【Q&A Question 117】April 27, 2018

1. The pressure testing equipment or the system must be properly isolated； 2. Activate the safety accessories of the pressure testing system and verify that they are in good working condition ； 3. Select an appropriate pressure testing medium; water pressure is used for heat exchangers ； 4. The maximum pressure during pressure testing shall not exceed the design pressure; for the first operation of the equipment, it shall be 1.25 times the design pressure ； 5. If it is a high-voltage device, the voltage should be increased in stages gradually, strictly in accordance with the required rate of voltage increase ； 6. When it is necessary to address leaks during the pressure testing process, reduce the pressure level as much as possible to carry out the repair ；

1. The pressure testing equipment or the system must be properly isolated； 2. Activate the safety accessories of the pressure testing system and verify that they are in good working condition ； 3. Select an appropriate pressure testing medium; water pressure is used for heat exchangers ； 4. The maximum pressure during pressure testing shall not exceed the design pressure; for the first operation of the equipment, it shall be 1.25 times the design pressure ； 5. If it is a high-voltage device, the voltage should be increased in stages gradually, strictly in accordance with the required rate of voltage increase ； 6. When it is necessary to address leaks during the pressure testing process, reduce the pressure level as much as possible to carry out the repair

1. The pressure testing equipment or the system must be properly isolated； 2. Activate the safety accessories of the pressure testing system and verify that they are in good working condition ； 3. Select an appropriate pressure testing medium; water pressure is used for heat exchangers ； 4. The maximum pressure during pressure testing shall not exceed the design pressure; for the first operation of the equipment, it shall be 1.25 times the design pressure ； 5. If it is a high-voltage device, the voltage should be increased in stages gradually, strictly in accordance with the required rate of voltage increase ； 6. When it is necessary to address leaks during the pressure testing process, reduce the pressure level as much as possible to carry out the repair

(1) The pressure testing standards must be strictly followed during testing. (2) During the pressure testing of pipelines, open the end valve slightly first and listen to the flow sound to check for smooth flow; when testing equipment, drain condensate from the highest point to ensure that water vapor fills the entire equipment. (3) Increase the pressure slowly – never rise or drop it abruptly. After reaching the test pressure, hold it for 5 minutes before reducing it to the operating pressure, in order to check for leaks, deformations, or cracks in welds, manholes, flanges, thermocouples, etc. (4) Where safety valves are present during testing, install blind plates to prevent them from opening. (5) The pressure gauges used for testing must be accurate and functional. (6) After testing, all water vapor must be removed. (7) Keep proper records of the pressure testing process, and sign off as the person responsible for the testing. (8) In winter, after testing, use air to blow away any remaining water to prevent freezing.

1) Before the test, when filling the system with water, the air in the system must be exhausted. 　　2) During testing, the ambient temperature should not be lower than 5°C; when it is below 5°C, anti-freezing measures must be taken. 　　3) During testing, the test temperature should be measured; it is strictly prohibited for the material’s test temperature to approach the brittle transition temperature. 　　4) The test pressure for above-ground steel pipes and non-ferrous metal pipes subjected to internal pressure shall be 1.5 times the design pressure; the test pressure for buried steel pipes shall also be 1.5 times the design pressure, and must not be less than 0.4 MPa. 　　5) When the pipes and equipment are subjected to pressure testing as a single system, if the test pressure for the pipes is equal to or less than that of the equipment, the testing shall be carried out at the pressure specified for the pipes. If the test pressure for the pipes is higher than that of the equipment, and the test pressure for the equipment is not less than 1.15 times the design pressure of the pipes, then, with the approval of the project owner, the testing can be conducted at the pressure specified for the equipment. 　　6) When the design temperature of the pipe is higher than the test temperature, the test pressure shall be calculated using the following formula: Ps=1.5P〔б〕1/〔б〕2 Where Ps is the test pressure (gauge pressure), in MPa; P is the design pressure (gauge pressure), in MPa; [б]1 is the allowable stress of the pipe material at the test temperature, in MPa; [б]2 is the allowable stress of the pipe material at the design temperature, in MPa. If [б]1/〔б〕2 is greater than 6.5, then 6.5 shall be used. 　　When Ps generates a stress exceeding the yield strength at the test temperature, the test pressure Ps should be reduced to the maximum pressure that does not exceed the yield strength. 　　7) The test pressure for buried cast iron pipes subjected to internal pressure shall be twice the design pressure when the design pressure is less than or equal to 0.5 MPa, and shall be the design pressure plus 0.5 MPa when the design pressure is greater than 0.5 MPa. 　　8) For pipes with a large alignment difference, the static pressure of the test medium should be included in the test pressure. The test pressure for liquid pipelines is based on the pressure at the highest point, but the pressure at the lowest point must not exceed the tolerance capacity of the pipeline components. 　　9) For pipes subjected to external pressure, the test pressure shall be 1.5 times the difference between the design internal and external pressures, and shall not be less than 0.2 MPa. 　　10) The test pressure for the inner tube of the jacketed tube shall be determined as the higher of the internal or external design pressure. 　　11) When a leak is detected during the test, it must not be repaired while under pressure; the pressure should be reduced to carry out the repair. Once the defect is eliminated, the test must be conducted again.

