsible for identifying and specifying any such requirements and submitting for BG Advance review and agreement. In the Standard, some specific activities or actions are subject to “review and agreement by Company”. This will typically be the responsibility of the appropriate asset Technical Expert or appropriate personnel assigned to the PMT with demonstrable competency in materials/corrosion/welding. In certain circumstances, additional review and agreement by BG Advance will be required and where this is the case, this will be stated in the text. Commentary: Typically, the asset Technical Expert will exercise this responsibility during the ‘Operate’ stage, whilst for new ‘green field’ and ‘brown field’ projects this responsibility will fall to the appropriate competent personnel in the PMT/Contractor’s organisation. The GTA may be consulted prior to making a final decision but this not mandatory unless this Standard explicitly states that BG Advance must be involved in the review process
It is the responsibility of the User to ensure that all activities involved in the selection of materials of construction and corrosion control measures are undertaken under an accredited quality management system that complies with a national or international standard. This shall be taken to mean compliance with the appropriate part of ISO 9000. Commentary: Company reserves the right to audit the quality management system to verify that the requirements of this Standard are being met
Where a specific national or international specification/standard is referenced in the text, alternatives may be acceptable providing any alternative specification or standard can be shown to provide an equivalent or better level of quality, safety and integrity. The range of business segments and development lifecycle stages to which this Standard applies are identified below: All developments/projects, world-wide Business Segment: Development Stage:
Upstream X Create
T&D X
Assess
Select
Power X Define X
Execute X
LNG X Operate X
Decommission
Note: Assess includes feasibility studies, Select includes option assessments, Define includes both pre-FEED definition and FEED studies, Execute includes detail design, procurement, construction and commissioning
1.3
Definitions Company
BG Group or a wholly owned subsidiary company or other client organisation
Contractor
The person, firm or company undertaking to supply services to Company
Vendor
The main supplier or manufacturer of the items of plant or equipment to which this document applies, including items that may be designed and/or manufactured by others. The definition shall include any third party contracted to provide services to the Contractor
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
7 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
User
Company’s project management team(s) and the selected engineering Contractor(s) during the ‘Assess’ through ‘Execute’ stages of a facility’s lifecycle and the Operations/Asset Integrity team during the ‘Operate’ stage.
Shall
A mandatory term - no dispensation is permitted without written agreement using the formal dispensation procedure
Should
A recommended term applied to this Standard, indicating a certain course of action is preferred but is not mandatory
Group Technical Authority
The manager or principal discipline engineer responsible for identifying, generating, approving and maintaining a given Standard/Guideline and either approving or rejecting dispensation requests made against BG Standards
Technical Expert
Asset-level designated person with responsibility to establish and maintain technical requirements and processes for their designated discipline
Ferritic steel
Steels with a nominal alloy content of less than or 12% i.e. carbon steels, Cr-Mo steels, Ni-alloy steels
Corrosion resistant alloy
Materials with a nominal alloy content of greater than 11% i.e. stainless steels, nickel-based alloys, cobalt-based alloys, aluminium alloys, titanium alloys
High-alloyed stainless steel
Stainless steel with PREN 40 or (%Ni + (2%Mo)) 30 with %Ni 2
Fibre reinforced plastic material
Composite material manufactured from a polymer matrix reinforced with fibres (e.g. glass, carbon or aramid)
Thermoplastic material
Non-metallic material capable of being repeatably softened by an increase in temperature and hardened by a decrease in temperature (e.g. PP, PE, PVC)
Critical Exposure Temperature
The lowest (coldest) metal temperature at the maximum credible coincident combination of pressure and supplemental loads that result in primary stresses greater than 55 MPa. The CET shall not be warmer than the minimum design temperature as defined in the relevant design code nor the temperature of the fluid causing shock chilling
Shock chilling
A rapid decrease in metal temperature caused by the sudden contact of liquid or a two-phase (gas/liquid) fluid with a metal surface when the liquid or two phase fluid is colder than the metal temperature at the instant of contact by more than 56°C
Hazardous fluid service
A fluid service that includes the following: All hydrocarbon fluids Liquids above their AIT or above 210°C if the AIT is not known Flammable liquids flashing on leakage to form a substantial vapour cloud (this will typically include LPG, LNG and NGL condensate or others as specified by Company) Fluids designated as Category M in accordance with ASME B31.3 Injection chemicals with low flash points (below 60°C) Heating media
Sour environments
Aqueous environments containing H 2 S within the limits defined in NACE MR0175/ISO 15156
Alkaline sour environments
Sour environments containing compounds such as amines, caustic, carbonates, ammonia
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
8 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Elevated temperature environments
Service environment where time dependent properties govern design (typically above 454ºC for ferritic steels and 550ºC for CRAs)
Cryogenic environments
Service environment with CET lower than -100°C
Cold environments
Service environment with CET between 0°C and -100°C
Cyclic fatigue environments
Service environments where time dependent properties under applied cyclic loads govern design Commentary:
Definition applies to service environments where cyclic loads arise from mechanical, flow, acoustic and/or wind induced vibration or pulsation in addition to thermal and/or pressure cycling. Normal start-up and shut down cycles need not be included providing these are limited in nature
High pressure environments
Service environments above ASME class 900# flange rating, including systems designed in accordance with ASME HPS-2003, ASME Section VIII-3 or Chapter IX of ASME B31.3
Oxidising environments
Service environments that can cause oxidation of materials e.g. hypochlorite, sulphuric acid, high temperature steam (typically above 400°C)
Special forging/casting
Forging or casting manufactured for a specific application (i.e. not ‘standard’ pressure components as defined in the relevant design code)
Pitting Resistance Equivalent Number
PREN = (%Cr + 3.3(%Mo + 0.5%W) + 16%N)
Tempering parameter
Parameter for calculating equivalent heat treatment conditions as follows: TP = (T+273)(20+log 10 t)10-3 where T = holding temperature (C), t = time (hours)
1.4
Small bore connections
Piping connections to the main run-pipe equal to or less than 1½”NB
Major attachment
An attachment where the maximum stress at the attachment weld is 30MPa or greater
Primary structural member
Structural member that provides the structure’s main strength and stiffness and whose failure would seriously endanger the safety of the structure
Secondary structural member
Structural member that if removed does not significantly alter the overall strength and stiffness of a structure
Acronyms ACCP
ASNT Central Certification Program
ASNT
American Society for Non-destructive Testing
AWS
American Welding Society
CET
Critical Exposure Temperature
CRA
Corrosion Resistant Alloy
CSWIP
Certification Scheme for Welding Inspection Personnel
DEA
Diethanolamine
DGA
Di-glycolamine
DIPA
Di-isopropanolamine
EAC
Environmentally Assisted Cracking (refer to BGA-ENG-MATL-TS-0001)
EGW
Electro-gas welding
EN
European Norm
FCAW-S
Self-shielded Flux Cored Arc Welding
FN
Ferrite Number
FPSO
Floating Production, Offloading and Storage
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
9 of 44
Value Assurance Framework (VAF)
1.5
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
FRP
Fibre Reinforced Plastic
GTAW
Gas Tungsten Arc Welding
HAZ
Heat Affected Zone
HB
Brinell Hardness
HDT
Heat Distortion Temperature
HSSE
Health, Safety, Security, Environment
HV
Vickers Hardness
LMC
Liquid Metal Cracking
LNG
Liquefied Natural gas
MDEA
Methyldiethanolamine
MEA
Monoethanolamine
MSDS
Material Safety Data Sheet
MT
Wet Contrast Magnetic Particle Testing (for use on magnetic materials)
MTR
Material Test Report
NDE
Non Destructive Examination (may also be known as Non-destructive Testing (NDT))
PAW
Plasma Arc Welding
PCB
Polychlorobiphenyls
PCN
Personnel Certification in Non-Destructive Testing
PMI
Positive Materials Identification (may also be known as alloy verification)
PQR
Procedure Qualification Record
PREN
Pitting Resistant Equivalent Number
PT
Penetrant Testing (for use on non-magnetic materials or where materials are susceptible to magnetisation e.g. 9%Ni-alloy steels)
PWHT
Post weld Heat Treatment
RMD
Regulated Metal Deposition
ROL/ROR
Run-out Length/Run-out Ratio
RT
Radiographic Testing
SCC
Stress Corrosion Cracking
SMAW
Shielded Metal Arc Welding
SMYS
Specified Minimum Yield Strength
STT
Surface Tension Transfer
T&D
Transmission & Distribution
TML
Thickness Monitoring Location
UT
Ultrasonic Testing
WFMT
Wet Fluorescent Magnetic Particle testing
WPS
Welding Procedure Specification
Units Company requirements are that metric Système International (SI) units shall be used throughout. If an asset requires imperial units to be used for clarity then SI units shall be stated followed by the local requirement in brackets. The following exceptions shall apply: Pressure shall be expressed as either gauge pressure in barg or absolute pressure in bara, gauge pressure being referenced to Standard Atmospheric pressure of 1.01325 bara. Temperature shall be expressed as degrees Celsius (ºC)
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
10 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Dynamic viscosity shall be expressed as centipoise (cP) In addition, the following common industry units shall also be used (applying dual units where appropriate): Volume gas flow in million standard cubic feet per day (MMscfd) Volume liquid flow in barrels per day (bpd) or US gallons per minute (gpm) as appropriate Stock tank oil/condensate flow shall be expressed in stock tank barrels per day (stbpd) and reflect the oil/condensate volumetric flow after flashing to stock tank conditions of 1.01325 bara and 15.5556ºC Pipe diameters shall be expressed as inches nominal bore (“NB). The definition of Standard Conditions for pressure and temperature that shall be applied is 1 atmosphere pressure (or 1.01325 bara) and 15.5556ºC (rather than 1 atmosphere and 273.15 degrees Kelvin (0ºC). Any deviations to this definition to be consistent with local standards shall be discussed and agreed with BG Advance Engineering but shall, as a minimum, be fully defined in the project Basis of Design. 1.6
Referenced/Associated Documents Appendix A contains a list of referenced and associated documents related to this BG Standard.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
11 of 44
Value Assurance Framework (VAF)
2.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
General Fabrication Requirements
2.1
Design
2.1.1
Forming, joining, inspection and testing of components shall meet the requirements of the appropriate design code and this Standard.
Commentary: Company does not mandate the use of specific design codes in its facilities. The following are the most common design codes that have used within Company facilities but alternatives design codes may be proposed as noted in Section Error! Reference source not found. (1)
API RP2A , EEMUA 158
Jetty structure/trestle, miscellaneous steel structures
AWS D1.1
Pressure vessels & heat exchangers:
ASME Section VIII, PD 5500
Atmospheric storage tanks:
API 650
Pressurised tanks
API 620
Fabricated machinery or valve casings:
ASME Section VIII
Power boilers:
ASME Section I
Power piping:
ASME B31.1
Process & utility piping:
ASME B31.3
Sub-sea manifolds
EEMUA 194
Pipe lines
ASME B31.4, ASME 31.4, DNV OS-F101
FRP pressure vessels, tanks:
ISO 13121 & BS 4994
FRP piping:
ISO 14692 & BS 7159
Thermoplastic piping
ASME B31.3
Fired heaters and furnaces:
API 560
Note 1:
2.1.2
(1)
Offshore jacket structures:
ISO 19902 has now been published which encompasses both API RP2A and EEMUA 158 scope but as yet Company has no experience in its use
Structures, equipment and piping shall be laid out to ensure ease of fabrication, inspection and testing including, but not limited to: Providing adequate clearance for welding, NDE, application of coating and insulation, installation of bolting (including any requirements for controlled tightening), pre-commissioning cleaning, and inspection and testing activities Minimising the number of joints required in piping systems
Commentary: Maximum use should be made of pulled or induction bends in-lieu of elbows where space permits –this can minimise the number of welds which in turn reduces inspection during installation and operation
Controlling dimensional tolerances for alignment of structural members, shell plates, nozzles/branches, welded attachments and supports, flange rotation, gasket seating surface flatness etc. Providing adequate clearance between welds toes and/or structural attachments to minimise weld encroachment - distance between weld toes and/or structural attachments shall be the greater of 50mm or 2Rt. Where this is not possible due to physical constraints, additional inspection, volumetric and surface NDE, heat treatment and/or stress analysis shall be specified Commentary: Weld encroachment can result in increased stresses at welds or at the weld ligament which in turn may increase the likelihood of fabrication-related or service-related cracking
Providing sufficient access for full volumetric and surface examination of welds Commentary: This requirement is intended to ensure the design and layout of weld joints results in a weld joint that can be fully inspected throughout its volume, particularly in relation to ultrasonic examination e.g. welds at flanges or fittings, jacket node construction will potentially have limited access from one side. Enhanced ultrasonic examination techniques may partially overcome this limitation but in practice this may require features such as installation of pup-pieces between the weld and flange/fittings; positioning the weld outside vessel support skirt etc.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
12 of 44
Value Assurance Framework (VAF)
2.1.3
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Appropriate procedures and quality assurance systems shall be developed to control the design, installation and testing of small bore tubing systems to ensure their long term mechanical integrity.
