Regarding valve packing, graphite, tetrafluoroethylene
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Recently, I summarized the choices of gaskets for valves in various projects and arrived at the following preliminary conclusions. I would appreciate it if experts could provide their feedback. The most commonly used materials are flexible graphite, graphite asbestos, PTFE, and fluorinated asbestos. Flexible graphite seems to be more expensive than PTFE, but it can operate at higher temperatures; PTFE is cheaper, though it may not be suitable for high-temperature conditions. The properties of graphite asbestos and fluorinated asbestos are not yet known to me. I welcome advice from experts
The cheapest option is graphite; it also has the highest temperature resistance. However, it has high viscosity, which increases the torque required to operate valves. Its thermal expansion and contraction are minimal as well. PTFE is polytetrafluoroethylene; its advantages include low torque and corrosion resistance, but it cannot withstand high temperatures, and it experiences significant expansion and contraction due to temperature changes. It is necessary to regularly tighten the packing gland, especially for valves installed outdoors. The other two are improved fillers designed to overcome the shortcomings of the two materials used for appeals, but they are costly.