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Responses to Technical Interpretations


Request Date: 03/04/2020

Thai Benkan Co.,Ltd. are a manufacturer of steel butt welding pipe fittings,Tee,Elbow,Reducer and Cap. Referring to clause 8.2,our products NPS lower than 6" has been needed separate tensile specimens taken from fitting representatives such as from base material pipes,plates,etc. but there is a limitation on use of separate test pieces covering by SR-23 that a separate test piece which has been exposed to all forming and heating/cooling cycles the fitting is exposed to. There is not a problem for heating /cooling cycles but exposing to all forming could be needed your interpretation. Our facilities of cold forming of Tee and Reducer are being doubted than hot formed Elbow that if the representative of cold formed Tee or reducer must be exposed or formed in the same molds ,one or more times pressing as same as the fitting, eventually the representative became fittings which the area and length not available to be taken tensile specimens.

Could you please clarify and advise?

Answer Date: 03/06/2020


Interpretation (Rephrased by Committee): Are the requirements in SR-23 mandatory?

Answer: No. Per the introduction to Appendix X1, Supplementary Requirements “are not applicable to product furnished to this Standard Practice, except when specified on the purchase order or otherwise agreed upon”.

Request Date: 01/27/2020

Seeking clarification about weld bend test for MSS SP-75. Paragraph 14.4.4 states “All butt welds shall have full penetration and be done with at least one pass from the inside.” SR-2 states “Transverse-weld test specimens shall be subjected to face and root-guided bend-tests.” A joint welded from both sides does not have a root pass (i.e. first weld bead in the joint) exposed to the inside of the fitting.

Questions: 1. Is the intent of SR-2 to test the weld surface on the inside of the fitting, or specifically testing the root pass weld (i.e. first welded pass)? 2. Are side bends an acceptable substitute for face and root bends?

Answer Date: 02/06/2020


Question 1 (Rephrased by Task Group providing answer): Is the intent of SR-2 to test the weld surface on the inside of the fitting?

Answer to Question 1: Yes, The intent is to check the quality of the weld from both the inside and outside surfaces.

Answer to Question2: No, SR-2 requires face (O.D.) and root (I.D.) bends.


Request Date: 04/23/2019

MSS SP-9-2018, Paragraph 2.3.4 states "Backfacing may be used as an alternate to spot facing at the manufacturer's option. When used, back facing shall provide a surface that will ensure full bearing of the bolting nut. The minimum diameter of the back face shall be no less than the bolt circle diameter less one spot face diameter as listed in Table 1..."

Based on the cited paragraph, the minimum back face diameter for a 1/2"-600# welding neck flange (in accordance with ASME B16.5) appears to be 2.62 - 1.12 = 1.50 inches. The maximum back face diameter (assuming perfect concentricity between features) appears to be 2.62- 1.061 =1.559 inch, where 1.061 is the max width across corners of a square head bolt (a square head bolt was assumed based on paragraph 2.1.1 of MSS SP-9).

The allowable back face diameter therefore appears to be 1.500 inch to 1.559 inch. The spot face diameters that would result in an equivalent material removal range would be 1.061 inch minimum, and 1.12 inch maximum, which is inconsistent with the minimum spotface diameter of 1.12 as shown in Table 1.

Can you confirm the above interpretation of allowable back face diameters is correct? For bolt seating purposes, it seems odd that the back face diameter fails to remove the material that would be removed if the spot face option were used, particularly since the bolt circle diameter has a tolerance of +/- .060 inch and a concentricity of +/- 0.030 inch per ASME B16.5.

Answer Date: 07/19/2019


Yes, it is now approved and posted at

SP-9-2018 Errata Sheet Issued 05/22/2019


Request Date: 01/31/2020

For the plate material for A516-60/65/70, the maximum allowable stress in tension is shown up to 750F in Table A2, ANNEX A. But would it provide service temperature up to 800F in ASME B31.1 and up to 1000F in ASME SEC II?


ASME B31.1 Para 121.2 Allowable stress Values (a) Allowable stress values tabulated in MSS SP-58 or in Mandatory Appendix A of this Code Section may be used for the base material of all parts of pipe-supporting elements.


Does it have any reason to limit the temperature up to 750F in MSS SP-58? Also can I use these materials for pipe support under 800F temperature?

Answer Date: 02/19/2020


The committee for this standard met and have provided the following response:

“Original values from Table A2 were from a historical consensus of the committee based on available codes, material standards, and first-hand information.  An engineered analysis may be required if a material is designed for temperatures outside the scope of ANSI/MSS SP-58.”

