asme b31.4 section committee interpretations

NOTE: THESE INTERPRETATIONS ARE FOR ASME COMMITTEE USE ONLY. THEY ARE NOT TO BE DUPLICATED OR USED FOR OTHER THAN

ASME COMMITTEE BUSINESS.

ASME B31.4 Section Committee Interpretations

WARNING: THERE ARE PROBABLY SOME TYPOGRAPHICAL

ERRORS IN THIS DOCUMENT. PLEASE REVIEW THE ACTUAL INTERPRETATION FOR THE EXACT WORDING.



Interpretation 4-1

Subject: 419.6.4(b), 1974 Edition Date Issued: February 9, 1978 File 1222 Question: In 419.6.4(b), the Note refers to the net longitudinal stress. Is this to be interpreted to mean the hoop stress due to temperature and internal pressure must be added to the longitudinal stress using an appropriate theory of failure to obtain an “equivalent tensile stress”? This equivalent tensile stress must then be compared to the allowable stress of 90% of the specified minimum yield strength of the pipe. Please inform me if this interpretation is correct. Reply: In 419.6.4(b), the designer is advised to add the compressive value of SL “directly to the hoop stress to increase the equivalent tensile stress available to cause yielding.” The intent of this instruction is to impose the maximum shear theory on the design criterion for restrained lines subjected to hoop stress (resulting from internal pressure) and longitudinal compressive stress resulting from restrained thermal expansion. By the specific phrase “adds directly to” the Code’s intention is to add the absolute values of SL (which happens to be negative) and Shoop (positive). This is consistent with the maximum shear theory for the combining of two principal stresses of unequal sign (the usual textbook description is the algebraic difference). The term “equivalent tensile stress” is intended to mean “two times maximum shear stress” (the ASME Pressure Vessel Codes, Section III and Section VIII, Division 2 refer to this as “stress intensity.” It is apparent fro the Code paragraph that only the hoop and longitudinal stresses are considered present. Of course, if a shear stress exists (resulting from a torsion or a transverse load), then it also must be appropriately included in evaluating the “equivalent tensile stress.”



Interpretation 4-2

Subject: 419.6.4(b) and (c) and 419.7 Date Issued: May 25, 1978 File 1216 Question (1): We have designed a manifold arranged piping system carrying various oils at elevated and ambient temperatures. Does the manifold, because of the restraint effect of ambient pipes connected to heated pipes, still fall under the criteria of 419.6.4(c)? Question (2): For this piping arrangement should we also check the design of the system using the criteria listed under 41 9.6.4(b)?

Question (3): In order to cover a general situation where aboveground piping is subject to substantial axial restraint without being rigidly anchored, should a paragraph be added to the Code to point the reader in the right direction? Reply: The equation for SL in 41 9.6.4(b) evaluates the upper limit thermal longitudinal stress in a pipe (or any other prismatic body), in which there is absolutely no flexibility and, consequently, all the thermal expansion must be absorbed in compressive strain. Physical arrangements complying with the requirements of "absolutely no flexibility" are: buried pipe or a straight run of aboveground pipe between two anchors. For the latter case, an analysis (computer or otherwise) based on 41 9.6.4(c) and 41 9.7 should yield the same results as the equation of 41 9.6.4(b). If a piping system is properly defined (geometry and restraints), then a flexibility analysis as indicated by 419.6.4(c) and 419.7 will fulfill the requirement of the Code. As implied above, if the system is subject to substantial axial restraints, the value of SL [from 41 9.6.4(b)] will represent the upper limit.

Based on the above observations, the answers to your questions are: Question (1)-Yes; Question (2)-No. Regarding question (3), the Committee will consider a possible revision to the Code. You are advised to review future addenda to the Code for any revisions.



Interpretation 4-3

Subject: 419.6.4(b), 1974 Edition Date Issued: May 25, 1978 File 1280 Question: In 419.6.4(b), would the equation for total hoop stress be: SH = Sh + vE α (T2 – T1) which is the result of both internal pressure and temperature change? Reply: The longitudinal compressive stress as defined in 419.6.4(b) is strain induced. The strain in the longitudinal direction causing this stress results from the free thermal expansion, α (T2 - TI), and the Poisson's Ratio contraction, vSb/E, due to the hoop strain. Since a restrained pipe does not allow these free expansions to take place, a longitudinal compressive stress is induced, namely, SL = E[α (T2 – T1) - vSh/E= E α (T2 – T1) - vSh. The hoop stress, on the other hand, results from equilibrium with the pressure force. Although there is a radial expansion due to (T2 – T1) and a radial contraction due to Poisson's Ratio, these displacements are unrestrained and do not have an effect on hoop stress.

Based on the above explanation, the hoop stress to be used in 419.6.4(b) is equal to PiD/2t in which it is the wall thickness of the pipe, as installed, with due consideration and allowance for the various underthicknesses and defect tolerances provided for in the specifications approved by the Code.



Interpretation 4-4

Subject: 423.2.4(b), 1974 Edition Date Issued: May 26, 1978 File 1257 Question: Would the manufacturer's certified hydrostatic test have any bearing on the use of a cast iron pump beyond the pressure limits defined in 423.2.4(b)?

Reply: It is the opinion of the Committee that the manufacturer's certified hydrostatic test does not allow operation of a cast iron pump in excess of 250 psi as set forth in 423.2.4(b).



Interpretation 4-5

Subject: Scope of the B31 Codes Date Issued: November 28, 1979 File 1310 Question: Your technical opinion is requested regarding: Crude Oil pipeline (two phase flow) with a crude oil relation of 459 m3/m3. Which is the B31 Code to be applied in order to determine the thickness of the pipeline in the following cases?

(a) Gathering lines, measurement lines and risers on offshore platforms. (b) From an offshore platform to 100 m out, not including the riser. (c) From 100, out to 100 m before reaching the shoreline. (d) From shoreline to 100 m off the shoreline. Your interpretation is also requested regarding paragraph (5), Clause 195.1, Part

195, Title 49, as well as paragraph (1), Clause 192.1, Part 192, Title 49 of the Federal Regulations. Reply: It is the opinion of the committee that:

(a) If a fluid has the operating characteristics of a liquid, ANSI B31.4 is the appropriate Code to follow.

(b) If a fluid has the operational characteristics of a gas, ANSl B31.8 Code should be used.

(c) When a combination of the two characteristics exist, the more stringent requirement of each code should be applied. In addition, special consideration should be given to the effects of possible slug flow in all positions along the system.

(d) In conclusion, neither the ASME B31 Code Committee nor any of its sections are in a position to offer an opinion as to the operating characteristics of the described gas-oil mix or to interpret U.S. Federal Regulations.



Interpretation 4-6

Subject: 437.4.1, 1974 Edition Date Issued: January 10, 1980 File 1385

Question: An 8 hour minimum duration is required in 437.4.1. Is this necessary or practical for components such as minfold systems, scraper traps, volume chambers, etc.?

Reply: The 1979 Code contains a revision to 437.4.1 to only require a 4 hour hydrostatic test for piping and components that can be visually inspected for leaks. We believe this answers your concern.



Interpretation 4-7

Subject: 1942 Requirements for Depth of Buried Pipelines Date Issued: February 25, 1980 File 1407

Question: In 1942, what were the applicable B31.4 requirements for the depth of buried pipelines?

Reply: In 1942, there was no B31.4 Code. At that time, B31 requirements for the various types of piping were all covered in one Code, ASA B31 .l-1942. There were no requirements concerning the depth of pipelines used for the transport of liquid petroleum products in ASA B31 .l-1942.



Interpretation 4-8

Subject: 434.5(b)(6) and 434.7.1, 1974 Edition Date Issued: October 2, 1980 File 1368

Question: In 434.5(b)(6), a reduction of 2% of the nominal pipe diameter in sizes greater than 12 3/4 in. O.D. is allowed by the Code for dents, and in 434.7.1(b) a reduction of 2 1/2% of the nominal diameter is allowed by the Code for bends. Is the 2 1/2% of the nominal diameter the maximum reduction allowed for any case? When calculating the diameter of the sizing plate, is the allowable reduction subtracted from the nominal pipe diameter or from the inside pipe diameter?

