Which standard specifies that flange gaskets can only be used once?
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I’m seeking help from fellow users – which standard specifies that flange gaskets can only be used once? Urgently searching for this specification. Please specify the standard name.
There shouldn’t be any. For safety reasons, it should be replaced with a new one. The ones that were used were defective; they exploded and leaked, resulting in financial losses. I don’t know how many gaskets I can afford to buy. Chemical companies cannot be managed with a small-scale farmer mindset.
There are no regulations stating that gaskets must be used only once; most are merely suggestions. It is generally recommended to use metal gaskets once, as their properties change after being used once； When it is to be used again, the pre-tension of the bolts must change (otherwise leakage is likely to occur), which may damage the sealing surface of the flange. It is also recommended to use gasketing materials once only, as they become deformed after a single use and can no longer provide a proper seal when used again; however, if the requirements for the medium are not stringent, it is possible to use them twice or more times
Generally, the owner’s specifications require this, and new ones must be used. If using the old ones, consent from the gasket manufacturer is required. Using the new one is no problem; it’s also the part that gets removed, so it needs to be replaced, and the amount required isn’t much.
There seems to be no such mandatory requirement, but in practice, the function of the gasket is to compensate for minor irregularities on the flange sealing surface through its own deformation; after installation, the surface of the gasket and the flange surface fit together, thereby achieving a sealing effect. After removal and reinstallation, the surface of the gasket cannot fit perfectly against the flange sealing surface. It is prone to causing leaks. Therefore, regular projects do not allow metal gaskets to be reused. It is said that DuPont requires three gaskets for each location when working on projects. One is used for pressure testing, one is for normal use, and one serves as a spare part.
Based on practical experience, it is best to replace all the gaskets that have been used; the cost of stopping operations to do so can be covered by purchasing a few hundred or even a few thousand new gaskets； If you really don’t want to discard it, it can be used in applications where the pressure and temperature are not high, such as in cooling water or air, for reduced-capacity use.
It seems that the sealing effect isn’t as good after using it
There is no specification for single use, nor for multiple uses
The installation of wound gaskets requires a certain compression ratio; a minimum preload pressure is needed to achieve a reliable sealing effect. After being used once, the surface finish of the gasket is damaged and its compression resilience also changes. Without proper repair, it will definitely leak when used again!
The principle is to use the new one whenever available; if none is available, check whether the sealing surface is intact – if it’s undamaged, it can be used (it has indeed been used in practice at a pressure of 4.0 MPA). The removed gaskets can be used for pressure testing, and for large-sized gaskets, the outer ring can be reprocessed, which helps to reduce costs significantly. The principle is: use the new instead of the old
There are no specific regulations, but generally, after a metal gasket is used once, its density changes; using it again is not advisable as it may not provide a proper seal. Moreover, gaskets are among the cheapest components in valve fittings, so unless there are special circumstances, it’s better to use them just once.