b31.1 interpretations 1.pdf

Interpretations No. 1 to ANWASME B31.1

(This supplement is not part of ANSVASME B31.1. It is included for information only.)

It has been agreed to publish Interpretations issued by the B31 Committee concerning B31.1 as part af the subscription service. This supplement incliudes Interpretations concerning B3 1.1 issued tetween January 1, 1980, and June 30, 1982. Future versions of this supplement will cover inquirieS i:isued over 6-month periods. Each Interpretation applies to the latest Edition or Addenda at the tnme of issuance of the Interpretation. Subseque~lt revisions to the Code may have superseded the r~eply.

B3 1.1 Interpretations No. 1

Interpretation: 1-1

Subject: Use of Antiblowback Device

Dated Issued: January 2 1, 1980

File: 1422

Inquiry: The term "antiblowback device'!' appears in Para. 5.6 of Appendix I1 of ANSI/ASME '

B3 1.1. What is the recommended device, and what are the regulations pertaining to the installation of such a device?

Reply: It is the opinion of the Committee that the selection and design of a discharge piping system from a safety valve shall be in accordance with the recommendations stated in Para. 122.6.2 of ANSI/ASME B3 1.1. The Committee is awiire of installations that can be provided that preclude the blowback of the relieving fluid, such as shown in Appendix 11, Fig. 1-2(B), and another as described in Para. 106.4(C), as well as specifically designed devices that permit a minimum of blowback.

However, the selection of the device or system most appropriate for an installation is left to the designer, as it is not the responsibility of the Cammittee. Additional information and recommendations may be available from the manufacturer of the safety valve.

Interpretation: 1-2

Subject: Use of ASTM A 53 and A 106

Date Issued: January 21, 1980

File: 1437

Inquiry: The ASA B3 1.1- 1955 Code for Pressure Piping limits the use of ASTM A 53 to 600 psig and ASTM A 106 to 2500 psig. No such llimitations appear in the current ANSI/ASME B3 1.1. Please clarify.

Reply: It is the opinion of the Committee that the current ANSI/ASME B31.1 permits the use 3f ASTM A 53 and A 106 as long as the requirements of 102, 104, 105.2.1, 122, and Appendix A ,are met. These referenced sections contain limiuations, but none as stated in the Inquiry.

It should be noted that ASTM specifies A 53 pipe to be made as seamless, furnace butt 'welded, or electric resistance welded pipe. The maximum allowable stress values of these products ;ire not the same for all these manufacturing processes and therefore must be analyzed separately lor each installation.


Interpretation: 1-3

Subject: Required Examination I

Date issued: March 24, 1980

File: 1433

Inquiry: When a weld, required by ANSI/ASME B31.1 to be examined only by visual means, is radiographed and found to contain defects greater than permitted by the RT acceptance standards, what NDE is required by the Code after the unacceptable defects have been removed and the weld repaired?

Reply: It is the opinion of the Committee that the method of examination and the limits of im~rfections for a repaired weld shall be the same as required by the Code or contract for the original weld. In the instance stated in the Inquiry, the repaired weld need meet only the visual acdeptance standard that was required of the original weld.

Interpretation: 1-4

Subject: Welding Requirements

Date Issued: April 14, 1980

File: 1440

Inquiry (1): Is it a mandatory requirement of ANSI/ASME B31.1 for the welding of the outer edge of the branch reinforcing pads to the pipe and the welding of pipe supports to the pipe, to be done only by qualified pipe welders?

Reply (2): It is the opinion of the Committee that welding of the outer edge of a branch reinforcing pad to the pipe and the welding of pipe supports to the pipe 'must be done by welders qualified in accordance with Section IX of the ASME Boiler and Pressure Vessel Code.

Inquiry (2): Does a welder who welds the outer edge of a reinforcing pad to the pipe need a fillet weld qualification, or can this weld be made by a welder with only a butt weld qualification?

Reply (2): The Committee wishes to advise that a welder who is qualified to make groove welds (butt welds) is also qualified to make Wet welds. However, a welder qualified to make fillet welds is not qualified to make groove welds.

Inquiry (3): Can a project specification specify a particular issue of the Code and, in addition, specify more rigid requirements for certain parts of the Code?

Reply (3): It is the opinion of the Committee that the Code prescribes minimum requirements for the design, materials, fabrication, erection, test, and inspection of certain piping systems. Where a project specification contains more rigid requirements than are contained in the Code, the more rigid requirements are a contractual matter between the contracting parties.


Interpretation: 1-7

Subject: Use of Tubing and Use of ASTM: A 179 Material

Date Issued: May 6, 1980

Inquiry: According to ANSI/ASME B31.1, what thickness of tubing is required for use in fuel oil systems? Is a safety factor of 4 adequate to calculate the wall thickness for ASTM A 179 material?

Reply: It is the opinion of the Committee that ANSI/ASME B31.1 permits the use of steel tubing having a wall thickness adequate for the design conditions and assembled with tubing fittings for fuel oil systems. The Code in Para. 115 prescnibes minimum requirements for tubing fittings.

The Code is sufficiently clear in Para. 104 in describing the basis for continuous service at the design pressure. Operating variances, that cause an increase in stress to a level higher than the allc,wable stress value for ASTM A 179 in Table A-1 of Appendix A, are limited, and are defined in l'ara. 102.2.4. Operation in excess of these variances is unsafe and is not permitted by AK SI/ASME B3 1.1.

Subject: Table 136.4, Mandatory Minimunn Nondestructive Examinations

Dale Issued: May 6, 1980

File : 1441

Inquiry: When a welded joint similar to Fig. 127.4.2 of ANSI/ASME B31.1 has a thickness greater than W in. which requires radiographic exiunination per Table 136.4, can the requirements for RT examination be waived if the design calculated thickness based upon the pressure and temperature conditions for the welded joint is less than 94 in.?