Commentary: Small bore tubing systems are particularly vulnerable due to their thin wall and small diameter and use of mechanical couplings and require adequate support and competent installation. The recommendations in the Institute of 1 Petroleum guidelines should be followed in developing the necessary procedures, competency and quality assurance systems to ensure their integrity during operation
2.1.4
The management of flanged and clamped joints shall meet the requirements of BGA-ENG-MECH-TS0012.
2.1.5
Pre-commission cleaning, pressure (strength) and leak testing of static equipment, pressure systems and pipeline systems shall meet the requirements of BGA-ENG-MECH-TS-0012.
2.1.6
The selection and application of protective coatings shall meet the requirements of BGA-ENG-MATLTS-0005.
2.1.7
The selection and application of thermal insulation systems shall meet the requirements of BGA-ENGMATL-TS-0004
2.2
Health and Safety
2.2.1
In specifying material selection and corrosion control measures to be adopted, all Company HSSE requirements shall be met including, but not limited to: Providing adequate ventilation, detection and extraction facilities in confined spaces to prevent the build-up of inert, toxic or flammable atmospheres, fumes, dust etc. Providing appropriate breathing and hearing protection Providing adequate access/scaffolding/working platforms and fall-arrest harnesses to ensure safe working environments at height Providing adequate access and secure, temporary formwork to ensure safe working environments below grade Providing adequate safety systems to prevent electric shock and build-up of static electricity Providing of appropriate safety systems for use of pressurised air, oxy-fuel cutting equipment, welding equipment etc.
2.3
Materials of Construction
2.3.1
Materials of construction shall be supplied in accordance with the requirements of BGA-ENG-MATLTS-0008.
2.3.2
Mixing of materials from different national or international material specifications in the fabrication of a component or system is not permitted unless acceptable to the appropriate design code.
2.4
Forming
2.4.1
Quality control procedures shall be developed to ensure that material properties are not affected by forming or bending operations including but not limited to:
2.4.1.1
Confirming all dies, presses, rolls etc are free of dirt, scale and surface contaminants prior to forming
2.4.1.2
Confirming materials used during forming are free of low melting point contaminants, halides etc. Mineral oil or grease shall not be used during the forming of CRAs
Commentary: Only solid lubricants such as graphite, molybdenum disulphide or fluoroploymers should be used for forming CRAs and these must be completely removed after al forming is completed
2.4.2 2.4.2.1
1
Heat treatment shall be performed after forming in accordance with the requirements of the design code and the following: Ferritic steel ‘cold’ spun heads with a nominal thickness in excess of 13mm, shall be heat treated regardless of the fibre strain induced
Guidelines for the Management, Design, Installation and Maintenance of Small Bore Tubing Systems
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
13 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Commentary: Cold spinning of heads can induce a high degree of cold work and high hardness. Particular care needs to be taken during cold spinning of integrally clad heads (including any welds) to avoid work hardening of the cladding or weld metal (due to the differential material properties compared to ferritic steel substrate) from the additional force applied to spin the head
2.4.2.2
Ferritic steel ‘cold’ formed components in direct contact with EAC environments shall be heat treated when the fibre strain after forming exceeds 5%
2.4.2.3
Austenitic and duplex stainless steels and nickel-base alloys shall be heat treated when the fibre strain after forming exceeds 15%
2.4.2.4
Titanium alloys and explosively clad titanium plates shall be heat treated when the fibre strain after forming exceeds 10%
2.4.2.5
Heat treatment conditions shall be appropriate to the material, including any CRA cladding, and any initial heat treatment performed during the original manufacture e.g. re-normalising or solution annealing, stress relieving. Materials shall be re-certified using actual production material that has been heat treated with the component
2.4.2.6
A minimum of one thermocouple shall be attached directly to the component to measure the actual surface temperature.
Commentary: Measurement of the temperature using furnace thermocouples is not acceptable for formed components
2.4.3
Hot forming, including induction bending, of ferritic steels with properties enhanced by heat treatment or CRAs is not permitted unless the combination of the material/thickness/component configuration precludes the use of cold forming techniques. Where Company agrees that hot forming is permissible, a procedure qualification shall be undertaken to demonstrate that no deterioration in material or corrosion resistant properties will result during the hot forming operation and this shall be verified by means of appropriate production testing. Any subsequent heat treatment after forming shall be undertaken as a separate operation
Commentary: Electric resistance or induction heating of thin wall CRA tubing is acceptable providing the bend area plus 250-300mm straight length is included in the heated area and an inert gas purge used during heating and cooling
2.4.4
The use of circumferential welds in tubular products subject to forming is not permitted. Where longitudinally welded pipe is used, the weld shall be placed along the neutral axis.
2.4.5
Each component shall subject to inspection after forming to ensure that it is acceptable for further fabrication including, but not limited to:
2.4.5.1
Removing all scale for visual inspection of surface to verify freedom from cracks, buckling, gouges, corrugations, die marks or any other unacceptable surface indications
2.4.5.2
Performing 100% volumetric NDE and 100% MT/PT of all welds in the formed component
2.4.5.3
Performing surface 100% MT/PT of the external surface of heads in the knuckle region and bend region of formed pipe
2.4.5.4
Performing thickness measurements of the predicted thickest and thinnest areas
Commentary: Excessive thickness at elbows and bends should be avoided as this can affect the flexibility of piping systems
2.4.5.5 2.5
Performing hardness tests on tempered components to confirm acceptable heat treatment.
Joint Preparation
2.5.1
Joints shall be prepared in a manner that results in joints that meet the specified mechanical and corrosion resistant properties including, but not limited to:
2.5.1.1
Segregated, clean areas shall be used for the assembly and welding of CRAs
2.5.1.2
Segregated, clean areas with controlled environmental conditions (temperature, humidity, cleanliness etc. as recommended by the resin system/adhesive manufacture) shall be used for the assembly and bonding of non-metallic materials
2.5.1.3
All surface contaminants, cutting dross, scale etc. shall be removed from within a minimum of 25mm of the joint edges
2.5.1.4
The use of backing strips shall be subject to the following restrictions:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
14 of 44
Value Assurance Framework (VAF)
o o
o 2.5.1.5
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Permanent metallic backing strips are not permitted in any service environment with the exception of clean air or gaseous nitrogen Temporary metallic backing strips are permitted providing the same nominal material specification is used, the backing strip is removed after welding and the surface ground smooth after removal Ceramic backing strips/tape and consumable inserts are permitted – in this case the welding procedure and welder shall be qualified with the ceramic strip or consumable insert present
The amount of weld deposited around integrally reinforced branch fittings (e.g. ‘O-lets’) shall be minimised, consistent with strength and reinforcement requirements and manufacturer’s recommendations
Commentary: Excessive welding can lead to severe distortion of the run pipe in thin wall piping, especially in CRAs – only weld up to the ‘weld line’ and not the shoulder of the fitting and ensure a smooth transition with the run pipe
2.5.1.6
All mill scale, welding flux or other foreign matter from the weld, HAZ and surrounding area
Commentary: Contamination around the weld area can reduce the effectiveness of any internal purging for CRAs and increases the likelihood of preferential weld and HAZ corrosion
2.5.1.7
The internal weld profile shall be ground flush with the adjacent base material at orifice flanges and other flow measurement devices
2.5.1.8
Misalignment and ovality at joints shall be controlled in accordance with the design code and, in addition, with BGA-ENG-MATL-TS-0001 for welded tubular components subject to cyclic fatigue or elevated temperature environments. Any permitted radial misalignment shall be distributed equally around the circumference of the joint
Commentary: Excessive misalignment should be corrected by machining providing this does not reduce the thickness below the specified minimum or by weld build up followed by surface and volumetric NDE
2.5.2
Where socket weld connections are permitted by Company standards, the gap to between pipe and socket after welding shall be 1.5-3mm
Commentary: As a minimum, the pipe needs to be engaged in the socket for at least a distance equivalent to the pipe wall thickness to minimise the bending stress on the root of the fillet weld – by specifying a minimum and maximum gap this should easily be achieved
2.5.3 2.5.3.1
Where threaded connections, including vent and drain plugs, are permitted by Company standards, the following requirements shall be met as a minimum: A thread lubricant shall be used during assembly unless the connection is seal welded
Commentary: The difference between ‘sealing’ and ‘lubrication’ must be clearly understood when selecting an appropriate material – ‘sealants’ such as PTFE tape are not permitted
2.5.3.2
Thread compounds or lubricants shall be suitable for the full range of design conditions, shall not react with the service environment and shall not cause corrosion or material degradation of materials with which it is in contact
Commentary: Some lubricants contain metallic materials, sulphides, chlorides or carbon which in certain circumstances may cause galvanic corrosion, LMC or SCC
2.5.4
Fabrication and inspection of components subject to coating in accordance with BGA-ENG-MATL-TS0005 shall meet the following requirements:
2.5.4.1
Surfaces to be coated shall have a smooth contour, free of discontinuities, crevices and sharp projections. All changes in contour should be finished to a radius of not less than 3mm for external coatings and 6mm for internal coatings
2.5.4.2
Weld profile and joint design shall provide a smooth transition from the weld metal to the base material
2.5.4.3
All welds and welded attachments shall be completed prior to commencing coatings activities
2.5.4.4
All surfaces, including welds and base materials, shall be free from surface or surface-breaking flaws. Any surface flaws shall be repaired by welding and/or grinding - caulking materials shall not be used
2.5.4.5
For internally coated components, the following additional requirements shall be met:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
15 of 44
Value Assurance Framework (VAF)
o o o
o o 2.6
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Fabrication, surface finish and inspection shall meet the recommendations in NACE SP0178 and appropriate parts of BS 6374 Branch/nozzle connections equal to or smaller than 4”NB shall be clad or weld overlaid due to the difficulty in reliably coating and inspecting small diameter pipes Connections shall be flanged otherwise agreed with Company. Where slip-on flanges are used, the internal fillet weld shall extend to the flange face and shall be rounded as required by BS 6374 All integrity testing shall be completed and accepted before surface preparation and lining activities commence No welding shall be performed on internally coated equipment.
Handling, Storage and Transport
2.6.1
On receipt, base material components shall be handled and stored in accordance with the requirements specified in BGA-ENG-MATL-TS-0008 and shall be segregated and stored in separate locations to prevent mixing of different ferritic steel grades or between ferritic steels and CRAs
2.6.2
Other components such as welding consumables, resin, adhesives, NDE consumables etc. shall be delivered in the Vendor's unopened, original containers bearing a legible product designation, batch number and date of manufacture to permit usage within the Vendor's recommended shelf life. They shall be stored in accordance with the Vendor's latest published instructions to prevent damage from moisture, direct sunlight and hot or cold temperatures until ready to use.
2.6.3
Welding consumables shall be stored and handled in accordance with the Vendor's recommendations and dried to ensure the specified maximum hydrogen levels are met prior to commencing welding. Quality control procedures shall be developed and implemented to control the storage, handling, issue and return of materials and welding consumables.
2.6.4
Fabricated items such as partially or fully completed static equipment items or pipe spools shall be handled, stored and transported as follows:
2.6.4.1
Precautions shall be taken to avoid direct contact with the ground, soil, water or other source of contamination that may lead to deterioration or damage.
2.6.4.2
Nozzles or open ends shall be protected by end covers or wooden blanks and with dessicant installed or with an inert gas blanket to prevent moisture ingress
2.6.4.3
CRA equipment or pipe spools shall be protected from contamination (both internally and externally) during transport and storage
2.6.4.4
Non-metallic equipment and pipe spools shall be stored to avoid direct sunlight and excessive heat or cold, and shall be provided with sufficient support to avoid sagging or permanent distortion.
2.6.5
During fabrication and installation, open ends of static equipment items or pipe spools shall be protected from damage or ingress of water, debris etc. at the end of each working shift.
2.6.6
Only canvas or nylon slings shall be used to lift and transport pipe spools and lifting points shall be selected to ensure that spools are properly balanced. Where steel slings are necessary for safety reasons, the pipe spool shall be protected from direct contact by appropriate and safe means.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
16 of 44
Value Assurance Framework (VAF)
3.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Welding Requirements
3.1
General
3.1.1
Welding, NDE and related activities shall be performed in accordance with the requirements of the design code and this Standard.
3.1.2
The guidelines and practices specified in API RP582 shall be considered mandatory and included in project specifications and procedures.
Commentary: API RP582 was developed as a recommended practice for welding in downstream refining facilities but the recommendations are equally applicable for upstream production or downstream LNG or steam generating facilities. EN 1011 is an additional set of standards that may also be referenced for good welding practice
3.1.3
All welding processes shall be protected from adverse weather conditions that may affect weld quality. When welding is performed outdoors in adverse weather conditions, temporary shelters shall be erected to completely enclose the work area. Windshields shall always be erected to prevent loss of shielding gas coverage when using gas shielded processes.
