Hydrostatic Pressure Test

Pneumatic vs. Hydrostatic Pressure Testing – What’s the Difference?

Before first use, many industrial components undergo stringent testing to determine their structural integrity. Conduits such as pipelines and storage vessels undergo various pressure-mediated checks to ensure they meet all relevant industrial safety standards. Depending on manufacturer or operator preferences, pressure testing can be done either hydrostatically or pneumatically.

When Should You Perform a Pressure Test?

Pressure testing is a vital part of the completion process for industrial equipment and systems. These checks ensure the inspected components function properly under operational conditions without posing an industrial safety hazard to the personnel who operate them.

There are various points in the operational lifespan of industrial systems where pressure testing is mandatory. Newly fabricated pipelines, containment vessels, and fittings must be subjected to a suitable pressure testing method. Further, pressure testing is indicated following equipment maintenance, component replacement, or repair.

In both newly assembled systems and component maintenance scenarios, the purpose of testing remains the same: safety of operation and maximal efficiency.

What’s the Difference Between Hydrostatic and Pneumatic Testing?

There are fundamental differences between a hydrostatic and a pneumatic test for piping systems, and the most obvious difference is the test fluid utilized. While hydrostatic testing utilizes water as its test medium, pneumatic testing is conducted by channeling air through selected components/equipment.

Other variations in the two testing methods include:

  • The pressure level set for hydrostatic testing is typically at least 30% higher than the maximum operational value. Pneumatic test pressure is usually 10% above the maximum value set by the component manufacturer.
  • Hydrostatic testing is more suited for high-pressure applications, while pneumatic testing is utilized more in low-pressure settings.
  • Lower rates of equipment failure are recorded with hydrostatic testing when compared to pneumatic alternatives.
  • Hydrostatic test media can be recycled or transferred to other sites after use, whereas the air used in pneumatic testing is typically not recyclable.
  • Pneumatic testing requires supervision by experienced personnel, while pneumatic testing can be conducted by semi-skilled staff members.
  • Pressure-relieving devices are mandatory in pneumatic testing but recommended in hydrostatic testing.
  • Hydrostatic testing requires a more extensive post-test clean-up (component drying/moisture elimination) when compared to pneumatic testing.

Pneumatic Testing

Pneumatic pipe testing is conducted using air as the test media to ascertain the structural integrity of a pipeline or other industrial containment or transport vessels. Pneumatic testing can be done using air, nitrogen, or other inert, non-toxic gases. Pneumatic testing requires the incorporation of pressure monitoring and release devices to allow for maximum operator safety.

Hydrostatic Testing

Hydrotesting is another pressure testing option where a liquid (usually water) is injected into a pipe system to check for structural flaws permitting leakage. Hydrostatic testing allows the detection of leaks that only become obvious at elevated operating pressures.

Hydrostatic Pressure Testing

Pneumatic Pipe Testing Procedure

As earlier mentioned, pneumatic pipeline/vessel testing is conducted at a pressure that exceeds the maximum value specified by the manufacturer by at least 10%. The test procedure involves shutting off all equipment valves except the delivery port for the test medium.

The test gas is used to gradually build the pressure within the pipeline until the required test value is met. This pressure is maintained while the system is analyzed for defects. Breaches can then be identified using a bubble-forming substance applied to the exterior of the component being tested.

Hydrostatic Pressure Test Procedure

Hydrotesting is a very straightforward process, requiring operators to shut off all equipment valves except a port through which the test liquid is introduced. A build-up of the test fluid is continued until a predetermined test pressure is achieved. This elevated pressure is sustained for a fixed period while the equipment being tested is checked for leaks.

Leak detection can be done by visual inspection or the use of chemical indicators that detect moisture. Additionally, fluorescent dyes can be added to the test liquid to make visual detection easier.

Which Pressure Test Method is Right for You?

While both hydrostatic and pressure testing methods can be used to objectively assess equipment integrity, operators must choose the test best suited to their unique systems. For high-pressure operations that are not moisture sensitive, hydrostatic pressure testing is recommended. For low-pressure applications where moisture might damage sensitive components or alter delicate chemical balances, pneumatic testing is the smarter choice.

NiGen Offers Hydrostatic and Pneumatic Pressure Testing Services

At NiGen, we offer cutting-edge hydrostatic and pneumatic pressure testing solutions in Houston, Texas.

To learn more about how we can help meet your unique testing requirements, please contact us today!

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