What are the requirements for pressure testing after the installation and maintenance of tower equipment?

After the installation and maintenance of the tower, it is necessary to clean the tower and pipelines, that is, by water flushing and purging. Then, the tower is pressurized, subjected to pressure retention tests, and checked for airtightness based on parameters such as its design pressure and operating pressure. (1) Decision on pressure testing: The pressure testing of tower equipment includes pressure resistance testing and airtightness testing. The withstand voltage test is carried out using clean water, that is, a hydrostatic test. For towers that are not suitable for hydrostatic testing, gas can be used instead of liquid for pressure resistance testing. For towers where even trace amounts of medium leakage are not permitted and in which toxic media are present, a leak-tightness test must be conducted after the pressure resistance test has been passed. The test pressure is determined based on the original design drawings of the tower and actual conditions, but generally, after maintenance and before putting it into operation, its airtightness should be checked using gas or liquid at the design pressure. (2) Inspection before testing: Before testing, an external inspection should be carried out to check whether the welds and connectors meet the requirements, whether the pipe fittings and auxiliary devices are complete, whether the operation is smooth and correct, and whether fasteners such as bolts are properly tightened. (3) Hydrostatic test: When a hydrostatic test is conducted on a tower after maintenance, for large low-pressure towers, it is necessary to prevent a negative pressure from developing inside the tower due to sudden temperature changes or leaks in the tower structure. For towers made of stainless steel, protection against corrosion caused by chloride ions is required. After the tower is filled with water, and once the wall temperature of the tower is roughly the same as the temperature of the water used in the test, the pressure is slowly increased to the specified level. This pressure is maintained for 30 minutes, after which it is reduced to the design pressure and held at that level for another 30 minutes. All welds and connection points are inspected; if there are no visible abnormalities, no leaks, and the pressure does not drop, then the test is considered successful. After pressure testing, the water should be drained promptly. Once drained, compressed air or other inert gases can be used to dry the interior surface of the tower. If the tower volume is greater than 100 m³, during the pressure test, as well as before filling with water, while filling it, after it is filled, and during water drainage, foundation settlement should be monitored and carefully recorded. (4) Pneumatic testing: The gas used for the pneumatic testing of the tower is dry, clean air, nitrogen, or other inert gases. For columns that require degreasing, oil-free gas should be used, with the gas temperature not falling below 15°C. During the pressure test, the pressure should be increased slowly to 10% of the specified test pressure and held for 10 minutes, after which a preliminary leak check is conducted on all welds and joints. Upon passing the test, continue to increase the pressure slowly to 50% of the specified test pressure; thereafter, raise the pressure in steps of 10% of the specified test pressure at a time until reaching that pressure, and hold it for 10 minutes. Then reduce the pressure to the design pressure and maintain it there for at least 30 minutes. Inspect all welds and joints for any visible abnormal deformation or leakage; if none are found and the pressure does not drop, the test is considered successful. (5) Airtightness test: Before conducting the airtightness test, the safety devices, valves, pressure gauges, level gauges and other accessories on the tower, as well as all internal components, must be complete and in good condition. The test gas is the same as that for pressure testing. During testing, the pressure should be increased slowly to the design pressure. Maintain this condition for at least 30 minutes, and simultaneously use methods such as spraying a foaming agent to check for any trace gas leakage at the joints of all welds; no pressure drop indicates that the test is successful.

(1) Decision on pressure testing: The pressure testing of tower equipment includes pressure resistance testing and airtightness testing. The withstand voltage test is carried out using clean water, that is, a hydrostatic test. For towers that are not suitable for hydrostatic testing, gas can be used instead of liquid for pressure resistance testing. For towers where even trace amounts of medium leakage are not permitted and in which toxic media are present, a leak-tightness test must be conducted after the pressure resistance test has been passed. The test pressure is determined based on the original design drawings of the tower and actual conditions, but generally, after maintenance and before putting it into operation, its airtightness should be checked using gas or liquid at the design pressure. (2) Inspection before testing: Before testing, an external inspection should be carried out to check whether the welds and connectors meet the requirements, whether the pipe fittings and auxiliary devices are complete, whether the operation is smooth and correct, and whether fasteners such as bolts are properly tightened. (3) When conducting a hydrostatic test on a pressure test tower after maintenance, for large low-pressure towers, it is necessary to prevent the formation of negative pressure inside the tower due to sudden temperature changes or leaks in the tower structure. For towers made of stainless steel, protection against corrosion caused by chloride ions is required. After the tower is filled with water, and once the wall temperature of the tower is roughly the same as the temperature of the water used in the test, the pressure is slowly increased to the specified level. This pressure is maintained for 30 minutes, after which it is reduced to the design pressure and held at that level for another 30 minutes. All welds and connection points are inspected; if there are no visible abnormalities, no leaks, and the pressure does not drop, then the test is considered successful. After pressure testing, the water should be drained promptly. Once drained, compressed air or other inert gases can be used to dry the interior surface of the tower. If the tower volume is greater than 100 m³, during the pressure test, as well as before filling with water, while filling it, after it is filled, and during water drainage, foundation settlement should be monitored and carefully recorded. (4) The gas used for the pressure test in the pressure test tower is dry, clean air, nitrogen, or other inert gases. For columns that require degreasing, oil-free gas should be used, with the gas temperature not falling below 15°C. During the pressure test, the pressure should be increased slowly to 10% of the specified test pressure and held for 10 minutes, after which a preliminary leak check is conducted on all welds and joints. Upon passing the test, continue to increase the pressure slowly to 50% of the specified test pressure; thereafter, raise the pressure in steps of 10% of the specified test pressure at a time until reaching that pressure, and hold it for 10 minutes. Then reduce the pressure to the design pressure and maintain it there for at least 30 minutes. Inspect all welds and joints for any visible abnormal deformation or leakage; if none are found and the pressure does not drop, the test is considered successful. (5) Airtightness test: Before conducting the airtightness test, the safety devices, valves, pressure gauges, level gauges and other accessories on the tower, as well as all internal components, must be complete and in good condition. The test gas is the same as that for pressure testing. During testing, the pressure should be increased slowly to the design pressure. Maintain this condition for at least 30 minutes, and simultaneously use methods such as spraying a foaming agent to check for any trace gas leakage at the joints of all welds; no pressure drop indicates that the test is successful.

After normal maintenance, it is airtight and purged.

Theoretically, it should be carried out according to the original design; in practice, normal airtightness is sufficient