3.1.4
Where socket weld connections are permitted by Company standards, the weld shall be a minimum of two passes – the first pass shall be predominately deposited on the socket, the second predominately on the pipe, with both passes clearly visible under close visual examination
Commentary: This requirement is intended to minimise the likelihood of a leak at the stop-start position and to maximise the amount of tempering of the socket HAZ. Any subsequent weld passes need to follow a similar technique
3.1.5
Where seal welding of threaded connections is specified, the following minimum requirements shall be met:
3.1.5.1
Thread lubricant shall not be used
3.1.5.2
Exposed threads shall be removed by grinding prior to welding and the weld shall completely cover the region of exposed threads
3.1.5.3
The connection materials shall be fully weldable without the need for preheat or PWHT
3.1.5.4
The welding process and welding procedure shall be selected to ensure there is no damage to adjacent components (such as soft seat valves).
3.2
Welding Processes
3.2.1
FCAW-S and EGW are not permitted for welding pressure retaining components but may be used for welding structural steel and API 650 storage tanks, subject to the following requirements:
3.2.1.1
Welding procedures are qualified with impact testing of the weld metal and HAZ at the lower of 0°C or CET
3.2.1.2
Production test plates are taken to represent each welding procedure used. The number of test plates shall be agreed with Company.
3.2.2
GTAW or GMAW shall be used for the root pass in single-sided welded joints where pre-commission cleaning is a requirement in accordance with BGA-ENG-MECH-TS-0012.
Commentary: The intent is to ensure that no flux is deposited on the internal root surface that may then be difficult to remove during the subsequent pre-commission cleaning operations
3.2.3
The use of mechanised or automated welding processes shall be maximised where they can be demonstrated to enhance the productivity whilst maintaining the specified quality, mechanical properties and corrosion resistance.
Commentary: This will typically include the use of SAW, orbital GTAW or GMAW
3.2.4 3.3 3.3.1
The use of welding processes utilising modern power sources, such as STT or RMD, are permitted subject to specific welding procedure qualification in accordance with requirements of Section 3.7. Welding Consumables Welding consumables shall be supplied with a specific product quality control MTR in accordance with EN 10204, Type 3.1 where the design code or Company standards specify additional requirements (e.g. impact or fracture toughness testing, corrosion testing, ferrite determination).
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
17 of 44
Value Assurance Framework (VAF)
3.3.2
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
When impact testing is required by the design code or BGA-ENG-MATL-TS-0001 each welding procedure shall be qualified with impact testing using the same consumable manufacturer and brand designation as proposed for production welding.
Commentary: Whilst Section 6 of API RP582 requires certification of the welding consumables at the CET if the base material is exempt from impact testing, the welding procedure used can significantly influence the performance of the weld at low temperatures and as such Company requires that the toughness of the weld metal and HAZ are demonstrated by representative welding procedure qualification testing supported by production testing when the CET is below -29°C
3.3.3
Welding consumables producing low hydrogen deposits (8ml H 2 /100g (H8) weld metal hydrogen levels) shall be used for welding all ferritic steels with the following exceptions:
3.3.3.1
The root, fill and cap for conventional carbon steel with a nominal thickness of 13mm or less may be made using cellulosic or rutile electrodes unless otherwise restricted by this Standard
3.3.3.2
The root, fill and cap for low carbon, micro-alloyed carbon pipeline steels subject to meeting the specified mechanical properties and any additional requirements of this Standard
Commentary: The above requirements presumes that ferritic steels are welded with nominally matching consumables – in cases where ferritic steels for service in cold or cryogenic environments are welded with a non-matching consumable (e.g. Ni-based consumables), the flux coating of SMAW consumables may not be specifically formulated to produce low hydrogen deposits
3.3.4
For welding similar ferritic steel materials, consumables shall be selected to deposit weld metal as follows:
3.3.4.1
For base materials with SMYS less than 450MPa and not subject to plastic deformation during construction, installation or service, the deposited weld metal shall not overmatch the actual yield strength of the base materials by more than 15%
3.3.4.2
For base materials with SMYS of 450-550MPa and for all grades subject to plastic deformation during construction, installation or service, the deposited weld metal shall not overmatch the actual yield strength of the base materials by more than 10%
Commentary: Company recognises that these requirements are conservative but are intended to limit potential problems with meeting tensile and toughness properties whilst ensuring weldability with low likelihood of hydrogen cold cracking of the weld metal or HAZ
3.3.4.3
The deposited weld metal Boron (B) content shall not exceed 0.0005% for welding base materials with SMYS of 415MPa or greater
Commentary: Boron has a potent effect on the steel hardenability but is not typically measured as part of the welding consumable certification and, as a consequence, can affect the likelihood of hydrogen cold cracking particularly in higher strength steels. Recent pipeline welding procedure qualification concerns in Australia have prompted a request to review the inclusion of Boron as part of weld consumable certification
3.3.5 3.3.5.1
For welding dissimilar materials, the following requirements shall be met: For dissimilar ferritic steels, consumables shall be selected to deposit weld metal which nominally matches either base material, subject to meeting any additional requirements of this Standard
Commentary: Additional requirements may include limitations on hardness levels or chemistry controls for preferential weld or HAZ corrosion
3.3.5.2
For ferritic steel-to-CRA, consumables shall be selected to deposit weld metal with nominally intermediate thermal expansion properties between the two base materials. Where only one material requires PWHT, a non-air hardenable weld metal shall be deposited on the heat treated side prior to PWHT and the dissimilar weld completed with an appropriate, non-air hardenable consumable after PWHT.
Commentary: The selection of consumables for these joints is generally a compromise between the properties of the two materials to be welded. These requirements are intended to minimise the thermal stresses imposed on the dissimilar metal weld in service as a result of the different thermal expansion coefficients of the base materials and weld metal
3.3.6
Where the likelihood of preferential weld and HAZ corrosion is identified in accordance with BGA-ENGMATL-TS-0001, the requirements in Appendix C of BGA-ENG-MATL-TS-0001 shall be met.
Commentary: Over-alloyed weld metal compositions have typically been specified for seawater/produced water environments whilst weld metal compositions nominally matching the base material chemistry have been specified for wet gaseous CO 2 environments as part of the chemical treatment testing regime
3.3.7
For welding 300-series austenitic stainless steels, the following requirements shall be met:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
18 of 44
Value Assurance Framework (VAF)
3.3.7.1
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Welding consumables for use in cryogenic environments shall be formulated to ensure consistent weld metal toughness at the specified test temperature as demonstrated during welding procedure qualification in accordance with Section 3.6.2 and confirmed during fabrication by production testing in accordance with paragraph 3.11.3
Commentary: The selection of consumable chemistry is a compromise between ensuring acceptable toughness and resistance to hot cracking – experience indicates that control of the Cr/Ni ratio and weld metal ferrite number to between 3FN and 8FN will deliver more consistent toughness whilst minimising the likelihood of solidification hot cracking. Some consumable chemistries (e.g. Type 16-8-2 ) will deposit weld metal with a lower weld metal ferrite number than 3FN whilst still ensuring freedom from hot cracking
3.3.7.2
Welding consumables for use in elevated temperature environments or subject to heat treatment above 550°C shall be formulated to limit Bismuth (Bi) in the deposited weld metal to less than 0.002%
3.3.7.3
When the weld groove thickness exceeds 25mm consumables and welding procedures shall be selected to minimise the likelihood of solidification and/or re-heat cracking occurring during welding and/or heat treatment.
Commentary: Use of basic coated SMAW electrodes and consumables with improved ‘creep ductility’(e.g. Type 16-8-2) should be considered for heavy wall applications or where weld joint restraint is a concern (e.g. nozzle-shell welds)
3.3.8
For welding duplex and high alloy stainless steels, consumables and shielding gases shall be selected to deposit weld metal with PREN values meeting the minimum PREN values for the base materials.
Commentary: High alloy stainless steels should typically be welded with on over-matching molybdenum content and niobium-free Nibase consumables in order to meet the PREN values whilst minimising the likelihood of hot cracking and microsegregation although the final selection will require satisfactory welding procedure qualification in accordance with Section 3.7
3.4
Shielding and Purging Gases
3.4.1
The use of shielding or purge gas in a confined space (e.g. inside vessels or large diameter piping) shall be subject to an appropriate Permit-to-Work entry system. Internal purge dams in piping systems shall be inspected before purging commences and thereafter no access for inspection or removal is permitted without a ‘Permit-to-Work’.
Commentary: Typical purge gases are heavier than air and can collect at low points. Sufficient fatal incidents and near-misses have occurred during welding with inert gases in confined spaces to demonstrate the seriousness of this requirement
3.4.2
For back purging, acceptable purge levels shall be confirmed by monitoring either the oxygen content or the dew point.
Commentary: The six-to-ten volume ‘rule-of-thumb’ for displacing air with a purge gas is difficult to measure accurately in practice and may not be sufficient to ensure acceptable purging has taken place. Quantitative measurements with an oxygen or dew point meter are simpler and quicker to make and can confirm the acceptable levels of purging as demonstrated during the welding procedure qualification - limits of 100-200ppm oxygen or a dew point of -40°C would typically indicate acceptable purging although higher limits may be acceptable if additional testing (such as corrosion tests) confirms those limits. Oxygen or dew point monitoring will typically be undertaken as part of the normal quality control checks by the relevant welding supervisory personnel
3.4.3
A purge gas shall be maintained until at least 6.4mm weld metal has been deposited. Where attachment welds are made to thin wall components (t 5.5mm) a purge gas shall be maintained until all welding is complete.
3.4.4
Shielding gases for welding low alloy steels, duplex and martensitic stainless steels or titanium and its alloys shall not contain hydrogen.
3.4.5
For welding titanium and its alloys, the following additional requirements shall be followed:
3.4.5.1
Purge gas and the trailing shielding gas shall be maintained until the weld and HAZ area cools below 400C
3.4.5.2
A purge gas shall be used to shield the back face of all titanium cover strip welds
3.4.5.3
All gases shall be 99.998% purity and contain no more than 10ppm moisture at the specified dew point.
3.5 3.5.1
Pre-heating Pre-heating shall meet the higher temperature of the design code or the table below:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
19 of 44
Value Assurance Framework (VAF)
Material Type(5)
Conventional carbon steel(1)(2)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Nominal Thickness at Weld (mm)
Minimum Preheat Temperature (C)
t 13
10(2) 75 100 150
13 t 25 25 t 50 t 50
HSLA steels
Per steel Vendor’s (3) recommendations
All
t 13
2¼Cr-1Mo
t 25
125 150 175
All
200
13 t 25
9Cr-1Mo 9Cr-1Mo-Nb-V
t 38 Duplex stainless steels (4)
t 38 Notes:
(3)
10
75(4)
1.
Preheat temperatures are based on 8ml H 2 /100g (H8) weld metal hydrogen levels and CE 0.45. Alternative preheat temperatures may be calculated in accordance with EN 1011-2, in which case, the WPS and PQR shall show all limiting factors such as combined thickness, CE value, weld metal hydrogen content and heat input or runout-length, upon which the preheat level is based
2.
Not required other than to remove moisture prior to welding
3.
The minimum preheat temperatures for HSLA steels shall meet the steel Vendor’s recommendations based on the P cm value of the weld metal
4.
Particular care shall also be taken in developing welding procedures for weld joints with high heat conductive paths such as tube-to-tube sheet joints – preheat shall be applied to limit the cooling rate
5.
Minimum preheat temperatures for other materials should comply with the design code
Commentary: The preheat levels defined in EN 1011-2 are based on a substantial body of work on conventional carbon steels and will minimise the likelihood of fabrication related HAZ hydrogen cold cracking. HSLA steels may be at higher risk of weld metal hydrogen cold cracking compared to HAZ hydrogen cold cracking in conventional carbon steels due to the higher hardenability of the weld metal – typically an increase of 50ºC is recommended above that required for conventional carbon steels
3.5.2
Preheat shall be applied in a uniform manner and maintained throughout welding. Once preheat is applied, welding shall not be interrupted or stopped (other than for rest breaks) until a minimum of 30% of the final weld depth has been completed. On completion of welding, the weld area shall be cooled slowly under insulation to ambient temperature or, if required by Section 3.5.4, subject to an intermediate de-hydrogenation heat treatment.
3.5.3
Preheat and inter-pass temperatures shall be measured in accordance with the requirements of API RP582 only after sufficient time has elapsed for temperature equalisation
Commentary: A typical figure to calculate this equalisation is two minutes per 25.4mm parent material thickness. Any crayons used for CRAs must certified free from injurious contaminants, such as sulphur and halides
3.5.4 3.6
Where the minimum specified pre-heat temperature is 150ºC or higher, an intermediate dehydrogenation post heat treatment shall be applied after welding prior to cool down. Post Weld Heat Treatment
3.6.1 3.6.1.1
PWHT shall comply with the design code requirements and the following as a minimum: Heating and cooling rates shall be selected to minimise the likelihood of distortion or induced thermal stresses based on the thickness and configuration of the component. Unless otherwise specified in the design code the following requirements shall be met: o
Above 315C heating rates shall not exceed 5600C/hour divided by the maximum thickness in millimetres but in no case less than 55C/hour nor greater than 222C/hour
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
20 of 44
Value Assurance Framework (VAF)
3.6.1.2
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
o
During the holding period, the maximum temperature shall not exceed the minimum specified holding temperature by more than 50C
o
Cooling rates shall not exceed 6875C/hour divided by the maximum thickness in millimetres but in no case less than 55C/hour nor greater than 270C/hour
For materials subject to a tempering heat treatment, the maximum PWHT temperature shall be at least 10ºC below the tempering temperature.