Reply: It is the opinion of the Committee that the mandatory minimum nondestructive RT examination requirements of Table 136.4 relative to pressure welds or welds to pressure retaining components, as stated by the conditions for examiriation shown for the type of weld, cannot be wailfed to suit a calculated lesser thickness dimension based upon the design pressure and tem~erature conditions.


Interpretation: 1-5

Subject: Stress Analysis of "Y" Connections


File: 1432

Inquiry: What are the flexibility factors, i factors, and associated parameters governing the stress analysis of "Y" connections to the requirements of ASME/ANSI B31.11

Reply: It is the opinion of the Committee that there are no accepted or published stress intensification or flexibility factors for "Y"-branch connection designs other than those for right angle branch connections as shown in Appendix D of the Code. This Committee ii cognizant of the absence of design factors for nonright angle branch connections and is attempting to develop this data.

ANSI/ASME B31.1 does not prohibit the use of Y-fittings. Pending the development of design rules, the Code in Para. 104.3.1(A) permits as a guide the application of the rules for the design of branch connections presented in Para. 104.3.1.

Further, it is recommended, in view of the absence of a specific design procedure, that an evaluation be made of the Y-fitting in accordance with the requirements described in Para. 104.7.

Interpretation: 1-6

Subject: Qualification of Personnel Performing Visual Inspection


File: 1438

Inquiry: Are personnel performing visual examination on boiler external piping required to be qualified and certified in accordance with Para. 136.1 of ANWASME B3 1. l?

Reply: It is the opinion of the Committee that personnel performing visual examination on boiler external piping shall be qualified and certified in accordance with Para. 136.1 of ANWASME B3 1.1.

Refer to PG-58.3 of Section I of the ASME Boiler and Pressure Vessel Code, which states that testing for boiler external piping shall be in accordance with ANWASME B31.1.


Interpretation: 1-9

Subject: Materials for Use in Compression Type Fittings of Proprietarj Design


File: 1439

Inquiry: Is it the intent of ANSI/ASME B3 1.1 that materials not listed in, Table 126.1 be permitted for use in compression type fittings of proprietary design?

Reply: It is the opinion of the Committee: that compression type fittings of proprietary design made from materials not listed in ANSI/ASME B3 1.1, Table 126.1, are acceptable for B3 1.1 construction provided all the conditions of Para. 115 are met.

Interpretation: 1-10

Subject: Para. 127.6, Qualification Records


File: 1448

Inquiry: What method shall be used by a welder or welding operator when applying his assigned symbol to permanently identify his work as required in Para. 127.6? Is the method ~utlined in NB-215 1.1 of the ASME Boiler ancl Pressure Vessel Code, Section 111, an acceptable method?

Reply: The Committee wishes to advise that the Code does not specify how a welder or 'welding operator shall apply his symbol to his work, other than that it is to be applied in a manner !specified by his employer. The method of marking, therefore, becomes a matter of agreement Ixtween the contracting parties. One acceptable method of marking may be that described in Para. IVB-215 1.1 of the ASME Boiler and Pressure Vessel Code, Section 111. There are other acceptable methods.



Subject: Table 132, Postweld Heat Treatment

Date Issued: June 17, 1980

File: 1418

Inquiry (1): In Table 132 of ANSI/ASME B31.1, is the term "material thickness" synonymous with the term "nominal thickness"?

Reply (2): No, "material thickness" is one of the factors involved with "nominal thickness," but it is not synonymous.

Inquiry (2): Is the term "attachment welds" in Table 132 limited to structural support, and not including "branch connections"? Similarly, in Table 132 for P-No. 1 materials under Note (l)(B), should partial or complete penetration grooved attachment welds have the same exemptions to PWHT as do "branch welds" or "fillet welds"?

Reply (2): "Attachment welds," as they are used in Table 132 [reference P-Nos. 4 and 5, Note (l)(A)], refer to the welds between pressure components and nonpressure components. However, "Welds in Pipe" would include "branch connections."

For P-No. 1 materials, partial or complete penetration grooved attachment welds fall under the exemption rules of Table 132, Note (I)@), if the weld thickness does not exceed % in.


Subject: Rules for Soldered and Brazed Joints


File: 145 1

Inquiry: What are the requirements of ANSI/ASME B31.1 regarding silver soldered joints in a copper steam line operating at 125 psi?

Reply: It is the opinion of the committee that the rules for soldered and brazed joints, which include silver, can be found in 1 17 and 128 of ANSI/ASME B3 1.1.

Also, refer to Para. 105.2.2(A) of the Code regarding limitations on nonferrous (copper) pipe.

E;3 1.1 Interpretations No. 1


Subject: Welds Connecting Systems Covered by Different Codes

Date Issued: July 8, 1980

F'ile: 143 1

Inquiry: If a piping system falls within the scope of ANSI/ASME B31.1 and is attached to a piping system or a vessel, the construction of which is within the scope of another Code, which Clode governs the requirements of the weld conr~ecting the two systems?

Reply: It is the opinion of the Committee t.hat the weld connecting the two systems shall comply with the requirements of ANSI/ASME B31.1 unless there are specific rules in the other Clode governing the making of the connecting weld.

Eaterpretation: 1-14

Subject: Para. 104.3.1 (D.2.2) Reinforce:ment Area in Branch Connections


File: 1387

Inquiry: Is it the intention of the ANSI/ASME B31.1 Code that the corrosion allowance be ir~cluded in the t,, factor for the required reinforcement area in branch connections as stated in Para. 104.3.1 @.2.2)? Past Editions of the Code have indicated that the corrosion allowance be excluded from the minimum required wall thickness factor t,,.

Reply: It is the opinion of the Committee that when determining the required reinforcement area by the equation in Para. 104.3.1 @.2.2), the worst case dimension of t,, should be considered. 111 doing so, the corrosion allowance should be subtracted from t,, to comply with the corrosion/erosion consideration of Para. 104.3.1 (D.2) in order that the required reinforcement area represent the condition of the header at the end of its expected corrosive service life.



