How does US Bellows define a hydro-test pressure based on design pressure?

When engineers design fluid networks, a common question arises: Exactly what is a hydro test, and how do you determine the correct parameters? 

A pipeline hydrotest ensures the structural integrity of the entire system before it enters active service. During this procedure, the piping is filled with liquid to apply hydrostatic water pressure against the internal walls of the entire system. 

Industry standards require that the hydrostatic test pressure be calculated as a specific multiplier of the maximum design pressure, corrected for the temperature to ensure its operational integrity. The specific multiplier and correction factor will vary based on the piping design code.

Establishing the correct hydro test pressure validates the safety of welded joints and mechanical connections. This careful evaluation also applies to the pressure testing of valves to guarantee zero leakage under stress.

When determining the pressure for hydrostatic testing of your expansion joints, the most important aspect is the applicable design codes. Normally, the ASME SEC VIII Div.1 general hydro-test pressure will be 1.3 x design pressure, but if you are testing for ASME B31.1, B31.3,B31.4, it will be 1.5 x design pressure. 

That being said, there are many other considerations that will determine the test pressure, such as:

• Test Duration
• Temperature
• End conditions of the assemblies
• Special cases based on the customer’s situation

Be sure to discuss with our engineers so that we can correctly test your bellows and expansion joints.