Commentary: This requirement is intended to prevent deterioration of the mechanical properties of the base material during PWHT. An exception to this would be if the final tempering of the materials and welds is accomplished during the final PWHT in which case the welding procedure qualification must represent the final heat treated condition and production weld test plates will be required to verify that the material specification and/or design code mechanical properties have been achieved in the final PWHT condition
3.6.1.3
All fabricated components, including pipe spools, shall be adequately supported to prevent deformation during PWHT
Commentary: Internal bracing should be applied to prevent deformation of large diameter, thin wall vessels (large D/t ratio)
3.6.1.4
For equipment items such as pressure vessels and heat exchangers heat treated in a furnace, a sufficient number of thermocouples shall be installed on the inside and outside surfaces of to monitor the minimum and maximum temperatures at the thinnest and thickest sections (including nozzles), at major structural discontinuities (e.g. internal heads) and enclosed or semi-enclosed areas (e.g. inside support skirts)
3.6.1.5
For pipe spools heat treated in a furnace at least one thermocouple shall be attached to each spool
3.6.1.6
For local PWHT, the recommendations in WRC Bulletin 452 and AWS D10.10 shall apply in addition to the requirements of the design code.
Commentary: These recommendations are intended to improve the heat treatment process and reduce harmful thermal gradients. Where other relevant standards are applicable (e.g. API RP945, NACE SP0403) the requirements specified therein shall also apply
3.6.2
Exemption from PWHT shall be subject to BG Advance review and agreement and the following:
3.6.2.1
Base materials shall be subject to fracture mechanics testing in accordance with BGA-ENG-MATLTS-0008
3.6.2.2
Welding procedures shall be subject to fracture mechanics testing in accordance with Section 3.7
3.6.2.3
An engineering critical assessment shall be undertaken to determine critical flaw sizes in accordance with BS7910 or API RP579 based on the maximum load case and calculated stress intensification at the weld, the results of the fracture mechanics testing and the ability of the specified NDE techniques to detect and size relevant flaws.
Commentary: Waiving of PWHT will only be accepted if the size of the component or equipment item precludes heat treatment in a furnace under controlled conditions or there is a demonstrable benefit to Company in terms of cost and schedule without compromising safety or technical/mechanical integrity
3.7
Special Procedure Qualification Requirements/Testing
3.7.1
In addition to the requirements of the design code all pressure retaining welds, including fillet welds and nozzle/branch welds, shall be qualified using a butt weld test piece with full mechanical testing.
3.7.2
Where additional testing of the base material is specified in accordance with BGA-ENG-MATL-TS0008, (such as corrosion testing, ferrite determination, impact testing, strain ageing) the welding procedure qualification shall be subject to an equivalent testing regime. Test specimens shall include the weld metal and HAZs.
3.7.3
For welding procedures subject to impact testing, heat input shall be recorded and calculated for each weld run as follows:
3.7.3.1
For manual SMAW, heat input shall be recorded and controlled by measuring the length of weld deposited per unit length of electrode ROL//ROR
3.7.3.2
For semi-automatic, automatic or machine welding processes, the heat input shall be recorded by measuring and controlling the amperage, voltage, travel speed and oscillation/maximum bead width and depth.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
21 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Commentary: Although design codes such as ASME IX permit both of the above methods for calculating heat input during welding with SMAW, the ability to consistently monitor the amperage, voltage and travel speed is difficult due to the nature of the process and measuring the ROL/ROR or volume of weld metal deposited is simpler and more consistent. If the former method is used then the Contractor/Vendor must be able to demonstrate that it can accurately and consistently monitor the welding variables to permit calculation of heat input for comparison with the PQR. Company reserves the right to require production test plates/welds to be tested to verify the heat input used
3.7.4
Where fracture mechanics testing is specified, the weld metal and HAZ shall be tested in accordance with BS 7448 and the following:
3.7.4.1
An all-weld metal tensile specimen shall be taken from the same weld test plate as that used for CTOD testing to obtain the yield strength used in CTOD calculations
3.7.4.2
Test assemblies shall have a “single bevel” or “offset-V” preparation such that one side of the preparation is almost vertical to allow accurate HAZ notch location
3.7.4.3
The test temperature and acceptance criteria shall meet the requirements specified in BGA-ENGMATL-TS-0008.
3.7.5 3.7.5.1
For welding duplex stainless steels the following requirements shall be met: Heat input shall be consistent with the combined base material thickness and obtaining adequate fusion and weld metal properties and shall be determined during welding procedure qualification
Commentary: The root pass of single sided welds in duplex stainless steels should be welded by depositing a heavier-than-normal root bead followed by a second “cold” pass using a lower heat input than that for the root pass
3.7.5.2
Welding procedures for thin-wall piping (t ≤ 5.5mm) shall be qualified using the production pipe or tube wall thickness in order to simulate the actual production heat sink effect
3.7.5.3
Welding procedure qualification testing shall include the appropriate specified tests for these materials in BGA-ENG-MATL-TS-0008
3.7.6 3.7.6.1
For welding tube-to-tube sheet welds the following requirements shall be met: Welding procedure qualification shall be in accordance with ASME Section VIII, Div.2, Article F-3, EEMUA 143 or ISO 15614-8 and subject to the following testing regime: o o o o o
Visual examination RT or sectioning of the test piece followed by etching to demonstrate the required weld throat thickness has been met and the weld is free from porosity and planer flaws 100% MT or 100% PT of the completed test piece Hardness testing (where Company standards specify specific hardness limits) Pull-out strength tests (where the weld metal properties are integral to the tube-to-tube sheet design)
Commentary: Pull-out strength tests are not required where the weld is simply a seal weld over an expanded tube-to-tube sheet joint
3.7.6.2
Tube-to-tube sheet welds shall have the root pass deposited with filler wire unless the proposed design precludes this (e.g. castellated or back face joint design).
Commentary: Autogenous welding of the root pass in welds with a groove or fillet joint design will potentially result in cracking which will not be removed by subsequent filler metal passes
3.7.7 3.7.7.1
In addition to the requirements of the design code, a welding procedure shall be re-qualified if any of the following changes, from that stated on the PQR, apply: A change in the nominal chemical composition of deposited weld metal or change between wire chemistry from one AWS or EN classification to another or to wire chemistry not covered by an AWS or EN classification
Commentary: A change in the nominal chemical composition of deposited weld metal (e.g. as permitted in ASME Section IX QW-442 A-No.1 to A-No.2 or vice versa) could permit the use of more hardenable weld metal for welding of carbon steel that could then result in higher than anticipated hardness in the weld metal – for sour environments this would be unacceptable
3.7.7.2
A change in the make or model of machine, weld geometry, diameter, direction of welding, base material chemistry, welding consumable manufacturer, thickness and welding variable settings from that stated on the PQR for mechanized or automatic welding processes or welding processes utilizing modern power sources
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
22 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Commentary: These variables can all influence the quality of the welds
3.7.7.3
A change in the consumable Vendor/brand designation when impact testing is specified
Commentary: A change in the consumable Vendor/brand designation can have a significant effect on the weld metal chemistry and hence toughness properties even when consumables have the same classification. If consumables from a different Vendor and/or brand designation are proposed, additional impact testing will be required to verify the properties are acceptable and this may be done as part of the welding procedure or welder performance qualification or production testing subject to Company agreement
3.7.7.4
A change in the consumable Vendor/brand designation and welding position when production ferrite determination is specified
Commentary: A change in the consumable Vendor/brand designation can have a significant effect on the weld metal chemistry and a change in the welding position can affect the heat input both of which can affect the final FN value. If consumables from a different Vendor and/or brand designation or changes in the welding position are proposed, additional ferrite determination will be required to verify the properties are acceptable and this may be done as part of the welding procedure or welder performance qualification or production testing subject to Company agreement
3.7.7.5
A change in the position of welding when production hardness testing is specified
Commentary: A change in the welding position can affect the heat input which in turn can affect the final hardness value. If a change in welding position is proposed, additional hardness measurements will be required to verify the properties are acceptable and this may be done as part of the welding procedure or welder performance qualification or production testing subject to Company agreement
3.7.7.6
A change in composition, or deletion of, a purge or trailing gas
Commentary: As a purge gas can react with the molten metal the composition of the gas can affect the final weld metal chemistry
3.7.7.7
A change in the following when welding low carbon, high strength ferritic steels:
o
A change in the SMYS of the material with the exception that qualification on a higher grade of material qualifies for a lower grade providing all other essential variables are met A change in the consumable Vendor/brand designation
o o
Any change in heat input of 10% A change in the wall thicknesses of 0.5t – 1.5t
o
Commentary: The above variables can all affect the final deposited weld metal chemistry and mechanical properties
3.7.7.8
A change in the following when welding duplex stainless steels: o o o
A change from 22%Cr base materials to 25%Cr base materials or vice versa Any change in the source of supply for 25%Cr base materials A change in the consumable Vendor/brand designation for welding 25%Cr base materials
o o
Any change in the heat input of 10% A change in the wall thicknesses of 0.5t – 1.5t
Commentary: The above variables can all affect the deposited weld metal chemistry and hence final mechanical and corrosion properties
3.7.7.9
A change in the following when welding high alloy stainless steels: o o
Any change in the heat input of 10% A change in the wall thicknesses of 0.5t – 1.5t.
Commentary: The above variables can all affect the deposited weld metal chemistry and hence final mechanical and corrosion properties
3.8
Weld Overlay/Clad Restoration and Metallic Hard-facing
3.8.1
Corrosion resistant weld overlay and clad restoration shall meet the requirements of the design code and API RP 582 and the following:
Commentary: EN 1011-5 is also a useful reference for welding clad components
3.8.1.1
The minimum thickness of weld overlay shall not be less than 3mm and the top 1.5mm of weld deposit (or final machined/ground surface) shall meet the nominal specified chemistry
Commentary: Particular care shall be taken during any grinding or machining operations of the weld overlay or back restoration to ensure that these operation do not reduce the thickness of the overlay/back cladding below the minimum qualified thickness and that the specified chemistry will be met in the final surface condition
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
23 of 44
Value Assurance Framework (VAF)
3.8.1.2
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
For major load bearing attachments, the integral cladding or weld overlay shall be removed around an area at least 50mm from the toe of the attachment weld, and the attachment welded directly to the base material. Attachments welded directly to the base material shall match the nominal metallurgy of the base material and shall be welded using matching consumables and subsequently weld overlaid. Other attachments may be welded directly to integral cladding and weld overlay subject to 100% UT of the entire area within 50mm of the attachment weld
Commentary: These requirements are intended to minimise the likelihood of dis-bonding of the cladding or weld overlay due to high tensile stress in the through-thickness direction
3.8.1.3
As-built drawings shall show the actual thicknesses of weld overlay and base metal at specific locations nominated by the Company and included in the baseline surveys requirements in accordance with Section 3.12
3.8.1.4
For weld overlay of ferritic steel hubs installed in sub-sea manifolds, the preparation and welding recommendations in EEMUA 194 shall be considered mandatory.
3.8.2
Metallic hard-facing weld overlay for wear resistance shall meet the requirements of the design code and the following:
3.8.2.1
The base material shall be thoroughly cleaned and degreased prior to welding to minimize spalling of the hard-facing weld overlay
3.8.2.2
Weld overlay shall be deposited with a minimum of two layers to ensure a minimum thickness of 3mm and minimum specified hardness in the final as-welded or machined/ground condition
3.8.2.3
Subject to satisfactory welding procedure qualification, where the base material requires PWHT a non air-hardenable buffer layer (e.g. Type 309L) shall be applied to the hardenable base material prior to any PWHT and the hard-facing weld overlay applied after PWHT
3.8.2.4
Preheat shall be applied prior to, and maintained during, welding of all passes of the hard-facing overlay in accordance with the consumable manufacturer’s recommendation. After welding is completed, the weld area shall be cooled slowly under insulation to minimize the risk of cracking
3.8.2.5
Any grinding or machining of the hard-facing weld overlay surface shall be minimized, and where necessary, shall be performed in such a manner as to minimize any “heat cracks” developing from improper techniques
3.8.2.6
The final surface (as-welded/machined/ground) shall be subject to 100% PT – narrow cracks of less than 1-2mm width are acceptable providing they do not extend to the base material
3.8.2.7
Proposal to use thermal spray process or other alternative hard-facing techniques shall be subject to BG Advance review and agreement.
3.9
Non Destructive Examination
3.9.1
Quality control procedures shall be specified and implemented to control all NDE activities, detailing the extent of examination, the nature of the anticipated flaws, proposed techniques to detect such flaws and appropriate acceptance criteria.
3.9.2
All NDE shall be completed prior to pressure (strength) testing.
