Hydrostatic Pressure Testing | Health and Safety


Hydrostatic Pressure Testing | Health and Safety

Saudi Aramco Oil Company is one of the biggest oil companies in the world with a 21000+ km long pipeline network having reliable customers around the globe. Safety is the highest priority, so routinely conduct tests designed to measure that pipeline segments are sound, often referred to as pipeline integrity. One of the common methods for checking pipeline integrity is the Hydrostatic Pressure Test.

Hydrostatic Pressure Testing is a process that uses water to exert pressure on a pipeline at levels greater than its usual operating pressure to see if it has any leaks. A segment of pipeline designated for testing is temporarily removed from service by closing the nearest valves on both ends to stop the flow of natural gas. To expose and access the pipeline, excavations are dug at both ends of the test segment and the gas remaining inside is safely vented.

The short sections of the pipeline are removed to isolate the test segment. Then the open ends on both sides of the test segment are sealed with test head caps. Next, the open ends of the main pipeline on either side of the test segment are sealed with end caps. Then, large tanks that have been brought to the test site are filled with water. These tanks are connected to a pump that is, in turn, connected to one of the test heads. Water from the tanks is pumped into the test head which also contains a foam plug. The pumped water propels the plug through the test segment, pushing the air out and filling it full with water. The water pressure is then increased to a point greater than the pipeline will normally operate. After holding the increased pressure for 8 hours or more, the test is complete.

If the hydrostatic pressure test results in a leak or a rupture, the segment will be repaired or replaced. After a successful test, compressed air issued to push the foam plug back through the test segment and drain the water back into the water tanks. The water is then disposed of in accordance with regulations and local requirements. The test heads are removed from both ends of the test segment and replaced with hinged caps to be used for the drying operation. A foam plug is loaded into one end of the test segment. Compressed air pushes the plug through to the other end to absorb the remaining moisture.

This procedure is repeated until the test segment is thoroughly dried. Once the test segment is completely dry, the hinged caps are removed from the test segment and the end caps are removed from the main pipeline segments. A new, pre-tested replacement pipeline is installed at both ends of the test segment to reconnect it into the system. Nitrogen gas is then injected into the restored pipeline segment and natural gas from a partially-opened valve pushes it to the other side to vent the remaining air. Natural gas is safely reintroduced into the pipeline segment and it is brought back into service by fully opening the valves.

Finally, the areas are graded and restored as closely as possible to their pre-construction condition. Aramco is committed to the communities and to the environment, so notify local officials about a test, obtain required permits, and comply with applicable regulations. Also, strive to minimize and mitigate any impacts the testing may have on nearby businesses and residents. Hydrostatic Pressure Testing is one of the many tools Saudi Aramco Company uses to help maintain the safety and integrity of our natural gas pipeline system.

*I have taken the name of “Saudi Aramco” to make you understand the pressure testing system better, it’s not for branding purposes.

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