Reply: Under the 1974 Code referred to, the 2% reduction for a dent was intended

to limit the inward deformation of a short, sharp crease or depression which would have the effect of stiffening the pipe at one point adjacent to a less rigid, undistorted area, which would result in a stress concentration. The adverse effect of a more severe dent can be readily appreciated. The structural integrity might not be so affected by gentler and longer ovality or out-of-roundness of the pipe, which, if it contained no stress concentrations, might safely exceed a 2% reduction. The relative safety of out-of-round pipe not only depends on the pipe material and service, but on the time at which it is measured, since it may well change during pressure testing and subsequent operations. Therefore, it would be the responsibility of the designer or operator with this information at hand to determine what minimum diameter he can tolerate.

Also, under the 1974 Code referred to, the 2 1/2% limit for pipe flattening during bending was to govern the deformation of the bend, not a dimensional determination of a sizing plate, except to state that any specified sizing plate used must be able to pass the bend. It is unlikely that one would like to use a larger sizing plate, but if they chose to do so, it would limit the flattening of the bend to less than the 2 1/2% limit. On the other hand, if one chose a sizing plate considerably smaller than that which might contact a 2 1/2% reduction (which would be the generally accepted practice), the Code would still limit the bend flattening to the specified 2 1/2%.

Neither of these paragraphs limits or determines either the minimum diameter of any other point in the pipeline or the minimum or maximum diameter of a sizing plate on a gaging pig. If the designer or operator elects to use a gaging pig, the choice of the sizing plate diameter must be determined by him on the basis of the requirements and materials and conditions of the specific pipeline. He is cautioned that larger-diameter, thin-wall, high-strength pipe is particularly notch-sensitive and that sizing plate contact can damage the pipe wall internally. Control of gaging pigs in larger sizes is erratic, at best, and the pig cannot be counted on to stop at an obstruction, but may pass it with resulting damage to pipe and/or pig, making location of the fault difficult, if not impossible. To determine pipe out-of-roundness or variations in diameter at locations where they might occur, commercial equipment is available which will detect and locate these pipe anomalies



without a possibility of internal damage. By the use of this equipment, a scraper with a sizing plate need be used only to clean the pipe of larger objects.

Your second question asking about the arithmetic of sizing plate determination is no longer relevant in view of the aforementioned.



Interpretation 4-9

Subject: 434.5, 1974 Edition Date Issued: October 6, 1980 File 1425

Question: Is 434.5 of ANSI B31.4-1974 applicable to the repair of fabricated items and pipe at the fabricating plant or pipe mill; or does this refer to repairs in the field?

Reply: Paragraph 434.5 applies only to repairs in the field. Pressure containing

items fabricated from pipe and fittings may be constructed using Chapter V as a specification. Specifications for pipe manufacture are not covered in this Code, except as referenced in Appendix A.

Furthermore, materials purchased as fabrications from manufacturers are built to specifications which cover such repairs.



Interpretation 4-10

Subject: 435.3.3 and 401.2.2 Date Issued: October 6, 1980 File 1452

Question: Please clarify the intent of 435.3.3 of ANSI/ASME B31.4-1979, which states "all values and fittings on pumping units shall carry the same pressure ratings as required for line operating pressures," with regard to line operating pressure.

Reply: Line operating pressures, as used in 435.3.3, are discussed in 401.2.2,

which states: 401.2.2 Internal Design Pressure. The piping component at any point in the piping system shall be designed for an internal design pressure which shall not be less than the maximum steady state operating pressure at that point, or less than the static head pressure at that point with the line in a static condition. The maximum steady state operating pressure shall be the sum of the static head pressure, pressure required to overcome friction losses, and any required back pressure. Credit may be given for hydrostatic external pressure, in the appropriate manner, in modifying the internal design pressure for use in calculations involving the pressure design of piping components (see 404.1.3). Pressure rise above maximum steady state operating pressure due to surges and other variations from normal operations is allowed in accordance with 402.2.4.



Interpretation 4-11

Subject: Fig. 434.8.6(a)-B sketch (f), 1974 Edition Date Issued: April 24, 1981 File 1403

Question: May a "runout weld" be used in lieu of a secondary 30 deg. maximum, 14 deg. minimum bevel [as shown in sketch (f) of Figure 434.8.6(a)-B of ANSl B31.4-1974], when the adjacent wall thickness exceeds 1.5 t? Refer to the attached sketch.

Reply: ANSl B31.4-1974 does not permit use of the detail you suggested in the

sketch. However, the ASME B31.4 Section Committee will consider your proposal as a possible revision to the Code.



Interpretation 4-12

Subject: 400(e) Date Issued: April 24, 1981 File 1453

Question (1): What are the definitions of "designer," "special or unusual problem," and "rigorous analysis" as mentioned in 400(e)?

Reply (1): designer-the responsible person who, by the use of his knowledge, training,

expertise, and experience, applies accepted engineering practice and criteria to arrive at the specific physical combination of pipe, fittings, structures, and materials meeting the requirements of this Code

special or unusual problem-a problem relating to the general subject of this Code, but not specifically covered by procedures or limitations detailed herein

rigorous analysis-a comprehensive and detailed investigation and/or assessment of a subject where specific rules are not given in the Code, or as a substitute for the simplified engineering approach usually presented in the Code. When used, the designer is responsible for demonstrating the validity of his approach.

Question (2): Is it the intent of 400(e) to allow pipeline operators to exceed flange

or valve designer/manufacturer's maximum working pressure based on the operators own testing or calculations?

Reply (2): ANSI/ASME B31.4 clearly states that when a designer/operator

exceeds or deviates from the requirements of the Code, based on a rigorous analysis, he alone is responsible for demonstrating the validity of his approach.



Interpretation 4-13

Subject: Table 404.1 .1 Date Issued: April 24, 1981 File 1500

Question: What were the methods and background used to derive the values shown in Table 404.1.1 of ANSI/ASME B31.4?

Reply: Table 404.1.1 first appeared in USAS B31.4-1966. The wall thicknesses in

the 1966 edition of the Code were the minimum wall thickness for each size of pipe diameter listed as available in the 1965 editions of pipe specifications. Table 404.1.1 has had only minor changes since the 1966 edition.

However, it should be noted that for any given design, other criteria in the Code usually require pipewall thicknesses greater than those listed in Table 404.1 .l.



Interpretation 4-14

Subject: Proposed Revision to Scope of B31.4 Date Issued: April 24, 1981 File 1501

Question: I suggest that alcohol be considered for inclusion in the scope of ANSI/ASME B31.4 or another appropriate B31 piping Code.

Reply: It is the opinion of the Committee that although not specifically addressed

in the scope of ANSI/ASME B31.4, the Code may be used for the design of alcohol transportation piping systems.

The Committee will consider the addition of alcohol to the scope of ANSI/ASME B31.4, or the possible publication of a Code Case.



Interpretation 4-15

Subject: Scope of B31.4 Date Issued: May 26, 1981 File 1391

Question: Can ANSI/ASME B31.4 be utilized for the design of closures? Reply: Devices for repeated rapid opening and closing "closures" such as those

utilized on scraper traps and similar applications under ANSI/ASME B31.4 (and other B31 Code Sections) are not covered by any national dimensional standards, and no national standards establishing pressure temperature ratings for such components exist. This classifies such devices as special (or proprietary) components. ANSI/ASME B31.4, 404.7 establishes the design basis required to qualify such components. (Other B31 Code Sections have similar requirements for design and acceptance of "special" or proprietary components.)



Interpretation 4-16

Subject: Proposed Addition to 404.3.1 (c) Date Issued: July 6, 1981 File 1342

Question: Would the Committee please consider the following as an addition to Paragraph 404.3.1 (c):

Branch connections made by welding an integrally reinforced branch connection fitting (contoured insert type) are acceptable to this Code provided it has been demonstrated by full scale internal pressure test that the branch fitting restores the header and branch pipes to their original pressure retaining strength. This demonstration is to be per the rules and guidelines of 404.7(a).

