Regarding the airtightness issue
Thread Content
There are several questions I would like to ask everyone: 1. Is there a mandatory requirement of 24 hours for the pressure retention time to ensure gas tightness of the system? 2. Is it feasible to use the leakage rate as the standard for determining gas tightness? 3. Do all instruments in the system need to be installed before ensuring gas tightness?
The basic requirements for airtightness can be found in GB50184; those for specific locations are specified in the design documents
Well, actually I’ve been looking up the regulations for three days now, and I haven’t found any clear provisions on this…
This post was last edited by Coffee Companion on 2020-7-10 at 14:03. 1. There are time constraints; the aim is to observe and eliminate the influence of temperature in order to obtain accurate leakage data. 2. The qualified standard for airtightness is determined based on the leakage rate, and DCS data must be available for reference. 3. When ensuring airtightness, all instruments within the airtightness range must be installed; otherwise, airtightness has no meaning. For reference only
Regarding the airtightness test of equipment, the most troublesome issue is the accuracy of the instruments used. There’s also the level of detail required. For example, I’ve encountered situations where a plate heat exchanger must not leak under any circumstances. Ordinary pressure and temperature measurements cannot be used as testing methods. There have been cases where multiple comparisons using U-tubes were required to determine the presence of micro-leaks. So, the airtightness test is sometimes just a formality. For proper leak testing, methods such as applying foam solution are still quite reliable. For some tests related to internal leakage, it is crucial to ensure everything is in order before installation. (Speculative opinions only; for reference.) These 3 questions require such an approach, and due to instrument errors, it’s quite possible for the calculation results to exceed 100%: lol
There is indeed no mandatory requirement in the airtight pressure retention specifications; generally, we require that the pressure drop within 1 hour not exceed 0.5% of the system pressure, and 8 hours of pressure retention is considered satisfactory. When the system is airtight, all instruments in the system must of course be installed, and checking for leaks in these instruments is also a key task.