Commentary:
3.9.3
Where ‘golden welds’ are permitted in-lieu of pressure (strength) testing as specified in BGA-ENGMECH-TS-0012, the following additional requirements shall be met:
3.9.3.1
All weld preparations shall be subject to 100%MT or PT
3.9.3.2
The weld shall be deposited with a minimum of three layers of weld metal – if the weld is singlesided, the root pass shall be welded with GTAW followed by at least two further layers of weld metal; if double-sided, there shall be at least two layers of weld metal on either side
3.9.3.3
The completed weld shall be subject to 100% volumetric examination and 100% MT/PT - where RT is not feasible, the requirements in Section 3.9.8 shall be met
3.9.3.4
The completed weld shall be subject to PMI in accordance with Section 3.9.14 (where applicable)
3.9.3.5
All production tests required by Section 3.11 shall be performed
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
24 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
3.9.4
All welds shall be subject to 100% close visual examination to verify acceptable workmanship standards, freedom from surface-breaking flaws or fabrication damage, acceptable weld profiles and cleanliness both during and on completion of welding activities.
3.9.5
The weld, HAZ and adjacent base material in CRAs shall not show any discolouration (‘heat tint’) darker than light straw. Oxidation, as indicated by a dark brown to dark blue or violet colour, with possibly a coked weld surface, is unacceptable. For CRAs (with the exception of titanium and its alloys), unacceptable oxidation shall be removed by wire brushing, light grinding (60-35 micron grade abrasive paper) or by pickling – for titanium or its alloys, the weld shall be completely removed and rewelded.
Commentary: In cases of dispute regarding acceptable discolouration of titanium, Company reserves the right to undertake a hardness survey on the weld, HAZ and base material to verify whether any unacceptable contamination has occurred
3.9.6
In addition to the requirements of the code, 100% volumetric examination shall be applied for the following: Longitudinal and circumferential welds in primary structural tubular members Longitudinal welds in and secondary structural tubular members T, K, Y connections in primary structural members and in secondary members where the predicted fatigue life is low or no redundancy exists Offshore jacket hook-up welds Longitudinal and circumferential welds in components fabricated from HSLA steels Longitudinal, circumferential and nozzle welds in components exposed to cyclic fatigue environments or high pressure environments Longitudinal and circumferential welds in components fabricated from CRAs when the nominal thickness at the weld joint exceeds 25mm Longitudinal and circumferential welds in components where impact testing is required by the design code or by BGA-ENG-MATL-TS-0001
Commentary: Where the design code and BGA-ENG-MATL-TS-0001 permits the use of exemption from impact testing due to depressurisation to temperatures below the CET but impact tested base materials are still specified, the requirement for 100% volumetric examination may be waived providing a high integrity protective system is in place to prevent repressurisation before the temperature has warmed up to the CET
Longitudinal and circumferential welds in components fabricated from ferritic steels and subject to pneumatic or combined hydrostatic-pneumatic testing Commentary: Company considers that additional inspection of all welds is necessary to minimise the consequences of failure as a result of the stored energy within a system under pneumatic test
Field-made welds in pressure vessels Dissimilar metal welds. 3.9.7 3.9.7.1
Radiography may be performed using X-rays or gamma sources and shall meet the following requirements: Gamma sources shall not be used for HSLA steels (SMYS ≥ 415MPa) or duplex stainless steels unless the source and inspection technique can demonstrate acceptable sensitivity and contrast to detect the smallest permitted flaw as defined by the design code
Commentary: Concern is with the ability of gamma sources to detect small planer flaws – this has happened in 25%Cr duplex stainless steel where these were only detected by subsequent UT. In these cases X-ray is required to provide acceptable contrast
3.9.7.2 3.9.8 3.9.8.1
Very fine grain, high contrast or ultra fine grain, high contrast film (e.g. ASTM E1815 Type I) shall be used. Where the nominal thickness at the weld joint is 50mm or greater, or radiography is not feasible (e.g. penetrated thickness too great), the following inspection shall be performed: All groove welds (including equipment nozzle welds and full penetration skirt-to-head/shell welds) shall be subject to full ultrasonic testing for axial and transverse flaws utilising at least two different
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
25 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
angle beam probes from both sides of the weld and on the inside and outside surfaces/nozzle bore (where access permits) to ensure complete coverage of the weld volume and the fusion line and HAZ of both base materials. Where an additional scan is performed along the weld axis to detect transverse flaws, the weld capping pass shall be dressed flush with the parent material to facilitate inspection. Commentary: The scanning patterns in EN 1714 using Quality Level C should be used to develop suitable procedures for manual UT to ensure complete volumetric coverage of the weld. Where access or weld configuration does not permit full volumetric coverage of the weld (e.g. welds between flanges/fittings/valves and pipe) alternative techniques will need to be proposed for Company review – where there are not feasible, the affected area must be clearly identified in the final handover documentation
3.9.8.2
For single-sided welds inspected from the outside surface only, the internal bore shall be tapered to at least 1:20 slope to facilitate UT of the root area and minimise the incidence of mode conversion and false calls
3.9.8.3
All attachment welds or pressure retaining fillet welds shall be subject to 100% MT or PT.
3.9.9
Where 100% volumetric examination is specified in Section 3.9.6, all pressure retaining welds and major structural attachment welds shall be subject to 100% MT or PT.
3.9.10 For ultrasonic testing of dissimilar CRA welds, welds in CRA components or CRA clad/weld overlaid components, procedures shall be developed to overcome the anisotropic nature and large grain size of the weld metal or differences in response at the interface of the cladding/weld overlay and base material. The proposed procedure shall be validated by means of demonstrable performance qualification and blind testing of the operator’s capability. Commentary: These procedures will typically involve the use of angled compression wave and creep wave probes
3.9.11 The use of enhanced UT techniques with computer based data acquisition in-lieu of radiography or manual UT shall be subject to BG Advance review and agreement and shall meet the following requirements as a minimum: 3.9.11.1
The technique(s) shall be subject to a procedure qualification to demonstrate it is effective over 100% of the weld volume including near and far fields and the fusion line and HAZ at both base material-weld metal interfaces. The test plate used for the procedure qualification shall meet the following requirements o o
o
It shall be manufactured by a third party, independent of the NDE Vendor undertaking the examination. Company reserves the right to witness the manufacture of the test plate It shall have a sufficient variety of surface, sub-surface and near-surface ‘flaws’ to represent the full weld volume and shall include both planer and volumetric flaws with acceptable and unacceptable dimensions in accordance with the design code or Company-agreed acceptance criteria. It shall represent the base materials, welding procedure, welding position and weld preparation to be used in production and nominal thickness of the production weld within 0.5t-1.5t
Commentary: Because the ultrasound propagation in austenitic weld metal is affected by the weld metal microstructure (particularly the grain angle distribution) which in turn is influenced by the welding process and welding position, it is important that the qualification test plate represents the production welding process as closely as possible. If a repair to a weld is made this will also potentially affect the ultrasound propagation and hence detection capability (particularly if using a different welding process to that used for the main weld) and this situation will also require qualification
o 3.9.11.2
The type, dimension, orientation etc. of each ‘flaw’ shall be verified by appropriate NDE techniques and the results presented to Company prior to procedure qualification
The technique(s) shall demonstrate the ability to detect, categorise, interpret, size and plot all flaws in the test plate and to distinguish between geometric or metallurgical indications (e.g. attenuation from large grain size, compound weld preparations) and relevant flaws. Any “missed” flaws or miscalls of either acceptable or rejectable flaws/regions shall be cause for rejection of the technique
Commentary: The root cause of the failure to meet the test criteria may be investigated further – if there is reasonable cause demonstrated for the failure, the test may be re-run at Company’s discretion. If necessary, the test plate may be sectioned to verify the results of the procedure qualification
3.9.11.3
A procedure shall be developed for examination of production welds including all essential variables as demonstrated during the qualification. Any change in the welding procedure, weld preparation, thickness out with the above range or in the essential variables shall require re-qualification
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
26 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
3.9.11.4
All operators shall be subject to blind testing using the procedure qualification test block to demonstrate their capability in using the technique. Any “missed” flaws or miscalls of either acceptable or rejectable flaws/regions shall be cause for rejection of the operator
3.9.11.5
Any limitations in the use of enhanced ultrasonic examination techniques (e.g. access restrictions) shall be identified and clearly reported in the final inspection reports. In such cases, supplementary inspection techniques shall be specified (e.g. radiography) and agreed with the BG Advance
3.9.12 Where WFMT is specified, the weld metal and base material for a distance of 25mm either side of the weld centre line shall be prepared to a surface finish of SSPC-SP3 minimum, with all mill scale removed, immediately prior to the examination. 3.9.13 NDE operators shall be certified as follows: 3.9.13.1
All Level I, Level II and Level III NDE personnel shall hold independent certification by a scheme meeting the requirements of ISO 9712 (e.g. PCN, CSWIP or ACCP). Acceptance of certification by the NDE operator’s employer in accordance with a written practice meeting the recommendations in SNT-TC-1A or ANSI/ASNT CP-189 shall be subject to review and agreement by Company
3.9.13.2
Re-certification after the second period of validity has elapsed shall be by practical examination for Level I and Level II personnel and by an approved written examination for Level III personnel
3.9.13.3
Company reserves the right to require all personnel responsible for performing and interpreting results from manual ultrasonic testing to undertake and pass a practical examination
3.9.13.4
Original “wet copy” certificates attesting to personnel certification shall be made available for review by Company - photocopies of certificates are not acceptable as proof of personal certification unless additional means of verification are agreed with Company.
Commentary: The above requirements are intended to demonstrate a high degree of competency and transparency in NDE operator’s certification
3.9.14 NDE results shall be recorded and included in the final handover documentation. 3.10 Positive Materials Identification 3.10.1 A PMI programme shall be specified and implemented to supplement the normal quality management systems in order to ensure that only the correctly specified generic base materials and weld metal are installed. Commentary: Carbon steel will typically not be included in PMI/alloy verification programmes but Company reserves the right to undertake spot checks to verify that hardenable ferritic steels or other materials have not been installed in carbon steel components or systems leading to an increased likelihood of cracking
3.10.2 The scope of PMI shall be based principally on the results of the corrosion risk assessment but shall include the following unless otherwise agreed with Company: CRA components where the alloy has been selected to resist corrosion Commentary: Where a CRA is specified for reasons of maintaining purity (such as lube or seal oil systems), or for cold or cryogenic environments, PMI/alloy verification is not required
Ni-alloy base components in cryogenic environments Commentary: This will include 3½%Ni through 9%Ni steels
Low alloy steel components in elevated temperature environments Commentary: This will include conventional and modified chromium-moybdenum steels
Low alloy steel and CRA components where replacement is not feasible or extremely costly (e.g. sub-sea systems) Low alloy steel and CRA components where supply or logistics preclude ready replacement Other systems as specified by Company on a case-by-case basis. 3.10.3 PMI shall not be considered as a substitute for material traceability. Any materials where traceability cannot be confirmed shall not be used. 3.10.4 Where PMI is specified, the following requirements shall be met:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
27 of 44
Value Assurance Framework (VAF)
3.10.4.1
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
PMI shall be undertaken after the components have been built into the completed item (or readily identifiable sub-assembly) or pipe spool but prior to any PWHT, pressure (strength) test or coating/insulation activities
Commentary: The exception to this will be pressure test plugs which will require testing upon completion of the integrity test
3.10.4.2
All pressure retaining welds, including base material components on either side of the weld, shall be tested
Commentary: This will include welds made during the original manufacture of a component (e.g. longitudinally fusion welded pipe), welds made during the fabrication/construction phase and repair welds
3.10.4.3
Bolts, and heat exchanger, boiler or furnace/heater tubes shall be subject to 5% random sampling on a heat/lot basis
3.10.4.4
All valve bodies and bonnets, including all pressure retaining welds, shall be tested
3.10.4.5
All in-line instruments, including pressure retaining welds, shall be tested
3.10.4.6
All rotating machinery casings, including all pressure retaining welds, shall be tested
3.10.4.7
All expansion bellows, including bellow convolutions and pressure retaining welds, shall be tested
3.10.4.8
All pressure retaining pressure test plugs (when permitted) shall be tested
3.10.5 Only quantitative analysis using either portable X-ray fluorescence or arc-emission analysers is permitted. Commentary: The use of alternative qualitative methods such as arc-emission spectrometers with output in the form of visible light spectra (e.g. Metascop) are not permitted unless appropriate ‘blind test’ operator performance qualifications are undertaken as agreed with Company
3.10.6 All acceptable materials and welds shall be clearly identified using a non-injurious method e.g. low stress stamps, and the identification retained until all inspection and documentation is complete. Unacceptable materials shall be quarantined or removed and replaced by acceptable material. 3.10.7 In addition to PMI of completed welds, PMI shall be performed on the root pass of single sided welds in CRAs to ensure that correct welding consumable have been used Commentary: On a recent (non-Company) LNG project, carbon steel consumables were used for the root pass in austenitic stainless steel welds to avoid the need for purging the piping - this could potentially have lead to failures during service as this substitution is not easily detected by conventional NDE or PMI of the completed weld. In case of doubt, Company reserves the right to specify enhanced NDE techniques to verify correct consumable use
3.10.8 PMI results shall be recorded and included in the final handover documentation. 3.11 Production Tests 3.11.1 Production weld test plates shall be produced in accordance with the requirements of the design code and the following: 3.11.1.1
The following components shall be tested: o o o o o
Longitudinal welds in primary and secondary structural tubular members Circumferential welds in primary structural tubular members Longitudinal and circumferential welds in pressure vessels and storage tanks subject to impact testing in accordance with this Standard Longitudinal and circumferential welds in pressure vessels constructed of ferritic materials with tensile properties enhanced by heat treatment Longitudinal and circumferential welds in large pressure vessels that cannot be heat treated as a whole in one heat treatment charge. Production test plates shall be provided for each heat treatment charge. The portions of the longitudinal weld that will be subject to two heat treatment cycles shall be represented by separate test plates that have undergone both heat treatment cycles
Commentary: The initial test plate may be subject to a simulated heat treatment prior to testing and providing the temperature and time of the final furnace heat treatment does not differ from the simulated heat treatment by a Tempering Parameter of 0.2, the results from the test plate with the simulated heat treatment can be considered valid
3.11.1.2
Test plates shall be welded by the same welders or welding operators assigned to weld the production welds
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
28 of 44
Value Assurance Framework (VAF)
3.11.1.3
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Test plates for circumferential welds shall be welded concurrently with the start of production welding.
