Hydrostatic and pneumatic test ammonia storage tank

[tarojm]

We have a 5000 ton double wall ammonia tank under construction in our plant designed with respect to API620. I would like to know the procedure for hydrostatic and pneumatic test of the tank after comletion of the construction.Is it necessary to check all the weld joints by solution film or it is enough to relay on the gauge during the pneumatic test.

 

[ApC2Kp]

tarojm,
Compare the volume of 5000 ton ammonia tank to the volume of a leak, and think of time needed for pressure decay to register on a gauge - you will want to do a soap solution film bubble test. Now, the welds can be tested by using a plexiglass vacuum box over a short portion of the weld, and injecting the solution film over the weld surface inside the vacuum box. Each weld could be leak tested the same day it was made. That way a leak test doesn't have to wait for the entire vessel to be completed. Repairs can also be done by same welders - this would be quick feedback to their welding quality.