Subject: Para. 123.2.8, Nonmetallic Pipe

Date-Issued: July 28, 1980

File: 1421

Inquiry: May flanges that consist of MIL-P-997, "Micarta" material be used in ANSI/ASME B3 1.1 construction?

Reply: It is the opinion of the Committee that safe design and selection of material such as "Micarta" is not specifically excluded from ANWASME B3 1.1 for specialized piping applications (ref. Para. 123.2.8), although it is not an approved material.

However, a nonstandard pressure containing component can be designed for use in an ANSI/ASME B31.1 piping system, provided the requirements of Para. 104.7 are met.


Subject: Para. 136.4.2, Visual Examination


File: 1456

Inquiry: What are the nondestructive examination requirements for seal welds or threaded connections of thermocouples, radiographic opening plugs, etc., in pressure retaining components in ANSI/ASME B3 1.1 construction?

Reply: The Committee wishes to advise that Para. 136.4.2 requires all welds to be examined visually and to meet the visual acceptance standards of Para. 136.4.2(A).



Subject: Size Limitations for Couplings in Para. 104.3.1.

Date Issued: August 18, 1980

File: 1419

Inquiry (a) Does Para. 104.3.1(C.2) of ANWASME B3 1.1 prohibit the use of 2% in. and 3 in.

couplings? (b) Does Para. 104.3.1(C.2) prohibit constructions not in accordance with the ?A diameter

rule (such as NPS 34 and NPS 1 couplings installed on a 2 in. header pipe) when supporting calculations in accordance with Para. 104.3.10) or 104.3.1(E) indicate that sufficient (reinforcement) material has been provided?

Reply: It is the opinion of the Committee that the size limitation for couplings used as branch connections is adequately stated in Para. 104.3.1(B.2), which limits their size to NPS 3. Constructions using couplings or half couplings as branch connections which are larger than NPS 2 (not to exceed NPS 3 per above), and not within the % diameter rule, are required to meet the reinforcement requirements of Para. 104.3.1 (D) or 104.3.2(E).


Subject: Miters


File: 1447

Inquiries (1) Please provide the basis for rules for miters contained inpara. 104.3.3 of ANSI/ASME

B31.1-1977. (2) Do you have records to indicate satisfactory operation of similar installations? (3) Please give advice on continued operation of a piping system containing miters with a

thickness of 0.562 in., although the rules require a thickness of 0.716 in.

Replies (1) Although the inquiry letter referred only to ANWASME B31.1-1977, it should be

noted that Para. 104.3.3 was extensively revised by the Summer 1977 Addenda to the Code.

The basis for the revised requirements was a paper authored by E.C. Rodabaugh and published as Bulletin #208 by the Welding Research Council in August 1975. The title of the paper was "Review of Data on Mitre Joints in Piping to Establish Maximum Angularity for Fabrication of Girth Butt Welds."

(2) The Committee does not maintain historical or operational files which would allow us to answer this question.

(3) The Committee cannot answer questions of this nature since to do so would place us in the role of consultants.



Subject: External Weld Reinforcement


File: 1468

Inquiry: For welds in Boiler External Piping built to ANSI B31.1-1973 with Addenda through Winter 1974, may external weld reinforcement be added, in accordance with Paras. 127.3.1(A.3) and 127.4.2p.2) in order to ensure that the finished wall thickness after welding is not less than the minimum design thickness, although the required Form P4A, Manufacturer's Data Report for Fabricated Piping (Note 5), states that the construction complies with the ASME Boiler and Pressure Vessel Code, Section I, PW-41?

Reply: It is the opinion of the Committee: (a) that external weld reinforcement may not be utilized in order to ensure that the finished

wall thickness after welding is not less than the minimum design thickness. Paragraph 100.2 defines Reinforcement of Weld as "Weld metal on the face of a

groove weld in excess of the weld metal necessary for the specified weld size." Since weld reinforcement is defined as that weld metal in excess of the minimum, it cannot be utilized to meet the minimum requirements.

However, Para. 127.3.1(A.3) provides "where necessary, weld of the appropriate analysis may be deposited on the inside or outside of the piping component to provide sufficient material for machining to insure satisfactory fitting of rings." Such welds, and the welding processes utilized in the deposition of the weld metal, must meet all provisions of this ANSI B31.1 including, but not limited to, avoidance of abrupt changes in weld profile, preheat and postheat treatment, etc.

(b) that the rules for materials, design, fabrication, installation, and testing of Boiler External Piping were transferred from ASME Boiler and Pressure Vessel Code, Section I to ANSI B31.1 by the Summer 1972 Addenda to ASME Boiler and Pressure Vessel - Code, Section I.

(c) that ASME Boiler and Pressure Vessel Code, Section I, PW-41 does not apply to Boiler External Piping, since the Summer 1972 Addenda to that Code added the following paragraph to PW-4 1 :

The rules in the following paragraphs apply specifically to the boiler proper and parts thereof.

8 3 1.1 Interpretations No. 1


Subject: Pneumatic Control Piping

Date Issued: September 25, 1980

File: 1445

Inquiry: Does pneumatic control piping fall within the scope of ANSI/ASME B31.1?

Reply: It is the opinion of the Committee that pneumatic control piping, when located in any of the plants mentioned in Para. 100.1.1 and not excluded by Para. 100.1.3, is included in the scope of ANSI/ASME B3 1.1.

Therefore, the piping should not only be inspected as per ANWASME B3 1.1, but should also follow the Code with respect to design, material, fabrication, erection, and test.


Subject: Use of Check Valves in Safety Relief Valve Discharge Lines

Date Issued: October 6, 1980

File: 1397

Inquiry: May a check valve be used in safety relief valve discharge lines where it is desirable to jlimit the reverse flow of hazardous fluids during maintenance work in ANWASME B3 1.1 piping?