3.11.2 Production hardness testing of welds shall be performed as follows: 3.11.2.1
The following components shall be tested: o o o
Ni-alloy steels in cryogenic environments - maximum hardness shall be 225BHN Low alloy steels in elevated temperature environments - maximum hardness shall be 241BHN Ferritic materials with tensile properties enhanced by heat treatment - maximum hardness shall be 241BHN.
Commentary: In-situ hardness testing can underestimate the true hardness but this should be minimised by suitable calibration and procedure and operator qualification - it is considered a simple qualitative test to indicate whether any significant problems exist with production welds
3.11.2.2
Sufficient tests shall be performed to represent each type of weld and welding procedure used and the extent agreed with Company
3.11.2.3
Portable hardness testing instruments shall only be used within the limits recommended by the Vendor and shall be calibrated prior to the start of each set of tests
Commentary: There are several types of portable instrument – indent comparator, dynamic rebound or ultrasonic contact impedence – all of which have limitations in their use. Particular care must be taken over surface preparation and their use on thin wall (low mass) components
3.11.2.4
Operators of portable hardness testing instruments shall have undergone a training programme in their use and records of such training
3.11.3 Production weld metal ferrite determination shall be performed as follows: 3.11.3.1
The following materials shall be tested: o o o
300-series austenitic stainless steels in cryogenic or elevated temperature environments Duplex stainless steels 300-series austenitic or duplex stainless steel weld overlay or clad restoration
3.11.3.2
Determination shall be performed prior to PWHT (if applicable) using either a suitably calibrated magnetic instrument in accordance with AWS A4.2 or by chemical analysis of the weld metal using the WRC-1992 diagram. Acceptance criteria shall be as specified in BGA-ENG-MATL-TS-0008
3.11.3.3
Sufficient tests shall be performed to represent each type of weld and welding procedure used and the extent agreed with Company
3.11.3.4
Operators of portable ferrite testing instruments shall have undergone a training programme in their use and records of such training.
3.12 Baseline Surveys 3.12.1 Contractor shall undertake a baseline survey of components when specified in BGA-ENG-MATL-TS0001 in accordance with the following requirements: 3.12.1.1
The baseline surveys shall be performed after the components have been built into the completed item (or readily identifiable sub-assembly) or pipe spool
3.12.1.2
The location of TMLs and extent of wall thickness measurements for each specific TML shall be agreed with Company but shall include a sufficient number of locations and measurements to represent all major components, differences in wall thickness and, to the maximum extent possible, anticipated areas of corrosion or material deterioration
Commentary: In selecting TML locations, the following requirements should be considered:
For piping or pipe line systems, the requirements in API 570 should be used in determining TMLs
For equipment items, each major component (such as shell plates, heads, major process nozzles), should be included in determining TMLs
The extent of measurements at each TML should be based on the methodology for conducting thickness readings in Section 4 of API RP579/ASME FFS-1 i.e. inspection plane system for each TML (taking individual readings at cardinal points is not considered an accurate enough method to identify localised corrosion)
Where techniques such as ultrasonic transducer mats are specified as part of the corrosion monitoring programme in BGA-ENG-MATL-TS-0001, these should be used to determine the baseline thickness at the specified location
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
29 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
3.12.1.3
The agreed locations shall be clearly identified on the component to permit repeat inspection.
3.12.1.4
The results of the baseline wall thickness surveys shall be shown on a marked-up version of the item general arrangement drawing (and detailed drawings if necessary) or the as-installed piping isometric (as appropriate) or alternative recording format as agreed with Company.
3.13 Repairs 3.13.1 Where base materials or welds are found to be unacceptable as a result of NDE, PMI or production testing, appropriate repair procedures detailing the method of removal, repair and re-inspection shall be specified and implemented. 3.13.2 Where a flaw is removed by arc-air, the area shall be ground to remove all residue and dross prior to inspection and any re-welding. 3.13.3 Where a local repair by welding is necessary, the repair area shall be contoured to permit access for welding followed by 100% MT/PT. Where a complete weld is to be removed, the weld metal, HAZ and at least 6mm of the adjacent base material shall be removed and the weld preparation re-made. In all cases, an approved repair WPS shall be used to complete the weld. 3.13.4 The repair shall be subject to 100% inspection and testing using the same technique(s) and procedures as used to detect the material or weld initially. 3.13.5 The number of welded repairs shall be limited as follows thereafter the complete weld shall be removed, re-welded and re-examined: Carbon steels with SMYS < 360MPa - only two repairs at the same location are permitted Carbon and HSLA steels with SMYS ≥ 360MPa - only one repair at the same location is permitted Ni alloy steels for service in cold or cryogenic environments - no repair welding is permitted Conventional 2¼Cr-1Mo steels - only one repair at the same location is permitted Modified 9Cr-1Mo steels - no repair welding is permitted For duplex and high alloy stainless steels - only one repair at the same location is permitted For non-ferrous alloys - no repair are permitted 3.13.6 All repairs and rectification work shall be fully recorded and evidence provided for Company review and agreement that all required NDE and production tests have been performed. 3.13.7 In exceptional circumstances where welded repairs are not feasible, a fitness-for-service evaluation may be undertaken subject to Company approval, using an agreed methodology based on the requirements of BS 7910 or API 579/ASME FFS-1. Contractor shall ensure that all appropriate data are available and that the analysis is undertaken by an independent third party, approved by Company.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
30 of 44
Value Assurance Framework (VAF)
4.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Non-Metallic Materials Fabrication
4.1
General
4.1.1
The fabrication, installation and inspection of non-metallic components shall only be undertaken by Contractors/Vendors with demonstrable experience in this field and in accordance with the material Vendor’s recommendations.
Commentary: The successful use of non-metallic materials requires the same level of commitment to quality and the use of appropriately trained and experience installers as for metallic materials
4.2
Fibre Reinforced Plastic Materials
4.2.1
The proposed materials and joining method for the components shall be demonstrated to meet the specified performance and properties by means of a procedure qualification test for the following joint configurations as a minimum: Main shell/pipe construction Nozzle/branch construction Nozzle/branch-to-shell/pipe construction Support-to-shell/pipe construction Tank bottom corner construction ‘Butt-and-strap’ joint construction Repair procedure Any special construction detail not covered above.
4.2.2
All laminators responsible for the fabrication and joining of components shall be experienced and able to demonstrate appropriate level of skill in the specified laminate system by means of appropriate performance testing of the following: Flat hand lay-up laminate ‘Butt-and-strap’ joint between two flat laminates Nozzle/branch connection ‘Butt-and-strap’ joint between two plain pipes Repair procedure Any special construction detail not covered above.
4.2.3
Each procedure and performance qualification shall be subject to a visual examination, tensile and shear testing (flat laminates only) and verification of Barcol hardness, thickness measurement, reinforcement arrangement, glass content and electrical continuity of laminated ‘butt-and-strap’ joint (if applicable).
4.2.4
Flanged joints shall meet the following requirements as a minimum:
4.2.4.1
FRP flanges, including equipment body flanges if applicable, shall be full flat-face type, laminated to plain pipe or shell and shall ensure compatibility with ASME B16.5/B16.47 flange dimensions and bolting
Commentary: If necessary the flange thickness and hub dimensions should be modified to meet this requirement
4.2.4.2
Any areas subject to machining, including the bolt holes, shall have the original corrosion resistant layer re-instated and sealed with a resin-rich coat
4.2.4.3
Where a carbon steel backing ring is required, the hub radius shall be a minimum of 6mm and the backing ring machined to ensure that adequate clearance exists between the ring and the hub radius
4.2.4.4
Gaskets shall be full face extending to the outside edge of the flange and shall have a maximum Durometer hardness of 70 (Shore A)
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
31 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
4.2.4.5
The flange joint make-up and tightening shall meet the requirements of BGA-ENG-MECH-TS-0012 including provision of a detailed bolt tightening procedure with acceptable torque figures for tightening of bolts to ensure that the flange joint withstands all bolt-up, pressure test and operating loads
4.2.4.6
Piping shall not be pulled to correct misaligned flanges
4.2.4.7
For non-conductive resin systems the back face of the flange may be spot-faced to accept a standard round washer – on conductive resin systems spot facing may remove the conductive layer and is not permitted unless specifically agreed with Company
4.2.4.8
For conductive resin systems the electrical continuity shall be maintained across all flange joints and shall be verified by electrical continuity testing.
Commentary: The preferred method is for the conductive corrosion resistant layer to continue over the gasket face and round to the back face of the gasket such that it is in full and intimate contact with the metallic washers and bolting or earthing strap
4.2.5
Laminate ‘butt-and-strap’ type joints shall meet the following requirements as a minimum:
4.2.5.1
Properties in the hoop and axial directions shall be equivalent to that of the main structural laminate
4.2.5.2
Prior to jointing, the surface layer(s) shall be cleaned followed by lightly abrading to remove the resin-rich layer over an area extending at least 25mm beyond the edge of the joint and subsequently cleaned immediately prior to laminating
4.2.5.3
For conductive resin systems the electrical continuity shall be maintained across all laminate joints preferably by continuing the conductive corrosion resistant layer over the internal laminate surface and verified by electrical continuity testing. Where access is restricted and the joint is accessible from the outside surface only, the structural laminate shall be ground to a taper to expose the original conductive corrosion resistant layer and a short section of conductive corrosion resistant layer applied between the two exposed ends prior to completing the laminate joint
4.2.5.4
The joint shall not be moved until the resin manufacturer’s recommended curing time for the environmental conditions has elapsed. Post curing shall only be undertaken in accordance with the resin Vendor’s recommendation to meet minimum specified Barcol hardness levels, residual styrene content and resin Vendor’s stated HDT.
4.2.6
Adhesive joints shall meet the following requirements as a minimum:
4.2.6.1
Limited to a maximum diameter of 12”NB and where electrical conductivity is not required
4.2.6.2
Properties in the hoop and axial directions shall be equivalent to that of the main structural laminate
4.2.6.3
Joint preparations shall be cut square with the component axis and shall be sealed with the relevant resin system to ensure all voids are filled and no glass fibres are left exposed
4.2.6.4
Prior to joining, the surface layer(s) shall be scraped to prepare a suitable chamfer over an area extending at least 25mm beyond the edge of the joint and subsequently cleaned immediately prior to application of the adhesive
4.2.6.5
Only the recommended Vendor’s adhesive for the process fluid shall be used. The adhesive shall be applied evenly and axially to pipes and fittings with excess adhesive removed once joint is completed
4.2.6.6
The joint shall not be moved until the adhesive Vendor’s recommended curing time for the environmental conditions has elapsed. Post curing shall only be undertaken in accordance with the resin Vendor’s recommendation.
4.3 4.3.1
Thermoplastic Materials The proposed materials and joining method for the components shall be demonstrated to meet the specified performance and properties by means of a procedure qualification test for the following joint configurations as a minimum: Solvent adhesive socket joint Socket fusion welded joint Saddle-fusion welded joint Butt-fusion welded joint
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
32 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Electro-fusion welded joint Hot gas welded joint Any special construction detail not covered above. 4.3.2
All operators responsible for the fabrication and joining of components shall be experienced and able to demonstrate appropriate level of skill in the specified joining method by means of appropriate performance testing
4.3.3
Each procedure and performance qualification shall be subject to a visual examination and tensile testing.
