No matter what kind of fluid is transported in the pipeline system, the working state, and the material performance of the pipeline, the gasket shall be used at the pipeline connection to participate in the sealing system. The connecting system of the pipeline mostly adopts flange sealing, and when flange sealing is used, the sealing gasket is also an indispensable part. The performance of sealing gasket plays a vital role in the normal operation of the pipeline system. Generally, there are three types of sealing gaskets used for pipelines: non-metallic gaskets: asbestos free, rubber, graphite, etc; Metal gasket: iron, copper, aluminum, stainless steel, etc; Semi metal gasket: spiral wound gasket, wrapped gasket, rubber coated gasket, foaming rubber gasket, etc.
Non metallic gasket is the most widely used sealing gasket, and its excellent resistance to most media, temperature and pressure resistance make it suitable for most sealing systems. Asbestos free fiber rubber gasket is the first choice, or even the only choice, for most enterprises. Due to different materials and processes, asbestos free gaskets have different properties and operating conditions, are easy to process and relatively low in cost, and can meet the sealing requirements of most pipeline interfaces. Polytetrafluoroethylene gasket has excellent corrosion resistance and aging resistance, and will not pollute any medium. It is more suitable for water treatment and chemical raw material transportation. Graphite gasket has high temperature resistance, and can withstand high temperature above 1000 ℃ after being compounded with metal.
The metal gasket is made of whole metal processing, which can withstand high temperature and high pressure, has relatively high safety performance, has a certain elasticity and pressure self sealing effect, and can be used when the equipment parameters change frequently. However, it has higher requirements for processing technology and sealing system itself, and the installation accuracy will also have a greater impact on the sealing effect.
The composite gaskets made of metal and non-metal materials have both advantages. They can be customized according to the actual use needs, meet the more stringent sealing requirements, and their own performance can also increase the service life, maintaining long-term excellent sealing performance when the parameters of the sealing system change.
According to the performance of the above common sealing gaskets, appropriate gaskets should be selected in different pipe sealing systems. The following are some suggestions for the selection and use of the above gaskets.
1. Asbestos free gaskets have the best cost performance under common conditions with low pressure and temperature requirements.
2. For occasions such as high temperature and high pressure steam and some flammable, explosive and toxic media, it is necessary to ensure the safety and reliability of flange seals. Metal and semi metal composite gaskets with excellent performance can be selected.
3. In case of frequent changes in temperature and pressure, vibration and impact, tooth shaped composite gasket or metal spiral wound gasket with good resilience shall be used.
4. High temperature system shall adopt graphite composite gasket, ceramic fiber gasket, etc. with strong medium and permeability resistance and no expansion, which can be sealed for a long time under high temperature working conditions.
5. PTFE gaskets can be selected for systems with high requirements such as highly corrosive media or condensate polishing, which will not pollute the media and will not age, and can play an excellent long-term sealing role in low temperature situations.