PNE00001

COMPLETE REVISION February 2002 

Process Industry Practices Piping

PIP PNE00001 Design of ASME B31.3  Metallic  Metallic Piping Systems

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has  been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not  be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time by the responsible Function Team and will be reviewed every 5 years. This Practice will be revised, reaffirmed, or withdrawn. Information on whether this Practice has been revised may be found at www.pip.org.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.

PIP will not consider requests for interpretations (inquiries) for this Practice. PRINTING HISTORY

 November 1996

Issued

 February 2002

Complete Revision

 Not printed with State funds

COMPLETE REVISION February 2002

Process Industry Practices Piping

PIP PNE00001 Design of ASME B31.3  Metallic Piping Systems Table of Contents 1. Introduction..................................3 1.1 Purpose ............................................. 3 1.2 Scope................................................. 3

2. References....................................3

6.5 6.6 6.7 6.8 6.9

Vents, Drains, and Sample Outlets ... 9 Check Valves................................... 10 Blanks (Blinds)................................. 10 Strainers and Filters ........................ 11 Utility Piping Connections to Process Equipment ......................... 11

2.1 Process Industry Practices................ 3 2.2 Industry Codes and Standards.......... 4 2.3 Government Regulations................... 4

7. Hot Tapping................................ 12

3. Definitions ....................................5

8. Piping Components................... 12

4. General .........................................5 5. Design Conditions ....................... 5 5.1 Design Pressures and Temperatures ............................. 5

6. Design Practices .......................... 6 6.1 6.2 6.3 6.4

Basic Layout ...................................... 6 Piping................................................. 7 Isolation (Block) Valves ..................... 8 Control Valve Manifolds..................... 8

Process Industry Practices

8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8

General............................................ 12 Pipe.................................................. 13 Joints and Fittings............................ 13 Branch Connections ........................ 14 Valves.............................................. 14 Flanges............................................ 16 Gaskets ........................................... 17 Bolting.............................................. 17

9. Piping Flexibility........................ 17 10. Piping Support......................... 17

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

COMPLETE REVISION February 2002 

11. Specific Piping Systems..........17 11.1 Instrument Air...................................17 11.2 Plant Air............................................18 11.3 Cooling Water ..................................18 11.4 Utility Water......................................18 11.5 Potable Water ..................................18 11.6 Steam and Steam Condensate Removal ...........................................18 11.7 Utility Stations ..................................19 11.8 Burner Fuel Piping ...........................20 11.9 Heat Transfer Fluid Piping ...............21

12. Fabrication, Assembly, and Erection .....................................21

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1.

PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

Introduction 1.1

Purpose This Process Industry Practice (Practice) provides guidance for designing metallic  piping systems to ASME B31.3, Process Piping  (hereinafter referred to as the Code).

1.2

Scope This Practice provides requirements for piping systems arrangement, design conditions, components, and joints. This Practice shall be used in conjunction with the Code. The requirements of this Practice are more stringent than the Code for the purpose of standardization and not because the Code is considered unsafe. Company representatives may waive some of the requirements of this Practice that exceed the Code requirements or may have additional requirements depending on the particular criteria of the project. Piping systems designed in accordance with other piping codes are not included in this Practice. This document is a complete revision of  PIP PNE00001, and therefore, revision markings are not provided.

2.

References The contractor shall comply with the editions of the following referenced standards in effect on the date of contract award. The following codes, standards, and publications are listed as a source of reference material and are not intended to form part of this Practice except as specifically invoked within the text of this Practice. Short titles will be used herein when appropriate.

2.1

Process Industry Practices (PIP)  – PIP PCSIA001 – Instrument Air Systems Criteria  – PIP PNC00001 – Pipe Support Criteria for ASME B31.3 Metallic Piping   – PIP PNC00003 – Process Unit and Offsites Layout Guide  – PIP PNC00004 – Piping Flexibility Analysis Criteria for ASME B31.3 Metallic  Piping   – PIP PNE00012 – Piping Examination and Leak Test Guide  – PIP PNSC0001 – Fabrication and Examination Specification for ASME B31.3  Metallic Piping   – PIP PNSC0011 – Specification for Installation of Metallic Piping   – PIP PNSC0021 – Specification for Leak Tests of Piping   – PIP PNSC0035 – Steam Tracing Specification  – PIP REIE686 – Recommended Practices for Machinery Installation and  Installation Design

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 –  PIP Piping Material Specifications Line Classes

2.2

Industry Codes and Standards •

American Petroleum Institute (API)  – API 570 – Piping Inspection Code: Inspection, Repair, Alteration, and  Rerating of In-Service Piping Systems  – API 602 – Compact Steel Valves  – API 614 – Lubrication, Shaft-Sealing, and Control-Oil Systems for Special Purpose Applications  – API 650 – Welded Steel Tanks for Oil Storage  – API 2201 – Procedures for Welding or Tapping on Equipment in Service