Reply: The Committee has carefully considered the additional paragraph you

suggested for addition to the ANSI/ASME B31.4 and has decided it is not necessary because a contoured insert type fitting is a proprietary item. The Committee cannot approve or disapprove such items. Use of proprietary items is provided for in ANSI/ASME B31.4 if the user complies with the requirements of 404.7.



Interpretation 4-17

Subject: Combination of B31.3 and B31.4 Date Issued: September 4, 1981 File 1538

Question: Why cannot the two piping Code Sections B31.3 and B31.4 be combined into a single Code Section?

Reply: It is the opinion of the B31 Committee that it is appropriate to continue publishing ANSI/ASME B31.3 and ANSI/ASME B31.4 as separate Code Sections for the following reasons.

(a) Established Practice. Publication of separate Code Sections began in 1952. In 1955, the B31 Committee decided, after review of pertinent factors, that other industry Sections should also be published separately. The last edition of a combined Code for Pressure Piping, ASA B31 .l-1955, appeared that same year.

(b) Basis for Decisions. Questions of combining Code Sections, as well as developing new Sections, have been raised periodically during the past twenty-five years and, in fact, decisions to combine two Sections have been made in two instances Decisions to merge, or to develop separate Sections, have been based on similarities and differences in the following factors:

(1) services - fluids handled, range of pressure and temperature, etc. (2) environments - surroundings which may impact on piping safety, or which

may be affected by possible piping failure (3) application - how the Code is used, actual or potential regulatory jurisdictions

These factors, where they differ substantially as in the case of piping for refineries and chemical plants versus piping for cross country oil transportation, account for crucial differences in philosophy relating to design, construction, operation, and maintenance of piping, which in turn necessitate separate Sections.

(c) Differences vs Similarities. Similarities among different Code Sections are natural and encouraged because of similarities in the basic subject matter. Several technical Committees are maintained by the B31 Committee to exploit opportunities for common practice among all Code Sections. But these similarities do no warrant merging one Section with another where basic differences in services, environment, and application exist.

(d) Specific Differences. A few of the major differences between B31.3 and B31.4 that arise from basic differences outlined above are listed here. There are many others.

(1) Allowable stress basis. The more extensive and complex criteria in B31.3 are necessitated by the extreme range of temperatures and material of construction.

(2) Unlisted materials and components. These are not permitted under B31.4 because services are of limited diversity. They are permitted, with rules for qualifying them, in B31.3 because unanticipated service can be expected to require them.



(3) Limitations on components and joints. These are expressed as straightforward rules in B31.4. In B31.3 they require complex guidelines (e.g., the safeguarding and severe cyclic conditions concepts) because of the diversity of services and environments.

(4) Operation and maintenance. These are not dealt with in B31.3 because the complexity of activities is too great for effective codification (e.g., corrosion can take so many forms and result from so many sources that the designer must rely on expertise not found in the Code). In B31.4 the fruits of many years of experience are summed up in useful rules (e.g., for corrosion protection and monitoring) which also aid in protecting the public.



Interpretation 4-18

Subject: Appendix A, Referenced Standards Date Issued: September 10, 1981 File 1454

Question: Why are NFPA 58 and 59 not referenced in ANSI/ASME B31.4? Reply: NFPA 58 Paragraph 112 Nonapplication of Standard, subparagraph

1120(b) states that this standard does not apply to marine and pipeline terminals, natural gas processing plants, refineries, or tank farms. Guidance for the design and construction of LP-gas installations at marine and pipeline terminals, natural gas processing plants, refineries, petrochemical plants, and tank farms is covered by API Standard 251 0-1 978.

NFPA 59 Paragraph 12 Application of Standard, Subparagraph 120 states this standard applies to utility gas plants. Since the scope of ANSI/ASME does not include utility gas plants or LPG distribution plants, referencing NFPA 59 would be inappropriate.



Interpretation 4-19

Subject: Use of ASTM A587 Date Issued: October 5, 1981 File 1464R

Question: Why is ASTM A587 not referenced in ANSI/ASME B31.4? Reply: ASTM A587 is not referenced in ANSI/ASME B31.4 for the following

reasons: (a) A587 is only made through NPS 4 which makes its application very limited. (b) At stations and terminals, where the use of A587 would be most probable, it is

the custom and practice of the liquid petroleum pipeline industry to use forged steel welding elbows and not steel pipe bends. Practically all cold field pipe bends used in the liquid petroleum pipeline industry are on cross-country pipelines.

(c) It is not the custom and practice of the liquid petroleum pipeline industry to use cold flanging since piping on stations and terminals is subject to considerable vibration caused by high pressure pumps.

(d) Para. 406.2.1(b) of ANSI/ASME B31.4 limits the radius of cold field bends in pipe, NPS 12 and smaller, to 18 pipe diameters. The fact that A587 can be bent to radii as small as 1 1/2 pipe diameters offers no advantages to the liquid pipeline industry since any radius less than 18 pipe diameters is not allowed by the Code because it cannot be pigged.



Interpretation 4-20

Subject: Use of ASTM A120 Pipe Date Issued: October 6, 1981 File 1502

Question (1): May ASTM A120 pipe be used for a buried pipeline for handling diesel fuel oil?

Reply (1): ASTM A120 pipe, while primarily classified for general use, is also

classified for use in oil pipelines. Question (2): May 6 5/8 in. O.D. - 0.275 in. wall ASTM A120 pipe be safely

operated at 300 psig working pressure in such service? Reply (2): A120 pipe may be used subject to the provisions of 402.3.1 (c) and

405.2.1(c).



Interpretation 4-21

Subject: Scope of B31.4; Half-Soling Date Issued: October 6, 1981 File 1514

Question: Is half-soling an acceptable repair practice according to the requirements of ANSI/ASME B31.4?

Reply: Half-soling is not presently covered by the Code. The only repairs allowed

in the Code are those outlined in 541.6. However, the Committee is presently considering a proposal to address half-soling in the Code.



Interpretation 4-22

Subject: Scope of B31.4 vs B31.8 Date Issued: December 1, 1981 File 1540

Question: Why was the Class Location concept developed for gas pipelines designed to ANSI B31.8 and not for liquid pipelines designed to ANSI/ASME B31.4? Also, why do gas pipelines have lower design factors than nonvolatile and volatile liquid pipelines?

Reply: ANSI/ASME B31.4 and ANSI B31.8 were developed by their respective

Section Committees in accordance with the design and operating history of the type of pipeline coming under their individual jurisdiction.

Both B31.4 and B31.8 recognize that one of their basic problems is dealing with the exposure of the pipeline to outside forces that exist in populated areas. B31.4 deals with this quite adequately in 402.1 in which it requires that "the design engineer shall provide reasonable protection to prevent damage to the pipeline from unusual external conditions." B31.8 deals with this in 840.1 with the following: "However, special conditions that may cause additional stress in any part of a line or its appurtenances shall be provided for, using good engineering practice."

In 1952, with the formulation of ANSI B31.8, the new Committee felt that the design of gas pipelines would best be served by utilizing the Class Location concept. This philosophy was adopted because of the compressible characteristics of gas.

It is not intended that either the ANSI B31.4 or B31.8 Codes be a handbook for design. These Codes place the responsibility on the design engineer to provide a prudent design in accordance with good engineering practices.



Interpretation 4-23

Subject: Requirements for LPG Pipelines Date Issued: December 1, 1981 File 1562

Question (1): Has the B31 Committee ever considered special requirements for LPG pipelines, such as class location factors?

Reply (1): Yes. Specific requirements, have been added to ANSI/ASME B31.4 to

cover LPG pipelines. The matter of class locations has been previously considered and rejected.

Question (2): Are there any current plans to adopt a specific individual B31 Code

for LPG pipelines? Reply (2): No. Question (3): What is the current general practice in the United States for LPG

lines in areas where building/population density becomes a factor of consideration in design?

