Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

June 2000

Process Industry Practices Piping

PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

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 This Practice will be revised, reaffirmed, or withdrawn.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 http://www.pipdocs.org.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3208 Red River Street, Suite 300, Austin, Texas 78705. PIP member companies and subscribers may copy this Practice for their internal use.

Not printed with State funds

June 2000

Process Industry Practices Piping

PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping Table of Contents 1. Introduction .................................. 2 1.1 Purpose ............................................. 2 1.2 Scope................................................. 2

6. External Load Limits on Equipment .................................... 5

3. General ......................................... 3

General .............................................. 5 Rotating Machinery............................ 5 Reciprocating Compressors .............. 5 Air Cooled Heat Exchangers ............. 5 Pressure Vessels and Heat Exchangers........................................ 5 6.6 Tank Nozzle Loads ............................ 5

4. Flexibility ...................................... 3

7. Pipe Flexibility Requirements..... 6

5. Design Basis ................................ 3

8. Piping Flexibility Analysis Record Keeping ........................... 6

2. References ................................... 2 2.1 Process Industry Practices ................ 2 2.2 Industry Codes and Standards .......... 2

5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

Thermal Effects ................................. 3 Weight Effects ................................... 3 Friction Effects ................................... 3 Wind Effects ...................................... 4 Seismic Effects .................................. 4 Pressure Relief Systems ................... 4 Water Hammer/Slug Flow ................. 4 Flanges .............................................. 4 Maximum Pipe Spans and Deflections .................................. 4 5.10 Special Requirements........................ 4

Process Industry Practices

6.1 6.2 6.3 6.4 6.5

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PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

1.

June 2000

Introduction 1.1

Purpose The purpose of this Practice is to outline the minimum basic requirements for analyzing aboveground metallic piping systems for flexibility.

1.2

Scope This Practice provides basic piping flexibility analysis, design conditions, and documentation requirements for the flexibility analysis. All piping systems shall be evaluated and, where appropriate, analyzed for applicable conditions in accordance with ASME B31.3 (henceforth referred to as the Code) and this Practice.

2.

References When adopted in this Practice, the latest edition of the following references in effect on the date of contract award shall be used, except as otherwise noted. Short titles will be used herein when appropriate. 2.1

Process Industry Practices (PIP) – PIP PNFS0001 - Miscellaneous Pipe Support Details – PIP RESE002 - Allowable Piping Loads on Rotating Machinery Nozzles

2.2

Industry Codes and Standards • American Petroleum Institute (API) – API 618 - Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services – API 661 - Air-Cooled Heat Exchangers for General Refinery Services • American Society of Civil Engineers (ASCE) – ASCE 7 - Minimum Design Loads for Buildings and Other Structures • American Society of Mechanical Engineers (ASME) – ASME Boiler and Pressure Vessel Code – Section VIII - Pressure Vessels – ASME B31.1 - Power Piping – ASME B31.3 - Process Piping • Welding Research Council (WRC) – WRC 107 - Local Stresses in Spherical and Cylindrical Shells Due to External Loadings – WRC 297 - Local Stresses in Cylindrical Shells Due to External Loadings on Nozzles - Supplement to WRC 107

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Process Industry Practices

PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

June 2000

3.

General 3.1

The designer shall consider the most severe anticipated coincident pressure and temperature condition(s).

3.2

The flexibility analysis shall consider the most severe specified temperature condition anticipated during start-up, normal operation, steam out/decoking, depressuring, shutdown, defined upset, cold branch, and regeneration. Analysis of this situation may require the combination of more than one load case to determine the total displacement stress range. Note: Cold branch shall include cases dealing with parallel lines where at least one line (not always the same one) may be cold at any time. An example is three parallel pumps where one pump (not always the same one) is normally shut down.

4.

5.

Flexibility 4.1

Any computerized pipe flexibility calculations shall be performed using ownerapproved software.

4.2

Piping systems shall be analyzed for expansion, contraction, differential settlement, relief valve reactions, and effects due to weight, wind, seismic, and other mechanical loading per the Code.

4.3

Expansion joints shall not be used unless approved by owner.

Design Basis 5.1

Thermal Effects The analysis shall be for the maximum temperature differential. Climatic effects shall be considered in determining maximum differential temperature. The metal temperature from the effect of solar radiation in the summer and the winter dry bulb design temperature should be used. Process conditions listed in Section 3.2 shall also be considered.

5.2

Weight Effects The weight of piping, piping components, refractory lining, piping insulation, fluid transported, and fluid used for testing shall be taken into account in the analysis. Snow and ice loads shall be considered when required by project specifications.

5.3

Friction Effects The effect of frictional resistance to thermal movement of the pipe shall be considered in the design of piping systems. Frictionless unrestrained movement of the piping system shall be assumed only when the entire system is supported by means of rod or spring hangers. The effect of friction shall not be added to the analysis to reduce either piping loads or stresses.

Process Industry Practices

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PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

5.4

June 2000

Wind Effects The wind loads on piping systems shall be determined by the procedure outlined in ASCE 7 or as specified by owner.

5.5

Seismic Effects Seismic loads on piping systems shall be considered when required by owner or by jurisdiction, and as outlined in project specifications.

5.6

Pressure Relief Systems The discharge piping shall be restrained to contain the thrust loads. Forces and moments due to valve discharge may be calculated by any method acceptable to the owner, such as ASME B31.1, Appendix II.