•

American Society of Mechanical Engineers (ASME)  – ASME Boiler and Pressure Vessel Code Section VIII – Pressure Vessels, Division 1  – ASME B16.5 – Pipe Flanges and Flanged Fittings  – ASME B16.25 – Buttwelding Ends  – ASME B16.36 – Orifice Flanges  – ASME B16.47 – Larger Diameter Steel Flanges: NPS 26 through NPS 60  – ASME B16.48 – Steel Line Blanks  – ASME B31.3 – Process Piping   – ASME B36.10M – Welded and Seamless Wrought Steel Pipe  – ASME B36.19M – Stainless Steel Pipe

•

Crane Technical Publication  – Crane Technical Publication 410 – Flow of Fluids

•

 National Electrical Manufacturers Association (NEMA)  – NEMA SM-23 – Steam Turbines for Mechanical Drive Service

•

Manufacturers Standardization Society (MSS)  – MSS SP-6 – Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings

2.3

Government Regulations •

U.S. Department of Labor, Occupational Safety and Health Administration (OSHA)  – OSHA 29 CFR 1910.147 –  Control of Hazardous Energy Sources (Lockout/Tagout)

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

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3.

Definitions As used in this Practice: dead leg : A pipe section connected to a flowing stream where the pipe section is not selfdraining and is not normally flowing  IREB: Integrally reinforced extended body operating : As applied to vents and drains, being used regularly when the source equipment or  piping is in service and/or pressurized  P&ID: Piping and Instrumentation Design  shall : Specification requirement unless otherwise authorized by the owner  should : Recommended good practice, not a requirement SMYS : Specified minimum yield strength

4.

5.

General 4.1

Piping systems shall comply with this Practice and with all applicable federal, state, and local laws.

4.2

New piping systems within the scope of this Practice shall conform to the Code.

4.3

Alterations to existing piping systems shall comply with  API 570. Changes in service or in design conditions are considered alterations.

4.4

Items that are normally fabricated from piping components (e.g., strainers and devices that serve such purposes as mixing, separating, snubbing, distributing, and metering or controlling flow), if identified by the owner as specialty piping (SP) items, shall be designed in accordance with this Practice unless otherwise specified  by the owner.

4.5

Design of piping at machinery shall be in accordance with PIP REIE686  and  NEMA SM-23, as applicable.

4.6

All piping shall be identified by the owner as either Category D, Category M, high  pressure, or normal fluid services as defined in ASME B31.3. “Severe cyclic conditions” per ASME B31.3 shall also be identified.

Design Conditions 5.1

Design Pressures and Temperatures 5.1.1

The internal and external design pressure and temperature of piping shall be determined by considering the following conditions: a. Normal operations

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

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 b. Start-up operations, including any start-up procedure, operation, routing, etc. c. Shutdown operations, including shutdown procedures, operations,  pumpout, etc. d. Switching operations, including any cyclic regeneration, spare pump switching, coke drum switching, etc. e. Regeneration procedures f. Equipment bypassing g. Turndown operations h. Pump shutoff (deadhead) pressure i. Any control valve in a fully opened or closed position  j. Any block valve in a fully opened or closed position, except for locked or car-sealed valves k. Blocked exits l. Equipment trip or shutdown m. Upset conditions n. Maintenance, repair, or neutralization procedures o. On-stream or purging operations  p. Steamout or purging operations q. Solar temperature effects r. Heat-tracing effects 5.1.2

The design minimum temperature shall be determined by considering the following: a. Normal conditions  b. Expected autorefrigeration effects, including emergency depressuring  Note: The design minimum temperature shall be the coincidental temperature when the pressure reaches 25% of the design  pressure. c. One-day-mean low temperature per API 650, Figure 2-2

6.

Design Practices 6.1

Basic Layout Piping layout shall be in accordance with  PIP PNC00003.