Reply (3): Current practice in the U.S.A. is the use of Title 49 CFR 195

(Government Regulations) and ANSI/ASME B31.4, Code for Liquid Petroleum Transportation Piping Systems.

Question (4): We are advised that ANSI B31.8 is no longer the prime high

pressure gas code in the USA, and that DOT Part 192 seems to take precedence in design. We also note that the DOT Regulations do not specify ANSI B31.8 as material incorporated by reference. Could you advise us of the reasons for this?

Reply (4): The preamble to the initial publication of Part 192 in the Federal

Register contained an acknowledgment that these regulations were for the most part a rewrite of ANSI B31.8-1968 in regulatory language. This rewrite was done in such a manner that a further reference to ANSI B31.8 was not necessary in the body of Part 192.

Most gas pipelines in the USA are required by law to meet requirements of Part 192. This precludes argument with a statement that "ANSI B31.8 is no longer the prime high pressure gas code in the USA."

The ANSI B31.8 standard continues in existence and represents the most up-to-date technology of the industry. It is anticipated that a full revision of B31.8 will be available in the near future to replace the 1975 edition of ANSI B31.8.



Interpretation 4-24

Subject: 451.6.2(c)(5) Date Issued: May 28, 1982 File 1561

Question: In ANSI/ASME B31.4, reference is made to repair by patching in 451.6.2(c)(5).

(a) Why is length of patch limited to 6 in. along the pipe axis? (b) What is meant by "pipe sizes NPS 12"? (c) Why is patching limited to grade X42 and lower? Reply: (a) The 6 in. limitation on patch length was taken from the first edition of

APR RP 1107, Pipeline Maintenance Welding Practices. This is an empirical number based upon experience with different repair requirements.

(b) Pipe sizes NPS 12 means 12 in. nominal pipe size as set forth in ANSI B36.10-1979, p. 1.

(c) The limitation of spot patching to X42 and lower grade pipe is derived from the experience that such patches are conducive to detrimental stress concentration and early failure when applied to higher strength pipe. The safe repair of high strength pipe therefore should be through the application of a full encirclement repair sleeve buttwelded to itself and thereby avoiding that fillet weld to the pipe which cuts across and weakens the circumferential line of hoop stress.



Interpretation 4-25

Subject: Table 404.3.1 (c) Date Issued: May 28, 1982 File 1563

Question: In the 1979 Edition, Table 404.3.1(c) was changed to base branch reinforcement requirements on the ratio of the nominal diameter of hole cut for branch connection to header diameter. In previous editions, the branch reinforcement criteria was based on the ratio of nominal branch diameter to nominal header diameter. Is the 1979 revision adequate?

Reply: The revision to Table 404.3.1(c) in the 1979 Edition is correct and there is

no basis for concern. The pressure reinforcement rules in the ASME Boiler and Pressure Vessel and B31 Codes are based on the replacement of area removed by a hole in the pipe (or vessel) wall. In addition, the limits of reinforcement (area replacement) are based on the "length of the finished opening in the header wall" and are substantially the same for all ASME Codes.



Interpretation 4-26

Subject: 402.3.1, Allowable Stress Values Date Issued: April 19, 1983 File 1612

Question: If underthickness is not allowed in a pipe fabrication specification, may a safety factor greater than 0.72 be used in ANSI/ASME B31.4 and ANSI/ASME B31.8 construction?

Reply: There is no provision in ANSI/ASME B31.4 or ANSI/ASME B31.8 to

permit a design factor greater than 0.72 to be used in the design of a liquid petroleum pipeline or a natural gas pipeline.



Interpretation 4-27

Subject: 434.8.9, Stress Relieving Date Issued: July 6, 1983 File 1620

Question: In 434.8.9, when two tapered parts of similar materials are connected with a welded joint, which thickness should be measured to determine the stress relieving requirement?

Reply: The greater thickness at the weld joint shall be used to determine the stress

relieving requirement.



Interpretation 4-28

Subject: 402.3.1, Allowable Stress Values Date Issued: July 6, 1983 File 1649 (B31-83-002)

Question (1): Does the design factor of 0.72 of 402.3.1 preclude the necessity of adding wall thickness to cover the possibility of localized underthickness and defects within the limits prescribed in the B31.4 Code?

Reply (1): Yes. Question (2): Is the result of the calculation of wall thickness as described in

B31.4 a minimum wall thickness or a nominal wall thickness? Reply (2): Nominal wall Thickness, tn. Question (3): Should an additional thickness be provided to offset the 12 1/2%

wall thickness tolerance? Reply (3): No.



Interpretation 4-29

Subject: 404.3.1 Branch Connections Date Issued: October 26, 1983 File 1681 (B31-83-034)

Question: Do the rules for extruded outlets apply to contoured integrally reinforced fittings? If not, what are the correct equations indicated in ANSI/ASME B31.1, B31.2, B31.3, B31.4, and B31.8, to be used in determining the limits of area reinforcement for contoured integrally reinforced branch connecting fittings (e.g., weldolet) and extruded outlets?

Reply: The contoured integrally reinforced fitting is not an extruded outlet. The

equations set forth in the B31 Codes for determining the reinforcing limits of an extruded outlet do not apply in determining the reinforcing limits of a contoured integrally reinforced fitting.

The equations set forth in the Code documents for fabricated intersection area reinforcement limits are the only equations available for contoured integrally reinforced branch connecting fittings.



Interpretation 4-30

Subject: Chapter VII, Operation and Maintenance Procedures Date Issued: June 27, 1985 File B31-85-010

Question: Chapter V of ANSI/ASME B31.4 defines damage limitations to systems operating above and below 20% SMYS. Why does Chapter VII only address systems operating above 20% SMYS and does not cover systems operating at less than 20% SMYS?

Reply: ANSI/ASME B31.4 sets forth engineering requirements deemed necessary

for safe design and construction of piping systems. The margin of safety inherent in pipelines operating at less than 20% SMYS allows for a greater latitude in the safe design, construction, and repairs of such facilities and therefore fewer details need be specified. Both Chapter V and Chapter VII contain more specific requirements for pipelines designed, constructed, and operated in excess of 20% SMYS.



Interpretation 4-31

Subject: Paragraph 400.1.2(d) Date Issued: May 16, 1986 File B31-85-029 Question: Does piping that is between the wellheads and the inlet manifold in the initial production facilities of an oil field, also referred to as gathering or flow lines, fall within the scope of B31.4? Reply: Paragraph 400.1.2(d) of B31.4 specifically excludes flow lines and all other production facilities. In the oil industry, gathering line begin at the field tank or meter where custody is taken by the transporter (pipeline company) from the producer. All production facility piping between the oil well and/or meter is considered flow lines. The custom and practice of major oil producing companies within the U.S. is to use B31.4 as a guide for oil production facility piping, even though production facility piping is specifically excluded from B31.4.



Interpretation 4-32

Subject: Para. 451.7, Derating a Pipeline to a Lower Operating Pressure Date Issued: May 7, 1987 File B31-87-001 Question (1): May the provisions of ANSI/ASME B31G be used as acceptable alternative rules to the rules of B31.4 for determining the remaining strength of corroded pipelines? Reply (1): Yes. Question (2): When a derated internal design pressure of a corroded piping system has been determined in accordance with the methods of para. 451.7, may the provisions of para. 402.4 be applied, where adequate controls and protective equipment are provided so that the level of pressure rise due to surges and other variations from normal operations do not exceed the derated internal design pressure at any point in the piping system and equipment by more than 10%? Reply (2): Yes. Note: This interpretation should have been issued in Interpretations Volume No. 2 covering replies from August 1, 1985, through July 31, 1987.



Interpretation 4-33

Subject: Para. 404.3, Intersections Date Issued: May 7, 1987 File B31-87-003 Question: When constructing a stainer in accordance with B31.4, what requirements must be followed? Reply: If the strainer is being built according to the criteria of pressure design of piping components, Table 404.3.1(c) applies. If, however, the strainer falls under the design of para. 404.7, Pressure Design of Other Pressure Containing Components, the options listed in that paragraph are to be followed. Note: This interpretation should have been issued in Interpretations Volume No. 2 covering replies from August 1, 1985, through July 31, 1987.



