Hydrostatic Test Rigs Design PSV/PRV

[kacarrol]

I have not had a chance to witness a pressure test and was wondering:

The test rigs that are set up in a shop, do they have a pressure safety valve set to pop at the highest pressure the test rig can handle and then use pressure relief valves to make sure the pressure test does not go above the test pressure required. Or do they have multiple pressure safety valves for the range of pressure tests they may do and just swap them out for each test? Or do they just watch the gauges very closely to be sure it doesn't go beyond the test pressure?

I was just thinking about it the other day after doing some pressure vessel calculations but haven't been able to find the answer and was curious how they have a rig that can handle multiple pressures but still keep it from going above the test pressure.

Thanks,
K

 

[rustbuster]

Typically,

Test headers are designed for the highest pressure. Requirements for overpressure protection is identified in testing procedures if warranted.

Typically the gauges are monitored and manually protected.

 

[jharris3]

rustbuster is putting it kindly

Generally, you are on your own to identify appropriate safety precautions with respect to overpressure.

There are requirements to be met per Code for protecting the vessel from unecessary yielding but its up to you to provide overpressure protection for your hydrotest equipment.

Just make sure you use machined valves (cast valves are brittle), good regulators, and a good throttle on the pump. Set yourself up to isolate the pump from the rest of the system without standing next to your vessels. Increment the pressure in enough steps to mitigate overshoot.