This guide explains how HydroProof sizes and plans a pressure test, from test pressure through water, safety and cost.

How hydrotest pressure is calculated

For ASME B31.3 the hydrostatic test pressure is at least 1.5 times design pressure times the stress ratio St/Sd (allowable stress at test temperature over allowable stress at design temperature), with the ratio capped at 6.5. For B31.1 it is 1.5 times design pressure. The stress ratio matters when the test is run cold on a system designed hot, because the metal is stronger at the lower test temperature.

Why pneumatic tests are dangerous

Water is almost incompressible, so a hydrostatic failure releases very little energy. A gas stores large elastic energy that is released violently on failure. HydroProof estimates that stored energy and an equivalent TNT mass, and gives an indicative scaled safe distance - but the real exclusion zone must come from a formal risk assessment.

Temperature correction

Because trapped water barely compresses, a small temperature rise produces a large pressure rise - on the order of 0.4 to 0.5 MPa per degree C in a rigid filled system. Plan venting and temperature monitoring so the test pressure does not drift above the maximum allowable during the hold.

Volume, water and logistics

The internal volume sets the fill water, which drives tanker loads, pump size, fill time and disposal. HydroProof works the package volume from pipe or vessel geometry, adds reserve and contingency, converts to water mass and tanker loads, and rolls duration, labor and cost into a single plan.

Standards

Methodology references ASME B31.3 and B31.1, ASME VIII Div.1, PCC-2, API 510/570/574/653, OSHA and Energy Institute safe-testing practice. HydroProof is a screening and planning aid; confirm test pressures, temperature correction and all safety distances against the governing code and a qualified test and safety procedure before any pressure test.