Interpretation 4-34

Subject: Hydrotest Preparation Date Issued: June 12, 1987 File B31-86-033 Question: May the joints, including welds, used in piping systems covered by ANSI/ASME B31.1, ANSI/ASME B31.3, ANSI/ASME B31.4, ANSI/ASME B31.8, ANSI/ASME B31.9, and ANSI/ASME B31.11 be primed and painted prior to hyrotest? Reply: Yes. Note: This interpretation should have been issued in Interpretations Volume No. 2 covering replies from August 1, 1985, through July 31, 1987.



Interpretation 4-35

Subject: Para. 434.8.3(b), Material Group Numbers Date Issued: March 15, 1988 File B31-86-034 Question (1): Paragraph 434.8.3(b) states that carbon steels with the specified carbon content and carbon equivalent are considered to come under material grouping P-No. 1 (of the ASME Boiler and Pressure Vessel Code, Section IX). Is the omission of te mention Group Numbers in this allowance to be interpreted that it is not necessary to consider the Group Numbers of Section IX when qualifying welding procedures requiring notch toughness tests? Reply (1): No. Question (2): If the answer to the above is no, are Group Numbers to be assigned to materials which are not listed in Section IX, QW-422, by comparing tensile strengths to those listed in Table QW-422? Reply (2): No.



Interpretation 4-36

Subject: Para. 451.6.2(a)(7) Date Issued: May 12, 1988 File B31-88-003 Question (1): Is the method of calculating the length of pitted area, as stipulated in para. 451.6.2(a)(7), applicable to the corroded region in the spiral weld area of spiral welded pipe? Reply (1): No. Question (2): What is the acceptance criteria for the corroded regions in the longitudinal weld area of pipes containing longitudinal seam made by either ERW or SAW conforming to API 5LS? Reply (2): See the first sentence of para. 451.6.2(a)(7).



Interpretation 4-37

Subject: “Last” Joint Test Date Issued: May 12, 1988 File B31-88-004 Question: Does ASME/ANSI B31.4 address how to test the last joint (connection) in a liquid transportation piping system? Reply: ASME/ANSI B31.4 only addresses welded joints in regard to last joint testing. Under para. 437.1.3 testing of fabricated items is allowed to proceed separately.



Interpretation 4-38

Subject: Para. 421.1 and 434.8.9 Date Issued: May 27, 1988 File B31-87-028 Question (1): Is it the intent of para. 421.1 to not allow a fabricator to attach weld positioners to fabrication with temporary welds? Reply (1): Paragraph 421.1 does not apply to the attachment of weld positioners. Question (2): Is a temporary weld used to hold on weld positioners in a fabricator’s shop permitted under Chapter V as long as the weld is blended smoothly into the surrounding surface after the positioner is removed? Reply (2): Chapter V does not address temporary welds.

Question (3): Does para. 434.8.9 permit stress relieving for wall thickness below 1¼ in. thick? Reply (3): Yes. Question (4): On fabrication that is stress relieved, are new physical tests required? Reply (4): No.



Interpretation 4-39

Subject: Paras. 400.1.2(g) and 422.3, Exclusion from Scope- Instrument Piping Date Issued: March 30, 1990 File B31-88-28C Question: Does ASME B31.4 require that the pressure containing portion of an in-line sensing device be designed, fabricated, examined, and tested in accordance with the rules of ASME B31.4? Reply: Yes. See, e.g., paras. 400.1.1, 400.1.2, and 422.3.



Interpretation 4-40

Subject: Longitudinal Stress Date Issued: March 30, 1990 File B31-89-031 Question: Does ASME B31.4 consider bending stress to be identical to longitudinal stress? Reply: Yes, but not necessarily in all cases.



Interpretation 4-41

Subject: Para. 451.6.2(b), Allowable Pipeline Repairs Date Issued: November 28, 1990 File B31-90-040 Question (1): Is the replacement of damaged pipe segments preferred over their repair in ASME B31.4? Reply (1): Yes, see paras. 451.6.2(b)(2) through (6). Question (2): If repair methods are used, is it the intent of ASME B31.4 that when it becomes “practical to take the pipeline out of service,” the repairs should be replaced with a cylindrical piece of pipe? Reply (2): No. Question (3): Mechanical spilt sleeves as repair devices are commonly used in the industry but are not covered by the above paragraphs as an acceptable repair method. Is it the intent of ASME B31.4 to exclude mechanical repair devices? Reply (3): No, see para. 451.6.2(c)(7).



Interpretation 4-42

Subject: Para. 418.1, Sleeve, Coupled, and Other Patented Joints Date Issued: November 28, 1990 File B31-90-041 Question (1): Under ASME B31.4, does the old edition of API 6D still apply to closures, connectors, etc.? Reply (1): ASME recognizes the 1988 Edition of API 6D as of August 8, 1990. Question (2): Is it the intent of para. 418.1(a) to require that the manufacturer of a mechanical split sleeve set and publish limits as to the amount of deformation a pipe can have for the joint to be used? Reply (2): No. Question (3): Is it the intent of para. 418.1 to have the joint tested and pressure rated by the manufacturer based on this amount of deformation? Reply (3): No. Question (4): Is it the intent of para. 418.1 to have the joints pressure tested and pressure limits specified? Reply (4): No. Question (5): Is it the intent of the Code to require weld up of mechanical split sleeves? Reply (5): No, see paras. 451.6.2(c)(1) and (2). Question (6): When these sleeves are welded, what are the Code requirements for welding them up? Reply (6): No, see paras. 451.6.2(c)(1) and (2).



Interpretation 4-43

Subject: Para. 451.6.2(a), Disposition of Defects-Limits and Dispositions of Imperfections

Date Issued: November 28, 1990 File B31-90-043 Question: Particularly since the U.S. Department of Transportation has some special requirements for general corrosion, does ASME B31.4 have definitions for “general corrosion” and “localized corrosion pitting”? Reply: No.



Interpretation 4-44

Subject: Para. 400.1.1, Scope Date Issued: November 28, 1990 File B31-90-048 Question: Does ASME B31.4 have a definition for gathering lines and if so what is it? Reply: No.



Interpretation 4-45

Subject: Para. 451.6.2(c)(6), Full Encirclement Welded Split Sleeves Date Issued: December 6, 1990 File B31-90-044 Question (1): Is there some provision in ASME B31.4 for how tightly full encirclement welded split sleeves must be installed? Reply (1): No. Question (2): Is a hardenable filler material required by ASME B31.4 for use with full encirclement welded split sleeves? Reply (2): No. Question (3): Is there a provision in ASME B31.4 which restricts the longitudinal weld of full encirclement welded split sleeves from penetrating into the base material of the pipe? Reply (3): No.



Interpretation 4-46

Subject: Para. 451.6.2(a)(7), Localized Corrosion Pitting Date Issued: December 6, 1990 File B31-90-047 Question (1): In light of the fact that the length versus depth corrosion pit limitations in para. 451.6.2(a)(7) are related to the length of the pit along the longitudinal axis of the pipe, are these criteria applicable if the corroded area of the pipe is subject to stresses in addition to the internal pressure (i.e., external pressure, seismic loading, subsidence, waves and currents, vibration, thermal expansion, etc.) Reply (1): Yes. Question (2): Is the nominal pipe wall thickness in para. 451.6.2(a)(7) the nominal pipe wall thickness of para. 404.1.1? Reply (2): Yes.



Interpretation 4-47

Subject: Para. 451.6.2(a)(7), Localized Corrosion Pitting Date Issued: December 6, 1990 File B31-90-049 Question: If the nominal wall thickness of the pipe, as defined in para. 404.1.1(a), is less than the actual thickness, does ASME B31.4 permit corrosion in the weld as long as the remaining thickness is equal to or exceeds the design thickness calculated in accordance with para. 404.1.2 decreased by an amount equal to the manufacturing tolerance applicable to the pipe or component? Reply: Yes.



