1、ASME B31.8 INTERPRETATIONS VOLUME 16ASME B31.8 INTERPRETATIONSVOLUME 16Replies to Technical InquiriesMarch 2010 Through March 2012Interpretations 16-1 Through 16-17It has been agreed to publish interpretations issued by the B31 Committee concerningASME B31.8 as part of the update service to the Code
2、. The interpretations have been asssignednumbers in chronological order. Each interpretation applies either to the latest Edition or Addendaat the time of issuance of the interpretation or the Edition or Addenda stated in the reply.Subsequent revisions to the Code may have superseded the reply.These
3、 replies are taken verbatim from the original letters, except for a few typographical andeditorial corrections made for improved clarity.ASME procedures provide for reconsideration of these interpretations when or if additionalinformation that the inquirer believes might affect the interpretation is
4、 available. Further, personsaggrieved by an interpretation may appeal to the cognizant ASME committee or subcommittee.As stated in the Statement of Policy in the Code documents, ASME does not “approve,” “certify,”“rate,” or “endorse” any item, construction, proprietary device, or activity.I-1ASME B3
5、1.8 INTERPRETATIONS VOLUME 16B31.8Subject Interpretation File No.Appendix F . 16-11 11-376Para. 802.12(f), Injection and Production Flow Lines . 16-13 07-1469,07-1470Para. 831.2.2, ASTM A307 Grade B Bolting for B16.5 Flanges in Classes 150and 300 Service 16-4 10-718Para 831.2.2, Follow-Up Inquiry on
6、 ASTM A307 Grade B Bolting forB16.5 Flanges in Classes 150 and 300 Service 16-10 11-371Para. 831.4.1(c) and Appendix F . 16-8 09-1699Para. 841.31, General Provisions . 16-3 07-1472Para. 842.2, Design of Plastic Piping, General Provisions . 16-9 10-1001Para. 845.2.2, MAOP and Para. 845.4.1, Capacity
7、of Pressure-Relievingand Pressure-Limiting Stations and Devices. 16-14 10-1195Para. 845.4.1, Transient Overpressure. 16-16 11-1574Para. 845.411, Hoop Stress Calculations. 16-2 10-162Para. A842.2.2, Design Against Yielding 16-12 11-377Para. A842.2.2, Design Against Yielding and Para. A842.2.3, Altern
8、ate Designfor Strain 16-15 11-1573Paras. A842.2.2(a), A842.2.2(b), and A842.2.2(c) 16-1 10-23Para. A842.2.2(a), Hoop Stress . 16-6 10-1056Para. A842.2.2(a), Hoop Stress and Para. A847.2, Test Pressure 16-5 10-1057Para. A842.2.2(a), Hoop Stress and Para. A847.2, Test Pressure 16-7 10-1644Para. A847.2
9、, Test Pressure 16-17 12-121I-2ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-1Subject: ASME B31.8-2007, Paras. A842.2.2(a), A842.2.2(b), and A842.2.2(c)Date Issued: March 10, 2010File: 10-23Question (1): The equation for hoop stress in para. A842.2.2(a) has a temperature deratingfactor in t
10、he formula, whereas the equations for longitudinal stress and combined stress inparas. A842.2.2(b) and A842.2.2(c) do not use a temperature derating factor. Is this correct?Reply (1): Yes.Question (2): Does ASME B31.8 use temperature derated values of Specified Minimum YieldStrength?Reply (2): No.In
11、terpretation: 16-2Subject: ASME B31.8-2007, Para. 845.411, Hoop Stress CalculationsDate Issued: March 10, 2010File: 10-162Question (1): Is it allowed to use the Lame formula to determine hoop stress when determiningincidental pressure for an onshore pipeline in accordance with para. 845.411?Reply (1
12、): No.Question (2): Is it required to multiply the hoop stress by the Location Class Basic DesignFactor, F, for the capacity check per para. 845.411?Reply (2): No.Interpretation: 16-3Subject: ASME B31.8-2003, Para. 841.31, General ProvisionDate Issued: June 30, 2010File: 07-1472Question (1): With re
