Installation notes for flange gaskets
Notes for gasket installation
The sealing surface of gaskets and flanges should be cleaned thoroughly, and there should be no defects such as scratches or spots that affect the sealing performance of the connection. The outer diameter of the gasket should be smaller than that of the flange sealing surface, and the inner diameter of the gasket should be slightly larger than the inner diameter of the pipeline.
The difference between the two inner diameters is generally twice the thickness of the gasket to ensure that after compression, the inner edge of the gasket does not protrude into the container or pipeline, so as not to hinder the flow of fluid in the container or pipeline. The pre-tightening force of the gasket should not exceed the design specifications to avoid excessive compression and loss of rebound ability of the gasket. When tightening the gasket, it is best to use a torque wrench.
For large bolts and high-strength bolts, it is best to use hydraulic tighteners. The tightening torque should be calculated based on the given gasket compression, and the magnitude of the hydraulic tensioner oil pressure should also be determined through calculation.
When installing the gasket, tighten the nuts in the order shown in the diagram on the right. But it should not be twisted once to reach the design value. Generally, it should be cycled at least two to three times to ensure even distribution of gasket stress. For pressure vessels and pipelines with flammable and explosive media, safety should be used when replacing gaskets.
All tools are used to avoid sparks caused by collisions between tools and flanges or bolts, which may lead to fire or explosion accidents. If there is a leak in the pipeline, it must be depressurized before replacing or adjusting the installation gasket. It is strictly prohibited to operate under pressure.
Special requirements for gasket installation
When installing the spiral gasket that matches the protruding flange, attention should be paid to ensuring that the seal is concentric with the pipeline. Generally, an external strong ring is used to contact the inner circumferential surface of the bolt for positioning, and eccentric installation is not allowed.
When installing the basic spiral wound gasket in the sealing surface flange of the mortise and tenon groove, attention should be paid to keeping the gap consistent with the groove wall surface.
When installing metal coated gaskets with narrow widths, a certain thickness of steel plate should be placed on the outside of the gasket, and then the flange should be tightened to prevent the filling material inside the gasket from being compressed and causing the interface (or lap joint) of the metal shell to expand and damage the gasket.
When the working temperature of the flange is higher than 200 ℃, sealant should be applied between the flange sealing surface and the gasket to prevent the gasket from sintering with the flange sealing surface under high temperature, which will increase the trouble of maintenance and gasket replacement.
If the sealing surface is irregular, apply sealant on the sealing surface before installing the gasket. Sealing glue is generally composed of manganese dioxide, graphite powder, and boiled linseed oil (dry oil). The corresponding type and grade of liquid sealant can be selected according to the sealing medium, working temperature, and medium pressure conditions.
For the installation of octagonal metal ring gaskets, when the machining of the metal ring gasket and flange sealing groove is not ideal, a tight fit can be achieved through mating. For large diameter metal ring pads, it is difficult to match and research them. In order to fill the small unevenness on the metal surface, sealant can be used.
