A105 Flanges used in place of A694 5

[texasmetal]

We have some small spool pieces that were fabricated offsite. The drawings called for A694 F52 6" 1500 series RTJ flanges. The material that was delivered to the offsite contractor was A105 6" 1500 series RTJ flanges. This is on a compressor station governed by B31-8. I can't find A694 in the B16.5 spec that B31-8 requires. But A694 B16.5 is on the bill of material on the drawing. The MTR for the A105 has a minimum yield strength of 42KSI on the MTR and is welding to a 6" X52 pipe. Would these flanges be considered equivalent? I can't find any information on the A694 flanges.

 

[DVWE]

No they are not.

X52 pipe has a yield strength of 52ksi minimum

F52 flange has a yield strength of 52ksi minimum

 

[LittleInch]

Texasmetal,

You're not the first and won't be the last to notice this issue.

Basically, whoever ordered the flanges should have ordered them using ANSI/MSS SP-44 where the use of Grade A694 is a listed material. Dimensionally they are the same as ASME B 16.5 flanges, but chemically and pressure-temp rating are different. MSS-SP-44 is listed in ASME B 31.8 under 831.2, the same section as B16.5.

However many people don't realize that A694 isn't listed in ASME B 16.5 hence your current problem.

IMHO, no, these flanges are not equivalent and should not be used. They are approx. 25% less yield strength. In reality sure, at 6" they are unlikely to be stressed to their limit and the issue is only really at the weld neck bit, but I would reject them.

If the drawing called for A694 F52 class 1500 flanges and the fabricator decided without asking anyone to use a different flange material, that's his problem which he needs to fix. The fact that the BoM incorrectly called up ASME B 16.5 is a bit of a problem, but if the fabricator was uncertain then he should have raised a technical query, or should have been experienced enough to know you can't just substitute one material for another without getting approval.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[texasmetal]

Thank you. These were my thoughts but I wanted confirmation.

But does SP-44 include 1500 series flanges?

 

[DVWE]

No, it does not, but what is important is the scope of SP-44.

SP-44 is for 12" and larger flanges. Flanges 10" and smaller are referenced to B16.5.

See 1.1.1 of SP-44.

 

[LittleInch]

Ah, good point which I'd forgotten to check.

No MSS SP-44 only goes up to class 900 in terms of pressure rating.

So you're kind of in no mans land here. I would have gone with
"A694 F52 class 1500 6" Weld neck flanges to MSS-SP-44, dimensions to ASME B 16.5"

And then answered the clarifications or technical query.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

DVWE, true, but 1.1.1 basically says if you make it out of material meeting table 1 requirements, then it shall be considered as complying with the standard, with dimensional and tolerance requirements to B 16.5

Given that section 5.1.1. and 5.1.2 basically state that the drilling template is the same as B 16.5, you are getting a B 16.5 flange dimensionally, though the hub bore might be thinner due to the extra strength of the material.



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Also: If you get a response it's polite to respond to it.

 

[DVWE]

though the hub bore might be thinner due to the extra strength of the material.

LittleInch,

I see your point, but you're probably correctly assuming the OP is asking about a welding neck flange, even though he didn't specifically say that.

If that is the case, which it probably is, then the bore of a 6" 1500 class WNF has to be specified by the purchaser according to B16.5

Sounds to me like there are a lot of unasked and unanswered questions in this scenario.

texasmetal,

You have stated RTJ, but are we correct to assume you're asking about welding neck also?

 

[LittleInch]

DVWE,

I think we're both on the right path. My point was just that 16.5 has some min thicknesses which may not apply when you have higher strength material.

I just wish B16.5 would include A694 in one of the groups.....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[texasmetal]

You have stated RTJ, but are we correct to assume you're asking about welding neck also?

Yes. They are welding neck.

My confusion is SP-44 stating for flanges under 12" dimensional and tolerance requirements should follow B 16.5. But, oustide of dimensional and tolerance requirements I am assuming it should follow SP-44. What about Temp/Pressure chart? It wouldn't exist for a 1500 series flange in SP-44.

 

[DVWE]

I believe you can use a similar material, such as A350 LF6 Class 1. Chemistry, tensile, yield, and elongation are quite similar between the two.

Temperature limits look similar between A350 and what is listed in SP-44

FWIW, A350 LF6 Cl 1 is also grouped with A105 in B16.5

 

[LittleInch]

texasmetal.

Correct, it's not included and thinking about this these are issues which should have been considered earlier in the design, not now you're actually building something....

