Hot Tap Testing?!
Hot Tap Testing?!
(OP)
I'm confused with the testing of piping hot taps in B31.3 piping, please help clear it up for me! I'm hearing all kinds of different opinion as to what the welds shall be tested at prior to cutting out the coupon in any scenario- whether it is a split tee or weldolet branch connection.
API RP2201 states you should test at 1.1x the current operating pressure in parent pipe so that you do not buckle the parent piping. However, if you do that, the welds are below what B31.3 states is the min hydrotest pressures required (1.5x design pressure x stress ratio). If this is done, would there not need to be additional NDE (100% radiography) done in order to certify those welds per B31.3?
Others say to test at B31.3 min pressure after running a crude buckling calc to verify it won't buckle.
And others say to take it further to the flange rating and test at 1.5x flange limit after running a crude buckling calc. This would certify the welds to absolute max that system could ever see.
Any thoughts?
API RP2201 states you should test at 1.1x the current operating pressure in parent pipe so that you do not buckle the parent piping. However, if you do that, the welds are below what B31.3 states is the min hydrotest pressures required (1.5x design pressure x stress ratio). If this is done, would there not need to be additional NDE (100% radiography) done in order to certify those welds per B31.3?
Others say to test at B31.3 min pressure after running a crude buckling calc to verify it won't buckle.
And others say to take it further to the flange rating and test at 1.5x flange limit after running a crude buckling calc. This would certify the welds to absolute max that system could ever see.
Any thoughts?





RE: Hot Tap Testing?!
The problem comes when your "crude" calculation (I haveno idea what this is) results in damage to the inner pipe . You're also in danger of applying loads to the tee it won't see in service and damaging the fillet welds.
Feel free to do more than anyone else does for no benefit but more risk. If you're that uncertain or inexperienced then appoint a competent contractor and consultant. And listen to them.
Hot taps are not for learning on from first principles.
The only way I know to check on the max differential pressure is by FEA.
Good luck and tell us what you decide.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Hot Tap Testing?!
I'm simply just gathering info, we let the experts do what they do, but it seems we hear from the hot tapping contractors and various pipe owners their approach is different from one another in the way I initially explained. The philosophies on test pressures they want to use are all over the place.
RE: Hot Tap Testing?!
A hot tap, almost by definition, is a modification or repair, otherwise you would take the pipe out of service, cut a hole and weld in a weldolet or a tee. As such using original specs for test pressure is accepted as being impractical in many circumstances.
You need to examine the welds in the best possible manner, but hydrotesting to a pressure > 110% of actual pressure in the main line at the time of the hydrotest is often not possible due to the collapse issue. Therefore other suitable inspection techniques need to be used and specialist experienced contractors used for the welding as the flowing fluid in the original pipe can cool the weld very rapidly if you don't use the correct equipment and techniques.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Hot Tap Testing?!
RE: Hot Tap Testing?!
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.