What is Hydrostatic Testing?

analytical assessment and test of mechanical equipmentHydrostatic testing of newly installed natural gas pipelines has been required by federal law since the 1970s. Most hydrostatic testing is done via the U.S. Department of Transportation’s Pipeline and Hazardous Material Safety Administration, and they administer the national regulatory program to assure safe transportation of natural gas. But what exactly is hydrostatic testing? Here we explain everything to know about this process.

What is it?

Simply speaking, hydrostatic testing is an analytical assessment and test of mechanical equipment with on site machining services. Basically, it is when components of an application, such as the piping, industrial gearboxes, or pressure vessels are tested for strength and leaks by filling the component with a pressurized liquid.

How does it work?

With hydrostatic testing, the component is completely filled with water until it reaches a specific pressure. The pressure is then sustained for a couple minutes in order to adequately check for leaks. In order to make sure every leak is properly sealed, some engineers apply a tracer of fluorescent dye to the liquid to find even the smallest of cracks.

Why is it required?

Typically, hydrostatic testing is used as the final analytical assessment and test of mechanical equipment before the machine is returned to service. While it does not ensure the longevity of the application beyond the time of the test, it is important to invest in a long-term testing procedure, such as a proper engine heads and valves repair and renewal.

Are there different methods of hydrostatic testing?

Yes, there are two primary methods used by engineers, mostly for cylinders and vessels.

1. Water jacket testing: the vessel is filled with water, placed in a sealed container, and connected to a calibrated gas tube. It is pressurized for a long period of time, which will force water out of the test jacket into the tube. This is a way for the engineers to figure out how much the vessel has expanded.

2. Direct expansion method: the vessel is completely filled with water, and additional water is continuously pumped in until the test pressure is reached. So, the amount and weight of the water pushed into the vessel allows the engineer to see how much the vessel expanded.

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