What is the difference between pressure tests and airtightness tests?
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A pressure test is a strength test, while a airtightness test is a leakage test. The pressure used in an airtightness test is the same as the design pressure, whereas the pressure used in a pressure test is higher than the design pressure. Other than that, what are their differences?
Just do a search on Baidu: 1) Different natures – A pressure test is a test to verify strength, while a leak-tightness test is a test to assess tightness. 2) Purposes of the test pressures – Pressure tests are primarily used to check the strength and sealing properties of equipment; leak-tightness tests are mainly aimed at detecting any minor leakage defects, with an emphasis on whether there are small leaks in the equipment. Pressure tests focus on the overall strength of the equipment, whereas leak-tightness tests focus on its tightness. 3) Media used – Air is generally used in pressure tests. For leak-tightness tests, in addition to air, gases such as ammonia, halogens, or helium are used when the medium is highly toxic and leakage or permeation must be avoided. 4) Safety accessories – Safety accessories are not required to be installed on the equipment during pressure tests. Leak-tightness tests are usually carried out only after the safety accessories have been installed. 5) Sequence – Leak-tightness tests need to be conducted after pressure or hydrostatic tests have been completed. 6) Test pressures – The pressure for pressure tests is 1.15 times the design pressure; for equipment under internal pressure, this value must also be adjusted according to temperature factors； When air is used as the medium for the airtightness test, the test pressure is the design pressure; if other media are used, the pressure must be adjusted accordingly based on the properties of those media. 7) Application scenarios: For pneumatic testing, hydraulic testing is preferred. Pneumatic testing is generally used when hydraulic testing is not possible due to the equipment’s structure or support conditions, or when the equipment has a large volume. For airtightness testing, this method is employed when the medium is highly or extremely hazardous, or when leaks are not allowed. 8) Stress verification: During pneumatic testing, the circumferential membrane stress in the container shell shall not exceed the product of 80% of the material’s yield strength at the test temperature and the welding joint factor of the cylinder. Airtightness testing is not required. 9) Safety: Since pressure testing is more dangerous than hydraulic testing, it demands higher safety precautions compared to the latter; in addition to necessary protective measures, safety officers from the testing organization must also be present to supervise the process.
1 Different purposes: Pressure testing is primarily used to evaluate the strength and sealing properties of equipment, while airtightness testing is mainly aimed at checking the tightness of the equipment, especially with regard to minor penetration defects. Airtightness testing focuses on whether there are any minor leaks in the equipment, whereas pressure testing focuses on the overall strength of the equipment. 2 Different testing media are used: Air is generally employed in pneumatic testing. For airtightness testing, in addition to air, ammonia, halogens, or helium are used when the medium is highly toxic and leaks or permeation must be prevented. 3 Safety accessories: During pressure testing, it is not necessary to install safety accessories on the equipment; airtightness testing is generally carried out only after the safety accessories have been installed. 4 Sequence: The airtightness test must be carried out after the pneumatic or hydraulic test is completed. 5 Test pressure: The pneumatic test pressure is 1.15 times the design pressure; for pressure vessels, a temperature correction factor must also be applied ； When air is used as the medium for the airtightness test, the test pressure is the design pressure; if other media are used, the pressure must be adjusted accordingly based on the properties of those media. 6 Stress verification: During the hydrostatic test, the circumferential membrane stress value of the vessel shell shall not exceed the product of 80% of the material’s yield strength at the test temperature and the welding joint factor of the cylinder. The airtightness test does not require verification. 7 Safety: Since pneumatic testing is more dangerous than hydraulic testing, it requires higher standards in terms of safety measures. In addition to the necessary protective measures, safety personnel from the testing organization must also be present to oversee the process.
What Baidu provides are all conceptual overviews. But the actual testing process is hardly mentioned at all; after all, there are differences in the methods used for testing safety measures
Is there anything more practical, such as the testing process or safety measures, the testing methods?
The pressure test is a type of strength test that focuses on the cross-welds, while the airtightness test is a type of leakage test that checks the sealing of the flanges.
What specifically to ask? A safety valve must be installed for the pressure test, and some vulnerable components need to be removed ； A gas-tightness test does not require a safety valve, but all removed components (including pressure gauges, safety valves, etc.) must be restored to their original positions.
Methods of inspection, locations, and requirements for site safety, etc
Air pressure is a strength test, while airtightness is a leakage sealing test.
The pressure for the pneumatic test is higher than that for the airtightness test