In principle, the selection of Dankai PTFE gaskets should be based on the working pressure, working temperature, corrosiveness of the sealing medium and the form of the combined sealing surface. At normal temperatures and low pressures, choose non-metallic soft seals; at medium and high pressures, choose metal and non-metal combination seals or metal seals; when there are large fluctuations in temperature and pressure, choose elastic or self-tightening seals; under low temperature, corrosive media or vacuum conditions, polytetrafluoroethylene gaskets with special properties should be considered.
1. It can only be used on low-pressure steam pipelines. Because PTFE will soften when heated and will break if the pressure is greater.
Example: A certain company had a medium-pressure steam pipeline. Because the high-pressure gasket was not available, the maintenance personnel did not understand and used PTFE gasket . It was not a big deal to open the valve very slowly. Once the valve opened a little faster, the entire pipeline was broken as long as it had PTFE gaskets. Fortunately, no one was hurt!
2. It depends on the type of steam and the temperature. If it is greater than 200 degrees (250 degrees in HG20592), generally we do not choose 4F. As mentioned above, it will become soft. , and 4F is generally used on corrosive material pipelines. General steam pipelines can use asbestos rubber gaskets. If the steam pipeline meets the conditions of temperature and pressure, it is not impossible to choose 4F, but it is a bit unreasonable. For details, please refer to the HG20592 series of standards.
3. It is not recommended to use it if the pipe temperature exceeds 180 degrees. For steam, that is, if it reaches 10 kilograms of pressure, it is not recommended to use it. Although polytetrafluoroethylene only melts at 220 degrees, it becomes soft at more than 100 degrees. For details, please refer to the PT diagram of each product.
Figure 1: PTFE gasket Source: Dankai
In addition, different flange forms and flange surface roughness have a great impact on the sealing effect. Especially when non-soft gaskets are used, the large sealing surface roughness is one of the main reasons for leakage. For example, the knife pattern on the turning flange surface is a spiral. When using the metal gasket , if the roughness value is large, the gasket cannot block the spiral groove formed by the knife pattern. Under the action of pressure, the medium will leak out along this groove. Soft PTFE gaskets have much lower requirements for the smoothness of the flange surface. This is because it is easily deformed and can block the machining knife lines, thereby preventing leakage. For soft PTFE gaskets, it is disadvantageous if the flange surface is too smooth, because the resistance to interface leakage becomes smaller at this time. The following are the performance parameters of PTFE gaskets produced by Dankai PTFE. Performance parameters of
PTFE gasket:
Appearance color: white;
Applicable temperature: -180～250;
Applicable medium: ph 0-14;
Regular size: 1524mm*1524mm, thickness 1.5～5mm.
Scope of application:
PTFE gasket is suitable for sealing parts with severe temperature and pressure changes. It is a static sealing element for flange joints such as pipes, valves, pumps, heat exchangers, towers, manholes, hand holes, etc. By changing the tension of the wound steel strip, the density (hardness) of the spiral wound gasket can be changed to meet the needs of various application parts. It is widely used in petrochemical, machinery, electric power, metallurgy, shipbuilding, medicine, atomic energy and aerospace industries.
This article was originally created by the Teflon pipe lady. Welcome to pay attention and bring you knowledge together!
