After construction, all hydrocarbon process system pipework is required to be subjected to a strength test, using water as the test medium. This is referred to as hydraulic testing or hydrotesting. Vessels are also required to be subjected to the same test and this is usually performed at the place of manufacture, though has to be carried out on-site in the event of re-commissioning after a 10-year shutdown.

Test hydraustatique

In order to perform an effective hydrotest, air needs to be removed from the system, otherwise it will negatively influence the results. Hydrotest packs are designed so that the system high-point has a vent to atmosphere, so that all the air within the system can be removed whilst being filled with water. But, it is never possible to eliminate all the air, so calculations need to be performed to take account of how much is present.

During filling of the system with water, chemicals are often included to prevent flash corrosion when the system is tested and drained. Once the system is filled, it will be pressurised in stages to its final test pressure, using a high-pressure fluid pump. Because water is virtually incompressible, the amount of water which must be injected to raise the pressure is very small relative to the volume of the system being tested. Sometimes this means that a hand-operated pump will be all that is needed, though more usually, a combination of hand and air-driven pumps are used.

Test hydraustatique sur site


Willda Group owns and operates many complete sets of process and pipeline hydrotesting equipment, all located at its base in Hassi Messaoud where very experienced Algerian personnel have been fully-trained in its operation and project management. All of our equipment and personnel are available on-site at a moment's notice.

Our equipment includes

  • Manual hydrotesting pumps
  • Full range of air-driven, high-pressure
    hydrotesting pumps
  • Certified hoses and fittings
  • Calibrated pressure test gauges
  • Calibrated pressure chart recorders
  • Calibrated temperature recorders
  • Test manifolds
  • Injection manifolds
  • Water storage tanks
  • Pressure relief valves