ASME BPVC VIII-2 2010 test pressure

[TerryR1]

I'm having trouble calculating test pressure for my vessel under this code.

Rule 8.2.1 (p8-4) has a pair of calculations for calculating test pressure. One involves a term ST, without mention of what it ST is.

Test pressure 1 = 1.43 x MAWP
Test pressure 2 = 1.25 x MAWP x ST / S

I'm pretty sure S is the allowable material stress as defined on page 4-12.

I found 2 definitions of ST, but am unsure about either:

ASME8-2 p4-313,325,325, "flange tangential stress". If the intention is to have a different test pressure for flanged pressure vessels, the verbiage below the equation doesn't add up: "The ratio ST/S...shall be the lowest ratio for the pressure boundary materials, excluding bolting materials, of which the vessel is constructed"


ASME II-D, p861, as the Tensile Strength of the material, but if I use that value, the test pressure is enormous:

For SA-564 - ST=140ksi , S= 58.3ksi
MAWP = 10,000psi
Which results in a test pressure requirement of 30,000psi. So I don't think that is right either.

Help? Thanks!

 

[TGS4]

ST is the allowable stress at the test temperature. You are testing the vessel to 1.25 times the design conditions as if they were at temperature, so you have to ratio the allowable stress at temperature to the allowable stress at the test condition.

This is particularly significant for high-temperature vessels.

 

[TerryR1]

Ok great! That makes total sense. Thanks much.