Structure Steel Fabrication and Installation Procedure by Esso

July 21, 2017 | Author: timetemasek | Category: Structural Steel, Metal Fabrication, Welding, Quality Assurance, Mechanical Engineering
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PURPOSE To assure that steel structure is fabricated and erected in accordance with industry codes and standards, and relevant project specifications, IFC drawings and Client MPDS requirements


SCOPE This procedure outlines the job site controls employed for structural steel Construction for fabrications, installation, and construction practices to meet the contractual requirements.


REFERENCE. • • • • • • • • • •

AWS D1.1 American Welding Society For Steel Structure BSI British Standard Institute MPDS 12-01-03 Preservation and Protection During Shipping and Construction MPDS 20-01-04 Upstream Project Quality Assurance MPDS 25-01-02 Fabrication and Load out of Jacket and Deck Structure MPDS 29-01-25 Structural Fatigue Life Improvement by Weld Grinding MPDS 29-01-34 Upstream Materials Identification and Traceability MPDS 29-01-45 Upstream Structural Materials for Decks, Jackets, Topside MPDS 29-02-02 Painting General Requirements MPDS 29-02-19 Upstream Hot Dip Galvanizing of Structural Steelwork

• • 4.0

MPDS 29-03-09 Offshore Structural Welding and Inspection IFC/AFC Drawings




EMEPMI Representative Shapadu Representative Malaysian Project Design Specification Inspection and Test Plan Construction Superintendent Non-Destructive Testing


5.3 5.4



The QA / QC personnel shall witness any installation, erection and fabrication activities that is ready for inspections. Project Manager/Construction Superintendent shall be responsible for organizing the steel structure work activities in accordance with industry codes and specifications, approved drawings and MPDS requirements. Structural Engineer shall be provided with all information needed during fabrication and installation. QA/QC Coordinator/Welding Inspectors / Supervisors shall ensure that the Quality expectation is maintain within the requirements of the industry codes and specifications and MPDS are met.

PROCEDURE General Prior to start of fabrication SEEN to submit the following to Client for review/approval: 1. For any new WPS requiring qualification OR WPS requiring re-qualification shall be submitted for Client review. 2. A Weld and Welder identification and marking system for all structure shall be provided for Client review.

6.0.1 Structural items shall include but not limited to pipe supports, electrical and instrument supports, and other tie in structures. 6.0.2 Whenever possible, structural steels will have their correlation number transferred and stamped and verified by EMEPMI representative prior to cutting at yard. 6.0.3 All structural steels will be marked with their identification piece mark number, weld joint numbers, welder number and date of inspection in accordance to latest approved drawings using industrial paint marker.. 6.0.4 All fit-up will be carried out using good engineering practice and subjected to visual inspection and dimensional check as per the latest approved drawings. 6.0.5 Fit-up assemblies for all structural items are to be inspected by CESSB Inspector and EMEPMI representative as per approved Inspection and Test Plan, inclusive of bevel angle, alignment /mismatch, straightness and levelness. 6.0.6 Cutting shall be done by oxyacetylene gas cutting either manually or automatic. The use of cut-off wheels shall be utilized for thinner materials ( < 10 mm WT ).

6.0.7 Upon acceptance of fit-up & dimensional inspection, welding will be carried out in a controlled sequence manner to minimize distortion. 6.0.8 All welding activities will comply to SEEN approved Welding Procedure Specification ( WPS ) and PQR. 7.0

HANDLING OF STRUCTURAL STEELWORK The structural steelwork shall be transported to site handled, stored and erected, so that it is not subjected to stresses in excess of those for which it was designed and is not damaged in any way. Any members, which in the opinion of the CLIENT found to have been damaged or over stressed, shall be removed from the site and replaced.


LOADING OF STRUCTURES The Construction Superintendent shall not at any time load any structures or any part thereof in excess of the designed working load. No loads shall be placed on any parts of the structure without the prior approval of the CLIENT.


INSPECTION OF FABRICATION AND ERECTION The CLIENT can inspect all steelwork in the course of fabrication and all facilities shall be granted to them by SEEN to do so. The CLIENT have the right to take all steps necessary in their opinion, including the rejecting of some or all of the steelwork, in order to ensure that the steelwork is fabricated and erected in accordance with the Specification.



SEEN shall establish specific columns and beams for which a permanent record shall be made. All construction shall be checked during fabrication and erection for elevation and plumbness and at least 5% (1 out of 20) of all beams shall be checked for proper elevation and dimension by the SEEN.


The Structural Alignment forms for shall be the controlling document for the structural steel inspection during fabrication and erection. The information to be recorded prior to installation: a) b) c) d)

Structure name Column line number and row number or beam piece mark. Column size. Target elevation for the bottom of base plate or the engineered elevation for the beam.


After the information has been recorded prior to bolting of column or beams, SEEN shall verify that the structure is ready for alignment check during erection.


