astm a694 class 900 flange

[pipeliner3000]

What is maximum test pressure I can subject a pipeline to with class 900 flange connected to it. The pipeline test pressure at 90% smys is 241barg but the only flange pressure rating I can find (MSS SP 44, 16.5) appears to be for a lesser material A105 with rating of around 153barg. This suggests I would only be able to test to 153*1.5 giving around 230barg max which is below the desired test pressure at 90% smys of adjoining line pipe. No account appears to have taken for the higher strength a694 f60 material? We have same problem for class 2500 where I cannot find flange max pressure rating for same material. Has anyone had this problem before?

Thanks

 

[LittleInch]

Yes and its not straightforward.

If the material is not listed in 16.5 then it can't use a higher strewth than group 1.1

Your get our of jail card is that in section 2.6 it says testing at a higher pressure is "the responsibility of the user".

Therefore it is up to you to convince yourself and others that it is good. 10bar in 230 isn't going to make any difference.

Whilst the flange may be a higher grade it is thinner at the bore than a lower grade flange so the two kind of balance out.

This implies you're design pressure is close to your flange rating. These sorts of things can happen when you cut the margins too close.

Plan B? Lower the pipeline design pressure or fit higher rated flanges.

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

 

[BigInch]

Looks like your pipeline test pressure and/or the design pressure is/are in error.

First, FIVE things you didn't say,
1) What pipeline design code is this?
2) What is the pipeline design pressure?
3) What wall thickness are the flanges
4) What is the design factor of the flange?
5) What is the diameter of the flange neck?


MSS SP-44 (1996 edition referenced by CFRs) allows the use of A694
True that MSS SP-44 states in Table 3 that the 900# limit is
2220 psig (153 barg) from -20[°]F up to 250[°]F
(BTW that is [highlight #CC0000]121.11[°]C[/highlight])
But also true that the 2220 psig (153 barg) 900# rating is true for all materials, of lesser and greater yield strength, than A694-Y60 900# Class. A105 is a lesser yield material, but a MSS SP-44 flange made of A105 is still rated to 2220 psig (153 Barg).

An A105 flange, being of lower yield stress, would obviously be furnished to a thicker wall to meet that same 2220 psig than would be the a Y-60 flange.

When you get down to it, from the admittedly little I know about this problem right now, it appears that it was a mistake for the pipeline designers to do what I think they did by selecting a design pressure of 161 barg, slightly above the 153 barg (2220 psig), 900# flange rating, hence requiring the excessive test pressure (1.5 * 161 barg = 241 barg) as well. Didn't they know that they would create this problem by selecting a design pressure greater than the flange class 900# limit? Maybe that was the problem.

The design pressure needs to be reduced to 153 barg, or you have to cut out the flanges and replace them with the 2500#, or you have to go to what may be 105% yield stress on the flanges, if you can find them in your required diameter. Usually testing to no more than 2% over yield is an absolute maximum.

Answering the Five questions that I have asked above, might lend some valuable information towards suggesting some other solutions to this problem, but I am not hopeful.

 

[LittleInch]

BI - I think the key is in the 90% SMYS test limit. You could easily have a design pressure < 153 barg, but with a bit of spare pipe, so to get to 90% SMYS you need more than 1.5 X DP.

I just used the data provided, but yes some more is always useful.

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

 

[BigInch]

BTW, where did that 90% come from?
1.5 x any DF >= 0.6 will get you >= 90% SMYS.

 

[LittleInch]

But only if the actual wall thickness at your DF of >0.6 is exactly what you've calculated. Taking the next wt up or adding CA can affect things whereby the effective DF goes down.

We don't have the data from the OP to work it out.....

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

 

[BigInch]

Oh you mean "spare pipe" is wall thickness.

 

[LittleInch]

Yes, sorry I was rather tired when I typed that. spare wall thickness was what I meant....

At those pressures it wouldn't make much but I take the point, even at a Df of 0.6, with a 90% SMYS of 241 bar that gives 160.8 bar, but I suppose with a small amount of wall thickness over and above what the design thickness is, that's not unreasonable.

what do you do about it? - Accept your #900 flanges are a little over the official limit or weld on #1500 ones for the test or weld in pipe instead of flanges, e.g. for line valves, then cut them out and weld flanges and treat as golden welds.

I know what I would do - use the #900 flanges.



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