ASME B31.3 Calculating Hydrostatic Test Pressure

[NKBeresford]

Carbon Steel system
165 psig
150°F
Normal Fluid Service
Is the hydrostatic test pressure 247.5 psig or 255 psig?

I have always calculated the hydrostatic test pressure in accordance with Equation 24 and used the allowable stresses of the pipe material (A106 Gr. B).

Is this correct? Interpretations 18-03 and 19-10 might make one think that all materials (A105 forgings, A234 WPB wrought fittings, A216 WCB castings) might need to be considered also.

A106 Gr B and A234 WPB have the same Allowable Stresses. A105 and A216 WCB have higher Allowable Stresses (that lead to a higher test pressure).

 

[NozzleTwister]

NKBeresford,

I saw your post and was a bit confused. I went and read the interpretations and per the interpretations, it looks like your test pressure would be 255 psig (I didn't check your math).

I've calculated a lot of hydrotest pressures over the years and I've always just used the piping material stresses to calculate the minimum test pressure. Thank goodness that was before Int. 18-03 & 19-10 came along to complicate things.

I have always looked at the different pipe materials in a hydrotest system to base the test pressure on the material that produces the highest pressure. And I always reviewed the system for any weak components that won't withstand the test pressure but, it never crossed my mind to also consider flange material stresses for calculating the hydrotest pressure.

I would like to think that we are misinterpreting the interpretations. Hopefully one of the Code gurus will chime in with their opinion.

Thanks for posting this question..........I think.

Kevin Monroe

NozzleTwister
Houston, Texas

 

[dtn6770]

Here's something else to think about...

If you test with stainless steel flanged thermocouples in the system, be aware that their ambient rating could be less than carbon steel flanges of the same class.


A-182 F304/F304H
class 150 = 275 psig
class 300 = 720 psig

A-182 F316/F316H
class 150 = 275 psig
class 300 = 720 psig

A-105
class 150 = 285 psig
class 300 = 740 psig