Hi Jon,
For the first time, I find myself in disagreement with you. It was bound to happen sometime.
The concern about temperature during hydro testing is brittle failure. Although the proper temperature of the test medium is not a bad place to start, brittle fracture is directly related to the temperature and load on the base metal. We have always measured the temperature of the base metal, and I believe in the NBIC (or one of the ASME Codes) the wording specifies "base metal temperature". This is from memory, but I believe it is accurate. When I can get my hands on my code books, I'll confirm it.
I hope things are well for you in land of K.
Charles
Most of the time you record Atmospheric temp, base metal temp and medium temp(if possiable). Usually the base metal temp and the test medium temp will be within 1 degree of each other.
B31.1 and .3 does not specify the time required. I have tested for 5 minutes up to 24 hours. It depends on the service, location and customer. If the piping system goes underground the time has to be extended.
BABRT's
One degree variation between base metal & test medium is possible if the test section is thermally stabilised (both are in thermal equilibrium- possible in under ground pipelines). But if the test section is exposed to the sun one degree variation cannot be expected.
Charles, no need to lay your hands on the code to confirm, I agree and stand corrected. :) The purpose is for brittle fracture. We just used to check both temps at former company. Things are well, I fly back to the states for a much needed holiday this Wednesday. :)
dbigkahunna,
Both B31.3 and 31.1 have minimum times for hydrotesting.
B31.3 Clause 345.2.2 Examination for Leaks : A leak test shall be maintained for at least 10 minutes, and all joints and connections shall be examined for leaks.
B31.1 Clause 137.4.5......."The pressure shall be continuously maintained for a minimum time of 10 minutes and may then be reduced to the design pressure and held for such time as may be necessary to conduct the examinations for leakages."
Regards,
Shane