Selection, use and installation requirements of metal spiral wound gaskets

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Selection, use and installation requirements of metal spiral wound gaskets 1. Types of metal spiral wound gaskets The main sealing parts of metal spiral wound gaskets are formed by alternately winding metal spiral tape and non-metallic filler tape. Among them, the common materials of metal spiral tape are 304SS stainless steel and 316L/316SS stainless steel, and the common materials of non-metallic filler tape are graphite (Graphite) and tetrafluoroethylene (PTFE).； In order to match the different types of flange sealing surfaces, the mechanism types of metal spiral wound gaskets are basically divided into four types.: Basic type A, type with inner ring B, type with outer ring C, type with inner and outer ring D ； Different types of flange surfaces stipulate the selection of different gasket types. 2. Selection of metal spiral wound gaskets. When selecting metal spiral wound gaskets, the gasket standard is determined according to the flange standard. Usually the gasket standard matches the flange standard selection. First, it is necessary to master the working condition pressure of the sealed medium, the standard and type of the flange, and specify the structure type and pressure level of the selected metal spiral wound gasket. ； Then according to the working temperature and chemical corrosion characteristics of the sealed medium, suitable metal winding tape materials and non-metallic filler materials are selected. In principle, metal and non-metallic materials that can withstand the working temperature and corrosion should be selected. ； Finally, select the corresponding gasket size according to the nominal diameter and structure of the flange, and mark the gasket you selected according to the marking examples stipulated in the standard, and you can determine the selection. ； If it is a non-standard spiral wound gasket, what needs to be determined is the metal and non-metallic materials, and the structural size and thickness of the gasket. Factors that should also be considered include:: Sufficient gasket stress to ensure sealing, the installation structure designed to prevent excessive compression of the gasket (generally determined by the structural dimensions of the two mating flanges), the safety features of large gasket installation, the impact of non-standard gasket structures on the overall equipment structure cost, etc. ； 3. Installation and use of metal spiral wound gaskets. The following matters should be paid attention to during installation and use.: 1. The sealing surfaces of the gasket and flange should be clean, and there should be no scratches, spots or other defects that affect the sealing performance of the connection. 2. The outer diameter of the sealing gasket should be smaller than the outside of the flange sealing surface, and the inner diameter of the sealing gasket should be slightly larger than the inner diameter of the pipe. The difference between the two inner diameters is generally twice the thickness of the sealing gasket to ensure that after compaction, the inner edge of the sealing gasket does not extend into the container or pipe, so as not to hinder the flow of fluid in the container or pipe. 3. The sealing gasket must be placed in the center of the flange, which is especially important for shoulder flanges; 4. When installing the sealing gasket, the connecting bolts must be tightened evenly and symmetrically; but it should not be tightened once to reach the design value. Generally, it should be cycled at least 2 to 3 times so that the stress of the sealing gasket is evenly distributed. 5. After the valve pipeline system has been running for one cycle, check and recalibrate the torque of the connecting bolts; 6. To ensure the service life of the sealing gasket, please do not use liquid or metal-based anti-stick agents or lubricants. 7. If there is leakage in the pipeline, the pressure must be reduced before replacing or adjusting and installing the sealing gasket.