4.3.4
Flanged joints shall meet the following requirements as a minimum:
4.3.4.1
Flanges shall be full flat-face type, compatible with ASME B16.5 flange dimensions and bolting
4.3.4.2
Gaskets shall be full face extending to the outside edge of the flange and shall have a maximum Durometer hardness of 70 (Shore A)
4.3.4.3
The flange joint make-up and tightening shall meet the requirements of BGA-ENG-MECH-TS-0012 including provision of a detailed bolt tightening procedure with acceptable torque figures for tightening of bolts to ensure that the flange joint withstands all bolt-up, pressure test and operating loads
4.3.4.4
Piping shall not be pulled to correct misaligned flanges.
4.3.5
Solvent adhesive joints shall meet the following requirements as a minimum:
4.3.5.1
Joint preparations shall be cut square with the component axis without breakage occurring. Cut edges shall be free of burrs both internally and externally
4.3.5.2
A 15 chamfer should be filed onto the leading edge to aid dispersion of the adhesive
4.3.5.3
Prior to joining, the surface layer shall be cleaned followed by lightly abrading or scraping to assist the joining process over an area extending at least 25mm beyond the edge of the joint and subsequently cleaned immediately prior to application of the adhesive
4.3.5.4
Only the recommended Vendor’s solvent adhesive for the process fluid shall be used. The adhesive shall be applied evenly and axially to pipes and fittings with adhesive removed once joint is completed. For pipe diameters greater than 4”NB, the adhesive shall be applied simultaneously by two operators
Commentary: Slight twisting of the pipe in the socket joint is typically required to ensure all surfaces are coated with the cement
4.3.5.5
4.3.6
The joint shall not be moved until the solvent adhesive Vendor’s recommended curing time for the environmental conditions has elapsed. Post curing (by heat pads) shall only be undertaken in accordance with the adhesive Vendor’s recommendation. Fusion welded joints shall meet the following requirements as a minimum:
4.3.6.1
Joint preparations shall be cut square with the component axis without breakage occurring. Cut edges shall be free of burrs both internally and externally
4.3.6.2
Prior to welding, the surface layer(s) shall be cleaned followed by lightly abrading or scraping to assist the joining process over an area extending at least 25mm beyond the edge of the joint and subsequently cleaned immediately prior to welding
4.3.6.3
Socket fusion welding shall be limited to 4”NB
4.3.6.4
Butt-fusion and electro-fusion welding machines shall meet the following requirements as a minimum: o o o
Components shall be rigidly clamped to ensure correct alignment and the required welding contact and pressure The heating tools shall be capable of reaching a consistent surface temperature in accordance with the component Vendor’s recommendation The tool faces that come into contact with the component surfaces shall be clean and free from deposits of softened plastic.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
33 of 44
Value Assurance Framework (VAF)
4.3.6.5 4.4
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
The completed joint shall not be moved until the component Vendor’s recommended cooling time for the environmental conditions has elapsed.
Inspection and Testing
4.4.1
All inspection shall be performed in accordance with a written procedure, detailing the extent of inspection, the nature of the anticipated flaws, proposed techniques to detect such flaws and appropriate acceptance criteria.
4.4.2
For FRP components, the following tests shall be performed as a minimum:
4.4.2.1
Visual inspection of the internal surface (as far as physically possible) and external surface. The latter shall take place once the structural layer is complete but prior to the application of the outer surface layer. Acceptance criteria shall comply with the requirements of the applicable design code
Commentary: Where the use of carbon powder is permitted by Company, visual inspection may not be practical due to the opacity imparted by the powder in which case Contractor must submit alternative inspection procedures for Company review to demonstrate that acceptable quality levels have been met
4.4.2.2
Sufficient Barcol hardness readings shall be taken to represent each batch of raw materials and laminate construction or butt-and-strap joint - the minimum hardness shall be at least 90% of the resin Vendor’s minimum specified cured hardness
4.4.2.3
Sufficient solvent (acetone) tests shall be performed to represent each batch of raw materials and laminate construction or butt-and-strap joint - the laminate shall show no signs of softening or tackiness. Where any doubt exists as to the degree of cure additional verification tests such as residual styrene monomer tests, HDT tests or mechanical tests on laminate samples shall be performed
4.4.2.4
Electrical conductivity of the completed component or system to determine maximum resistance to earth between any point on the inside surface and an earth point does not exceed 1106 or as required by the design code.
Commentary: ISO 3915 can be used to develop procedure qualification for continuity testing – if ‘butt-and-strap’ joints are required for the fabrication of the equipment or piping system, a similar joint must be included in the qualification test plate
4.4.3
Thermoplastic joints shall be subject to visual inspection of the internal surface (as far as physically possible) and external surface. Acceptance criteria shall comply with the requirements of the applicable design code.
4.4.4
Where any doubt exists as to the integrity of a joint (e.g. voids, delaminations, ‘cold’ welds, slit defects, misalignment) Company reserves the right to require Contractor to perform additional NDE of suspect areas. Specific details of the proposed NDE method shall be agreed with Company prior to the application of the NDE technique.
4.4.5
Flanged joints shall be inspected in accordance with BGA-ENG-MECH-TS-0012.
4.4.6
A full dimensional survey shall be performed to ensure conformity to code requirements and fabrication drawings, including the minimum specified laminate thickness.
4.4.7
Equipment and piping systems shall be subject to an integrity test in accordance with BGA-ENGMECH-TS-0012.
4.4.8
Piping systems designed to operate under vacuum shall be subject to either a vacuum test or external pressure test in accordance with the code.
4.5 4.5.1
Repairs Any unacceptable flaws or damage found during inspection/NDE shall be repaired by complete removal of the joint or damaged section. Local repairs, other than for removal of minor surface damage, are not permitted.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
34 of 44
Value Assurance Framework (VAF)
5.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Additional Fabrication Requirements for Sour Environments
5.1
Fabrication Requirements
5.1.1
In addition to the requirements of Section 2.0, the following requirements shall be met:
5.1.1.1
Joint preparation shall be limited to butt welded construction only. Socket welded and threaded connections are prohibited in direct contact with sour environments
Commentary: Butt welds allow full volumetric inspection as well as a lower stress intensity factor at the weld and as such should increase level of assurance and asset integrity. Refer to BAG-ENG-MAT:-TS-0001 for more specific details
5.1.1.2
‘O-let’® type fittings are not permitted unless full access can be obtained from the internal bore of the fitting to inspect the root pass. Where permitted, the internal surface shall be constant bore (i.e. no change in section). Preference shall always be given to the use of fittings that permit the use of radiography.
Commentary: Inspection of the root pass and volumetric inspection of these types of fittings can be difficult – taper machining of the internal bore in the root area increases the difficulty. Butt weld fittings permit easier volumetric inspection and should be used wherever possible
5.1.1.3
Heat treatment after forming is mandatory for cold spun or cold formed/pressed carbon and low alloy steel components in all thickness’ irrespective of fibre strain induced when exposed to sour environments that fall within Region 2 or Region 3 of NACE MR0175/ISO 15156-2 or to an alkaline sour environment.
Commentary: Cold formed carbon steel components may have localised areas of high stress or hardness – heat treatment may be performed after forming or during final heat treatment of the fabricated component. Components that are exposed to sour environments that fall within Region 1 must still meet the specified heat treatment and hardness limits in NACE MR0175/ISO 15156
5.2
Welding Requirements
5.2.1 5.2.1.1
In addition to the requirements of Section 3.0, the following requirements shall be met: Welding consumables shall be selected to deposit weld metal meeting the hardness requirements of NACE MR0175/ISO 15156 and the mechanical and toughness properties of the design code and Company Standards. The use of consumables that deposit a nickel (Ni) level greater than 1% shall be subject to successful SSC testing in accordance with NACE MR0175/ISO 15156.
Commentary: Historically, NACE MR0175 limited the level of Ni in the weld metal to 1% maximum due to its perceived influence in SSC susceptibility but other work has indicated that other factors apart from the level of Ni alone influences a weld’s susceptibility to SSC. Where higher levels of Ni are considered necessary (e.g. to meet toughness requirements) this will be subject to the appropriate SSC qualification in NACE MR0175/ISO 15156, Table B.1
5.2.1.2
GTAW or PAW using filler wire shall be used for the root pass in single sided process piping welds. Cellulosic SMAW consumables may be used for the root pass in single-sided pipeline welds subject to meeting the NDE acceptance criteria in Section 5.2.1.12.
5.2.1.3
Only welding consumables capable of achieving a maximum hydrogen level of less than 4 ml H 2 /100g weld metal (H4) are permitted
5.2.1.4
Temper bead welding may be used to control hardness values in the HAZ subject to the following: o o o o
Shall only be used on multi-pass welds Shall comply with the requirements of ASME Section IX with respect to nomenclature and bead placement Surface temper beads shall not contact the base material Distance from the weld toe to the edge of the final surface temper bead shall not exceed 3mm, subject to meeting the specified hardness levels
Commentary: This corresponds to dimension ‘S’ in ASME Section IX, QW-462.12
o
o
Where temper bead welding is used for minor weld repairs without PWHT the flaw cavity shall be excavated to a minimum of four times the electrode diameter and the weld completed using a minimum of two layers The cap layer and surface temper bead placement shall be subject to visual inspection in the aswelded condition prior to any dressing/grinding to meet specified acceptance criteria for the cap layer profile.
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
35 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Commentary: As bead placement is critical to ensuring the desired properties will be met, grinding may result in removal of the weld beads making inspection to verify that bead placement conforms to the qualified welding procedure difficult
5.2.1.5
Dissimilar metal welds shall not be directly exposed to sour environments – material specification breaks shall be made at flanged connections
Commentary: Bimetallic welds may produce uncontrolled microstructure and compositions which can lead to hard areas in the HAZ of the ferritic steel component - these hard areas increase the susceptibility to SSC
5.2.1.6
Welding procedure qualifications for ferritic steels shall meet the following additional requirements: o
For ferritic steels the test pieces shall be selected from actual production material with the highest CE IIW /P cm and micro-alloying analysis or on non-production material with CE IIW /P cm and micro-alloying analyses that are representative of the production materials
Commentary: The use of pre-qualified welding procedures using non-production material will require full material certification to be made available to verify that the CE IIW /P cm and micro-alloying analyses, as well as the qualified thickness range and welding consumables, are representative of the production materials and will require review by Company to verify this
o
Where the production thickness at the weld exceeds 25mm, the test piece thickness shall be within the range 0.75t to 1.5t with a minimum thickness of 25mm and shall be manufactured to approximately represent the heat sink of the production weld
Commentary: Most design codes allow a range of thicknesses to be welded based upon a single qualified welding procedure thickness – the above requirements are intended to represent the actual production welding in terms of steel hardenability, weld cooling/heat sink and predicted hardness levels for heavier sections in excess of 25mm
o
Where fillet welds are permitted they shall be qualified using a fillet weld test piece welded with the minimum number of weld passes specified on the WPS and shall be manufactured to approximately represent the heat sink of the production weld
Commentary: The above requirements are intended to represent the actual production welding in terms of steel hardenability, weld cooling/heat sink and predicted hardness levels – because of the increased heat conduction path for fillet welds there is no lower limit for this requirement (as there is for butt weld qualifications)
o
o
5.2.1.7
Hardness surveys shall be performed on all test pieces in accordance with the NACE MR0175/ISO 15156 using Vickers HV 10 or HV 5 method. Samples for hardness testing shall be selected from sections of weld with the lowest predicted heat input Where Company agrees to maximum cap hardness limit of 275HV in accordance with Table A.1 of NACE MR0175/ISO 15156-2, the restriction for cathodically protected structures may be waived.
Welding procedures shall be re-qualified if any of the following changes from that stated on the PQR, apply: o o o o o o o o
Any change in the heat input of ±10% A change in the wall thickness of 0.75t to 1.5t for production thickness at the weld in excess of 25mm (subject to minimum qualified thickness of 25mm) Any increase in CE IIW /P cm greater than 0.03%/0.01% respectively Any increase in maximum micro-alloying analyses Any change in the welding consumable manufacturer and brand designation Any reduction in preheat temperature Any reduction in PWHT temperature or time Any change in the bead placement when using temper bead welding.
Commentary: The above restriction on the range of qualified welding variables is intended to limit the likelihood of higher hardness limits from those demonstrated during the welding procedure qualification
5.2.1.8
Unless specified otherwise in this Standard, PWHT is mandatory for all ferritic steel pressure retaining welds and attachment welds exposed to the following environments: o
Sour environments that fall within Region 2 or Region 3 of NACE MR0175/ISO 15156-2
Commentary: Components that are exposed to sour environments that fall within Region 1 will still need to meet the specified heat treatment and hardness limits in NACE MR0175/ISO 15156
o 5.2.1.9
Alkaline sour environments with design temperature limitations as specified in BGA-ENG-MATLTS-0001
The minimum PWHT temperature and time shall be:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
36 of 44
Value Assurance Framework (VAF)
o
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
620°C for 1 hour per 25mm thickness, 1 hour minimum, for conventional carbon steels, subject to acceptable welding procedure qualification
Commentary: For heavy wall components and where impact testing is a requirement, the selection of material grades, original and subsequent heat treatment, and welding procedures need to be carefully evaluated to ensure the material and weld metal properties are maintained whilst achieving high degree of stress relief
o
The PWHT conditions for HSLA steels shall be selected to ensure the specified mechanical properties are met based on the materials chemical composition and shall be demonstrated during welding procedure qualification testing
Commentary: The addition of micro alloying additions will typically require a higher PWHT temperature than for conventional carbon steels. Company experience is that a minimum PWHT temperature in excess of 620°C is required to achieve acceptable hardness levels especially for wall thickness’ above 25mm but specific note must be taken if TMCP steels are used in these environments as temperatures in this range will degrade the TMCP steel properties
o
680°C for 1 hour per 25mm thickness, 1 hour minimum, for low alloy steels, subject to acceptable welding procedure qualification.
