2 units in stockAPI · ASME · ISO · NIST · UKAS
Hydrostatic pressure testing of pipelines, tanks, and pressure vessels to verify structural integrity, detect leaks, and confirm safe operating conditions.
Hydrostatic testing fills a pipeline, vessel or piping system with water and raises it to a defined test pressure above the design pressure to prove both mechanical strength and freedom from leaks. Water is used because it is nearly incompressible, so a failure releases little stored energy.
We calculate the correct test pressure and hold time, pressurise with calibrated pumps, record the pressure throughout the hold, then safely depressurise and dewater — and issue a stamped test certificate with the pressure chart.
A hydrostatic test proves two things at once: strength — the component withstands a pressure well above its normal operating pressure without rupture or permanent deformation; and tightness — no water escapes through welds, joints, gaskets or the parent material during the hold.
Passing gives documented assurance that the system is safe to commission at its design pressure.
We prepare and clean the system, install test blinds and calibrated gauges, fill with clean water while venting all air, then raise pressure in controlled steps with high-pressure test pumps to the calculated test pressure — commonly 1.3 to 1.5 times design pressure per the governing code. Pressure and temperature are logged continuously against a chart recorder or data logger for the full hold period.
Where hydrotesting is impractical, a pneumatic test to code may be used under stricter exclusion zones. Afterwards we depressurise in stages, dewater and, where required, dry and preserve the system.
Test pressure and minimum hold time are derived from the applicable code and the component's design pressure, material and temperature — for example ASME B31.3 process piping, B31.4/B31.8 pipelines, or BPVC Section VIII vessels. The system is accepted when it holds the test pressure for the required period with no pressure drop attributable to leakage, no visible leaks and no permanent distortion.
Any drop is investigated, corrected and re-tested. Ambient temperature effects are accounted for so a genuine leak is not confused with thermal contraction.
Pressure testing stores large forces, so control of the work is paramount. We use a written test pack, calibrated relief devices, isolation and venting plans, and enforce exclusion zones sized to the stored energy. Pneumatic tests, which store far more energy than hydro, get correspondingly larger barriers and stricter step-holds.
Test water is managed responsibly — sourced, treated where needed, and disposed of per site environmental rules.
On acceptance we issue a hydrostatic test certificate stating the test medium, test pressure, hold time, result and calibration references, accompanied by the original pressure–time chart and a marked-up test package. This is the permanent record that a line, spool or vessel was proven before commissioning.
We hand over a complete, traceable dossier suitable for client, insurer and authority review.
Water is almost incompressible, so it stores very little energy under pressure. If a component fails during a hydrotest it releases that energy safely, whereas compressed air or gas can fail explosively. Pneumatic testing is used only when hydro is impractical, and always with larger exclusion zones.
From the governing code and the item's design pressure, material and temperature. For process piping to ASME B31.3, for example, the hydrostatic test pressure is generally not less than 1.5 times design pressure, adjusted for temperature. We document the calculation in the test pack.
The minimum hold time comes from the code and the component — often ten minutes for strength, then a longer tightness examination, and much longer for buried pipelines. The line must hold without any pressure drop caused by leakage over the full period.
We safely depressurise, locate the leak or weakness — often with the pressure chart and a visual or NDT check — the defect is repaired, and the system is re-tested from scratch. Nothing is certified until it holds cleanly.
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