13、spect to para. 841.31, is a flange-end valve considered to be a nonweldedtie-in connection?Reply (1): Yes, provided the valve serves as a tie-in point after construction and testing of thepipeline or piping.Question (2): Is it mandatory for a pretested flange-end valve to be part of the piping syste
14、mduring hydrotesting?Reply (2): No. Per para. 841.31, nonwelded tie-in connections not pressure tested after construc-tion shall be leak tested.I-3ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-4Subject: ASME B31.8-2010; Para. 831.2.2, ASTM A307 Grade B Bolting for B16.5 Flanges inClasses 15
15、0 and 300 ServiceDate Issued: July 7, 2010File: 10-718Question: Does ASME B31.8 allow the use of ASTM A307 Grade A bolts in addition to Grade Bbolts in para. 831.2.2(b)?Reply: No.Interpretation: 16-5Subject: ASME B31.8-2010, Para. A842.2.2(a), Hoop Stress and Para. A847.2, Test PressureDate Issued:
16、July 30, 2010File: 10-1057Question (1): In para. A842.2.2(a), eq. (2) is for thin-walled pipe, and eq. (3) is for thick-walledpipe. However, if we go by what is given in these two Code equations, the pipe thickness forthick-walled pipes will be less than the pipe thickness for thin-walled pipes. The
17、refore, is therea typographical or drafting error in eqs. (3) and (5) in this section?Reply (1): The equations are all correct, but it is not clearly identified that eqs. (2) and (4) arefor U.S. Customary Units and that eqs. (3) and (5) are for SI Units. Furthermore, there is apublishing error in th
18、e Note following these equations. The Note should read: “It is recommendedthat eq. (2) or (3) be used for D/t greater than or equal to 30 and that eq. (4) or (5) be used forD/t less than 30.” Errata has been issued to correct these publishing errors.Question (2): We have a pipeline where the corrosi
19、on allowance is 6 mm and 12.5% fabricationallowance. Is the hoop stress calculation under ASME B31.8, Chapter VIII (para. A842.2.2) to bebased only on nominal wall thickness?Reply (2): Yes.Question (3): If no, then what are the maximum limits for corrosion and fabrication allowancesbeyond which we n
20、eed to factor them while calculating the Hoop Stress?Reply (3): The hoop stress calculations under ASME B31.8, Chapter VIII are to be based onlyon nominal wall thickness.Question (4): When reading paras. A842.2.2(a) and A847.2, our interpretation for F1, hoop stressdesign factor for offshore pipelin
21、es, for a pressure test is that it should be equal to 1. Therefore,is it correct to take the F1design factor for offshore pipelines for a pressure test to be equal to 1?Reply (4): No. As stated in Table A842.2.2-1, the hoop stress design factor, F1, for offshorepipelines shall be 0.72. There is no h
22、oop stress design factor, F1, for pressure tests.Question (5): If no, then what is the correct design factor for the above case?Reply (5): See reply to Question (4).I-4ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-6Subject: ASME B31.8-2010, Para. A842.2.2(a), Hoop StressDate Issued: October
23、 20, 2010File: 10-1056Question: Can the hoop stress formula in para. A842.2.2(a), eq. (4), be revised as noted below?For an isotropic elastic pipe, this technical inquiry proposes the following formulation for hoopstress calculation.Shp(Pi Pe)H9256 Pi(1)whereH9256pH209022H20900H20898tDH20899H20898tD
24、H208992H20901H209031p 2H20898AoAsH20899(2)Aop external cross sectional area of pipeAsp pipe material cross sectional area (cross sectional area of pipe steel)The proposed formulation, eq. (1), is based on Lames solution for hoop stress at the insidediameter of a cylinder subject to a differential pr
25、essure, i.e., internal and external pressure.Equation (1) predicts the hoop stress exactly when results are compared to finite element solutionusing eight-node solid continuum element.The proposed formulation of eq. (1) is a replicate of the second equation of para. A842.2.2(a)but in a more concise