Request Date: 07/02/2019

For the A387-P91 plate material, if it is required the heat treatment after forming and PWHT after welding. Do we apply the heat treatment after finishing 2 process(forming and welding)? In the MSS SP-58, the heat treatments are mentioned each paragraph but it did not limited to apply each process or not? We want to know it will be applied each steps or just one time after finish forming and welding.

The Heat Treatment after foming according to Para. also it is required PWHT after welding according to Para. 12.4.7.

Answer Date: 07/19/2019


Within ANSI/MSS SP-58, the maintaining Committee 403 endeavors to provide common material information. To that end, they are working to improve the material information for Grade 91. However, your question delves into the engineering of the support and of the fabrication process. ANSI/MSS SP-58 provides suggested minimum design requirements; however, it is not the intent of ANSI/MSS SP-58 to provide guidelines on how to manufacture various supports with each available material. As the application, loading, and design of each support is different, the committee recommends that you follow guidelines from the base material standard, material manufacturer, and perhaps consult a metallurgist to create a procedure for these special situations.

As an informational clarification, Section 12.4.7 specifies that welding-related Heat Treatment/PWHT
requirements shall be outlined in Tables 7/7M.


Request Date: 06/26/2018

In Section 10.1, production shell testing, it states that "Leakage through the shaft seal shall not be cause for rejection."

Is this only for shaft seals which are adjustable or can be tightened, or for any shaft seal design?

Answer Date: 07/18/2018


The statement in Section 10.1 cited by the inquirer only applies to shaft seals that are adjustable or can be tightened. However, the manufacturer shall demonstrate that all shaft seals are capable of retaining a seat test pressure of 1.1 times the rated cold working pressure (CWP). If non-adjustable shaft seals such as O-rings or fixed single rings are used, then shaft seal leakage is not permitted during shell and seat tests. Note: The committee chair will address these matters with the committee and a revised document or other corrective action may result.

Request Date: 06/26/2018

In determining production shell test times, the chart (Section 10.1, page 6) establishes durations based on designs shown in subsequent figures (pages 12-14). However, there is confusion as to how to classify a product which may fall into more than one of those figures simultaneously and thus to what duration it should be tested. For example, if a BFV has an integral flange gasket (Figure 1B) but is also single flanged or flangeless (Figures 3 & 4), should it test in accordance with durations based on its face-to-face design (Figures 1A, 1B, or 1C) or its bolting options (Figures 2, 3, 4, 5, or 6)?

Answer Date: 07/18/2018


The confusion results from Figures 2, 3, and 4 included within Column 2. These figures, showing bolting options, should not be included as they are not relevant to the shell test. Only the end connections and the method for sealing should be considered. As such, Figures 1B, 5, and 6 should be in Column 1 and Figure 1A and 1C should be in Column 2. Figures 2, 3, and 4 should not be considered for the shell test.


Request Date: 08/18/2016

The qualification section speaks to Radiation aging "to the requirements of the Design Specification or a dose level equivalent to the service life, as specified in Section 4.0." Does there need to be information as to qualification information that would address those applications used inside containment for an accident dose?

Answer Date: 10/17/2017


Answer: The initial response previously provided (see Attachment 1) was determined to be adequate and it is advised that this issue is not covered by MSS SP-100 at this time.

Note that the issue was further discussed during the 2017 TC-406 meeting and was determined that because the data related to accident dosage is not well defined in the industry and varies significantly from one customer to another, that no immediate changes to SP-100-2015 are necessary. However, a Task Group within TC-406 has been established to further address the issue in preparation for the next review cycle and subsequent edition.

Attachment1: It is believed you make a valid point, in that there is nothing in SP-100 that covers the application where a diaphragm may be subject to an accident dose of radiation. SP-100 currently provides guidance for normal operation of a diaphragm valve in a Nuclear plant that is subject to radiation dosages consistent with a typical radioactive environment. However, for those special cases where a customer has a requirement for a valve to continue to operate after a one-time accident dose (which is usually quite large), SP-100 does not yet account for that. SP-100 has served us well for a number of years because while many sites use diaphragm valves in Nuclear service, not every site has accident dose requirements. Complicating things greatly is the fact that every site seems to have their own accident dose requirements concerning duration, magnitude, and expectation of the diaphragm after the accident has occurred (i.e., must the valve still be able to shut off against operating pressure and temperature, or does it just need to function as a gasket? Does it need to be able to cycle once or twice or a full year’s worth of cycles and still shut off?). Accounting for inside containment / accident dose conditions per this request would be complicated.

