Hydrostatic pressure testing is carried out on completed pipelines to verify their integrity before commissioning. The pipeline is filled with water and pressurised to a level exceeding the design operating pressure, typically 1.5 times the working pressure. A failure during testing can propel pipe fittings, end caps, and water with lethal force. Exclusion zones, trained test personnel, and strict adherence to the approved test procedure are essential for every hydrostatic test.
Key Hazards
Violent pipe or fitting failure under test pressure causing fatal projectile injuries
End cap or blank flange blow-out from inadequate restraint against thrust forces
Uncontrolled pressure build-up from malfunctioning test pump or blocked vents
Personnel entering the exclusion zone during the pressurisation or hold period
Control Measures
Produce a written test procedure specifying the test pressure, duration, and exclusion zone requirements.
Calculate the thrust forces on end caps and blank flanges and provide adequate mechanical restraint.
Establish and maintain a physical exclusion zone around the test section for the entire test duration.
Ensure the test pump has a calibrated pressure gauge and a functioning pressure relief valve.
Fill the pipeline slowly and vent all trapped air completely before beginning pressurisation.
Increase pressure gradually in stages, inspecting for leaks at each stage before advancing further.
Appoint a trained test engineer to supervise the test and control access to the exclusion zone.
Record pressure and temperature readings at the intervals specified in the test procedure.
De-pressurise the system gradually and confirm zero pressure before removing any end cap or restraint.
Emergency / Rescue
If a leak or failure occurs during testing, shut down the test pump immediately and evacuate the exclusion zone. Do not approach the failure point until the system is fully de-pressurised. Call for the test engineer.
Remember
A pipeline failure under test pressure can propel components hundreds of metres with lethal force.
End caps and blank flanges must be mechanically restrained against the thrust force during testing.
The exclusion zone must be physically enforced and no one may enter during pressurisation or the hold period.
All air must be vented from the pipeline before pressurisation because compressed air stores lethal energy.
Pressure must be increased gradually in stages with leak checks between each increment.
De-pressurise fully and confirm zero pressure before removing any restraint, cap, or fitting.
Applicable Legislation: Pressure Systems Safety Regulations 2000 · CDM Regulations 2015 · Health and Safety at Work etc. Act 1974 · BS EN 805 (Water Supply)