Interpretation 4-48

Subject: ASME B31.4-1989 Edition, Para. 434.8.3(a); Welding Qualifications Date Issued: May 1, 1991 File B31-90-069 Question (1): Does ASME B31.4 allow welding procedures for pipelines to be qualified to standards other than API 1104? Reply (1): Yes. Question (2): Does ASME B31.4 allow welding procedures for auxiliary piping to be qualified to standards other than ASME Section IX? Reply (2): Yes.



Interpretation 4-49

Subject: ASME B31.4-1989 Edition, Para. 404.3.1(c)(2), Welded Branch Connections

Date Issued: May 1, 1991 File B31-91-010 Question: According to ASME B31.4, para. 404.3.1(c)(2), does an elbowlet fitting qualify as a “welding outlet fitting”? Reply: Yes.



Interpretation 4-50

Subject: ASME B31.4-1989 Edition, Para. 434.15.2(d), Mainline Valves Date Issued: December 9, 1991 File B31-91-032 Question (1): Is it the intent of ASME B31.4, para. 434.15.2(d) to require a check valve at each (and every) mainline block valve on LPG and liquid anhydrous ammonia pipelines? Reply (1): No. Question (2): If check valves are not required at each mainline block valve, are the following criteria appropriate in determining applicability?

(a) elevation and terrain features; (b) Proximity to other automatic block valves; (c) Pipeline operation (i.e., bi-directional flow requirement); (d) Etc.

Reply (2): Yes.



Interpretation 4-51

Subject: ASME B31.4-1979 Edition, Table 404.1.1, Least Nominal Wall Thickness Date Issued: December 9, 1991 File B31-91-040 Question: In the 1979 Edition of ASME B31.4, Table 404.1.1 contained “Least Nominal Wall Thickness for Steel Pipe.” However, in the 1986 and 1989 Editions the table has been deleted. When qualifying to the 1989 Edition, what provisions should be made? Reply: Use ASME B31.4-1989 Edition, para. 404.1.



Interpretation 4-52

Subject: ASME B31.4-1989 Edition, Para. 400(e), General Statements Date Issued: December 9, 1991 File B31-91-041 Question (1): A designer determines that a higher safety factor than specified in ASME B31.4 is desired for a particular application; is this allowed by ASME B31.4? Reply (1): Yes, see para. 400(e). Question (2): Are there guidelines in the ASME B31.4 for determining location classification? Reply (2): No.



Interpretation 4-53

Subject: ASME B31.4-1989 Edition, Para. 434.5(b)(3), Damage to Fabricated Items and Pipe

Date Issued: April 7, 1993 File B31-92-057, B31-93-002 Question: According to ASME B31.4-1989, para. 434.5(b)(3), are weld repairs allowed to be made to defects, such as notches, grooves, gouges, blowouts, etc., along the weld bevels of the longitudinal and circumferential ends? Reply: No.



Interpretation 4-54

Subject: ASME B31.4-1992 Edition, Para. 437.6.4, Determination of Weld Joint Factor

Date Issued: November 19, 1993 File B31-93-025 Question: According to ASME B31.4-1992 Edition, para. 437.6.4, for pipe over NPS 4, if the pipe is of unknown specification and weld joint, shall the weld joint factor E not exceed 0.80? Reply: Yes.



Interpretation 4-55

Subject: ASME B31.4-1992 Edition, Para. 435.5, Auxiliary Liquid Petroleum, Liquid Anhydrous Ammonia, or Liquid Alcohol Piping

Date Issued: May 31, 1994 File B31-93-056 Question: In accordance with ASME B31.4, para. 434.5(a), does B31.4 prohibit a manufacturer of full-encirclement welded split tees from repairing notches, grooves, gouges, and blowouts by welding? Reply: No.



Interpretation 4-56

Subject: ASME B31.4-1992 Edition, Para. 401.6, Weight Effects, Para. 402.3, Allowable Stresses and Other Stress Limits

Date Issued: April 23, 1997 File B31-93-054 Question: For an exposed submarine pipeline resting on the seafloor and where it can not be conclusively proven that hydrotesting has removed the longitudinal stresses due to pipeline route curvature, should the stress due to curvature be accounted for in the equivalent tensile stress calculation which is required to be less than 0.9 SMYS in the restrained section [para. 402.3.2(c)] and less than 75% of the allowable stress value [para. 402.3.2(d)]? Reply: Yes.



Interpretation 4-57

Subject: ASME B31.4-1992 Edition, Para. 434.8.6(a), Butt Welds, Fig. 434.8.6(a)-(2), Acceptable Butt Welded Joint Design for Unequal Wall Thickness

Date Issued: April 23, 1997 File B31-94-032 Question (1): Is it permissible to butt weld a weld neck flange made from material with a specified minimum yield strength of 35 ksi (for example, A 105) directly to Grade X60 pipe as long as the pressure class rating of the flange meets the design requirements? Reply (1): Yes. The inquirer is cautioned to review the requirements of para. 434.8.6 and Fig. 434.8.6(a)-(2). Question (2): Is it permissible to weld a slip-on flange made from material with a specified minimum yield strength of 35 ksi (for example, A 105) directly to Grade X60 pipe as long as the pressure class rating of the fitting meets the design requirements? Reply (2): Yes. Question (3): Is it permissible to weld a fitting made from material with a specified minimum yield strength of 35 ksi (for example, A 105) directly to Grade X60 pipe for all other types of weld joints except butt welds (e.g., as a branch connection attached with a full penetration groove corner joint) as long as the pressure class rating of the fitting meets the design requirements? Reply (3): Yes.



Interpretation 4-58

Subject: ASME B31.4-1992 Edition, Requirements for Reconverting a Steel Pipeline’s Function

Date Issued: April 23, 1997 File B31-94-054 Question: Under ASME B31.4-1992 Edition, are there any requirements for reconverting a steel pipeline, originally used for liquid transportation, back to liquid transportation after being used for several years for gas transportation? Reply: No, there is no requirement under B31.4-1992 Edition.



Interpretation 4-59

Subject: ASME B31.4-1986 Edition, Fully Welded Partial Encirclement Half Soles in an Oil Pipeline

Date Issued: April 23, 1997 File B31-97-006 Question: Is the installation of half soles on an X-42 pipeline constructed in 1965 acceptable to ASME B31.4-1986? Reply: No.



Interpretation 4-60

Subject: ASME B31.4-1992 Edition, Para. 406.2.2, Mitered Bends Date Issued: April 23, 1997 File B31-97-007 Question (1): What is the basis of para. 406.2.2? Reply (1): The inquirer is referred to para. 400 for the purpose and principles of the Code. Question (2): Does the limitation of 20% of the yield apply even if a full analysis has been carried out? Reply (2): Yes. Refer to para. 400(e). Question (3): Would a successful finite element analysis of the pup piece be considered acceptable in lieu of compliance with para. 406.2.2? Reply (3): Yes. Refer to para. 400.



Interpretation 4-61

Subject: ASME B31.4-1986 Edition, Para. 419.7.3(b), Expansion and Flexibility Analysis, Fig. 419.6.4(c), Flexibility Factor k and Stress Intensification Factor i

Date Issued: April 23, 1997 File B31-97-008 Question: Is the stress intensification factor calculation shown in Fig. 419.6.4(c) for welding tees applicable for extruder outlet headers? Reply: Figure 419.6.4(c) does not address extruded outlet headers.



Interpretation 4-62

Subject: ASME B31.4-1986 Edition, Certification of a Listed Material to Another Listed Material Specification

Date Issued: August 29, 1997 File B31-94-035 Question: Is it permissible under the requirements of the above mentioned Code for a steel service center/ processor to certify a Listed Material to another Listed Material specification by using the chemical analysis performed by the material manufacturer (the mill) and physical test performed by the service center or the manufacturer and provided all test results, method and process of manufacture, heat treatment, and quality control meet the requirements of material specification in question and meet the requirements of this Code. Reply: No.