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6.2

Piping 6.2.1

General 6.2.1.1 Piping should be located above grade. Exceptions include firewater supply systems, cased road and tank dike crossings, lines in concrete trenches, oil-free compressed air lines, lines with secondary containment and a leak-detection method, and other lines as designated by the owner. All below-grade piping, including piping in trenches, shall be protected from external corrosion. Buried steel  piping in hazardous materials service shall be externally coated and cathodically protected. The minimum cover over buried process  piping shall be 18 inches (46 cm) in paved or unpaved areas and 30 inches (76 cm) under paved roads except under a reinforced concrete slab or other protective cover approved by the owner. Sewers may be covered by this Practice if specified by the owner. 6.2.1.2 When a block valve bypass is required, it shall be shown on the applicable Piping & Instrument Diagrams (P&ID). Bypasses shall be integral with the valve or installed in the piping immediately adjacent to the valve. 6.2.1.3 Piping layouts in all services shall be designed to eliminate the  presence of dead legs. Where dead legs cannot be avoided, utilize either corrosion resistant materials or an approved coating system for the dead leg section. Live dummy legs are not permitted. 6.2.1.4 In locations where potentially severe vibration can occur, small  piping branches (i.e., NPS 2 and smaller) shall be adequately designed to minimize its effects. The following examples are acceptable practices/configurations, depending on the severity of the vibration: a) Brace all nipples (with reinforcing pads if required).  b) Where bracing cannot be effectively provided, install schedule 160 nipples with reinforcing pads. c) Use an API 602 IREB valve. d) Brace all configurations that have a nipple between the welding boss and the root valve. 6.2.1.5 Blind flanges shall be used as end closures on flanged ends and valves, unless end caps are clearly indicated by design necessity. 6.2.1.6 Flanged connections with long exposed bolts for sandwiched components, e.g., wafer type valves, should not be used in fire hazardous areas unless the bolting is protected by a fire-resistant shield. This recommendation does not apply to standard spectacle  plates and blinds. 6.2.1.7 Jackscrews shall be used to facilitate flange separation for maintenance. Joint assemblies that often require frequent separation include orifice plates, spectacle plates, spacers, screens, and dropout

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spools. Piping layout shall be designed such that flanges can be separated without excessive force. Jackscrews shall be accessible from both sides of the pipe. For orifice flanges, jackscrews shall be installed at three- and nine-o’clock positions. When flange separators are used, jackscrews are not required.

6.3

Isolation (Block) Valves 6.3.1

Block valves shall be provided at vessel and storage tank nozzles as follows: a. In piping at all nozzles below the maximum operating liquid level of storage tanks  b. In liquid draw-off lines of vessels containing 10,000 pounds (4,550 kg) or more of a flammable liquid at the maximum operating liquid level when the line does not contain a block valve located within 30 feet (9 m) in a horizontal direction from the vessel

6.3.2

Block valves shall be provided for piping crossing the plant limits and operating unit limits as required for the planned operation, isolation, and maintenance of the plant as directed by the owner.

6.3.3

Where positive isolation is required or cross-contamination cannot be tolerated, one of the following shall be used: a. Blanks  b. Two block valves with a bleeder valve between them c. A double-seated valve (e.g., expanding gate or plug, trunnion-mounted  ball, through conduit slab gate, etc.) and with body bleeder d. Removable spool

6.4

6.3.4

Valving of operating vent, drain, and sample connections shall have one  block valve as a minimum. Additional block valves shall be per owner requirements.

6.3.5

Equipment that may be removed from service during unit operation shall be furnished with single block valves with provisions for blinding or blanking.

6.3.6

In all process services, branches sized NPS 2 and smaller shall have a root valve located as close as feasible to the run. The root valve shall be no farther than three times the branch diameter (except for insulated lines) measured from the far end of the boss to the near end of the valve. Unions shall not be installed in the pipe section between the main pipe run and the root valve.

6.3.7

Flangeless valves shall not be used as the first block valve against storage tanks or vessels containing hydrocarbons or hazardous materials.

6.3.8

Crane Technical Publication 410  provides information on sizing valves.

Control Valve Manifolds 6.4.1

Page 8 of 21

When specified, control valves shall be installed with a valved bypass and a  block valve on each side of the control valve. As a minimum, block and

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

February 2002

 bypass valves shall be provided in the control valve manifold for the following cases: a. Control valves where loss of control function would adversely affect  plant operations as determined by the owner  b. Services where shutdown cannot be tolerated (e.g., fuel lines to furnaces or boilers, steam reducing stations [main headers], etc.) c. Services in which the absence of blocks and bypass valves would inhibit start-up efforts as determined by the owner 6.4.2

6.5

Bleed valves shall be provided for each control valve manifold. One bleed valve shall be located between the upstream block valve and the control valve. An additional bleed valve on the downstream side of the control valve shall be provided when specified.

Vents, Drains, and Sample Outlets 6.5.1

Valved vent and drain connections shall be furnished on all equipment that is not self-venting or self-draining. Connections shall be located on equipment, if practical, but may be located in connecting piping when there are no  blocks between the vent or drain connections and the equipment.

6.5.2

Vent connections shall be furnished for trapped high points of piping and shall be one of the following: a. Valved when required for operational purposes or removal of process fluid  b. Plugged, valve omitted, for hydrostatic test purposes

6.5.3

Drain connections shall be furnished for the low points of all lines located above grade and shall be one of the following: a. Valved when required for operational purposes or removal of process fluid  b. Plugged, valve omitted, for hydrostatic test purposes

6.5.4

Vent, drain, and sample outlet connections shall be NPS 3/4 minimum size, unless otherwise specified. All connections from piping in services involving fluids with suspended solids or materials that are of high viscosity shall be  NPS 1 minimum size.

