In accordance with ASME Section VIII Division I, the hydrostatic pressure is conducted at a pressure of 1.5 times the design pressure. If a container is designed to hold a pressure of 1.0 kg / cm2.g, the hydrostatic pressure test should be performed at 1.5 kg / cm2.g.
Hydrostatic testing is also applied to existing equipment and pipes to check for leaks after they are repaired or maintained. The number of hydrostatic jobs increases during the plant’s rotation period. Because at that time, most of the equipment is open for review, inspection, cleaning, repair, replacement of certain parts or internal modifications.
The use of high pressure is the main source of hazards associated with hydrostatic pressure testing. The hydrostatic test stores energy. High pressure could damage facilities and endanger worker safety. You should have included this in your own hazard identification.
Safety checklist:
To avoid accidents in hydrostatic test operation, we must do good preparation before testing, during pressurization process and depressurization operation. These jobs should be performed in the form of standard operating procedure. And here are the safety checklists for each stage.
Hydrostatic test preparation:
The equipment and / or pipe specification sheet, listing pressure and temperature designs, is available and complete.
* The hydrostatic test pressure and temperature standard are already clearly defined in the related document.
* Supported documents such as P&ID and isometric drawings are available and fit for field built facilities.
* The pressure test schedule should be distributed to all relevant sections on the plant site at least two days prior to the execution date.
* Carry out a good coordination between the related sections involved in the test.
* All test equipment and tools should be inspected for wear and damage.
* Pressure measurement tools are calibrated and their calibration states are still valid.
* The pressure gauges used in the test have sufficient capacity. It is recommended that the pressure gauges have 150% of the maximum allowable working pressure.
* The pressure gauge is safety, with blowout.
* Gauges should be installed in a suitable location so that they can be easily read and will not create additional hazards to hydrostatic testing or expose personnel to the container under test.
* All temporary tools (such as valves, fittings, hoses, flanges, blanking plate, etc.) must be rated higher than maximum hydrostatic pressure.
* Isolate other equipment and pipes that are not included in the hydrostatic test.
* Vents are available and installed at high points to ventilate the air. Check the vent line before testing and make sure it is not blocked.
* Choose the drain valve at the lowest point to completely empty the container and pipe.
* The safety relief valve is already installed. The safety relief valve setting is 1.5 times the maximum allowable working pressure.
* The safety valve is calibrated.
* Isolate the test area and surround it with a security line. Post a suitable safety sign in that area.
* Do not allow persons unrelated to hydrostatic testing to enter the testing area.
* If possible, test from a remote area.
* Make sure all pipe and container supports are in good condition and have been inspected.
* All hoses must be tied together.
* The water temperature must be above 16oC (60 F).
* The hydrostatic pressurization pump is completed with a safety valve.
* Wear appropriate personal protective equipment.
* Do not start the test if a problem is identified.
* Issue a work safety permit by authorized personnel.
Pressurization process:
* Remove all air from container and pipe with water through vent line.
* Pressurization is done gradually / slowly.
* Mark all leak points and repair before testing.
* Do not monitor during the pressurization step directly from the front of the sight glass or the glass level.
Depressurization process:
* Start depressurization by gradually opening the vent valve. Do it slowly.
* Do not open the drain valve if the vent valve is still closed. This is to avoid vacuum conditions inside the container.
* Open the lowest drain point to completely remove the water from the container and pipe.
* Make sure there is no remaining pressure trapped inside the pipe or container.
The hydrostatic pressure test safety checklist above will ensure the safety of the worker and plant facilities. Therefore, do not try to ignore them.