Hydro test per B31.3

[rfitts]

We are being contracted to fabricate an austenitic(316) pipe in pipe lance feeding a dual liquid nozzle(air and steam). Process pressures are 80psi. 80 psi in the inner pipe and 80 psi in the outer pipe. Lance will be operated in a duct exposed to 1400°F gas temp. Typically we receive only process pressures and temperatures. If one was to use B31.3 Paragraph 345.4.2 Test Pressure to determine hydro test pressure. In this case St/S exceeds the allowable 6.5...what does one do when this happens? If I do the calculation using the process info the ratio equals 8.7 and the hdro pressure equals 1069 psi. Any help would be appreciated.

 

[metengr]

According to my review of B31.1 (2004 Edition), my interpretation of paragraph of 345.4.2 Test Pressure under the section titled Hydrostatic Leak Test states that the hydrostatic test pressure is 1.5X design pressure in subparagraph (a). You have decided to use subparagraph (b) as well. However, this only applies if your design pressure is a function of operating temperature. In your case, you have a fixed pressure at 80 psi regardless of service temperature. So, your hydrostatic test pressure would be 1.5X 80 psi.

 

[metengr]

My review was of B31.3 not B31.1.

 

[rfitts]

metengr, thanks for the reply. I read (b) as for design temps above the test temps.....this application design temp is 1400°F and the test temp is ambient. Am I missing something here?

any additional comments?

 

[metengr]

rfitts;
Yes, I see your point indeed. I should have stuck with ASME B31.1 because this is the piping code I deal with more frequently than B31.3.

Well, if you read further in (b) the limit would be capped at 6.5 for this ratio, and not 8.7, so that might help you with having to test at 520 psig.

 

[metengr]

Correction 780 psig, 1.5 X * 6.5 =