6.5.5

Operational vent and drain connections shall be designed to drain liquid from equipment and piping in 2 hours or less, unless otherwise specified.

6.5.6

Hydrocarbon vapors or mixtures of hydrocarbon vapors and other vapors (e.g., steam) may be discharged to the atmosphere contingent on adequate safety and environmental considerations.

6.5.7

All vents and drains open to the atmosphere shall be provided with plugs or  blind flanges.

6.5.8

Cooling shall be considered for sample outlets in piping or equipment operating at 140 °F (60°C) or higher. One cooler may be used for multiple sample outlets.

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

6.5.9

COMPLETE REVISION February 2002

For horizontal piping, the sample connection shall be located at the side of the pipe for liquids and at the top of the pipe for gases, unless otherwise specified.

6.5.10 Discharge from drains emptying into open hubs (e.g., drain cups or sumps) shall be visible from the location of the drain valve when practical. 6.5.11 Operating vents and drain lines shall discharge into a closed system when releasing controlled materials, as defined by the owner.

6.6

6.7

Check Valves 6.6.1

Check valves shall be installed in the discharge piping of centrifugal pumps, unless otherwise specified.

6.6.2

Check valves shall be used where utility or chemical injection lines are  permanently tied into process lines or equipment.

6.6.3

In no case shall a check valve serve as a substitute for a block valve for flow isolation purposes.

6.6.4

Check valves in vertical piping shall be installed for upward flow only and shall be installed with a drain connection immediately above the check valve.

6.6.5

When a lower pressure rated system flows into a higher pressure rated system, a check valve shall be installed in the lower pressure connection and the higher pressure rating shall extend to include the check valve.

6.6.6

A check valve in the higher pressure system should be considered where a sudden loss of pressure in the higher pressure system could lead to undesirable contamination from the lower pressure system.

6.6.7

For all sizes NPS 3 and above, a turbulence-free minimum distance of five  pipe diameters upstream and two pipe diameters downstream of every check valve should be maintained. No pipefittings (e.g., elbows, reducers, tees, etc.) or flow-restricting devices (e.g., orifices, control valves, etc.) should be installed in these zones. Valves in intermittent service and valves in skidmounted systems are exempt from these requirements.

6.6.8

Crane Technical Publication 410  provides information on sizing check valves.

Blanks (Blinds) 6.7.1

The piping layout should provide for the insertion of line blanks for flanged equipment isolation for maintenance, inspection, testing, and alternative operation. If piping flexibility and equipment arrangement do not permit the insertion of temporary maintenance blanks at convenient flanges, permanent line blanks shall be provided as follows: a. At piping connections at equipment that can be physically entered  b. At plant limits in process, utility, and auxiliary (e.g., fuel oil, fuel gas)  piping connected to other piping outside plant limits that may be in use during shutdown of the plant

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

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6.7.2

6.8

Figure-8 type blinds shall not exceed 100 pounds (45 kg) or NPS 12. Figure-8 type blinds within these limits are shown in the following table: Class

Max. Figure-8 Size (NPS)

150 and 300

12

600 and 900

8

1500 and 2500

6

6.7.3

Circular blanks or spacers shall be used for sizes exceeding the limits of Section 6.7.2.

6.7.4

Circular blanks or spacers shall be used in place of figure-8 type blinds for cold-insulated piping below 70 °F (21°C).

6.7.5

Commercially available blinding systems acceptable to the Code are  permitted.

6.7.6

Guidance for blanks is available in ASME B16.48.

Strainers and Filters 6.8.1

When strainers are not furnished as part of the equipment, strainers in the  piping shall be considered for the protection of the following equipment: a. Mechanical equipment per PIP REIE686   b. Steam traps and steam jet ejectors in steam inlet lines c. Burners in main fuel oil supply piping d. Upstream of low noise design control valves

6.8.2

When filters are not furnished as part of the equipment, filters shall be  provided in the piping for the protection of the following equipment: a. Pneumatically actuated equipment in air supply piping  b. In the air piping, upstream of air dryers c. Open-air intakes for blowers, compressors, or engines

6.9

6.8.3

Providing permanent strainers with plugged connections for the installation of differential pressure measurement across the strainer shall be considered.

6.8.4

Installation of spacer rings may be required after temporary strainers are removed.

Utility Piping Connections to Process Equipment 6.9.1

Firewater systems shall not be connected to process equipment except via a temporary connection when the equipment is not in operation and not under  pressure.

6.9.2

No permanent connections other than air or steam shall be made to process equipment operating above 212ºF (100ºC) nor shall water or steam be  permanently connected to equipment that operate below 32ºF (0ºC).

