Re: [MW:26391] Pressure Drop During Hydro test due to temperature difference

yes the same case is happen with my testing also. Can any one give the exact reason for this

On Tuesday, March 5, 2013 at 5:05:21 PM UTC+4, madhan wrote:

Hi DESAI,

As you mentioned temperature difference does make a difference in pressure. Also kindly check the pump in line to the spool is closed and the line is isolated from pump.

Engage another pressure gauge in the highest point and lowest point of the line and note down the pressure difference.

Try to vent the line from the highest point and then pressurize to the test pressure gradually in 3 or more steps to stabilize the pressure.

As far as ug99 is concerned there is nothing mentioned about the pressure drop without visual leakage.

Regards,
Madhan

On Mar 5, 2013 4:57 PM, "hard" <hvdes...@gmail.com> wrote:

Dear Experts,

                      I have gone through the Hydrostatic test @ 32 kg test pressure, on site, for Piping spool(Line size - 4" X Sch 40).

                      Holding time - 1hr.Spool was having total 32 Groove weld joint & some portion of spool is in upstream side (Directing towards upward oppsite gravitation)

                      Test start time at 32 kg pressure - 1:20 p.m.

                     

                      After 1 hr (at 2:20 p.m.) pressure went down to 30 kg? - There is no leakage observed visually (or felt during direct check by rubbing the hands on the joints) on the welded joints or on the temporary joints. First of all can it be acceptable (Any small amount of pressure drop, like this, is acceptable as per code? is code specifies some tolerance for this kind of conditions? May be due to Temperature difference)

                     

                      We have continued the test for additional 1 hr in order to find the exact reason for this 2 kg pressure drop.After 3:20 p.m. we have observed the pressure dropped up to 22 kg? and all the other conditions were remain same.No visisble leakage observed or felt.Only differece between conditions is the Temperature difference during 1:20 p.m. and 3:20 p.m.This difference might be 5-7 deg.So This Temperature difference will effect this condition in this manner i mean it is possible to have around 10 kg pressure drop due to Temperature drop (if we consider here 10 deg Temperature drop then also this amount of pressure drop) can be expected?

                       

                      Can we use any valve as a temporary joint during Hydro Test?  i think code is not denying for the use of valve as a temperary joint? (Instead of Flanges).

                      

                      Last but not the least, During this type of conditions, can we accept the test on the bases of no leakage found during visual inspection.I think UG-99 and ASME B31.3 chapter VI clause 345 is not exactly specifying the acceptance criteria. can any one guide me for any interpretation with respect to ASME? or can any one suggest me any other code or standard which is specifying the exact acceptance criteria for Hydeo test?  

 

Regards,

Hardik Desai

 

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