The tolerance requirements for oval gaskets mainly revolve around size, shape, and surface condition, ensuring a tight fit with the flange sealing surface and no leakage of the medium.
Firstly, look at the key dimensions. The inner and outer diameters need to match the sealing groove of the flange, and the general tolerance will depend on the specifications. For small-sized oval gaskets (such as those with an inner diameter of tens of millimeters), the inner and outer diameter tolerance is usually within ± 0.2 to ± 0.5 millimeters, while for large-sized gaskets, it may be relaxed to around ± 1 millimeter. If the size difference is too large, either it cannot fit into the groove or there is a gap when installed.
Then there is the thickness tolerance, which has a significant impact on the sealing effect because the oval gasket achieves sealing through compression deformation, and excessive thickness deviation can lead to uneven compression. Usually, the thickness tolerance is controlled within ± 0.1 to ± 0.3 millimeters. For example, for a gasket designed with a thickness of 5 millimeters, the actual thickness needs to be between 4.7 and 5.3 millimeters, otherwise the thin areas may not be tightly pressed and the thick areas may not be able to move, which can easily lead to leakage.
The shape mainly depends on ellipticity and flatness. The oval gasket should be a regular oval shape, not flat and bulging on one side. The deviation between the long and short axes on any section should generally not exceed 0.5 millimeters, otherwise it will not match the flange groove during installation and the fit will not be complete. Flatness is also required, and the upper and lower sealing surfaces of the pad must be flat without warping. The flatness error per meter of length usually does not exceed 0.1 millimeters, otherwise there will be gaps in contact with the flange surface, and the medium is prone to penetration.
The surface roughness cannot be ignored. The sealing surface should be smooth, and the Ra value is generally required to be between 1.6 and 3.2 microns. If it is too rough, there will be small patterns on the surface, and the medium will leak along the patterns; But it doesn’t need to be too smooth, as being too smooth can actually affect the sealing performance during bonding.
If the oval gasket is made of metal material (such as copper or stainless steel), sometimes a hardness tolerance is required. For example, the hardness of the stainless steel gasket should be controlled within HRB 80-100. If the hardness is too high, it is difficult to compress, and if it is too low, it is easy to be crushed, which will affect the sealing life.
There are many types of RTJ gaskets, including R Gasket,RX Gasket,BX Gasket, SBX Gasket,IX Gasket,and various customized products.We will do more sharing about ring joint gasket.