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

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COMPLETE REVISION February 2002

6.9.3

Permanent connections without a break tank shall not be made except when the required service is continuous or frequent (at least twice per week) or is needed for emergencies.

6.9.4

When air is injected as a reaction agent, the control shall be such that the hydrocarbon/air mixtures shall not enter the flammable range unless required  by the process. Instrumentation shall be provided to shut off the airflow if the  process flow fails. In addition, a restriction orifice shall be provided.

6.9.5

For all components of permanent connections, the pressure/temperature rating shall be suitable for either the process or the utility service, whichever is more severe.

6.9.6

For temporary connections, the pressure/temperature rating of the process side shall extend to the hose or breakaway spool.

6.9.7

If the process fluid requires internal lining or material other than that used in the utility system, the lining or the material shall extend from and include the check valve on the process side. Valves with bodies of gray cast iron, ductile iron, or low melting point alloys (e.g., brass or bronze) shall not be used in a  permanent connection including the utility side. The material selection of the valve bodies and trim in a permanent connection shall be suitable for both the  process and the utility fluid.

6.9.8

Operator access shall be provided to the block valves on either side and to the blind or breakaway spool of the connection. Chain-operated valves shall not be used.

Hot Tapping Hot tapping shall be in accordance with  API 2201 and OSHA 29 CFR 1910.147 .

8.

Piping Components 8.1

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General 8.1.1

Recommended piping components are shown in the PIP Piping Material Specifications Line Classe s. Other piping components and constructions that are acceptable to the Code not mentioned in these Practices are permitted.

8.1.2

The minimum pipe size shall be NPS 3/4, except for Category D fluid service, individual instrument leads, pump and compressor auxiliary piping, steam tracing, and for reduction at instruments or other equipment provided with smaller than NPS 3/4 connections. Pipe sizes NPS 1-1/4, NPS 2-1/2,  NPS 3-1/2, and NPS 5 should not be used, except for connections to equipment requiring these sizes and in jacketed pipe systems. In such cases, the transition to standard sizes shall be made as soon as practical.

8.1.3

Pipe sizes and schedules shown in the PIP Piping Material Specifications Line Classes are in accordance with  ASME B36.10M  and ASME B36.19M .

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

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8.2

Pipe 8.2.1

Nominal wall thickness for carbon and low-alloy steel pipe joined by welding in new construction shall be, as a minimum, as follows: a. Utility (Category D) fluid services NPS 1/2 – 2 NPS 3 – 6

Not normally welded Standard

NPS 8 – 32

0.250 inch (6.4 mm)

NPS 34 and larger

Diameter/135

 b. Normal and Category M fluid services

8.2.2

8.3

NPS 1/2 – 1-1/2

Extra strong

NPS 2 – 6

Standard

NPS 8 – 32

0.250 inch (6.4 mm)

NPS 34 and larger

Diameter/135

Nonferrous alloy and stainless steel (> 13% Cr) piping joined by welding in new construction shall be, as a minimum, as follows: NPS 1/2 – 3/4

Schedule 40S

NPS 1 and larger

Schedule 10S

Joints and Fittings 8.3.1

Piping joints shall be of welded construction, unless otherwise specified. Flanges, unions, and threaded connections shall be used minimally, except in Category D fluid services.

8.3.2

Butt-welded fittings shall be used for pipe greater than NPS 1-1/2, except as required at equipment or control valve connections.

8.3.3

Butt-welded or socket-welded fittings shall be used for pipe sizes not covered in paragraph 8.3.2, except as follows: a. Threaded fittings may be used downstream of a welded or flanged block valve to instruments, at equipment connections, and for terminal vent and drain connections.  b. Threaded fittings may be used for Category D fluid services.

8.3.4

Socket-welded and threaded constructions should be avoided in services where corrosion is accelerated in crevices.

8.3.5

In lube oil and seal oil lines, only butt-welded or flanged joints shall be used  between filters and equipment per API 614.

8.3.6

Butt-welded piping systems shall utilize long radius elbows. Short radius elbows are permissible only where required by space limitations.

8.3.7

Flush bushings, close nipples, locknuts, street elbows, and street tees are not  permitted.

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

8.4

COMPLETE REVISION February 2002

Branch Connections 8.4.1

Branch connections shall be at a 90-degree intersection to the run pipe centerline, unless otherwise specified. In no case shall a welded branch connection be designed with an intersecting angle of less than 45-degrees, unless approved by the owner.

8.4.2

NPS 2 and Smaller 8.4.2.1 Straight tees shall be used when the branch size is equal to the header size. 8.4.2.2 For header sizes NPS 2 and smaller, reducing tees (or straight tee with butt-welding reducer or swage nipple) shall be used when the  branch size is smaller than the header size. 8.4.2.3 For header sizes NPS 3 and larger, branch connections shall be made with integrally reinforced branch connection fittings. 8.4.2.4 Integrally reinforced extended body valves per API 602 may be used for valved piping connections (e.g., pressure gauges, vents, and drains).