It is advised that this issue is not covered by SP-100 at this time. However, due to your request, the committee will address this matter at its next meeting to determine if SP-100 should be revised to account for this issue during its next review period. This request will be considered an open Official Inquiry until the 2017 Committee 406 meeting and the result of committee discussions will be processed by the Executive Director and separately by the committee with regard to any potential revisions.


Request Date: 10/08/2008

ASTM A403 Standard for Wrought Stainless fitting calls the MSS SP-25 marking requirement. The MSS SP-25 explicitly requires fittings be marked with "... numerals, letter, or symbols cast, forged, stamped, or otherwise made integral with the product..." there do not appear to be exemptions allowing the use of laser, ink, or paint marking. Are there any official interpretations of the MSS SP-25 that would allow use of the non-integral markings?

Answer Date: 10/27/2008


The term "integral" in Section 2.2 of SP-25-1998 does not prohibit the otherwise suitable marking methods described in ASTM A403.


Request Date: 04/29/2019

When guide bars are welded in tees by the manufacturer, does Section 9.1.1 of SP-75-2019 require stress relieving of guide bar welds?

Answer Date: 07/16/2019


Answer: No

Informational Note: SP-75 fittings are to be heat treated above the transformation temperature and stress relieving alone is not satisfactory. Stress relieving may only be utilized when scraper bars are added, after the tee has been normalized (9.1.2), normalized and tempered (9.1.3), or quench and tempered (9.1.4), in accordance with the relevant section of SP-75.

Request Date: 02/29/2016

My questions are directed at MSS SP-75-2014. I am trying to determine the intent of 14.4.8 and 9.1 to establish the required PWHT of welded fittings.

1. Is the longitudinal weld seam required to receive the same normalizing or Q&T heat treatment as the fitting? (i.e., form, weld, PWHT)

2. Is an as-welded longitudinal weld seam permitted on a normalized or Q&T fitting?

3. Is stress relief PWHT permitted on longitudinal weld seams of a normalized or Q&T fitting? (i.e., form, Q&T, weld, stress relief).

Answer Date: 03/21/2016


1. Yes

2. No

3. Yes, for repair welded parts provided they meet 14.5.3. It is also advised that SR 16 be consulted for PWHT after installation.


Request Date: 04/24/2019

Question: If a full size and reducing branch outlet fitting are geometrically similar, may a test on a full size fitting be used to qualify reducing fittings? Proposed Answer: Yes.

Paragraphs for review: B3. It is not necessary to conduct an individual test of fittings in all combinations of sizes, wall thickness, and pressure class. A successful proof test on one prototype fitting may represent other similarly proportioned fittings to the extent described herein. B3.1 A successful test on a full size fitting may be used to qualify other full sized fittings no smaller than one-half nor larger than two-times the size of the test fitting.

Drawing Link:

Background: 90° branch outlet fittings are typically available in two styles. 1) with a flared inlet that tapers from a larger opening to one that matches the inside diameter of the branch pipe and 2) with a straight inlet that matches the inside diameter of the branch pipe. (See drawing MSSC105SWO.) Now when you compare detail 1 and detail 2, you will see that full size and reducing branch outlet fittings with flared inlets are not geometrically similar. The full size fitting has an elliptical opening while the reducing fitting has a round opening. Essentially, their longitudinal sections are similar but their circumferential sections are not. For these fittings it makes sense that a proof test on a full size fitting would not qualify reducing fittings. However when you compare detail 3 and detail 4, you will see that full size and reducing branch outlet fittings with straight inlets are geometrically similar. Both have identical branch openings and both have similar longitudinal and circumferential sections. For these fittings, a proof test on a full size fitting should also qualify reducing fittings. As a final note, a proof test on a full size fitting is more rigorous than a test on a reducing fitting. For example, review the target pressures of a 1 x 1 Class 3000 socket weld outlet and a 1 1/4 x 1 Class 3000 socket weld outlet. (For this example I used the minimum tensile strength of A106 Grade C.) The full size test has a target pressure that is 18% higher than the reducing test. 1 x 1 CL.3000 19057 P = 2ST/D 1.315 D = RUN PIPE OUTSIDE DIAMETER 0.179 T = RUN PIPE NOMINAL WALL THICKNESS 70000 S = RUN PIPE TENSILE STRENGTH


Answer Date: 06/06/2019


NO. While the case that the inquirer makes may be technically persuasive, the
current wording of the Standard Practice is explicit, and as written, Section B3.1 does not
specifically allow a test on a full size fitting to qualify a reducing fitting.
Note that the committee chair invites the inquirer to engage the technical committee in proposing a
solution, as warranted.


