Hydrostatic test of steel pipe(Pipeline)
Hydrostatic test of steel pipe(Pipeline)
Hydrostatic testing is a method in which pressure vessels such as pipes, cylinders, boilers and fuel tanks can be tested for strength and leakage.
Hydraulic testing involves filling containers or piping systems with liquids, usually water, which can be stained to aid visual leak detection and pressurized to a specified test pressure. The pressure seal can be tested by closing the supply valve and observing whether there is a pressure loss. If water contains colorants, it is easier to visually identify the location of the leak. The strength is usually measured by measuring the permanent deformation of the pipe or container.
Abstract
Hydrostatic test is carried out under the restriction of industry or customer specifications, or may be prescribed by law. A tube or container containing almost incompressible liquids, usually water or oil, is pressurized to test pressure and to check for leaks or permanent changes in shape. Red or fluorescent dyes can be added to the water to make the leak easier to see. Test pressure is always a higher safety factor than operating pressure. The safety factor is usually 166.66%, 143% or 150% of the design working pressure, depending on the applicable regulations.
Purpose of hydraulic test
Hydrostatic test is the most commonly used method for testing pipelines and pressure vessels. Using this test helps maintain the safety standards and durability of steel pipes.
Pipeline testing
Hydraulic tests of pipes, pipes and containers are performed to expose previously undetected defective materials, to ensure that any remaining defects are insufficient to allow operation under design pressure, to expose possible leaks, and to serve as a final verification of the integrity of the construction system.
Strength is measured by pressurizing it at any point in the pipe length to at least 125% of its maximum allowable working pressure (MAWP). Because many long-distance pipelines are designed to have a steel hoop stress of 80% of the specified minimum yield strength (SMYS) at maximum permissible working pressure MAOP, this means that the steel is subject to SMYS and above stress during testing, and the testing part must be selected to ensure that no excessive plastic deformation occurs.
If the design temperature of the steel pipe is higher than the test temperature, the test pressure must be adjusted according to the relevant allowable stress at the design temperature. This is achieved by multiplying 1.5 MAWP by the ratio of the allowable stress at the test temperature to the allowable stress at the design temperature.
Hydrostatic test procedure:
(1) Fill the pipe or container with water until the gas is exhausted and the surface of the pipe is dried.
(2) During the test, the pressure should be slowly increased to the design pressure. After confirming that there is no leakage, the pressure should be raised to the prescribed test pressure for 30 minutes, and then the pressure should be reduced to 80% of the test pressure. All welds and joints should be inspected for a long enough time.
(3) If any abnormal phenomena such as leakage, abnormal noise, pressure drop, failure of pressurizing device are found in the test, the pressure should be slowly lowered to zero and the test should be stopped immediately to find out the cause and eliminate the hidden danger before proceeding.
(4) Qualification requirements: no abnormal sound, no visible abnormal deformation, no leakage of weld and joint during the test.