Hydro Test Pressure

Tushar Zope,

First calculate the test pressure as per B31.3, i.e. 1.5 x Design Pressure x temperature correction, then check that it does not exceed the yield strength. If this calculated test presure exceeds the 1.5 times the flange rating you have two alternatives. Here, you need to use your engineering judgement. 1) reduce the test pressure. e.g. this may be done when design pressure is actually very low but due to higher temperature correction factor, test pressure reaches very high value which is never going to occur. 2) Increase the flange rating. However let me tell you even if your calculated test pressure exceeds the 1.5 times flange rating, you can still use the same flange rating at your own risk as code does not restrict it.

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Friends,

Please assist me with a problem with hydrotest pressures?

For some lines with "calculated" wall thickness (new lines tie-ing into

existing lines), I have calculated the test pressure as per B31.3, ie 1.5 x

Des Px temperature correction, then checked that it does not exceed yield

strength.

But there is also a question of full flange rating, this calculated test

pressure exceeds 1.5 x full flange rating at ambient.

If we test at the calculated test pressure (as long as it is within yield),

we would risk distorting the flanges, but the hydrotest would fulfil its

purpose.

If we test at 1.5 x full flange rating, the flanges would be safe, but the

test pressure would be too low to fulfil the purpose of the hydrotest.

Which is the correct method?

Best Regards.

Tushar Zope

Extn: 162

[Non-text portions of this message have been removed] Received on Thu Sep 04 00:01:00 2003