8.4.3

NPS 3 and Larger 8.4.3.1 Branch connections shall be of all welded construction (e.g., unreinforced fabricated tees, reinforced fabricated tees, reducing tees, and forged integrally reinforced welded fittings). When the branch is the same size as the header, a straight tee shall be used. 8.4.3.2 Branch connections for piping at reciprocating equipment shall be welding tees or forged integrally reinforced weld fittings.

8.5

8.4.4

Branch tables in the PIP Piping Material Specifications Line Classes provide reinforcing pads designed for full area replacement.

8.4.5

Weep holes of 1/4-inch (6-mm) diameter shall be provided on reinforcing  pads for branch connections, on wear pads, and on support reinforcing pads if they cover a weld that is not a pipe manufacturing seam weld. Weep holes shall also be provided to vent gases on piping that requires heat treatment after fabrication, or in special cases where hydrogen buildup could occur. Weep holes shall be packed with heavy grease.

8.4.6

Branch tables in the PIP Piping Material Specifications Line Classes reflect minimum requirements. The designer may select other equal or better configurations to suit a particular project need.

Valves 8.5.1

General 8.5.1.1 Ball, butterfly, and plug valves shall have gear operators in accordance with the PIP Piping Material Specifications Line Classes.

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

February 2002

8.5.1.2 Block valves and bypass valves at control valve manifolds, equipment, and pressure-reducing stations shall be of the higher  pressure rating. 8.5.1.3 For soft-seated valves, pressure-temperature ratings for the same class valve may vary between manufacturers and may be lower than the ratings shown in PIP Piping Material Specifications Line Classes. 8.5.1.4 Screwed bonnet and screwed body valves shall not be used in any hydrocarbon or hazardous material services unless the  bonnets/bodies are seal-welded. 8.5.1.5 Union bonnet valves shall not be used in any hydrocarbon or hazardous material services.

8.5.2

Gate Valves Gear operators for wedge gate valves are recommended as follows:

8.5.3

Class

Gate Valves Sizes (NPS)

150

14 and larger

300

12 and larger

600 and 900

8 and larger

1500 and higher

6 and larger

Check Valves 8.5.3.1 Dual- and single-plate wafer check and swing check valves shall not  be used in reciprocating pump and compressor suction and discharge services or similar pulsating services. 8.5.3.2 In parallel pump or compressor systems, check valves installed at the discharge of pumps or compressors should be of a nonslam internalspring-assisted type. Swing check valves should not be used in this service. 8.5.3.3 For parallel pump systems with individual pump discharge piping of  NPS 20 and larger, a hydraulic analysis shall be conducted to verify that the selected check valves have the correct dynamic response to  prevent slamming and limit pressure surge to an acceptable level. The analysis shall include consideration of the “worst case” operating mode scenario.

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COMPLETE REVISION

PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

8.5.4

February 2002

Globe Valves Gear operators for globe valves are recommended as follows:

8.6

Class

Globe Valves Sizes (NPS)

150

14 and larger

300

10 and larger

600

8 and larger

900

6 and larger

1500

4 and larger

2500

3 and larger

Flanges 8.6.1

Flanges in sizes NPS 24 and smaller shall be in accordance with  ASME B16.5 for the listed materials. Steel flanges larger than NPS 24 shall  be in accordance with ASME B16.47, Series B, unless otherwise specified.

8.6.2

The use of flanges in piping shall be minimized. Flanges are typically used: a. At flanged equipment  b. At valves c. At blanks d. In removable sections of pipe e. Where frequent dismantling of piping is required f. Where piping lined with nonmetals or nonmetallic piping cannot be  bonded or otherwise joined g. To provide for erection requirements h. To allow for modifications in areas where welding is not permitted i. To provide clearance for dismantling of equipment (e.g., compressors, reactor heads, etc.)  j. For maintenance cleaning, decoking, or slurry service

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8.6.3

Slip-on flanges may be used up to NPS 24 maximum in Classes 300 and  below at design temperatures to 800 °F (430°C).

8.6.4

Lap joint flanges may be used in Classes 300 and below at design temperatures to 500ºF (260ºC).

8.6.5

Except for proprietary flanges, flange facing shall normally be raised-face for Classes 150 through 2500.

8.6.6

Flat-faced flanges with full-faced gaskets shall be used for connecting piping to flat-faced flanged valves and equipment manufactured from nonductile materials.

8.6.7

Flange facing finish for cast iron, ductile iron, and bronze shall be in accordance with MSS SP-6 . Flange facing finish for steel, nickel alloy, and other alloys shall be in accordance with ASME B16.5.

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COMPLETE REVISION

PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

February 2002

8.6.8

Orifice flanges shall be in accordance with ASME B16.36 .