26、and a practical format. The proposed hoop stress formulation of eq. (1) isin terms of Aoand As(i.e., pipe outer and material cross-sectional areas), which gives a directimplication of material usage in resisting the tensile hoop stress. The proposed hoop stressformulation is also shown in terms of w
27、all thickness-to-diameter ratio (t/D), to assist designersin performing normalized parametric studies.The proposed formulation of eq. (2) is more appropriate for deepwater application, wherehydrostatic collapse pressure often results in pipe diameter-to-wall thickness ratios of less than20, where th
28、e existing equation in ASME B31.8 may grossly overestimate the hoop stress.Reply: Thank you for your considered discussion on the hoop stress equation formulation.However, use of the proposed Lame equation to compute the hoop stress at the pipeline internaldiameter for offshore pipelines does not ha
29、ve any significant advantage over the current equation,and is more difficult to use for development of pipeline wall thickness design. We do not agreewith your assertion that the formula in para. A842.2.2(a), eq. (4) will grossly overestimate thehoop stress. We consider that the existing eq. (4) in
30、para. A842.2.2(a) is appropriate for the D/tranges covered in ASME B31.8.I-5ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-7Subject: ASME B31.8-2010, Para. A842.2.2(a), Hoop Stress and Para. A847.2, Test PressureDate Issued: November 9, 2010File: 10-1644Question: Previously, I had sent an In
31、quiry to ASME asking if it was correct to take the F1design factor for offshore pipelines for a pressure test to be equal to 1 when considering thewording stated in paras. A842.2.2(a) and A847.2. The reply to this Inquiry (Interpretation 16-5,File 10-1057) stated that there is no hoop stress design
32、factor, F1, for pressure tests. However, Ihave an additional question related to this response. Is the following the correct formula forcomputing the hoop stress for a pressure test?S STReply: No. There is no maximum hoop stress limit identified in the Code for a hydrotest. TheCautionary Note in par
33、a. A847.2 was written to caution the Code user that conditions may existthat could yield the pipe.Interpretation: 16-8Subject: ASME B31.8-2010, Para. 831.4.1(c) and Appendix FDate Issued: March 22, 2011File: 09-1699Question: In a fabricated branch connection, where the opening made in the header wal
34、l issmaller than the inside diameter of the branch pipe, may the full thickness of the header wallbetween the undersized branch hole and the inside of the branch pipe be considered to bereinforcement for purposes of area replacement calculation?Reply: Yes.I-6ASME B31.8 INTERPRETATIONS VOLUME 16Inter
35、pretation: 16-9Subject: ASME B31.8-2010, Para. 842.2 Design of Plastic Piping, General ProvisionsDate Issued: March 22, 2011File: 10-1001Question (1): Reinforced thermoplastic pipe (RTP) as described in, for example, ISO TS 18226,Plastics pipes and fittings Reinforced thermoplastics pipe systems for
36、 the supply of gaseousfuels for pressures up to 4 MPa (40 bar), or API RP 15S, Qualification of Spoolable ReinforcedPlastic Line Pipe, is not specifically identified as acceptable in para. 842.2. Is RTP allowed to beused for gas pipeline service?Reply (1): No. However, certain products may be qualif
37、ied for use by methods described insection 811.Question (2): Is reinforced thermoplastic pipe (RTP) subject to the same pressure design limita-tions as thermoplastic pipe per para. 842.2.2?Reply (2): No. See response to Question (1). The ASME B31.8 Code Committee is consideringmodifications to the c
