TEMPERATURE READINGS FOR HYDROTEST

By jon20013 (*****)

Date 05-04-2008 13:33

We always used the temperature of the test medium. I have been on jobs where there was wild fluctuations in pressure but this was over the course of a 24 hour hydro, as required by our customer. If it's possible to measure the temperature of the test fluid AND the external surfaces you should be able to calculate for any pressure changes noted. On a majority of jobs I've worked hydro was only held for minimum durations; 10 minutes, or long enough for all the joints to be inspected.

By chall

Date 05-04-2008 16:40

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

By dbigkahunna (****)

Date 05-05-2008 00:28

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

By mujibali_m_a (*)

Date 05-05-2008 05:40

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.

By jon20013 (*****)

Date 05-05-2008 00:36

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. :)

By Shane Feder (****)

Date 05-05-2008 07:07

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

By G.S.Crisi (****)

Date 05-05-2008 19:35

Gentlemen,
just for your information, the specifications set forth by The Lummus Company for hydro tests of pressure vessels say that the minimum water AND vessel temperature during the test should be 70 ºF (approx. 20 ºC).
The Lummus Company is (or at least was) a highly respectable engineering firm specialized in design of oil refineries and petrochemical plants. They built plants all over the world.
By the way, does someone know if it is still in business?
So many firms went into bankruptcy or were purchased by other outfits along the last 20 years ............
Giovanni S. Crisi
Sao Paulo - Brazil