Is Hydrotesting Really Necessary on Low Energy Piping Systems? 3

[meyerske]

Is Hydrotesting Really Necessary on Low Energy Piping Systems?

For low temperature (but moderate pressure) piping systems where high quality piping material is used, what does a hydro test buy you that a pressure test at the max operating pressure wouldn't?

 

[eeromatti]

Hydrotest during service can slow down growing of fatigue cracks. It could be explained by local hardening of material.

 

[metengr]

eeromatti;

Hydrotest during service can slow down growing of fatigue cracks. It could be explained by local hardening of material.

This is not a completely accurate statement and can be misleading. A one-time hydrotest on new material can be beneficial. Once the material has been placed into service, the disadvantages of hydrotest outweigh the benefits. Existing flaws in components can propagate from other damage mechanisms other than fatigue crack propagation. Using the hydrotest to blunt existing cracks in pressure containing objects without knowing the current condition of the material, and associated risks of brittle fracture or other pre-existing damage to the object is down right dangerous and an unsafe practice.