1. During pressure testing, the system’s safety valve should be set to the selected test pressure value. 2. When feeding oil into the system, the system’s air release valve must be opened; it can be closed only after all air has been removed, and at the same time, the throttle valve should be opened. 3. If abnormal noises are heard in the system, the testing must be stopped immediately; testing can resume only after the cause has been identified and resolved. 4. Safety measures must be taken care of during testing. 5. The pressure should be adjusted according to the design requirements, increasing it gradually, and all operations must be carried out in accordance with the established procedures.

1) Before the test, when filling the system with water, the air in the system must be exhausted. 　　2) During testing, the ambient temperature should not be lower than 5°C; when it is below 5°C, anti-freezing measures must be taken. 　　3) During testing, the test temperature should be measured; it is strictly prohibited for the material’s test temperature to approach the brittle transition temperature. 　　4) The test pressure for above-ground steel pipes and non-ferrous metal pipes subjected to internal pressure shall be 1.5 times the design pressure; the test pressure for buried steel pipes shall also be 1.5 times the design pressure, and must not be less than 0.4 MPa. 　　5) When the pipes and equipment are subjected to pressure testing as a single system, if the test pressure for the pipes is equal to or less than that of the equipment, the testing shall be carried out at the pressure specified for the pipes. If the test pressure for the pipes is higher than that of the equipment, and the test pressure for the equipment is not less than 1.15 times the design pressure of the pipes, then, with the approval of the project owner, the testing can be conducted at the pressure specified for the equipment. 　　6) When the design temperature of the pipe is higher than the test temperature, the test pressure shall be calculated using the following formula: Ps=1.5P〔б〕1/〔б〕2 Where Ps is the test pressure (gauge pressure), in MPa; P is the design pressure (gauge pressure), in MPa; [б]1 is the allowable stress of the pipe material at the test temperature, in MPa; [б]2 is the allowable stress of the pipe material at the design temperature, in MPa. If [б]1/〔б〕2 is greater than 6.5, then 6.5 shall be used. 　　When Ps generates a stress exceeding the yield strength at the test temperature, the test pressure Ps should be reduced to the maximum pressure that does not exceed the yield strength. 　　7) The test pressure for buried cast iron pipes subjected to internal pressure shall be twice the design pressure when the design pressure is less than or equal to 0.5 MPa, and shall be the design pressure plus 0.5 MPa when the design pressure is greater than 0.5 MPa. 　　8) For pipes with a large alignment difference, the static pressure of the test medium should be included in the test pressure. The test pressure for liquid pipelines is based on the pressure at the highest point, but the pressure at the lowest point must not exceed the tolerance capacity of the pipeline components. 　　9) For pipes subjected to external pressure, the test pressure shall be 1.5 times the difference between the design internal and external pressures, and shall not be less than 0.2 MPa. 　　10) The test pressure for the inner tube of the jacketed tube shall be determined as the higher of the internal or external design pressure. 　　11) When a leak is detected during the test, it must not be repaired while under pressure; the pressure should be reduced to carry out the repair. Once the defect is eliminated, the test must be conducted again.

1. During pressure testing, the safety valve of the system should be set to the selected test pressure value. 2. When supplying oil to the system, the air inlet valve of the system should be opened; it can be closed only after all air has been removed, and at the same time the throttle valve should be opened. 3. If abnormal noises are heard in the hydraulic system, the test should be stopped immediately; testing can resume only after the cause has been identified and resolved. 4. Safety measures must be observed during testing.

1. Pressurization of the pipelines should be carried out in advance; test the pressure as soon as one pipeline (one system) is installed, rather than waiting until everything is completed before doing so； 2. When applying pressure, a blind flange must be used; never rely on the valve for sealing ； 3. The instrument components that need to be isolated should be isolated ； 4. Do not connect the equipment without approval ； 5. Pipes under the same pressure can be pressurized together as a single system ； 6. It can be divided into several systems for simultaneous pressure testing based on the pressure level ； 7. Systems under different pressures can also be connected for pressure testing; testing can be carried out from low pressure to high pressure, with blind flanges used for isolation during the process.

Verify the welding quality of the X-ray images of each weld joint; for systems that require pressure testing with nitrogen, install blind flanges to isolate them on their steam purge lines; during pressure testing, all safety valves on the relevant equipment must be in operation