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Pressure Measurement · Glossary

What is Hydrostatic Test Pressure?

proof test with waterPressure Measurement

Hydrostatic test pressure is the pressure at which piping or vessels are tested with liquid to prove strength and leak tightness.

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Hydrostatic Test Pressure Explained

Equipment is filled with water and pressurised above its design pressure for a set time. Water stores little energy, so a failure is much safer than with gas.

Instruments that cannot take the test pressure, such as low range transmitters and gauges, must be isolated or removed during the test.

Hydrostatic Test Pressure Formula

Ptest = 1.5 × Pdesign × (ST ÷ S)
Pdesigndesign pressure
ST, Sallowable stress at test and design temperature
Example: ASME B31.3 process piping. ASME VIII Div 1 vessels use 1.3 × MAWP × stress ratio.
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Calculators for Hydrostatic Test Pressure

CalculatorHydrostatic Test Pressure CalculatorFree online calculator with formula and worked example.CalculatorPressure Decay Leak Test CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Hydrostatic Test Pressure?

Hydrostatic test pressure is the pressure at which piping or vessels are tested with liquid to prove strength and leak tightness.

Why isolate instruments during a hydro test?

The test pressure may exceed their overpressure limit, and test debris can block small ports.

Why not test with air?

Compressed gas stores far more energy, so a rupture can be violent. Pneumatic tests need extra safety measures.

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Instrumentation and control standards

A practical guide on instrumentationblog.in with more detail on hydrostatic test pressure and how it is applied on real plants.

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More Pressure Measurement Terms

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All pressure measurement terms · Full glossary A to Z

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