Structural alignment inspection during erection shall include the following: a) b)

Determine if bottom base plate design matches the configuration. Check drawings for correct piece mark number.

c) d) 13.0

Check column plumbness in two directions 90 % apart. Tolerances for plumbness shall be applicable engineering specifications. Document all structural alignment data concerning plumbness of columns and elevation of structural beams on the appropriate form.


Where shrinkage and distortion is likely to affect the adequacy of the member or structure during fabrication or erection, welding sequences shall be developed to control distortion, warping, creeping and he build- up of excessive internal stresses in the structure and shall be submitted to CLIENT for approval before the welding activity commence.


The approved welding sequence shall be briefed to the welders and displayed prominently at the working area.


QA/QC personnel or supervisor shall supervise the welding, of the assembly to ensure the planned sequences are followed.


Welding sequence shall include i. ii. iii. iv. v. vi.

WPS to be applied Sequence of joints to be welded Number and location of welders at each stage of assembly Tack – welds, temporary attachments and spacers used in the assembly of components. Preheating of joint to be welded Qualified Welder


Whenever practical, two welders are required to weld a joint from both sides simultaneously. For welding of pipes or tubular with diameter greater than 20 inch, two or more welders are required to weld simultaneously.


Avoid welding component at both ends simultaneously because this will cause high stress in the component due to weld metal shrinkage when cooling. The high stress can cause distortion of component or crack in the weld joint.


Special attention is required when welding a large panel of tubular, beams or plates to minimize distortion. Welding of the panel shall start from the center and out to the perimeter.


Preheating temperature shall be carried out by electrical resistance or with gas burner (not exceeding 250 ° C) for carbon steel and shall be checked by means of thermocouple or tempilstick. The preheating temperature shall be established to a distance of at least 75mm from the joint groove and through the wall thickness prior to welding. Heating torches must not be lighted by striking an arc on the steel surface.


Shelter and windbreaker shall be provided at all times to give protection to the weld areas from wind, rain and moisture.

13.10 Rapid or abrupt cooling rate shall be avoided. The completed welds shall be covered

with asbestos blankets or any other method. If it is raining during welding, The Welding activities must be immediately stopped and incomplete weld shall be covered with asbestos blanket with water-resistant material. 14.0



Distortion can be induced by heat especially during welding.


Preparation of weld edges shall be by thermal cutting or machining. Wherever practicable, thermal cutting shall be done with a mechanically guided torch. For thermal cutting the cut surfaces shall be ground to a smooth uniform surface. The edge preparations shall be visually checked for any lamination and defect at the cut and ground edges. Grinding and counter check with MPI shall remove any lamination or defect observed. The main member weld area shall be UT prior to fit up to ensure they are free from lamination.


The alignment and dimension of the material to be welded shall be checked during fit up inspection during fabrication and erection. The offset at structural butt joints shall not exceed T/10 (where T is the thickness of the thinner material) or 6mm, whichever is less.


The offset or misalignment of the abutting pipe ends of a same nominal thickness shall not exceed 1.5mm. For joints of unequal pipe ends thickness, the external offset shall not exceed 1.0mm and internal offset shall not exceed 1.5mm. All offsets or misalignments greater than 2mm shall be machined or ground to a 1: 4 tapered transition.



Tolerance table for alignment . TABLE FOR ALIGNMENT TOLERANCE.

S. NO.



LEVELS: Deviation in level at each end of same beam Deviation from specified level at survey control station. Deviation from relative horizontal levels for adjacent beams within a distance of 5 meters. Horizontal deviation relative to an adjacent beam floor to floor. Height < 3 meter Height < 3 meter Deviation relative to next column. VERTICALITY: Deviation of top relative to base of height H




LINEAR DIMENSIONS: Deviation in Length or width: Less than 30 meter More than 30 meter CAMBER (Other than designed)

TOLERANCE LIMIT (MM) 5mm + 10mm + 5mm

5mm Height/600 10mm + H/600 or 5mm Maximum: + 25

20mm 20mm + ¼ (L-30)mm (Where L-Length or width)



Note :-

Maximum deviation of any point of the surface from Straight-line joining the extremities of the surface. ˜ For extremities up to including 3 meters apart ˜ Over 3 meters up to including 9 meters apart ˜ Over 9 meters apart TWIST (distance of one corner from the plane Containing the other 3 corners) ˜ For diagonal up to including 3m ˜ For diagonal over 3m up to and including 8m ˜ For diagonal over 8m SQUARENESS OF CORNER ˜ Short side up to and including 0.5m ˜ Over 0.5m up to and including 2.0m ˜ Over 2m

+ 10mm + 15mm + 20mm (maximum)

+ 5mm + 5mm + 20mm (maximum)

+ 5mm + 10mm + 20mm (maximum)

Where there is a conflict between the above tolerance and the contract drawings . The most stringent Tolerance or criteria to be governed .

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