8.6.9

Blind flanges shall not be drilled for connections (e.g., drain, vent) unless a stress calculation per ASME  Boiler and Pressure Vessel Code, Section VIII, Appendix 2, shows that the flanges will not be overstressed.

8.6.10 For pipe of minimum wall thickness, the bore of welding neck flanges shall not be larger than the inside diameter (ID) of the attached pipe, and shall be within ASME B16.25 tolerances. 8.6.11 The design thickness of the flange hub at the welding end of flanges with a SMYS less than that of the attached pipe shall be at least equal to the pipe wall thickness multiplied by the pipe-to-flange ratio of the SMYS, except as stated in paragraph 8.6.12. See ASME B16.5, Figure 14. The SMYS ratio must be from 1.0 to 1.5 for this criterion to hold. 8.6.12 The bore of welding neck flanges of the lower SMYS may be equal to the ID of the attached pipe of the higher SMYS, if calculations per  ASME Boiler and Pressure Vessel Code, Section VIII, Appendix 2, show that the flanged  joint will not be overstressed.

8.7

Gaskets Gasket selection shall be in accordance with the individual line classes.

8.8

Bolting Bolting selection shall be in accordance with the individual line classes.

9.

Piping Flexibility Piping flexibility analyses shall be in accordance with  PIP PNC00004.

10.

Piping Support Piping supports shall be in accordance with  PIP PNC00001 (under development).

11.

Specific Piping Systems 11.1

Instrument Air 11.1.1 Instrument air systems shall be in accordance with PIP PCSIA001. 11.1.2 Instrument air branch lines shall be taken from the top of the header. Block valves are required for branch connections less than NPS 2 and shall be located at the header. 11.1.3 The main instrument air header size should be NPS 1-1/2, as a minimum. 11.1.4 The instrument air supply to an individual user should be NPS 1/2, as a minimum.

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

11.2

COMPLETE REVISION February 2002

Plant Air Plant air branch lines shall be taken from the top of the header. Block valves are required for branch connections less than NPS 2 and shall be located both at the header and at the equipment.

11.3

Cooling Water 11.3.1 Block valves for every branch from cooling water supply and return headers shall be located either at the header or at the equipment being served. Block valves are not required on return lines operating at or below atmospheric  pressure unless needed for equipment or system isolation. 11.3.2 When exchangers are provided with process isolation valves for inspection and cleaning during plant operation, block valves in the cooling water inlet and outlet piping shall be provided. In freezing climates, an antifreeze bypass from the inlet to the outlet or other means to prevent freezing shall be furnished. 11.3.3 All aboveground cooling water supply and return branch lines shall be connected to the top of the headers.

11.4

Utility Water Utility water branch lines shall be taken from the top of the header. Block valves are required for branch connections less than NPS 2 and shall be located both at the header and at the equipment.

11.5

Potable Water 11.5.1 Potable water shall not be connected to any other system unless isolated in accordance with state and local requirements. 11.5.2 Connections to the potable water system shall be in accordance with applicable ordinances and approved by the owner.

11.6

Steam and Steam Condensate Removal 11.6.1 Steam headers shall run level or shall pitch downward in the direction of steam flow. A vertical rise required in the direction of steam flow shall be via a vertical leg equipped with a drip leg at the low point. 11.6.2 Steam branch lines shall be connected to the top of the headers. Branch lines shall run level or pitch downward in the direction of the steam flow. A vertical rise required in the direction of steam flow, downstream of the connection to the steam header, shall be via a vertical leg equipped with a drip leg at the low point. 11.6.3 Block valves shall be provided in the branch lines from the steam headers located at and above the elevation of the steam header and installed in such a manner that no pocket is formed where condensate may collect. 11.6.4 Steam tracing shall be in accordance with PIP PNSC0035 (under development).

