Hydrostatic Testing

November 20, 2018

 Hydrostatic testing, AKA hydro-testing, assesses pressure vessels such as oil tanks, boilers, pipelines, gas cylinders, and fuel tanks for strength and leaks. Hydrostatic testing is typically part of a routine check after a system shutdown or after a repair to make sure the system is still operable.

The Importance of Hydrostatic Testing

Hydro-testing will tell you:

●        The ratio of test pressure to operating pressure

●        How the system will handle pressures well above the Specified Minimum Yield Strength (SMYS)

●        How to prepare pressure-to-volume plots

●        Inline conditions of existing pipelines

●        How a pressure reversal will affect the system

How Hydro-Testing Is Done

Hydrostatic testing takes place following the installation of new pressure equipment or the repair of an existing system. With the system shut off, a system component is completely filled with water, oil, or air. Additional pressure is then applied and the equipment is examined for leaks. The examination can be done by visual inspection or with the aid of sensors, fluorescent dye, or tracers.

Common Types of Hydrostatic Testing

There are three common methods of hydrostatic testing. These three techniques are effective for testing pressure vessels up to 10,000 PSI.

The Water Jacket Method

Equipment vessels are filled with the testing substance and then loaded into a sealed water-filled chamber, AKA the test jacket. Pressure is applied to the vessel causing it to expand and force water out of the water jacket. This water is measured for volume. If the volume of displaced water reaches or exceeds the vessel’s permanent expansion value, the vessel should be taken out of service.

Direst Expansion Method

This technique involves filling the equipment to be tested with water, applying pressure, and then measuring the volume of water displaced after the pressure is released. If this volume, the total expansion value, is greater than the permanent expansion value, the equipment should be decommissioned.

Proof Pressure Method

The proof pressure method, AKA modified hydrostatic test, involves applying pressure on a vessel  two-to-six times greater than normal operating pressure. If the vessel can withstand twice its normal operating pressure, it meets safety requirements.


Learn how Rain for Rent supports refineries with hydrostatic testing, providing tanks and boxes, pumps, pipe and hose, filtration units, spill containment, and more.

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