Reply: It is the opinion of the Committee that the use of check valves in safety relief valve discharge lines is not prohibited. However, Para. 122.6.2(A) specifically prohibits the use of stop valves, in this service, while not currently defining stop valves. The Committee interprets this as reflective of a concern that safety relief valve discharge piping not be obstructed during the time when it may be necessary to obtain pressure relief. It is known that check valves have the potential to jam or corrode and become inoperative or, as a minimum, to restrict flow. Therefore, use of a check valve in a safety relief valve discharge line is not recommended practice, except under special conditions and appropriate controls.



Subject: Addition of ASTM A 194 Materials to Table 126.1

ate Issued: October 6, 1980

File: 1436

Inquiry: Would the Committee consider adding ASTM A 494 Grades CZ-100, M-35, N-12M-1, N-12M-2, CY-40, CW-12M-1, and CW-12M-2 to the list of acceptable cast materials in Table 126.1 of ANSI/ASME B31.1? What allowable stress values shall apply?

Reply: Allowable stress values for materials accepted by this Committee are taken from the ASME Boiler and Pressure Vessel Code, Section I or Section VIII, Division I, or are established by reference to an ASTM specification for equivalent material when values for the equivalent material are shown in Section I or Section VIII, Division I. In the absence of published allowable stress values for ASTM A 494 material, or equivalent material in ASME Section I or Section VIII, Division I, it is the opinion of the Committee that this material is unacceptable for ANSI/ASME B3 1.1 components.

ASME Section VIII has published Code Case 1349-1 which permits the use of and lists allowable stress values at temperature for ASTM A 494-76 Grade CW-12M-1 only. The Committee is presently considering approval of a Case based on the ASME Section VIII Case. In the event approval by B31.1 takes place, such a case will be published in Mechanical Engineering magazine.

Allowable stress values are established by ASME for new materials in accordance with the policy spelled out in the ASME Boiler and Pressure Vessel Code, Section I, Appendix, A-75 through A-80 and A-150, or Section VIII, Division 1, Appendix B, UA-110 through UA-115 and Appendix P, UA-500. Approval of ASTM A 494 and the establishment of allowable stress values may be pursued through one of these channels.



Subject: Configuration in Table 127.4.8(F)

.Date Issued: October 6, 1980

File: 1442

Inquiry: Does a branch connection, such as an NPS 2 or smaller integrally reinforced sockolet that abuts the outside surface of a run wall for service not exceeding 750°F or 1025 psi maximum pressure, fall under the provisions of Fig. 127.4.8(F) of ANSI/ASME B31.1, making a partial penetration weld acceptable for this application?

Reply: Branch connections shall be made by full penetration welds, with the exception of the construction shown in Fig. 127.4.8(F) [see Para. 127.4.8(C)]. The reason for the exception made for the construction shown in Fig. 127.4.8(F) is the configuration of the fitting. That portion of the fitting which extends into the header wall is, in effect, an integral backing ring. A weld made against that integral ring would be considered a full penetration weld for the depth of the weld groove.

It is, therefore, the opinion of the Committee that an integrally reinforced sockolet that does not conform to the configuration shown in Fig. 127.4.8(F) must be attached by a full penetration weld, regardless of its size or the service conditions to which it is subjected.


Subject: Exposure of Joints


File: 1462

Inquiry: An interpretation is requested of the term "exposed" in reference to Para. 137.2.1 of ANSI/ASME B31.1. Also, must the joint be free from paint and coatings both internally and externally prior to testing?

Reply: The term "exposed" in Para. 137.2.1 means that the joint must be free from anything that would inhibit the leakage examination requirements of the leak test being performed. Painting or coating that will not interfere with the required examination may be applied prior to testing. However, some coatings could possibly mask a leak during a test and fail later while the line is in service. It is the responsibility of the designer who specifies the coating to determine whether or not it may be applied to the joints prior to leak testing. The term "exposed" does not apply to the internal surface of the piping which may be lined with rubber, concrete, nylon, etc.

B3 1.1 interpretations No. 1


Subject: Use of Standard Class Valves

~ate'1ssued: October 30, 1980

File: 1472

Inquiry: Do standard class valves complying with the specifications listed in Table 126.1, such as ANSI B16.34, fulfill the ANWASME B31.1 requirements without additional nondestructive testing?

Reply: Yes.


Subject: Welding Procedures

Date Issued: January 9, 1981

File: 147 1

Inquiry: According to ANWASME B31.1, may a welding procedure qualified to weld a P-No. 4 material to a P-No. 4 material be used to weld a P-No. 4 pressure retaining material to a P-No. 1 pressure retaining material, if the procedure qualification tests require a PWHT of the joint at 1300°F-1375"F?

Reply: Yes, provided the following requirements are met: (a) there is no metallurgical damage to the P-No. 1 material subjected to the 1300°F-1375°F

temperature; and (b) the PWHT temperature does not exceed the lower critical temperature of the P-No. 1

material shown in Table 129.3.2. It is the responsibility of the employer of the welder making the weld to ascertain

that no metallurgical damage will occur to the P-No. 1 material during PWHT. One method of providing this assurance is by qualification of the weld procedure. If the lower critical temperature of the P-No. 1 material is exceeded during PWHT, ASME Boiler and Pressure Vessel Code, Section IX (and ANWASME B3 1.1 by reference to ASME Boiler and Pressure Vessel Code, Section IX) requires qualification of the weld procedure at a PWHT temperature above the critical temperature range.



Subject: Appendix D on Stress Intensification Factors

a Date Issued: February 23, 198 1

File: 1470-1

Inquiry: Is it the intent that the stress intensification factors shown in Appendix D of each respective Code be applied for sustained and occasional loads as well as for expansion loads?

Reply: Stress intensification factors (SIFs) listed in Appendix D of the various ASME B31 Code Sections are intended for design against fatigue failure and were to a large extent developed from cyclic bending tests of piping components. Therefore, the application of the SIF for cyclic bending and torsion loads is appropriate. Sustained and occasional loads may not be cyclic loads; however, it is the intent of the various Codes to provide adequate protection from component collapse. It has been shown that the SIF of 0.75 (but not less than 1.0) found in ANSI/ASME B3 1.1 applied to sustained and occasional bending and torsion loads provides a conservative margin against component collapse.


