Dear All,
When carbon steel/LTCS material is used for ethylene plant piping these material is subjected to -104 Deg C as an alternate design temperature.
In this case the line should be checked for overstress with a stress factor of 0.3 as per ANSI B 31.3. I am finding difficulties in satisfying this condition in many cases which almost force me to go for stainless steel material.Is there any alternate method or satisfy this condition?

Hello Haider Shariff,

Have you looked into the vaious grades of ASTM A-333 piping material?

Regards, John.

or Stainless Steel??? .....!!!!!!!

Dear Haider,

Please go through the following link. Your temperature may be pretty low for LTCS. But, consult some good steel makers for help as sometimes low cost of material comes with some drawbacks & possible pitfalls. If you know the same well before they occur, at least you can hedge by getting your choise peer checked.

regards,
sam

http://www.key-to-steel.com/Articles/Art61.htm

Haider,

As Breen & Luf Sirs pointed out, you must have checked from material handbooks for A-333 & SS piping materials lower temperature limits.

From Bednar's 1981 Ed of Pr Vessel Handbook, I got the following for you:
- DEG F
SA-333 Gr-1/6 4 to -20
SA-333 Gr-6 -21 to -50
SA-333 Gr-3 -51 to -150
SA-333 Gr-8 -151 to -320

regards,
sam

For some or maybe most very cold cryogenic piping systemsAustenetic Stainless steels are popular and perform well.

Take a look at the "Piping Handbook"

Dear All,
Thanks for the guidence.
I already know that stainless steel is good for very cold temperatures.
However, in my case as per normal operating conditions the carbon steel or LTCS is enough.
But I have some occasional conditions where the temperature drop upto -104 Deg C.Hence selecting a stainless steel is not economical to satisfy only the occasional condition.
For this type of conditions I would like to satisfy (as per my project specification) the conditions mentioned in clause 323.2.2, Table 323.2.2 and Fig 3232.2.2B of Chapter III of ASME31.3. In doing this I find difficulties in solving the stress to the maximum limit of 0.3 * Sc, which otherwise call for major routing change or switching over to Stainless steel.
For this I request our members to help to avoid changing the material to Stainless steel.

Can i use A312 316L for -85c?

I am finding the Code (pages 42,43,44)
Somewhat confusing

Without impact testing other than that required by material specification, you can if you keep stress ratio within 0.3 upper limit, otherwise with impact testing of base metal and weld metal deposits - as I understood by reading 2002 Ed of code B 31.3 for A312 316L. To be sure please consult any cryogenic piping vendor that structure change from FCC to BCC should not occur within your temperature of application.

regards,
sam

For Haider,

Why don't you SS flexhose instead of changing piping layout, with that, you may find it easy to keep stress ratio within 0.3.

I presume you noticed that the use of SIF's in the calc is not required, and that it is the state of stress in the cold condition that is evaluated, not the stress range. However, also note that there is a more conservative treatment of allowances that is required in the calc.

Here's an out of the box idea to consider

Talk to your process engineers and make sure the -104 case is a realistic one and not an overconservative bit of rounding on their part. Particularly for upset cases, I've often found that process engineers can justify more favorable conditions when they are challenged to do a more rigorous examination.

This may not alleviate all of your trouble, but if they can bring that temperature up, it may increase the pool of materials that you can consider.

A good suggestion!

However what it turns up who knows, I have had process engineers tell me that water lines tied to a safety shower had to be designed for 600F or so.

After getting the thumbscrews out I finally got the fact theyt were citing a fire event temperature! The correct Max and Min op temps are very important and usually hard come by....