Request Date: 06/10/2015

I have two questions: 1.) what is the difference between welded flexolet & weldolet ? 2.) what is the design procedure for olets?

Answer Date: 05/27/2020


  1. It is believed the question is in reference to MSS SP-97, not SP-79.  Please see this standard.  In addition, Flexolet and Weldolet are trade names used by companies to represent fittings found in SP-97.  Note that the unauthorized use of another companies trade name is illegal under US Copyright laws without explicit written permission of the trademark owner.
  2. SP-97, Section 6 explains design requirements.


Request Date: 09/19/2016

1. Interpretation of Stress Relieving Treatment on copper nickle fittings: 15.3 Copper nickel fittings shall be stress relieved, except as allowed in Section 15.1. Heat treating shall be performed at 1300 +/- 50 °F for one hour at temperature per inch of thickness. We interpret the temperature given, as the temperature of the oven and not of the fitting.

2. Interpretation of Concurrent Fitting Qualifications of Different Sizes and Types: 7.3 ...In addition, tests performed on belled end fittings qualify street end fitting of the same geometry and manufacturing method. We interpret this to mean that it will also cover the same ranges of size as the belled end fittings, one half to twice the size of the size the test was performed on for the belled end fitting.

3. Interpretation on Manufacturing Method Proof Testing: MSS SP-119 does not make any distinction between MIL-T-16420 pipe Type I (Seamless) and Type II (Welded), so we interpret that a successful manufacturing method proof test on Type I pipe will qualify Type II pipe and vice versa, granted the manufacturing method is the same.

Answer Date: 09/07/2017


1. Yes

2. Yes

3. Yes


Request Date: 05/31/2018

My question is in regards to the interpretation of the dimensional annotations throughout the specification. Specifically; the interpretation of trailing zero's in respect to the typical rounding rules of math. For example: Table 2 on page 11 of the referenced specification defines the tolerances and minimum wall thicknesses. In several dimensions those numbers may be expressed in two (2) decimal place notation or in three (3) decimal place notation. Such as 1/4 NPS, Socket Depth Tolerance = +/- 0.03 and Class 200 Socket ID = +/-0.015. If I do not use standard rounding, then I can interpret these dimensions to possess infinite trailing zero's i.e., such as ¼ NPS, Socket Depth Tolerance = +/-0.03000000000 and so on and Class 200 Socket ID = +/-0.0150000000 and so on. If I employ standard rounding, then I can interpret these dimensions as follows: 1/4 NPS, Socket Depth Tolerance = +/-0.03 rounded to the nearest 1/100th and Class 200 Socket ID = +/-0.015 rounded to the nearest 1/1000th. The primary reason for this request is that if I measure the socket depth for the above example, nominal depth + 0.031, how do I interpret this result. Do I round the socket depth and accept the fitting or do I not round the socket depth and reject the fitting?

Answer Date: 07/31/2018


The tolerance dimensions that are stated in MSS SP-119-2003 are the limit dimensions for manufactures and there is no rounding applied. The Socket Depth “B” (Table 3) is stated in 1/100 inch and Socket Depth “B” Tolerance (Table 2) is stated to the same degree of accuracy for the manufacturing of product specified to SP-119-2003. The Socket Inside Diameter “C” for Class 200 (Table 3) is stated in 1/1000 inch and the Socket Inside Diameter “C” for Class 200 Tolerances (Table 2) are, again, stated to the same degree of accuracy for the manufacturing of product specified to SP-119-2003.


Request Date: 11/15/2015

In SP-75-2014 there is a new section, 13.6 setting a minimum bore of 93% of the nominal pipe inside diameter. CFR 192 and 195 incorporate by reference the earlier version of SP-75-2008 which does not include this clarification. What is the minimum bore allowable in a SP-75-2008 Fitting? Where is this minimum bore tolerance to be found in the SP-75-2008 document?

Answer Date: 01/20/2016


The minimum bore allowable in MSS SP-75-2008 is not specified.


Request Date: 11/11/2009

We have an order of bends, we have run the test bend and want to have it Normalized then the Mechanical Testing done. Our Customer Inspector says that Para 8.3 in conjunction with Para 8.5 requires that the Test Bend be Normalized in the same furnace, and at the same time that we will Normalize the Production bends. Our interpretation of the Para 8.3/8.5 is that the Test Bend can be done in a furnace meeting the requirements set forth in Para 8.5, i.e..... calibration, 50 Deg F range of control etc.. Then when the mechanical testing is done and approved, the lot of bends can be made and then Normalized in A furnace (not necessarily the same furnace) again meeting the requirement set forth in Par 8.5 and following the same Heat Treat Procedure that was used on the Test Bend. We feel he is looking at Para 8.3 and applying the statement "and which has been heat treated in a lot with any of the fittings it represents" to the test bend. Our understanding of this paragraph is that there are two options in Para 8.3: 1) Test specimens shall be taken from the fitting after final Heat treatment. 2) OR from a piece of pipe or plate of the same nominal thickness, same heat of steel from which the fitting is made, and which has been heat treated in a lot with any of the fittings it represents.