Subject: Para. 104.8.1, Stress due to Sustained Loads

Date Issued: March 23, 1981

File: 1470-2

Inquiry: Is it the intent that Eq. (1 1) in Para. 104.8.1 of ANSI/ASME B3 1.1 not include longitudinal stresses caused by effects other than pressure?

Reply: No, Para. 102.3.2@), additive stress, requires that the sum of the longitudinal stresses due to pressure, weight, and other sustained loads shall not exceed the allowable stress in the hot condition S,. Equation (1 1) of Para. 104.8.1 requires that longitudinal stresses caused by pressure and bending be included when evaluating the stresses in piping componehts. The moment term used in Eqs. (1 1) and (12) includes both the bending moments and the torsional' moment.

In most piping systems, the longitudinal stresses caused by axial for* in the pipe are insignificant when compared with the stresses caused by pressure and bending moments, and t h y can be safely ignored. For this reason, they are not specifically mentioned.

However, the design of a piping system could be such that there are significant axial forces due to sustained loads other than internal pressure. These axial forces must be considered when : evaluating the longitudinal stresses in the pipe, even though they are not included in Eqs. (1 1) and (12).

The ANSI/ASME B3 1.1 Code is not a design handbook that can be used without competent engineering judgement with regard to the design analysis of a piping system.



Subject: Para. 104.8, Analysis of Piping Components


File: 1459

Inquiry: In ANSI/ASME B31.1, why are axial forces resulting from thermal expansion not included in the calculations of longitudinal stresses?

Reply: Paragraph 104.8 requires that longitudinal stresses caused by pressure and bending be included when evaluating the stresses in piping components.

The ANSI/ASME B3 1.1 Code is not _a design handbook that can be used without engineering judgment. The design of a piping system could be such that there are no bending moments in it, only pressure and axial forces, or only axial forces. These axial forces must be considered when evaluating the longitudinal stresses in the pipe, even though they are not included in Eqs. (1 1) through (14). In most designs, flexibility is provided by changes of direction (see Para. 119.5).

For additional information on this subject, see "Fatigue Test of Piping Components" by A. R. C. Markel, paper # 5 1-PET-21, which is in ASME transaction 195?, dated May 28, 1951. This paper is available from ASME.


Subject: Fig. 104.3.1(D), Reinforcement of Branch Connections

Date Issued: April 1, 198 1

File: 1479

Inquiry: Please advise the intent of ANSI/ASME B3 1.1 for determining the limit of reinforcement "L" for integral branch connections typified by details (a) through (e) of Fig. 104.3.1(D).

Reply: Example C of Fig. 104.3.10) applies only to the case where the run and integrally reinforced branch connections are mutually perpendicular when the axis of an integrally reinforced branch connection and the axis of the run pipe t, = 0. Therefore, the altitude of the reinforcement zone L, as defined in Para. [email protected]), then becomes equal to 2.5 T,,. It is the intent of the Code that Example A of Fig. 104.3.10) will apply to integral branch connections when 45 deg. < a < 90 deg. as permitted by Para. 104.3.1 (C.3). If an integral branch connection meets the limits of reinforcement as specified by Para. 104.3.1@), the Code requirement for the opening has been adequately compensated for.

83 1 . 1 Interpretations No. 1

:Subject: Integrally Reinforced Branch Connections

:Date Issued: April 24, 1981

Inquiry (1): In ANSI/ASME B3 1.1, how should the weld thickness of integrally reinforced I3ranch connection fittings be determined?

Reply (1): The weld thickness may be calculated in the same manner as are the other branch connections of Para. 132.4.2(E), considering t , to be the thickness of the branch at the weld. This subject is under consideration by the Committee, and the inquirer is advised to watch future .4ddenda for any possible change regarding this subject.

Inquiry (2): Are the PWHT exemption criteria in Table 132 P-No. 1 materials applicable to integrally reinforced branch connection fittings? If not, what criteria should be used?

Reply (2): Yes, the exemption criteria of Table 132 P-No. 1 materials use nominal thickness as determined by Para. 132.4.1 as a basis. The weld thickness as determined by Para. 132.4.2(E) for integrally reinforced branch connections is a part of that determination.

1-32 B3 1.1 Interpretations No. 1


Subject: Stress Intensification Factors to Be Used With Fig. D-1 Branch Connections


File:

Inquiry: What is the stress intensification factor to be used for the branch end of branch connections shown in Fig. D-1 of ANSI/ASME B31.11

Reply: The stress intensification factor (SIF) to be used in evaluating stresses for the branch end of branch connections depends on the piping structure in the vicinity of concern. Stresses higher than nominal* occur at and near points of structural discontinuity, e.g., elbows, tees, notches, welds, and branch connections.

(a) If the area of concern is sufficiently remote from the branch connection (i.e., structural discontinuity), then the nominal stress of the branch pipe without an applied SIF would be appropriate to use in Code stress evaluations.

(b) If the area of concern is the general area of the junction of the branch connection and the surface of the run pipe, then an "effective" nominal stress is determined using the effective section modulus formula in Para. 104.8.qC). The branch connection SIF is applied to this "effective" nominal stress, and the resulting stress would be appropriate to use in Code stress evaluations. Note that in calculating the effective section modulus and applying the branch connection SIF, the greater of the following is determined and used in Code evaluations: (1) the branch pipe nominal stress, i.e., stress remote from a structural discontinuity

described in (a) above; or (2) the branch connection intensified stress, i.e., stress local to the junction of the

branch connection and the run pipe surface using a "junction" section modulus calculated with the branch pipe mean radius and the run pipe nominal thickness.

