Tightness Tests of Piping Systems
With the rise of the shipping market, ship repair and construction have entered a prosperous period, and the quality control of ship piping systems is an important part of ship repair and construction. Completing the prefabrication, installation and use of ship piping systems with quality and quantity is an important part of on-site construction.
Tightness tests of piping systems
1) Test equipment
For the same pressure test pipeline, at least two pressure gauges or recorders that have been calibrated within 6 months must be prepared, and a calibration certificate is required. The measuring range of the meter and recorder shall be twice or close to the test pressure. If the pressure test lasts more than 4 hours or the ambient temperature changes greatly, it is necessary to record the changes in the pressure in the pipe and the ambient temperature.
2) Inspection before pressure tests
Before the pressure test, it is necessary to confirm that the welding seam of the pressure test system has completed the required flaw detection. All joints including welded joints and connections shall be exposed during the test. The piping should be adequately fixed, preferably permanently. During the pressure test of the piping system, the equipment shall be isolated by blind plates or valves. If a valve is used for isolation, it must be ensured that the valve used can meet the test pressure. When testing the water pressure and filling the system with water, a vent should be provided at a high position. When purging at the end of the test, the low point should be provided with a discharge port. Before the pressure test, remove or isolate all safety valves, expansion joints, transmission instruments and other equipment, and all outlets will be blocked with plugs or blind flanges. Replace removed components with bulkheads or short pipes with flanges on both ends. If the pressure of the valve is greater than the test pressure, it is not necessary to remove the valve, but all valves (ball valves, butterfly valves and gate valves) should be fully opened during the test to ensure that the valve core is not stressed and the pipeline has connectivity. When the pressure test pipeline is tested with gas, the gas must be free of oil and impurities, because the airtight test may cause dangerous situations. During the entire test stage, a safe area for pressure test isolation should be set up, the warning tape should be provided, and there should be special personnel. Each system to be airtight tested should be as small as possible. For this purpose, a large system should be divided into many small parts for airtight testing. When the pressure test pipeline is tested with fresh water or drinking water, it must be ensured that the freshwater or drinking water does not contain suspended solid particles that may block the pipe. For freshwater used for testing stainless steel pipe, the chloride content should not exceed 50 ppm and a water quality test report should be provided.
3) Pressure tests
Begin the leak test with a pressure of 0.5 bar or 7.25 psi (1 bar is equal to 100 kPa and 1 psi is equal to 6.895 kPa) and check all connections for leaks. When the pressure is stable, gradually increase it to 50% of the specified pressure and keep it for 10 minutes to balance the stress and deformation. Afterward, the pressure shall be gradually increased by 10% of the specified test pressure, and the pressure shall be stabilized for 10 minutes each time to balance the stress and deformation until the specified test pressure is reached and shall be maintained for at least 30 minutes. Check whether there is any leakage at the pipe joints and flanges. If there is a leak point during the test, mark it and repair it after the pressure is released. After the repair, the pressure test must be repeated.
Tightness tests of piping systems
1) Test equipment
For the same pressure test pipeline, at least two pressure gauges or recorders that have been calibrated within 6 months must be prepared, and a calibration certificate is required. The measuring range of the meter and recorder shall be twice or close to the test pressure. If the pressure test lasts more than 4 hours or the ambient temperature changes greatly, it is necessary to record the changes in the pressure in the pipe and the ambient temperature.
2) Inspection before pressure tests
Before the pressure test, it is necessary to confirm that the welding seam of the pressure test system has completed the required flaw detection. All joints including welded joints and connections shall be exposed during the test. The piping should be adequately fixed, preferably permanently. During the pressure test of the piping system, the equipment shall be isolated by blind plates or valves. If a valve is used for isolation, it must be ensured that the valve used can meet the test pressure. When testing the water pressure and filling the system with water, a vent should be provided at a high position. When purging at the end of the test, the low point should be provided with a discharge port. Before the pressure test, remove or isolate all safety valves, expansion joints, transmission instruments and other equipment, and all outlets will be blocked with plugs or blind flanges. Replace removed components with bulkheads or short pipes with flanges on both ends. If the pressure of the valve is greater than the test pressure, it is not necessary to remove the valve, but all valves (ball valves, butterfly valves and gate valves) should be fully opened during the test to ensure that the valve core is not stressed and the pipeline has connectivity. When the pressure test pipeline is tested with gas, the gas must be free of oil and impurities, because the airtight test may cause dangerous situations. During the entire test stage, a safe area for pressure test isolation should be set up, the warning tape should be provided, and there should be special personnel. Each system to be airtight tested should be as small as possible. For this purpose, a large system should be divided into many small parts for airtight testing. When the pressure test pipeline is tested with fresh water or drinking water, it must be ensured that the freshwater or drinking water does not contain suspended solid particles that may block the pipe. For freshwater used for testing stainless steel pipe, the chloride content should not exceed 50 ppm and a water quality test report should be provided.
3) Pressure tests
Begin the leak test with a pressure of 0.5 bar or 7.25 psi (1 bar is equal to 100 kPa and 1 psi is equal to 6.895 kPa) and check all connections for leaks. When the pressure is stable, gradually increase it to 50% of the specified pressure and keep it for 10 minutes to balance the stress and deformation. Afterward, the pressure shall be gradually increased by 10% of the specified test pressure, and the pressure shall be stabilized for 10 minutes each time to balance the stress and deformation until the specified test pressure is reached and shall be maintained for at least 30 minutes. Check whether there is any leakage at the pipe joints and flanges. If there is a leak point during the test, mark it and repair it after the pressure is released. After the repair, the pressure test must be repeated.