5.2.1.10
The use of alternative, lower temperature, conditions as permitted by the code (e.g. ASME Section VIII, UCS-56) are not permitted where PWHT is specified for components exposed to sour or alkaline sour environments
5.2.1.11
In-situ hardness testing shall be performed in accordance with Section 3.11.2 to demonstrate that the maximum hardness levels of NACE MR0175/ISO 15156 are met. Where hardness limits cannot be met in the as-welded condition, PWHT shall be applied.
5.2.1.12
Welds shall be subject to the following NDE: o
All ferritic steel welds shall be subject to 100% volumetric examination. Where radiography is specified, acceptance criteria shall be in accordance with ASME B31.3, “Cyclic Service” criteria or ASME B31.3 Appendix K for high pressure service, as appropriate
Commentary: The use of these acceptance criteria is intended to limit the type and extent of root flaws which may lead to initiation of SSC
o o 5.3
All ferritic steel welds surfaces exposed to sour environments shall be subject to 100% WFMT All CRA weld surfaces exposed to sour environments shall be subject to 100% PT
Specific Equipment Requirements
5.3.1 5.3.1.1
The following additional requirements shall be met for pressure vessels and heat exchangers: Reinforcing pads are not permitted for equipment that is exposed to sour environments that fall within Region 2 or Region 3 of NACE MR0175/ISO 15156-2
Commentary: The use of reinforcing pads limits the ability to undertake full volumetric examination of the pressure retaining weld during operation without undertaking an intrusive inspection
5.3.1.2
Attachment welds to pressure retaining components that are directly exposed to sour environments shall meet the following requirements: o
Fillet welds shall be completely welded all round with the exception of a small (6mm maximum) space to vent the void behind the weld
Commentary: ‘Stitch’ welding is not permitted due to the likelihood of corrosion products building-up but a small vent hole is required to prevent the build-up of hydrogen gas in the void behind the weld
o 5.3.1.3
Full penetration groove welds are required for major attachment welds.
Where tube-to-tube sheet welding is required, fabrication procedures shall be developed to ensure that hardness levels are met including but not limited to: o o
For carbon steel assemblies, weld overlay with low carbon weld metal and PWHT prior to tubeend welding For low alloy steel assemblies, weld overlay with CRA weld metal meeting requirements of NACE MR0175/ISO 15156-3 and PWHT prior to tube-end welding
Commentary: The above two options will increase flexibility during operation should repairs to, or plugging of, tube ends be required
o
PWHT.
Commentary: This latter option is non-preferred due to the difficulty of controlling the PWHT process to ensure uniform heating without distortion of the tube bundle and to guarantee hardness levels will be met in the production welds – production hardness testing of these welds is not feasible. Where PWHT is agreed with Company, appropriate procedures will be required to control the PWHT process
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
37 of 44
Value Assurance Framework (VAF)
6.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
In-service Modifications and Repairs
6.1
General
6.1.1
In-service modifications and repairs shall be subject to an appropriate level of change management in accordance with the requirements of BGA-BGA-GEN-OS-0003.
6.1.2
Acceptable processes for in-service modifications or repairs are: Welding onto in-service components during a shutdown Hot tap welding onto ‘live’ in-service components Temporary wraps using either specialised mechanical clamps or composite wraps
6.2 6.2.1 6.3 6.3.1 6.4 6.4.1
Welding to In-service Components TO FOLLOW Hot Tapping Where the User proposes to use a hot tap fitting to make a connection to ‘live’ in-service components, the requirements in BGA-ENG-MATL-TS-0009 shall be met. Temporary Wraps TO FOLLOW
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
38 of 44
Value Assurance Framework (VAF)
7.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Quality Assurance
7.1
General
7.1.1
In addition to an accredited Quality Management System, Contractors/Vendors responsible for the fabrication, welding and inspection of components shall have in place appropriate quality control procedures to ensure these activities are adequately controlled
Commentary: ISO 9000 considers welding as a ‘special process’ and therefore places additional requirements on the quality assurance of this activity. ISO 3834 defines additional requirements to ensure that welding is performed in a technically satisfactory manner and should be used to assess each Contractor/Vendor’s competency
7.1.2
Specifications shall be developed to ensure that the requirements of this Standard are included in the appropriate purchase order, contract and sub-contract documentation.
7.1.3
Procedures and quality control systems shall be specified and implemented to ensure acceptable performance of welders/welding operatives and laminators/bonders including but not limited to:
7.1.3.1
Allocation of a unique identification number or symbol to each operative which shall be marked adjacent to the weld or joint using a method that is non-injurious to the material
7.1.3.2
Performance qualification testing at the start of work unless otherwise agreed with Company
7.1.3.3
100% inspection (including any specified NDE) of the first five joints of each operative irrespective of design code requirements
7.1.3.4
Re-testing or re-training or operatives when their repair rates consistently exceed an agreed figure with Company.
7.1.4
Welding supervision shall only be performed by personnel having demonstrable and current experience and training and certified in accordance with an internationally recognised scheme (e.g. AWS, CSWIP). Evidence of personal certification shall be made available to Company on request
7.1.5
Company reserves the right to inspect all phases of fabrication and testing to verify that Contractor/Vendor procedures and systems are working effectively and that the requirements of Company standards and project specifications are being met.
Commentary: This inspection shall not be used as a substitute for adequate Contractor/Vendor supervision and inspection
7.1.6 7.2
All welding, joining, heat treatment, NDE and inspection equipment shall be suitably calibrated and verified on a regular basis during production. Quality Records
7.2.1
The complete fabrication history of each equipment item or piping system shall be maintained including, but not limited to: Allocation of unique joint reference numbers Record of all forming operations including MTRs, relevant heat treatment charts and inspection certificates Record of all materials joined including MTRs Record of all welding/laminating/bonding procedure specifications and supporting procedure qualification records, welders/laminators/bonders with supporting performance qualification certificates Record of all heat treatment of joints including procedures and charts Record of all inspection, NDE, PMI and production tests including procedures and relevant test reports, NDE and PMI operatives involved in inspection with supporting performance qualification certificates Record of all repair or rectification work, including any design changes to the equipment or piping isometric and subsequent inspection/testing Record of all baseline survey results.
Commentary: This information should be collated using computer based systems to enable appropriate information to be included in the asset integrity database as required by BGA-ENG-MATL-TS-0001
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
39 of 44
Value Assurance Framework (VAF)
8.0
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Feedback Where inaccuracies, errors, omissions or other general areas for quality or performance improvement are identified in this document; then the Feedback Form given in Appendix B shall be completed and returned to the Group Technical Authority (document custodian) identified in the Document Information Sheet (page 2).
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
40 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Appendix A:
References
BG Standards BGA-BGA-GEN-OS-0001
Purpose, Development and Application of BG Standards and Guidelines
BGA-BGA-GEN-OS-0003
Management of Change
BGA-BGA-GEN-OS-0004
Dispensation Against BG Standards
BGA-ENG-MATL-TS-0001
Material Selection and Corrosion Control
BGA-ENG-MATL-TS-0003
Piping in Sour Service (withdrawn)
BGA-ENG-MATL-TS-0005
Protective Coatings
BGA-ENG-MATL-TS-0008
Materials of Construction Requirements
BGA-ENG-MATL-TS-0009
Hot tapping on Pipelines, Piping and Associated Equipment (Operating at pressures up to 100 Bar)
BGA-ENG-MECH-TS-0012
Flange Management, Commissioning and Pressure Testing
BGA-ENG-MECH-TS-0003
Piping Design
International Standards Organisation (ISO) ISO 13121
GRP Tanks and Vessels for use Above Ground
ISO 13703
Petroleum and Natural Gas Industries -- Design and Installation of Piping Systems on Offshore Production Platforms
ISO 14692
Petroleum and Natural Gas Industries - Glass-reinforced Plastics (GRP) Piping
ISO 15614-8
Specification and qualification of welding procedures for metallic materials – Welding procedure test – Part 8: Welding of tubes to tubeplate joints
ISO 19902
Petroleum and Natural Gas Industries – Fixed Steel Offshore Structures
ISO 3834
Quality Requirements for Fusion Welding of Metallic Materials
ISO 3915
Measurement of Resistivity of Conductive Plastics
ISO 9000
Quality Management Systems - Requirements
ISO 9712
Non-Destructive Testing – Qualification and Certification of Personnel
NACE International MR 0175/ISO 15156
Petroleum and Natural Gas Industries - Materials for use in H 2 SContaining Environments in Oil and Gas Production
SP0178
Fabrication Details, Surface Finish Requirements and Proper Design Considerations for Tanks and Vessels to Be Lined for Immersion Service
SP0403
Avoiding Caustic Stress Corrosion Cracking of Carbon Steel Refinery Equipment and Piping
American Petroleum Institute (API) RP 579/ASME FFS-1
Fitness-for-Service
RP 582
Welding Guidelines for the Chemical, Oil, and Gas Industries
RP 945
Avoiding Environmental Cracking in Amine Units
RP2A
Planning, Designing & Construction of Fixed Offshore Platforms
Std 1104
Welding of Pipelines and Related Facilities
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
41 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Std 560
Fired Heaters for General Refinery Service
Std 570
Piping Inspection Code
Std 620
Design and Construction of Large, Welded, Low-pressure Storage Tanks
Std 650
Welded Steel Tanks for Oil Storage
British Standards BS 4994
Design and Construction of Vessels and Tanks in Reinforced Plastics
BS 6374
Lining of Equipment with Polymeric Materials for the Process Industries
BS 7159
Design and Construction of Glass Reinforced Plastics (GRP) Piping Systems for Individual Plants or Sites
BS 7448
Fracture Mechanics Toughness Tests
BS 7910
Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures
American Society of Mechanical Engineers (ASME) B16.47
Large Diameter Steel Flanges
B16.5
Steel Pipe Flanges and Flanged Fittings
B31.1
Power Piping
B31.3
Process Piping
B31.4
Pipeline Transportation Systems for Liquid Hydrocarbons & Other Liquids
B31.8
Gas Transmission & Distribution
HPS-2003
High Pressure Systems
Section I
Power Boilers
Section IX
Welding & Brazing Qualifications
Section VIII
Pressure Vessels
European Norms (EN) EN 1011
Welding - Recommendations for Welding of Metallic Materials
EN 10204
Steel and Steel Products – Inspection Documents
EN 1714
Non destructive testing of welded joints. Ultrasonic testing of welded joints
American Welding Society (AWS) A4.2
Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic and Duplex Ferritic-Austenitic Stainless Steel Weld Metal
D1.1
Structural Welding Code - Steel
D10.10
Recommended Practices for Local Heating of Welds in Piping and Tubing
Engineering Equipment Manufacturers & Users Association (EEMUA) Publication 143
BGA-ENG-MATL-TS-0007 Issue 03
Recommendations for Tube End Welding: Tubular Heat Transfer Equipment
July 2009
42 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Publication 158
Construction Specification for Offshore Structures in the North Sea
Publication 194
Guidelines for Materials Selection and Corrosion Control for Subsea Oil and Gas Production Equipment
American Society for Non-destructive Testing (ASNT) CP-182
Qualification and Certification of Non-Destructive Testing Personnel
SNT-TC-1A
Personnel Qualification and Certification in Non Destructive Testing
American Society for Testing and Materials (ASTM) ASTM E1815
Standard Test Method for Classification of Film Systems for Industrial Radiography
Welding Research Council (WRC) Bulletin 452
Recommended Practices for Local Heating of Welds in Pressure Vessels
Institute of Petroleum (IP) Guidelines for the Management, Design, Installation and Maintenance of Small Bore Tubing Systems
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
43 of 44
Value Assurance Framework (VAF)
BG Standard Fabrication of Structures, Equipment, Piping & Pipelines
Appendix B:
Feedback Form
FEEDBACK FORM This form should be used to notify comment or suggestions for improvement, relating to any aspect of the document identified below. Please return the completed form by Email, to the Technical Authority identified in the associated Document Information Sheet. Document No: BGA-ENG-MATL-TS-0007
Document title: Fabrication of Structures, Equipment, Piping & Pipelines
Issue No: 03
Issue Date: July 2009 Comments by:
Date: …………………………
Name: ………………………………………………..
Email address / Contact Tel.No: …………………………
Position: …………………………………………..
Project / Business Unit: ………………………….. Comment
Page/Section No:
BGA-ENG-MATL-TS-0007 Issue 03
July 2009
44 of 44
