Impact test temperature & UG-84

[There_Will_Be_Mud]

Hello all,

I have a vessel I am working on made of 16" sch 140 106C pipe. MDMT is -20°F. Without impact testing I am only good to about 16°F so I will have to do the impact testing. We will have 11 of these vessels which results in quite a bit of pipe and I would rather not switch to 333 GR6 because the cost difference is pretty substantial.

My question is: Compress is allowing me to get away with impact testing at 5°F and then taking a further reduction of 26°F per UCS-66.1. This puts me at MDMT of -21°F so all good. However, UG-84(b)(2) says "unless permitted by table UG-84.4, impact test temperature shall not be warmer the than the minimum design metal temperature". Since I have a yield stress of 40,000 psi I should be able to test 10°F warmer than my MDMT per table UG-84.4 meaning I could do my impact testing at -10°F, but still a far cry from the +5°F that compress is letting me get away with.

Am I missing something here?

Thanks!

 

[GD2]

OP,
I don't work with compress and so don't clearly understand your statement in first line of para 2.
What I know is that Table UCS-66.1 provides rules to have colder MDMT based on a thickness/stress ratio from your material/thickness MDMT you have determined by UCS-66, which is 16F.

Check if you have by any chance checked as impact tested for A106C in your data input. Usually, if you use an impact tested material, your MDMT will be set at test temperature minus 5F. This could be the reason you are seeing the 5F in your compress. A A106 pipe will not be impact tested at the mill unless you ask for.

Also check on the impact test requirements for welds and HAZ. Rules are different for base material and welds/HAZ.

GDD
Canada

 

[Geoff13]

Send your file to Compress Support and have them explain their outputs.