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COMPLETE REVISION

PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

February 2002

11.6.5 Steam traps discharging into the atmosphere shall be provided with upstream  block valves. Steam traps discharging to a condensate collection system shall  be provided with both upstream and downstream block valves. 11.6.6 Condensate from vacuum steam systems shall be re-evaporated into the system by means of a condensate flash pot or removed by eductors, pumping traps, or other suitable means. 11.6.8 All steam traps shall be provided with an internal strainer or a strainer located upstream of the trap. The strainer shall be equipped with a blowdown valve piped to a safe location. 11.6.9 A steam separator or other means of condensate removal (e.g., pumping trap) shall be provided in the steam piping to each group of steam turbines operating on saturated steam and also to each group of steam-driven reciprocating compressors and other water-sensitive equipment. 11.6.10 A minimum of one steam trap shall be provided for each steam separator, header drip leg, branch drip leg, and low point where condensate may collect. Each steam trap shall be sized and specified to operate at all anticipated  pressures and condensate loads for the installed location. Steam traps shall be sized and specified to discharge noncondensable gases at the maximum rates required to purge the steam system of these gases. Staged large and small steam traps may be required to handle large flows of condensate from startup and small flows of condensate from normal operations. 11.6.11 Steam-trap discharge and other condensate lines shall be consolidated into headers and returned to the condensate collection system. Discharge to the waste system may be made only if a collection system is not economically feasible or if condensate is contaminated. 11.6.12 Drip legs equipped with steam traps shall be installed at the bottom of steam headers as follows: a. At dead ends of steam headers and branch lines  b. At low points c. Upstream of risers and vertical legs d. Upstream of expansion joints and raised expansion loops e. Upstream of block, reducing, and control valves f. At intervals of approximately 150 feet (45 m) in straight, horizontal steam lines (i.e., without natural drainage points), but not greater than 300 feet (90 m) 11.6.13 Provisions shall be made to protect steam and condensate lines from freezing where freezing conditions are encountered. Freeze protection shall include  provisions for operating locations and shutdown conditions.

11.7

Utility Stations 11.7.1 The following equipment shall have utility stations:

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

COMPLETE REVISION February 2002

a. Pump and compressor areas shall have permanent utility stations as follows: (1) Stations shall have steam, water, air, and nitrogen outlets as required for anticipated needs. (2) Station spacing shall be such that equipment can be covered with 50-foot (15-m) hose lengths.  b. Columns and vessels shall have steam, water, air, and nitrogen, as required for anticipated needs. c. Exchangers and furnaces shall be provided with steam, water, air, and nitrogen connections as required for anticipated needs. The locations of the connections shall be as specified by the owner. 11.7.2 Each utility take-off connection for steam, water, air, and nitrogen shall be located at the top of the horizontal main header or auxiliary header. Root valves shall be provided for each utility take-off connection from a main header or auxiliary header that cannot be taken out of service without shutting down a complete processing unit or operating facility. 11.7.3 Each utility line shall be provided with an isolation valve just upstream of the specified hose connector at the termination. Pressure bleed-off valves shall  be provided in accordance with the owner’s requirements. Each line shall have a service nameplate indicating the service. The utility pipe and the ends of hoses provided with the station shall be color-coded in accordance with the location standard. 11.7.4 Color-coding and type of connectors shall be in accordance with the location standard. 11.7.5 Hose connections, where applicable, shall be positioned approximately 4 feet (1.2 m) above finished plant grade or above platform of multilevel equipment. The piping shall be securely bolted to a supporting structure. 11.7.6 When an overhead system is used in a freezing climate for water or steam, either an additional block valve shall be furnished at the header or other measures shall be taken to ensure that the piping is protected against freezing. 11.7.7 Hose connections to nitrogen systems shall have special fittings to provide  positive segregation from the air system. 11.7.8 The nitrogen system shall have a check valve at each connection and at each utility station to prevent the introduction of air or hydrocarbons into the nitrogen system. 11.7.9 Other requirements for utility stations shall be specified in accordance with the location standard.

11.8

Burner Fuel Piping 11.8.1 Burner fuel piping shall conform to the following requirements: a. Piping for fuel oil with viscosity exceeding 20 centistokes shall be arranged for continuous circulation of the oil through the headers.

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PIP PNE00001 Design of ASME B31.3 Metallic Piping Systems

February 2002

 b. Fuel gas supply piping shall be arranged to produce equal distribution of flow and to allow condensate drainage, unless dry gas is assured. 11.8.2 Where a safety shutdown valve is required in fuel piping at furnaces or fired heaters, the valve shall have remote and local shutoff capability and shall be located in close proximity (i.e., within 50 feet [15 meters]) to the equipment. An emergency shutoff valve shall always be provided at a safe distance (i.e., minimum of 50 feet [15 meters]) from the equipment.

11.9

Heat Transfer Fluid Piping 11.9.1 The use of flanged and threaded connections should be minimized. Welded construction should be used wherever possible. 11.9.2 Any connection that is expected to be disassembled shall be provided with an upstream double block-and-bleed valve arrangement to protect personnel. 11.9.3 Some heat transfer fluids will freeze at ambient temperatures. When appropriate, heat tracing of the system should be provided to prevent freezing of lines when the system is shutdown. 11.9.4 If the piping system is cleaned or flushed using a water solution, the entire system should be thoroughly dried. 11.9.5 Thermal fluids have a high coefficient of thermal expansion. Therefore,  provisions shall be made to safely absorb the increased volume at operating temperatures (e.g., an expansion tank).

12.

Fabrication, Assembly, and Erection Fabrication, assembly, and erection of piping systems shall be in accordance with  PIP PNE00012, PIP PNSC0001, PIP PNSC0011, and PIP PNSC0021.

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