Interpretation 4-63

Subject: ASME B31.4-1992 Edition, Temperature Limitations for Underground Ethylene Pipelines

Date Issued: August 29, 1997 File B31-94-047 Question (1): Do the corresponding chapters (materials, welding, design, installation, and testing) of ASME B31.8 also apply to underground ethylene pipelines? Reply (1): No. ASME B31.4 is the appropriate Code for ethylene pipelines. Question (1b): Except as specified in this Code, are there any extra regulations which should be followed for the safety considerations of ethylene transmission? Reply (1b): The ASME B31.4/11 Section Committee cannot respond to questions concerning other regulations. Question (2) Should cathodic protection measures be taken for underground ethylene pipelines in soil with low resistivity less than 10 Ω-m?

Reply (2): Yes. Refer to ASME B31.4, Chapter VIII. Question (3): Does ASME B31.4 have temperature limitations for underground ethylene pipeline transmission? Reply (3): No.



Interpretation 4-64

Subject: ASME B31.4-1992 Edition, Fig. 434.8.6(a)-(2), Acceptable Butt Welded Joint Design for Unequal Wall Thicknesses, Note (1)

Date Issued: August 29, 1997 File B31-95-051 Question (1): Is it the intent of the Code that the 3/32 in. dimension shown in Fig. 434.8.6(a)-(2), sketch (a) is nominal dimension? Reply (1): Yes. Question (2): Is the mismatch requirement of sketch (a) met when welding two adjoining pipe ends ordered to API 5L with the same diameter and nominal wall thickness as long as the difference between the maximum and minimum wall thickness does not exceed 3/32 in.? Reply (2): Yes. Question (3): Is the mismatch requirement of sketch (a) met when welding two adjoining pipe ends ordered to API 5L having the same diameter and nominal wall thickness if the mismatch (difference between the maximum and minimum wall thickness) exceed 3/32 in.? Reply (3): Yes. Question (4): Is the mismatch requirement of sketch (a) met when welding two adjoining pipe ends ordered to API 5L, having the same nominal diameter but different nominal wall thickness (one pipe is nominally greater than 3/32 in. thicker than the other)? Reply (4): No. Correction in accordance with sketch (b), (c), or (d) is required.



Interpretation 4-65

Subject: ASME B31.4-1992 Edition, Para. 451.6.2(a)(7), Disposition of Defects Date Issued: August 29, 1997 File B31-97-005 Question (1): According to ASME B31.4-1992 Edition, para. 451.6.2(a)(7), is the significance of the depth of corrosion pits located in girth or longitudinal welds or related heat affected zones to be evaluated to the same criteria as corrosion pits in the base pipe (i.e., must be deep enough to reduce the wall thickness below the design thickness less the manufacturing tolerances in order to warrant repair, replacement, or operating pressure reduction)? Reply (1): Corrosion pit depth in welds is not presently addressed in ASME B31.4-1992 Edition. Question (2): According to ASME B31.4-1992 Edition, para. 451.6.2(a)(7), is the depth of a corrosion pit located in girth or longitudinal welds or related heat affected zones to be evaluated relative to the nominal pipe wall thickness (i.e., ignoring weld reinforcement)? If so, should the corrosion pit depth be measured from the top of the weld reinforcement or from the location where the corrosion pit intersects the extension of the plane of the surface of the pipe? Reply (2): Corrosion pit depth in welds is not presently addressed in ASME B31.4-1992 Edition. Question (3): According to ASME B31.4-1992 Edition, para. 451.6.2(a)(7), are corrosion pits of significant depth (i.e., deep enough to reduce the wall thickness below the design thickness less the manufacturing tolerance, but less than 80% of nominal wall thickness) that are located in girth or longitudinal welds or related heat affected zones, cause for line repair, replacement, or operation at reduced pressure regardless of their length? Reply (3): Corrosion pit depth in welds is not presently addressed in ASME B31.4-1992 Edition.



Interpretation 4-66

Subject: ASME B31.4-1992 Edition, Para. 401.2.2, Internal Design Pressure, Para. 404.1.2, Straight Pipe Under Internal Pressure, Para. 402.3, Allowable Stresses and Other Stress Limits

Date Issued: August 29, 1997 File B31-97-011 Question (1): Does the statement in para. 401.2.2, “Credit may be given for hydrostatic external pressure, in the appropriate manner, in modifying the internal design pressure for use in calculations involving the pressure design of piping components (see para. 404.1.3),” also apply to the formula in para. 404.1.2 for subsea systems? Reply (1): Yes. Question (2): May hydrostatic external pressure be accounted for in calculations involving the internal pressure design of piping components? Reply (2): Yes. Question (3): Is it possible to incorporate “Maximum Distortional Energy Theory (von Mises Combined Stress)” in para. 402.3? Reply (3): No.



Interpretation 4-67

Subject: ASME B31.4-1992 Edition, Mill Certificates, Para. 402, Design Criteria, Para. 436, Inspection

Date Issued: August 29, 1997 File B31-97-023 Question: Does the Code require Mill (material) Certificates – chemical composition - for the line pipe and its components to be provided as part of the specification? Reply: No.



Interpretation 4-68

Subject: ASME B31.4-1998 Edition, Para. 406.2, Bends, Miters, and Elbows Date Issued: February 15, 2000 File B31-00-058 Question (1): Are Single Joint miter bends of an angle up to 12.5 deg permissible in systems to be operated at a hoop stress between 10% and 20% of the specified minimum yield strength of the pipe? Reply (1): Yes. Question (2): Does the requirement “and the minimum distance between miters measured at the crotch shall not be less than one pipe diameter” imply that a miter bend should be made up of a minimum of two joints even when the miter bend angle is within 12.5 deg? Reply (2): No. Question (3): Is the “angle of miter bend” referred to in ASME B31.4, para. 406.2.2 the same as the angle θ shown in ASME B31.4, Fig. 419.6.4(c)? Reply (3): Yes.



Interpretation 4-69

Subject: ASME B31.4-1998 Edition, Para. 400.1.1(c), Scope; and Fig. 400.1.1, Diagram Showing Scope of ASME B31.4 Excluding Carbon Dioxide Pipeline Systems

Date Issued: February 15, 2000 File B31-00-059 Question: Does ASME B31.4 specify minimum required width or other limitations for corridors referred to in Fig. 400.1.1? Reply: No.



Interpretation 4-70

Subject: ASME B31.4-1998 Edition, Para. 423.1, Acceptable Materials; and Table 423.1, Materials Standards

Date Issued: February 22, 2000 File B31-00-060 Question: Is it permissible to use API 5L Grade X80 pipe in pipeline systems designed in accordance with ASME B31.4? Reply: Yes.



Interpretation 4-71

Subject: ASME B31.4-1998 Edition, Para. 437.4.3, Leak Testing Date Issued: February 23, 2000 File B31-00-061 Question: Do the limitations on hydrostatic test media for proof testing in para. 437.4.1(c) apply to leak testing, para. 437.4.3? Reply: Yes.



Interpretation 4-72

Subject: ASME B31.4-1998 Edition, Fig. 434.8.6(a)-(2), Acceptable Butt Welded Joint Design for Unequal Wall Thickness

Date Issued: November 13, 2000 File B31-00-062 Question (1): Does General Note (a) of Fig. 434.8.6(a)-(2), which states that “the sketches in Fig. 434.8.6(a)-(2) illustrate acceptable preparations for joining pipe ends having unequal wall thicknesses and/or materials of unequal specified minimum yield strength by butt welding.” Mean that the examples are acceptable preparations for joining pipe ends having unequal specified minimum yield strength by butt welding. Reply (1): Yes. Question (2): Does General Note (b) of Fig. 434.8.6(a)-(2), requiring that the thickness of the pipes to be joined, beyond the joint design area, comply with the design requirements of the Code, also apply to the tapered portion of the pipe within the joint design area? Reply (2): No. Question (3): Is it permissible to weld a 12.75 O.D. x 0.500 w.t. API 5L X46 pipe directly to a 12.75 in. O.D. w.t. API 5L X60 pipe, without a transition nipple, per detail (b) of Fig. 434.8.6(a)-(2)? Reply (3): Yes.



