B31.3 does not seem to mention any duration for an hydrostatic leak test performed on a casted pipe.
We presently perform a 4 hours test.
On your opinion ,what could be an "optimized" test duration?
Test duration. The minimum test duration shall be ½ hour. The test duration shall not be less than a minimum of ½ hour for each 500 cubic feet (14.2 m3) of pipe volume or fraction thereof. For piping systems having a volume of more than 24,000 cubic feet (680 m3), the duration of the test shall not be required to exceed 24 hours.
The hydrostatic test duration should be long enough for an Inspector to visually determine if there are any leaks. I have seen procedures that state 1 hour, 4 hours, etc. It all depends on what you and the Inspector agree with in a procedure.
According to ASME B31.3 para 345.2.2 (a) "A leak test shall be maintained for at least 10 min, and all joints and connections shall be examined for leaks".
So, technically, metengr is correct.