The sealing gasket and the flange sealing face must be thoroughly cleaned; they must be free of any defects-such as scratches or blemishes-that could compromise the integrity of the sealed connection.
The outer diameter of the sealing gasket should be slightly smaller than the outer diameter of the flange sealing face, while the inner diameter of the gasket should be slightly larger than the inner diameter of the pipe. Typically, the difference between these two inner diameters is set at twice the thickness of the gasket; this ensures that, once compressed, the inner edge of the gasket does not protrude into the vessel or pipe, thereby preventing any obstruction to the flow of the internal fluid.
The pre-tightening force applied to the sealing gasket must not exceed the limits specified in the design, to prevent the gasket from being over-compressed and losing its elastic recovery capabilities.
When compressing the sealing gasket, it is highly recommended to use a torque wrench. For large-diameter or high-strength bolts, the use of hydraulic tensioners is preferred. The required tightening torque should be calculated based on the specified gasket compression requirements; similarly, the hydraulic pressure for tensioners should be determined through calculation.
During gasket installation, the nuts should be tightened sequentially in the prescribed order. However, the full design torque value should not be achieved in a single pass. Generally, the tightening process should be cycled at least two to three times to ensure that the stress distribution across the gasket is uniform.
For pressure vessels and piping systems containing flammable or explosive media, safety tools must be utilized when replacing gaskets. This precaution prevents sparks-which could result from tools striking the flange or bolts-that might otherwise trigger a fire or explosion.
If a leak occurs in the piping system, the internal pressure must be reduced before any attempt is made to replace or adjust the gasket; performing such operations under pressure is strictly prohibited.
