Why are liquid ammonia storage tanks subjected to a gas-tightness test?

It is not necessary; liquid ammonia is a highly penetrating medium, and a gas-tightness test may not be able to detect penetration defects in liquid ammonia. However, many design firms in this industry are accustomed to airtightness, so it is recommended to conduct an ammonia leak test at 20%.

Thank you, I’m glad to hear it’s not mandatory anymore

It’s not mandatory, but we do it for everything we design; in fact, we carry it out during the actual work process. Users are very strict when it comes to environmental protection – with other substances, a small leak might go unnoticed, but with ammonia, its strong odor makes it easy to detect. . .

Ammonia has strong permeability; before the use of helium testing, ammonia was used for testing

Liquid ammonia storage tanks do not necessarily have to undergo a gas-tightness test

Many people are confused about what hydrostatic testing, pneumatic testing, and airtightness testing are, and often mix them up. I. Pressure resistance test: The purpose is to verify strength; it is a mandatory test upon leaving the factory. For details, refer to TSG 21-2016 3.2.12. 1. Hydrostatic (water) test: Clean water is typically used for this test, which is commonly referred to as a hydrostatic test. The test pressure is generally about 1.25 times the design pressure; for specific details, see the relevant requirements in TSG 21-2016 ； 2. Pressure and gas-liquid combination tests: Used when hydraulic tests are not applicable; the test pressure is generally around 1.10 times the design pressure ； II. Leak test: The purpose is to verify the integrity of the pressure vessel. After passing the pressure resistance test, leak tests should be conducted on those pressure vessels that contain media with an extremely high or high level of toxicity, or those for which even minor leaks are not permitted according to the design requirements. 1. Airtightness test: The test pressure is the design pressure/allowed (monitoring) operating pressure ； 2. Ammonia leak detection test: Ammonia-air method, ammonia-nitrogen method, 100% ammonia gas method, etc., shall be carried out in accordance with the design drawings or the requirements of relevant test standards ； 3. Halogen leak test: Conduct in accordance with the requirements of the design drawings or relevant test standards ； 4. Helium leak test: Conduct it in accordance with the requirements of the design drawings or relevant test standards. Safety accessories are required for pressure tests, gas-liquid combination tests, and airtightness tests. The above are general requirements; any other provisions shall prevail. Among them, the airtightness test and sealing test of safety valves should not be confused either. The purpose of the safety valve airtightness test is to verify the tightness of the valve body outside the sealing surface; the test pressure is the maximum back pressure, which must be at least 0.20 MPa ； The purpose of the safety valve sealing test is to verify the leakage rate of the safety valve, with the test pressure being 90% of the set pressure ； Please comply with the relevant regulations regarding air pressure; a detailed list is not provided. In summary, do not confuse pressure resistance tests, hydraulic tests, pneumatic tests, and airtightness tests; it is common to find units that can be used interchangeably, which leads to the omission of essential inspection items.