(c) If a structural discontinuity exists at the transition of the branch connection to the branch pipe, such as a weld or tapered transition as shown in Fig. D-1 sketches (a), (b), and (c), and this discontinuity is sufficiently remote from the discontinuity at the junction of the branch connection and run pipe surface, then an SIF for a weld or a tapered transition could be applied to the nominal branch pipe stress and the resulting stress would be appropriate to use in Code stress evaluations. Note that if the angle of the tapered transition exceeds 30 deg., then the Table D-2 SIF may not provide a conservative bound. Also, the existence of an r , radius would increase the conservatism of the tapered transition SIF, as would a transition angle less than 30 deg.

(d) If the transition from the branch connection to the branch pipe is sufficiently close to the run pipe surface that the transition stresses affect junction stresses, then neither the junction SIF nor the transition SIF may be conservative. It is the Committee's opinion, however, that this branch connection geometry would be so compact or abrupt or would employ fabrication methods outside the bounds of good workmanship, such that an experienced engineer or fabricator would recognize this as a design or fabrication deficiency and provide a qualitative assasment or remedial recommendations.

* M / Z stresses where Z is the section modulus of the nominal pipe.



Subject: Design and Analysis of a Complete Piping sy$tem


Inquiry: In ANSI/ASME B3 1.1, is there any rule requiring a calculation be made of the whole piping system which considers the combined influence of its thermal, pressure, weight, and !;upporting elements, and whether the resulting stresses must be compared against a certain ~naximum allowable stress?

Reply: The Code covers the limits of calculated stresses due to sustained loads and thermal expansion as described in Para. 102.3.2. The design and analysis of a complete piping system and rusociated components must satisfy Para. 104.8. Therefore, system supports and other constraints which impose moments on the piping must be included in the evaluation procedure outlined in Para. 104.8.

The allowable stress S, is used as the limit of calculated stress due to sustained loads described in Paras. 102.3.2(A) and (D). See Para. 104.8.1 for a further discussion of sustained loadings.

The allowable stress range So of Para. 102.3.2(C) provides a comparison for the calculated stress range due to cyclic strains from thermal expansion and flexibility as related to the stress range concept (Para. 119.2) and the consideration of intermediate restraints to thermal expansion in flexibility calculations [Para. 119.7.1(D)].

The Code does require an evaluation of the entire piping system between connected equipment and/or rigid anchors which considers the influence of thermal, pressure, weight, and sustained mechanical loads, including those loads that are a result of intermediate restraints and support elements. Paragraph 104.8.3 permits the combined effects of sustained plus thermal expansion stresses to be evaluated using Eq. (14) as an alternative to meeting Eq. (13) of Para. 104.8.3(A) and as permitted by Para. 102.3.2(D).


Subject: Acceptable Weld Metal Deposit Profile


Inquiry: Would the Committee provide guidance as to what it would consider an acceptable weld metal deposit profile on the side of the run pipe at the branch intersection point where no integrally reinforced branch connection is used? The situation which exists when the branch pipe size approaches or equals the run pipe size is of particular interest.

Reply: The weld metal profile on the side of the pipe branch connection shall have a "through the weld" thickness equal to or greater than the nominal wall thickness of the branch pipe. The weld shall blend with the adjacent base material.



Subject: Para. 100.1 Scope


File: 1521

Inquiry: Does the Committee consider building heating and distribution hot water heating systems designed for above 30 psig as power piping systems that come under the rules of ANSI/ASME B31.1, rather than the ASME Boiler and Pressure Vessel Code, Section IV? Is it possible that the limitation of 30 psig given in Para. 100.1.3(C) is a misprint; should it really be 160 psig?

Reply: Hot water piping systems having design pressures of over 30 psig are covered by the rules of ANSI/ASME B31.1, except as may be limited by Paras. 100.1.3(A) and (B). The limitation of 30 psig is not a misprint. This limitation has been in the Code since the 1951 Edition.


Subject: Welding Details for SlipOn Flanges in Fig. 127.4.4(B)

Date Issued: June 24, 198 1

File: 1516

Inquiry: Paragraph 127.4.4 states "Typical minimum fillet weld details for slipon flanges and socket-welding components are shown in Figs. 127.4.4(B) and (C)." Figure 127.4.w) seems to indicate that all "slip-on flanges" require welding on both the I.D. and O.D. Is this interpretation true, and are there any exceptions?

Reply: Double fillet welds (front and back) for slip-on flanges are 'required without limitation as detailed per Fig. 127.4.4(B) of ANSI/ASME B31.1.



Subject: Valves Conforming to Para. 107.1(A)


File: 1493

Inquiries (1) For valves that conform to Para. 107.1(A) of ANSI/ASME B31.1, is it a requirement

that the welding procedures used for hardsurfacing of the valve disk and body seating surfaces be qualified in accordance with ASME Boiler and Pressure Vessel Code, Section IX?

(2) Same as above, but for valves conforming to ANSI B31.7.

Replies (1) ANSI/ASME B31.1, Para. 107.1(A) requires that valves conform to the standards listed

in Table 126.1. The Committee does not interpret the requirements of the standards listed in Table 126.1. Questions concerning the requirements of the standards listed in Table 126.1 of ANSI/ASME B31.1 should be sent to the organization that is responsible for the specific standard. The name and address of each organization is provided in the Notes to Table 126.1.

(2) Same as above.


Subject: Use of Carbon Steel Pipe


File: 1503

Inquiries (1) Does ANSI/ASME B31.1 allow the use of carbon steel pipe for any service where the

design temperature exceeds 800"M (2) Do the provisions of Para. 102.2.4 of ANWASME B31.1 permit the use of ASTM A

106 Gr. B pipe in the extraction piping for a controlled extraction turbine? The normal temperature for the extraction piping is 500°F. During the no-load condition, the temperature of the extraction piping rises to 86YF. The maximum anticipated duration of the no-load condition is 3 hr.

Replies (1) No. (2) The provisions of Para. 102.2.4 are not relevant to the situation described in the

Inquiry. The no-load condition is part of the normal operation of the extraction piping system and must be considered when specifying the system design temperature.

