Selection, installation of sealing gaskets, and reasons for failure in use

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Selection of gasket materials: For any type of gasket, to ensure effective sealing over an extended period in harsh operating conditions, it must possess the following eight important characteristics: The gasket’s airtightness – the gasket must not leak under the medium involved in the sealing system, at the recommended temperatures and pressures, over a certain period of time. Compressibility of the gasket: The contact surface between the gasket and the flange should fit well together after the connection bolts are tightened, in order to ensure a proper seal. Creep resistance of gaskets: Under the influence of pressure loads and operating temperatures, gaskets should have good creep resistance; otherwise, it can lead to a loss of bolt torque, resulting in reduced surface stress on the gaskets and thus leakage in the hydraulic system. Chemical resistance of gaskets: The gaskets selected must be resistant to corrosion by chemical agents, and they must not contaminate the medium. The resilience of the gasket ensures that, even when the system is stable, the two flanges connected together will experience slight displacements due to temperature and pressure effects; the elastic properties of the gasket are meant to compensate for these displacements in order to maintain the system’s sealing integrity. Adhesion resistance of gaskets: Gaskets should be able to be removed from the flanges easily after use, without sticking. Corrosion resistance of gaskets: Gaskets must not cause corrosion to the surfaces of the flanges they are connected to. Temperature tolerance of gaskets: The gaskets selected must ensure proper operation at both the lowest and highest temperatures of the system. There are four types: metal wound gaskets, externally wound with internal reinforcement gaskets, internally wound with external reinforcement gaskets, and gaskets with both internal and external reinforcement – which are essentially the basic type, the type with internal reinforcement, the type with external reinforcement, and the type with both internal and external reinforcement. Specific applications: Basic type – tenon-and-socket surfaces and ribbed flanges; Internal reinforcement type – ribbed flanges; External reinforcement type – flat and convex flanges; Internal and external reinforcement type – flat and convex flanges. Installation of gaskets: To ensure the sealing of the system, in addition to using good sealing materials, it is also necessary to follow the correct installation methods outlined below: 1. The gasket must be placed right in the center of the flange, which is especially important for convex flanges ； 2. Ensure the flatness and machining precision of the sealing surface ； 3. The connecting bolts must be tightened in a uniform and symmetrical manner ； 4. Spring washers must be used to ensure even loading; a torque wrench should be employed when tightening the bolts ； 5. After the system has been running for a day, check and readjust the torque of the connection bolts ； 6. To ensure the service life of the gasket, do not use adhesives or lubricants based on liquids or metals. 1. Auxiliary spare parts – Insufficient initial pressure – Uneven bolt load – Damaged threads on bolts – Incorrect bolts – Misaligned flange surfaces. 2. Gasket materials – Reuse of old gaskets – Incompatibility with the medium – Unsuitable for industrial conditions – Use of incompatible composites – Improper dimensions – High leakage rate. 3. Design factors – Insufficient bolt load – Excessive load – Incorrect selection of flanges and bolts. 4. Flanges – Damaged surfaces – Uneven working surfaces