Answer Date: 01/13/2010


1.Question: Does a "test bend" constitute "any of the fittings in a lot which it represent" as required in paragraph 8.3 of MSS SP-75?

Answer: MSS SP-75 does not address "test bend", therefore the status becomes a contractual one between the parties involved.

2. Question: If a test bend is normalized in a controlled furnace per paragraph 8.5 does that normalization fulfill the requirements of paragraph 8.3?

Answer: No  See question number 1.

3. Question: If a lot as defined as in paragraph 8.5 is normalized requires more than one furnace load or more than one furnace, will a specimen be required for each separate furnace load?

Answer: Paragraph 9.1.2 requires that any differences in furnace or load size be accounted for to achieve uniform temperature throughout the mass of the load in order to determine the number of representative specimens. Proof of this is most readily established by a specimen from each furnace or load size.


Request Date: 11/29/2016

1. Is MSS SP-58-2009 Pipe Hangers and Supports intended to apply to creep strength enhanced ferritic steel (ASME P-No.5B) materials, such as ASTM A387 Grade 91, listed in Table A2/A2M?

2. MSS SP-58-2009 Pipe Hangers and Supports tables A2/A2M contains allowable stress values for ASTM A387 Grade 91, but does not specify the "Condition". Do the allowable stress values provided in Tables A2/A2M represent material in the normalized and tempered condition, as required by Section 5.1.1 of ASTM A387 for Grade 91?

3. Is Section 12.3.1 the only place throughout MSS SP-58-2009 where heat treatment is required after forming?

4. Is heat treatment after hot forming of ASTM A387 Grade 91 required?

5. MSS SP-58-2009 Section 12.3.2 Hot Forming specifies a range of 1550F to 2000F for Chrom-Moly Alloy Steel. Does this apply to ASTM A387 Grade 91?

6. Has MSS SP-58-2009 considered these potential damaging effects to creep strength enhanced ferritic steel materials, such as ASTM A387 Grade 91, anywhere in the standard?

Answer Date: 01/04/2017


1. Yes, The temperature range of allowable stresses is identical to ASME B31.1, which includes the creep/stress rupture range for ASTM A387, Grade 91.

2. Yes

3. No, Section 12.3.3 also adresses heat treatment after forming.

4. No, Section 12.3.3 does not explicitly require or exclude heat treatment after hot forming. The requirements for heat treatment should be based on project spcifications and/or manufacturing procedures.

5. Yes

6. Yes, See response to question 1.

Request Date: 09/25/2014

1. Does MSS SP-58-2011 address I.D. tolerances for Pipe Straps (Pipe Clips)?

2. If a manufacturer’s tolerance for strap I.D. meets the tolerance shown for corresponding Pipe Clamp I.D., then these straps meet the intent of MSS tolerances?

Answer Date: 05/28/2015


Answer 1.  No

Answer 2.  MSS does not address specific manufacturer’s tolerances. Design tolerances shall be per the individual manufacturer’s drawings and standards.


Request Date: 01/24/2010

What is the standard or remedy recommended by MSS if the pipe fitting marking is not satisfying SP 25? I have a few connection fittings where I can see both weld and punch marks. It looks like it was done at two times. Do we need to scrap these fittings or do we need to re-mark with manufacturer/Third Party presence or do nothing?

Answer Date: 03/29/2010


Answer 1. SP-25, Section 2.4 does not prohibit the use of different marking methods on a given product.

Request Date: 11/17/2009

Sections 1 and 2 set out the Scope and General Marking Requirements for a standard marking system.

Assume that a flange has been marked by the manufacturer with the information required by the relevant ASME standard, but those markings were applied to bare metal using a light stamp. Those markings are then rendered invisible by painting of the flanges and associated pipe work. Does the flange still comply with MSS SP-25 after application of the paint?

Is the answer to this question affected by whether or not the flange marking was inspected and approved by an independent inspector before the paint was applied?

Answer Date: 12/08/2009


Irregardless of independent inspection, if the product was initially marked in accordance with SP-25, it is still in compliance after painting.

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November 26, 2020

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