MSS Sp-44 is designed for pipeline flanges and it's pretty rare for a pipeline to be operating at class 1500, hence why it's not in MSS-SP 44.

I would revert back to 16.5 as DVWE says and look at group 1.1 materials in B 16.5 and see if your design pressures and temp (we don't now what they are) fit inside a Grp 1.1 B 16.5 pressure temp range.

If they do, just use those and state that somewhere in a design or mechanical design report.

If not then you might need to either up rate, reduce design pressure or find some fancy way to make your A694 flange be suitably rated at a higher temp than B 16.5

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[texasmetal]

Temp is -20/120 and design pressure is 3000 psig. My concern is with the weld neck. It is .432"wt and according to the MTR only 42ksi. I would assume the working pressure in B16.5 would apply to the entire flange. So my immediate thought is the flange will be suitable for the requirements. But having a 42ksi flange in a X52 system seems off.

 

[DVWE]

Yes, let me clarify my last post a bit...

I meant "use" by means of comparison. Compare the properties of A694 to the LF6. With some sound engineering judgment, I don't see any issue with putting A694 in the same material group as LF6 and using the pressure/temperature charts in B16.5

 

[LittleInch]

-20 to 100F at class 1500 group 1.1. gives you a max pressure of 3705psig and even 200F gives you 3395 so your 3,000psi is well inside that value. Therefore for class 1500 flanges just use the B16.5 pressure/temp rating.

I thought though we had got away from trying to use A105 - You are correct that the issue is at the weld neck / attachment to the pipe where the flange is a different (lower) strength than the pipe, but the same thickness. This is not acceptable IMHO.

You really need to get flanges made from A694 F52 to MSS-SP-44, dimensions to ASME B 16.5, bore to be determined based on the bore of the connecting line pipe.




Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DVWE]

You really need to get flanges made from A694 F52 to MSS-SP-44, dimensions to ASME B 16.5, bore to be determined based on the bore of the connecting line pipe.

Agree completely with LI on this...

You have a non-conforming situation here that needs to be dealt with properly. The fix is exactly what LI has stated above.

 

[GD2]

Guys,
Welding materials with different yield strengths is acceptable to code rules. Welding a A105 of 42ksi SMYS is allowed to weld with a X52 pipe of 52ksi SMYS.
The way it works is: S1 x t1 = S2 x t2, where, S1, t1 is the SMYS and the minimum thickness at the welding hub of the flange and S2 and t2 are the SMYS ans nominal wall thickness of the pipea end, provided that S2/S1 ratio do not exceed 4.

Texasmetal, find out the nominal wall thickness of the X52 pipe and then calculate the hub thickness required to use A105 flange. Of course, there will be thickness difference at the weld joint but then look at the different end prep options allowed under the construction code and B16.5.

Bottom line, a A105 flange with 42ksi SMYS can be used with a X52 SMYS pipe. The ideal situation would have been to use the A694 with matching SMYS and therefore, same weld end thickness.

Had A694 used, the other job would have been to find the P-T rating of the flange at design temp when it came to testing as A694 is not listed in B16.5 tables. In that situation, you will take the guidance from B16.5 Appendix A.


Ganga D. Deka, P. Eng
Canada

 

[LittleInch]

Ganga,

I accept that, but purposely didn't go there ( different wall thickness on the ID).

1) the OP indicated it has already been welded and although not stated, I assumed it was bored out to the same wall thickness as the pipe
2) For a pipeline, if this is a piggable section ( we have no idea) then a step change at the flange interface isn't a good idea.
3) It's usually quite difficult to get a good weld where the ID is different



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GD2]

That's true LI.
The designer correctly specified A694 F52 in the BOM but looks like the Fabricator may have ?? made a short cut by providing a A105 flange which are more easily available in the market. We have no idea about the flange bub minimum thickness unless texasmetal finds some RFIs approved by the designer.

If I go back to Texasmetal's original question, I would assume that the spools were made for station piping, not the mainline. If that's the case, it should be all good if the A105 were procured with the correct hub thickness. If not, it will always be a question mark until the joint fails and an investigation opens.

Texasmetal, Is it possible to find the spec. of the A105 flanges, the Fabricator (or whoever) procured? If it was specified as, "bore to match ....Schedule/XS/XXS X52 pipe' or "welded to ...Schedule/XS/XXS X52 Pipe", most likely a correct A105 flange may have been procured.

Ganga D. Deka, P. Eng
Canada

 

[texasmetal]

Ganga,

I will have to look into that. I suppose I can get one of our onsite reps at the fab shop to measure that bore. You are correct this is station piping.