Low temperature fittings, and /or pipe

[Daianto]

Hi,

We are revising our standard specifications for tanks and piping, etc. Our projects are located in Arctic and Sub-Arctic and the installations are outdoors.

Our current specs for tanks call for low-temp steel, of course, and we ask for low temp pipe flanges and valves.. but piping is currently only ASTM A53 Grade B piping and ASTM A234 Grade B fittings, because "of the low pressure and low stresses on the
piping and fittings" -how it was explained to me .. Although we have had no problems thus far, none of these installations to these specs are very old. It would make sense to me to have piping specced for low temps as well. Our consultant doing spec revisions suggests this strongly. Any thoughts please--my metallurgy is rusty!

 

[BigInch]

Listen to your consultant.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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[Daianto]

Thanks, Big Inch! You are my Petroleum "other topics" guru!

Daianto (Caluna)

 

[BigInch]

Thanks for the vote of confidence.

There are a lot of brittle failures for non-impact tested and non-killed steels in the low temperature environment (-40°F to 32°F). I think it is appropriate to use pipe for low temperature service in Arctic conditions. When I was doing gas work in northern Minnesota, we did use API 5L, but with extra V-notch toughness. I would imagine you're looking at temperatures near -40F or worse.

Is he recommending A334?

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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[dcasto]

I wouldn't change all the specs.. If the pipe is less than 20% smys and the temperature goes below -40F, you are still OK. This how we can depressure our ethylene lines made A53 and never get into trouble. The same is true for refrigeration systems. It's in there in B31.3 and ASME VIII under refrigeration.

 

[Daianto]

Yes we have 1% design temps down to -48 C in some locations, and all our design temps are at least minus 40 C.

Consultant recommends A333 grade 6.

 

[BigInch]

And its hardly worth building a pipe system to operate at 20% SMYS.

dcasto, your system gets cold when its being depressured, but this system is cold when it is being pressured, right?

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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[Daianto]

I looked at B31.3 and the design minimum of A53 is -20 F. But B31.3 Table 323.2.2, says no Charpy impact tests are required on carbon steel pipe at metal temperature to minus 46ºC, provided operating pressures are 25% of the maximum allowable design pressure at ambient temperature, and the combined longitudinal stresses do not exceed 41.37MPa. So one one hand the A 53 sounds acceptable for temps above minus 46..
(Some of our locations have temperatures below minus 46.)

 

[BigInch]

I was thinking you could have -60.
I wasn't thinking you have pressures < 25%.


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[Daianto]

Yes we can have those temps, -55 and -60 , and probably those pressures.
I meant to say in that post that our spec (currently) does not ask for Charpy tests on the A 53 pipe, which it should as our conditions are outside those of the exclusion.

the A333 pipe is quite a bit more costly so management will need good justification....
I have heard of API 5L pipe-is it more commonly used in petroleum industry than others? Should we consider it- (with charpy testing)?

 

[BigInch]

I've used 5L to grade X60 in cold climates with V-notch requirements, but not down to -60 and not with B31.3. They were gas pipeline designed to B31.8 only down to about -20C.

B31.3 uses allowed stresses, B31.4 & 8 use specified minimum yield stresses with reduction factors to get the allowed stress and I think B31.3 does not recognize the higher yield stresses of 5L above the 30,000 psi of grade B. Double check that, as I have not looked at that particular clause in a few years, so I'm not sure how at how using 5L would be affected by that code difference.


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[Daianto]

Thank you all so much for your input. Really appreciate it. We've made the switch in our specifications so we'll be speccing the low-temp pipe from now on. Consultant is happy and so am I.

 

[BigInch]

me2

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