1-39, 140 B3 1.1 Interpretations No. 1


Subject: Holding Temperature During Postweld Heat Treatment


File: 1528

Inquiry: According to ANWASME B31.1, may the time at the holding temperature during PWHT of nonboiler external piping be accumulated rather than continuous?

Reply: The time at the holding temperature may be accumulated rather than continuous only when the heating rates of Notes (9) and (10) of Table 131 are followed for each portion of the heat treatment.


Subject: Stop Valves


File: 1430

Inquiry: We request that ANWASME B31.1 do the following: (a) Somewhere in the Code define "stop valve." (b) Revise the Fig. 100.1.2(B) to represent the valves in a standard way (e.g., see ANSI

Y32.11, Code Nos. 5, 6, and 7).

Reply: The functional classifications and definitions of components, such as valves, pumps, vessels, etc., are outside the scope of the Code. The choice of a particular type of valve to satisfy the specified requirements and to operate most satisfactorily in a given system is the prerogative and responsibility of the designer.

Comprehension of the diagrams showing jurisdictional boundaries would not be enhanced by the use of a multiplicity of valve symbols. The valve symbols in Figs. 100.1.2(A) and 100.1.2(B) have an associated reference paragraph which describes the functional requirements of the valve. These functional requirements can generally be met by several types of valves. ANSI Y32.11 has not indicated a symbol for stop valves that can be used in Fig. 100.1.2(B).

The foregoing considerations lead to the conclusion that: (a) a "stop valve" is any type of valve that when in a closed position will adequately stop

fluid flow; (b) the valve shown in Fig. 100.1.2(B) has been adequately identified as a stop valve,

considering ANSI has not adopted a standard symbol for a stop valve.



Subject: Postbending or Postforming Heat Treatment


File: 1534

Inquiry: According to ANSI/ASME B3 1.1, if the bending or forming operation is performed on ferritic alloy steel (excluding P-No. 1 materials) piping at a temperature above the lower critical temperature, is the postbending or postforming heat treatment as specified in Paras. 129.3.2(A) and (B) required?

Reply: If a bending or forming operation is performed on ferritic alloy steel (excluding P-No. 1 materials) piping with NPS 4 and larger or with a nominal thickness of M in. or greater, at a temperature above the lower critical temperature, the material shall receive a full anneal, or a normalize and temper heat treatment cycle, as specified by the designer.

Interpretation: 142

Subject: Protection Against Overpressure


File: 1525

Inquiry Is it the intent of Para. 102.2.5(B) to provide relieving capacity for a single reducing valve failure or multiple reducing valve failures?

Reply: The intent of the Code is to provide protection against overpressure.


Subject: Compression Type Fittings


File: 1511

Inquiry: Is it permissible to use compression type fittings on NPS 2 pipe (2.375 in. O.D.) for systems designed to meet ANSI/ASME B31.1, provided all the requirements of Para. 115.4 are met?

Reply: As stated in Para. 115 of ANSI/ASME B31.1, the use of compression type fittings for tube sizes over 2 in. (50 mm) O.D. is prohibited. However, Para. 115 only addresses tubing. See Para. 118 for other applications of proprietary joints.

144,145 B3 1.1 Interpretations No. 1


Subject: Para. 104.8.3(B), Sustained Plus Thermal Expansion Stresses

Date Issued: September 15, 1981

File: 1473R

Inquiry: When determining the allowable "sustained plus thermal expansion stresses" per Para. 104.8.3(B), it appears that the SA value in the (Sh + SJ term of Eq. (14) may be determined in two ways:

(a) the SA value from Eq. (1) of Para. 102.3.2(C); or (b) the SA value obtained by adding the difference between S,, and the sum of the sustained

longitudinal stresses (Sh - SLr) to the SA value from Eq. (1) per Para. 102.3.2(D). Is this the intent of the ANSI/ASME B3 1.1 Code? If not, what is the intent of the Code for

the allowable "sustained plus thermal stresses"?

Reply: It is the intent of the Code that the term SA, when used in Eqs. (13) and (14), be calculated per Eq. (1) of Para. 102.3.2(C). The Code in Para. 102.3.2(D) allows a greater stress range for thermal expansion when the stresses due to sustained loads are small. Equation (14) defines how this is done.

The Code recognizes that there is small difference between Eq. (14) and the rules stated in Para. 102.3.2@) when there is a large number of thermal expansion cycles (greater than 7000).


Subject: B31.1 and B3 1.3, Synfuel Plant Piping


File: 1541

Inquiry: What section of the ASME Code for Pressure Piping B31 may be used for materials, design, fabrication, assembly, erection, examination, inspection, and test of piping within coal based synfuels plants for the production of electric power and/or industrial steam?

Reply: ANSI/ASME B31.1 applies to piping associated with power boilers and subject to ASME Boiler and Pressure Vessel Code, Section I inspection and stamping. [See B31.1, Para. 100.1.3 and Fig. 100.1.2(A).]

Either ANWASME B3 1.1 or B3 1.3 is applicable to other piping associated with the production or distribution of industrial steam or production of electric power (see B31.3, Fig. 300.1.1).

ANSI/ASME B31.3 applies to all other piping.



Subject: Definition of t , in Para. 104.3. I@)

~ a i e Issued: November 6, 1981

File: 1536

Inquiry: Is it permissible to use alternative rules for the definition of t , in Para. 104.3.1 of ANSI/ASME B3 1.1 as applicable to branch connections subjected to external pressure requiring reinforcement per Para. 104.3.1 (E)?

Reply: The use of alternative rules for the definition of t , in Para. [email protected]) of ANSI/ASME B3 1.1 is acceptable using Formula (3) or (3A) in Para. 104.1.2(A) or 104.1.3 for the design applicable to Para. 104.3.10. In lieu of the limited information which has been supplied in the Inquiry, the use of Para. 104.1.3 is compatible with the general philosophy outlined in the Foreword to B3 1.1.


Subject: Reference to AWWA C-504 in Table 126.1

Date Issued: February 22, 1982

File: 1547

Inquiry: Has the Committee considered including AWWA G504 (rubber seated butterfly valves) in Table 126. l?

