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ASME Sec.8- fig. UCS-66.2

ASME Sec.8- fig. UCS-66.2

ASME Sec.8- fig. UCS-66.2

(OP)
In regards to calculating the coldest recommended metal temperature during hydrostatic test, I am not able to interpret the general note (6) given for fig.UCS-66.2. It does refer to UG-99(h)which is clear, but the basis for arriving at 17 deg from Fig-UCS-66.1 is not clear. Could somebody please explain with a simple example showing calculations.

RE: ASME Sec.8- fig. UCS-66.2

You should be able to calculate an adjusted MDMT per the steps in UCS-66. Then, for minimum hydro test temperature, increase this MDMT by 30F (17C) per UG-99(h).

RE: ASME Sec.8- fig. UCS-66.2

(OP)
Thanks codeeng! But what is not clear how did they arrive at this value of 30F(17C). Of course it is given in UG-99(h). But what is the calculation basis for this. Thanks.

RE: ASME Sec.8- fig. UCS-66.2

Here is a thread that contains a file attachment regarding ASME Section VIII impact testing;
Thread292-116022

RE: ASME Sec.8- fig. UCS-66.2

The 30F is just margin because your stress at hydro testing can be higher than operating.

RE: ASME Sec.8- fig. UCS-66.2

(OP)
Codeeng, you are right that 30F is the margin to take care of the higher stress at hydrotest. I am only curious to know the basis for this value 30F. My question is why 30F, why cant 20F or 40F. I am sure the Code must have had some basis in arriving at this margin 30F. I only want to know what is this basis. Thanks

RE: ASME Sec.8- fig. UCS-66.2

Your original question was:

"....the basis for arriving at 17 deg from Fig-UCS-66.1 is not clear."

The 17C (30F) does not come from UCS-66.1. Its a margin to be added to the MAWP calculated from UCS-66.1.

As to why 30F ? Its a safety factor established from experience. It is not calculated, its just a rule. There are many other Code requirements based on rules rather than analysis.

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