Interpretation 4-73

Subject: ASME B31.4-1998 Edition, Paras. 434.7.1 and 437.4.1 Date Issued: March 22, 2001 File B31-01-006 Question: If a section of pipe meets the following requirements: pretested for use as a replacement pipe in accordance with section 437.4.1 of B31.4; then cold bent in accordance with section 434.7.1 of B31.4; and complies with the quality requirements of section 434.7.1 of B31.4; does the pipe bend need to be retested in accordance with section 437.4.1 of B31.4 after completion of the bend? Reply: No.



Interpretation 4-74

Subject: ASME B31.4-1998 Edition, Para. 401.2.2, Internal Design Pressure Date Issued: March 23, 2001 File B31-01-007 Question: May a piece of pipe that has been subjected to a hydrostatic test by a manufacturer to a pressure level less than or equal to 1.25 times its design pressure as per paragraph 401.2.2 for a period of less than 4 hr be subjected to a hydrostatic test in the field to a pressure level of 1.25 times its design pressure for a period of 4 hr or more? Reply: Yes.



Interpretation 4-75

Subject: ASME B31.4-1998 Edition, Para. 409, Used Piping Components and Equipment

Date Issued: March 22, 2001 File B31-01-008 Question: May B31.4 be interpreted to consider an existing pipeline built per B31.8 as “used” in accordance with para. 405.2.1(b) or (c) and para. 409 of B31.4 and then operated at an operating pressure established in accordance with paragraph 451.1 of B31.4? Reply: Yes.



Interpretation 4-76

Subject: Request for Interpretation of Pipe Design Conditions from ASME B31.4 1989 Edition

Date Issued: June 12, 2002 File 02-3680 Question: Is it right, that the equation defined under clause 404.1 of the ASME Code B31.4 (tn=t+A) fully covers the negative pipe wall thickness tolerances as defined in API 5L. Therefore the minus tolerance as permitted by API 5L does not have to be deducted from the nominal pipe wall thickness used for calculation of allowable internal pressure. Reply: Yes.



Interpretation 4-77

Subject: ASME B31.4 Item 411-02-02- Interpretation of Sections 434.8.5, 437, and 421.1

Date Issued: December 19, 2002 File 02-2486 Question (1): Should the reference to operating above 20% SMYS in 421.1 (d) actually reference operating at a hoop stress of more than 20% SMYS? Reply (1): Yes. Question (2): Does the reference of hoop stress in sections 434.8.5 (a) (4) and 437.1.4 (a) (2) & (3) and 437.4.1 (a) mean only the circumferential stress due to internal pressure as calculated in 404.1.2? Reply (2): Yes.



Interpretation 4-78

Subject: ASME B31.4 Item 411-02-03- Interpretation of Section 434.8.5 Date Issued: December 19, 2002 File 02-2487 Question (1): Are there NDE inspection requirements in para. 434.8.5 (a) (4) for pipelines to be operated at a hoop stress of 20% or less of SMYS? Reply (1): No, see para. 436.5 for Inspection requirements. Question (2): Do the requirements for complete inspection of girth welds in the locations or conditions detailed in 434.8.5 (a) (4) (a-f) apply only for pipelines to be operated at a hoop stress of more than 20% of SMYS? Reply (2): Yes.



Interpretation 4-79

Subject: ASME B31.4 Item 411-02-01- Interpretation of Sections 434.13.4 (c) and 451.9 (a).

Date Issued: December 19, 2002 File 03-331 Question (1): Should the design factor for the use in API 1102 4.8.2 Checks for Fatigue, be the same as the design factor in B31.4 402.3.1? Reply (1): Yes. Question (2): Should the references to circumferential stresses and total stress in Section 451.9 (a) actually be references to effective stress as per Section 434.13.4 (c)? Reply (2): Yes.



Interpretation 4-80

Subject: ASME B31.4 Item 02-03681- Interpretation of Section 451.6.2 (b)(3) Date Issued: February 20, 2003 File 02-3681 Question: Does B31.4 (1998 Ed. As revised) permit repairing a scratch, gouge, or groove in a dent by grinding the scratch, gouge or groove out to a smooth contour and evaluating the resulting metal loss similarly to metal loss from corrosion? Reply: No.



Interpretation 4-81

Subject: ASME B31.4 Item 02-03682- Interpretation of Section 404.1.2 Date Issued: February 20, 2003 File 02-3682 Question: Does the design factor include allowance for residual stresses that may be present in the pipes manufactured in accordance with API 5L, specifically Helical Seam Submerged Arc Welded Pipes? Reply: Yes.



Interpretation 4-82

Subject: ASME B31.4 - Paragraph 451.6.2 (a)(7) equation Date Issued: January 16, 2006 File 05-1581 Question (1): For equation found under 451.6.2 (a)(7), does then defect length “L” represent the length of the defect measured longitudinally along the pipeline axis or can it be measured circumferentially? Reply (1): No, “L” cannot be measured circumferentially. Question (2): If a defect in a pipeline is 3/8 inches along the pipeline axis but 14 inches circumferentially, can equation found under 451.6.2 (a)(7) be applied using the circumferential length of the defect to represent the parameter “L” in the equation? Reply (2): No, the parameter “L” remains 3/8 inch.



Interpretation 4-83

Subject: B31.4-2006: Interpretation paragragh 423.2.3 Date Issued: January 25, 2008 File 07-1458 Question: If ASTM A 106 pipe is operating over 7,000 psi (20% of 35,000 psi), shall the material be impact tested? Reply: Yes.



Interpretation 4-84

Subject: B31.4-2006: Injection Flow Lines Interpretation Date Issued: February 12, 2008 File 07-1459 Question (1): Are flow lines between oilfield injection wells and oilfield injection facilities excluded from the Scope of ASME B31.4? Reply (1): No. Question (2): Are flow lines between oil production wells and oilfield separation facilities excluded from the scope of ASME B31.4? Reply (2): No.



Interpretation 4-85

Subject: B31.4-2006: Interpretation of Paragraphs 421.1 (d) and 423.2.3 Date Issued: March 25, 2008 File 08-417 Question: In 421.1 (d) and 423.2.3 does 20% SMYS refer to the hoop stress? Reply: Yes.



Interpretation 4-86

Subject: ASME B31.4-2006 Edition, Para. 434.8 Date Issued: October 20, 2009 File 09-1450 Question (1): Is it the intention of B31.4-2006, paragraph 434.8, that the pipeline owner/operator supply the contractor with the owner’s pre-qualified Welding Procedure Specification and Procedure Qualification Record for use on a project? Reply (1): No. Question (2): Is it acceptable per B31.4 for the contractor to perform welding on a pipeline/metering station using his own previously qualified Welding Procedure Specification if all of the essential variables are the same? Reply (2): Yes, provided that the procedure is approved by the owner, para. 434.8.3(b)(2).



Interpretation 4-87

Subject: B31.4 Interpretation Pig Launcher Receiver Inquiry Date Issued: June 7, 2010 File 10-809 Question: Does any part of a pig launcher/receiver need to be stamped in accordance with Section VIII, Divisions 1 or 2? Reply: No. Please see paragraphs 404.7.1 and 404.7.3 of B31.4-2009.



Interpretation 4-88

Subject: B31.4 Interpretation - Clause 402.3 and 403.2.1 of B31.4-2009 Date Issued: July 28, 2010 File 10-1154 Question (1): Should the hoop stress be calculated per Para, 402.3 of B31.4-2009? Reply (1): Yes. Question (2): Should the nominal wall thickness be calculated per Para. 403.2.1? Reply (2): Yes.



Interpretation 4-89

Subject: B31.4-2009 Interpretation on Para.423.2.3 and Table 423.1-1 Date Issued: September 29, 2010 File 10-1604 Question: In B31.4-2009, is impact testing only mandatory for the materials listed under “Pipe” in Table 423.1-1? Reply: Yes.

asme b31.4 section committee interpretations

Documents

hoop stress

shear stress

allowable stress

stress intensity

net longitudinal stress

term equivalent tensile

asme committee use

asme committee business