5.7

Water Hammer Piping systems subject to water hammer shall be analyzed accordingly. Forces due to water hammer shall be determined and suitable pipe restraints shall be provided.

5.8

Flanges External bending moments on flanges shall be considered. External loads may be analyzed by the equivalent pressure method or other methods acceptable to owner. Acceptance criteria shall be in accordance with project specifications.

5.9

Maximum Pipe Spans and Deflections In determining pipe spans, maximum sag deflections shall be limited to 5/8 inch. Any deviations shall be approved by owner.

5.10

Special Requirements 5.10.1 The increased stiffness of piping systems caused by a refractory lining shall be included in the piping flexibility analysis. The increased stiffness due to refractory shall not be included in either the span calculations or the sustained load case (to protect against incremental collapse due to creep). 5.10.2 Large diameter thin wall (D/T ≥ 100) lines shall be analyzed for crushing loads at local stress points and reinforced as necessary. 5.10.3 When piping lifts off a support due to thermal movements, either that support shall be removed for sustained load calculations or spring supports shall be considered. 5.10.4 Attachments on welded ells or within two pipe diameters of the welds of an ell decrease its flexibility. This reduced flexibility shall be considered in the piping flexibility analysis. In the absence of better information, this decreased flexibility may be simulated (in a computer analysis) by placing a flange pair at the nearest weld. Although not addressed directly by Appendix D of the Code, 45 degree ells shall have their flexibility reduced by placing a flange pair at each end.

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Process Industry Practices

PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

June 2000

5.10.5 Branches at angles other than 90 degrees are not addressed by Appendix D of the Code. For flexibility purposes, testing has shown that these branches act like unreinforced connections. In the absence of applicable data or rigorous analysis, these branches may be modeled by doubling the default stress intensification factor for unreinforced fabricated tees. 5.10.6 Tees with aspect ratios of 3:4 have been found to be non-conservative. These tees shall have their stress intensification factor increased by 25%. 5.10.7 Piping systems supported primarily by rod hangers shall accommodate the rod’s rotation and the consequent load impact on near by nozzles. 5.10.8 Unless otherwise approved by owner, use of cold spring for piping systems that connect to rotating equipment (compressors, turbine pumps) shall not be allowed.

6.

External Load Limits on Equipment 6.1

General Loads imposed on equipment by the piping shall not exceed the lesser of that allowed by the equipment manufacturer or that listed in the applicable references in this Practice unless otherwise approved by owner.

6.2

Rotating Machinery Allowable nozzle loads for rotating machinery shall be in accordance with PIP RESE002.

6.3

Reciprocating Compressors Reciprocating compressor piping shall be analyzed in accordance with API 618.

6.4

Air Cooled Heat Exchangers Nozzle loads shall comply with the load criteria of API 661 unless otherwise stated in project specifications.

6.5

Pressure Vessels and Heat Exchangers Where appropriate, nozzle loads shall be evaluated in accordance with WRC 107 and WRC 297, as applicable. If the nozzle/vessel geometry is outside the geometry limit of WRC 107 or WRC 297, other acceptable client-approved local stress analysis methods may be used; extrapolation of the curves in these documents is not acceptable. Allowable stresses shall be based on ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 or 2, as applicable.

6.6

Tank Nozzle Loads Nozzle loads shall be evaluated per owner’s requirements.

Process Industry Practices

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PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

7.

June 2000

Pipe Flexibility Requirements 7.1

All piping systems shall be reviewed to identify those that may be outside the requirements of Section 7.2 and that may still require flexibility analysis.

7.2

A formal flexibility analysis shall be performed on all of the following piping systems (see Code, Paragraph 319.4.2): a. All lines connected to load/stress-sensitive equipment b. All process, regeneration, and decoking lines to and from steam generators and fired heaters c. Process lines to and from centrifugal compressors, turbo-expanders, and blowers d. All working fluid lines to and from turbines e. Suction and discharge lines to and from reciprocating pumps and compressors f. Lines NPS 3 and larger to and from centrifugal pump nozzles g. Lines NPS 4 and larger to air cooled heat exchangers h. All relief systems, whether closed or relieving to atmosphere, with considerations for attached or detached tail pipes i. All piping requiring proprietary expansion devices (e.g., bellows expansion joints) j. Lines NPS 3 and larger subject to significant differential settlement of vessels, tanks, equipment, or supports k. Lines subjected to mixed phase flow (liquid and vapor) and lines identified as severe cyclic or vibrating service l. Jacketed piping m. Piping as required by applicable codes and standards (e.g., Code Category M) n. All plastic lined piping systems

8.

7.3

Figures 1 and 2 provide a guide to evaluate situations not covered in Section 7.2.

7.4

Analysis for other materials shall be per agreement with owner.

Piping Flexibility Analysis Record Keeping 8.1

The designer shall assign calculation numbers and store the flexibility analysis files.

8.2

When the project has been completed, the designer shall furnish all stress calculations and documentation as required by owner.

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Process Industry Practices

PIP PNC00004 Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping

June 2000

Figure 1. Guide for Analysis of Carbon Steel or Low and Intermediate Alloy Steel

Figure 2. Guide for Analysis of Stainless Steel Pipe

Notes: 1. Lines in this category may be analyzed by the use of engineering experience or approximate methods. 2. Lines in this category require formal analysis. Analysis may be done by approximate or comprehensive methods. Documentation is required. 3. Lines in this category require a comprehensive analysis (typically by computer). Other methods may be used with owner’s approval. Documentation is required.

Process Industry Practices

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