Hello stressers,
I have an query now I am dealing with pipe system with temp -48 and material is A333 6 which its minimum design metal temperature is -45.5 but it is a flare system and normally operate as ambient temperature and -48 is only occasional so our client accept to use this material in our system without do any impact test.
But when I input temperature (-48) in CAESAR II I find SH1 is zero.

So how can I deal with it?

Can I ignore this and check stresses with -48?

You can manually input the allowable stress. Though you did not specify which piping code you're using, you should be aware that there are additional rules within B31.3 regards to allowable stresses below MDMT without impact testing.

See figure 323.2.2B and note corresponding text.

Thank you Michael,
I read paragraph 323.2.2 (d) and it's refer to material covered by 323.2.2 (a) and (b) and paragraph 323.2.2 (b) talks about material with letter designation in table A-1 but my material is A333.
So I think that figure 323.2.2B doesn't applicable for my material, Am I right or not ?

And Michael I have one more question if this figure is applicable for my material and I get stress ratio then I multiply it with stress for material at temperature 21 ? Am I right or not?

It is a bit of word spaghetti, isn't it?

Paragraph a basically states that in order to use a a material above its MDMT, its components have to have been qualified via Table 323.2.2 column A.

Paragraph d's inclusion of it basically states "if it's not good for above MDMT, it's not going to be good for MDMT."

Paragraph b states "this is how you calculate MDMT without impact testing." Some 99% of materials we're going to typically run across are going to fall into these designations.

You can impact test materials (for new construction) to get it below the listed MDMT. However, you can't normally do that for existing construction, so here we are with Figure B, which I contend to be applicable to any material covered within Figure A.

Do the following:
1. Run the analysis at the requested temperature. Make whatever modifications are required in order to get the stresses (sufficiently) below 100%.
2. Calculate MDMT via Figure A, which you did.. -48°C.
3. Rerun the analysis at the requested temperature with SIFs set to 1.
4. Let's say you calculate 64% code stress. Read the stress ratio via Figure B, and read the Temperature Reduction value. For 64%, that's approximately 20°C.
5. If MDMT minus temperature reduction value is less than or equal to the temperature you used in your analysis, then you can conclude that you can use the requested material at the requested temperature at the requested piping configuration.

Notes:
1. This doesn't tell you what the MDMT of the material and pipe configuration is. To determine that requires cycling until temperature input = MDMT - temperature reduction.
2. Anytime stresses are below 30%, MDMT is not really a concern.
3. Consider user safety and other effects of extremely cold lines. Does it need insulation? Will it collect ice? Etc.

Thank you very much Michael I appreciate your help. But unfortunately A333 GR6 doesn't have designation letter in Table A (have -45 C) so I think it is not right to use Figure A & B for it. Is that right