Reply: No. However, in response to the Inquiry, the Committee is now considering including AWWA C-504 in Table 126.1.

B3 1.1 Interpretations No. I


Subject: Paras. 122.1.3(A. 1) and 102.2.5(D)

Date Issued: February 24, 1982

File: 1558

Inquiry (1): What is the reason for the design pressure for the feedwater piping from the economizer inlet header to and including the required stop and check valves to be either 25% or 225 psig (whichever is lesser) greater than the maximum allowable pressure of the boiler as stated in Para. 122.1.3(A.l) of B31.1?

Reply (1): The design pressure requirements of Para. 122.1.3(A. 1) were originally established as design rules in Section I, Power Boilers, of the ASME Boiler and Pressure Vessel Code. These, along with design rules for other boiler external piping, were transferred to the Power Piping Code without change via the ANSI B3 1.1.0d-1972 Addenda to the 1967 Edition of the Code. These rules remain unchanged in the 1977 Edition and the current 1980 Edition. Therefore, your question regarding those rules has been directed to the Subcommittee on Power Boilers of the ASME Boiler and Pressure Vessel Committee for response.

Inquiry (2): What is the purpose of Para. 102.2.5(D), which requires that the pump discharge piping be designed for the maximum sustained pressure exerted by the pump at any load? Does this require designing the pump discharge piping to the pump shut-off head?

Reply (2): The intent of Para. 102.2.5@) for pump discharge piping is the same as expressed more generally in Paras. 101.1 and 101.2. The maximum sustained fluid operating pressure is a function of several fluid system design variables, among which may be pump characteristics, configuration, valving, controls, and any overpressure protection that may be provided. It is, therefore, the responsibility of the Designer to establish the value of maximum sustained pressure expected to be imposed on the piping system being designed, and to design the piping system for this pressure and corresponding temperature. It is not the responsibility of the Committee to evaluate particular systems or the conditions which may produce the maximum sustained pressure.




File: 1564

Inquiry: Are piping components, such as valves and strainers, within the scope of ANSI/ASME B3 1.1, and if so, are there any certification requirements for piping associated with removal of condenser noncondensables?

Reply: As stated in Para. 100.1.1, piping components, such as valves and strainers, are within the scope of ANSI/ASME B3 1.1 and must comply with the standards and specifications listed in Table 126.1. There are no certification requirements for the service described other than what may be required by the pertinent standards and specifications listed in Table 126.1.



Subject: Preheat and Postweld Heat Treatment Requirements

Dated Issued: April 5, 1982

File: 1570

Inquiry: What preheat and postweld heat treatment rules in ANWASME B31.1 would apply if a hanger lug of 1% in. thickness is attached to a A 106 Gr. B pipe with a 51 in. wall thickness, using a fillet weld with a 34 in. throat dimension?

Reply: A preheat of 200°F (992) is required. No postweld heat treatment is required.




File: 1520

Inquiry (1): Shall the steam piping which extends from the boiler nozzle to and including the valves required in Para. 122.1.7 be constructed in accordance with Section I of the ASME Boiler and Pressure Vessel Code or the ANSI/ASME B3 1.1 Code?

Reply (1): Both Codes are applicable. As specified in Para. and Fig. 100.1.2, as well as in the Preamble to ASME Boiler and Pressure Vessel (BPV) Code, Section I, the ASME BPV Code has total administrative jurisdiction (mandatory certification by Code Symbol stamping, ASME Data Forms, and Authorized Inspection) of Boiler External Piping. Technical responsibility (materials, design, fabrication, erection testing, and inspection) has been assigned to ANSI/ASME B31.1 Code.

Inquiry (2): Shall steam piping beyond the required stop valves (Non-Boiler External Piping) be designed, fabricated, erected/installed, examined, and tested in accordance with the ANWASME B3 1.1 Code?

Reply (2): Yes.

B3 1 . 1 Interpretations No. 1

Interpretstion: 1-52

Subject: Para. 13 1 Welding Preheat


File: 1571

Inquiry (1): Does the 1 in. (25.0 mm) thickness referred to in Para. 131.4.2(A) refer to throat . thickness or material thickness for fillet welds?

Reply (1): The thickness referred to is the greater of the nominal thicknesses at the weld for the parts to be joined (Para. 131.4.1).

Inquiry (2): Does the nominal thickness defined in Para. 132.4.1 also apply to preheat requirements?

Reply (2): No, the nominal thickness defined in Para. 132.4.1 does not apply to preheat requirements. The nominal thickness referred to in Para. 13 1.4.1 is the material nominal thickness.


Subject: Material for Use in Boiler External and Non-Boiler External Pipe


File: 1476

Inquiry: May material be used in ANSI/ASME B3 1.1 Boiler External and Non-Boiler External piping if the material has slight deviations in chemistry from the chemical values specified in ASTM and SA specifications?

Reply: The Committee will not grant approval to use material that deviates from the material specifications required for Code use.

B3 1.1 Interpretations No. 1 1-54


Subject: Components and Materials Manufactured to an Edition of a Standard or Specification * Which Has Been Superseded


File: 1526

Inquiry: May a component for ANSI/ASME B31.1 power piping systems manufactured to the requirements of an edition of a standard listed in Appendix F be used, even though the applicable issue of Appendix F lists a later edition of that standard?

Reply: Components manufactured to a standard listed in Appendix F, but not to the edition of the standard prescribed in the applicable issue of Appendix F, may be used in ANSI/ASME B3 1.1 piping, provided that the Manufacturer certifies to the PurchaserEnd-User that all of the following requirements are met.

(1) The component was manufactured to an American National Standard which has become superseded by an edition of the standard referenced in the applicable issue of Appendix F.

(2) The rating selected for the component does not exceed the rating included in the edition of the standard listed in the applicable issue of Appendix F.

(3) The component meets the requirements of Para. 102.2.2 or 104.7.

b31.1 interpretations 1.pdf

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