38、urrent code specifically to include certain types of reinforced thermoplasticpipe that may be described in API RP 15S, ISO TS 18226, and other reinforced thermoplastic pipestandards.Interpretation: 16-10Subject: ASME B31.8-2010, Para 831.2.2, Follow-Up Inquiry on ASTM A307 Grade B Bolting forB16.5 F
39、langes in Classes 150 and 300 ServiceDate Issued: March 22, 2011File: 11-371Question (1): Is there a conflict between ASME B31.8, para. 831.2.2 referencing ASME B16.5and ASTM A307, Grade B bolting?Reply (1): No. ASME B16.5 references ASTM A307 Grade B bolts in Table 1B under the categoryof Low Stren
40、gth Bolting. In ASME B16.5, the Grade B bolts are limited to use with Classes 150and 300 flanged joints, used with nonmetallic gasket materials at temperatures between 29Cto 200C (20F to 400F). These same conditions are required in ASME B31.8, para. 831.2.2. Thetemperature range in the ASME B31.8-20
41、10 actually reads 29C to 232C (20F to 450F). Thereisanerrata scheduledforpublicationto correctthehightemperaturediscrepancy. TheASTMA307statement that the Grade B bolts are intended for use with cast iron flanges does not precludetheir use in steel flanges under the conditions stated above.Question
42、(2): Since ASME B31.8 is referencing ASME B16.5, which is for steel flanges, shouldntit also reference ASTM A307, Grade A bolts since these are used for general purpose (steel)?Reply (2): No. ASTM A307, Grade A bolts are not referenced in ASME B16.5. The Grade Abolts allow sulfur levels up to 0.15%
43、for ease of machining, and therefore may possess low fracturetoughness properties unsuitable for natural gas service.I-7ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-11Subject: ASME B31.8-2010, Appendix FDate Issued: March 22, 2011File: 11-376Question (1): In the examples in Appendix F illu
44、strating the application of the rules for reinforce-ment of welded branch connections for an onshore pipeline system, is the Design Factor, F, takenfrom Table 841.1.6-1?Reply (1): No. A welded branch connection on an onshore pipeline system is a FabricatedAssembly, as defined in para. 841.1.9(a). Th
45、erefore, the Design Factor, F, is taken fromTable 841.1.6-2.Question (2): In the examples in Appendix F illustrating the application of the rules for reinforce-ment of welded branch connections, would the Design Factor, F, be taken from the Hoop Stresscolumn in Table A842.2.2-1 for an offshore pipel
46、ine system?Reply (2): Yes.Interpretation: 16-12Subject: ASME B31.8-2010, Para. A842.2.2, Design Against YieldingDate Issued: March 22, 2011File: 11-377Question (1): My understanding of the test pressure criterion is the following:Shp (Pi Pe)D2t SMYSIs this correct?Reply (1): No. The formula that you
47、 have noted is used to compute hoop stress. It is not a testpressure criterion. Furthermore, Shas defined in eqs. (1) and (2) in para. A842.2.2 includes aDesign Factor, F, and a Temperature Derating Factor, T.Question (2): Since the nominal wall thickness is used in eq. (2) in para. A842.2.2 to comp
48、utehoop stress, does this mean that during a hydrotest, ASME B31.8 allows hoop stress to be 12.5%higher than SMYS when assuming a pipe manufacturing mill tolerance of 12.5%?Reply (2): No. When the Design Factor is included in the hoop stress formula, the hoop stressduring a hydrotest will not be 12.
49、5% higher than SMYS.I-8ASME B31.8 INTERPRETATIONS VOLUME 16Interpretation: 16-13Subject: ASME B31.8-2007, Para. 802.12(f), Injection and Production Flow LinesDate Issued: March 23, 2011File: 07-1469 and 07-1470Question (1): In accordance with ASME B31.8-2007, does the Code exclude flow lines betweengas injection wells and gas injection facilities?Reply (1): Yes.Question (2): In accordance with ASME B31.8-2007, does the Code exclude flow lines betweengas production wells and gas separation facilities?Reply (2): Yes.Interpretation: 16-14Subject: ASME B31.8-2007, Par
