For valves operating at 200 degrees and 10 kilograms of pressure, is PTFE packing better or flexible graphite?
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This post was last edited by WQC on 2010-11-4 at 19:28. For general process media at around 200 degrees and a pressure of 10 kilograms, is PTFE packing better or flexible graphite? Thank you
I recommend using metal-graphite wound gaskets; they work very well
Flexible graphite – well, it’s used these days; PTFE fillers, when used for an extended period of time, make it more difficult to open and close the valve
Oh, is it that PTFE fillers used domestically generally cannot withstand 200 degrees?
Just a question: which of these two types of fillers is more expensive? Thank you!
Reply to 4# steven_zmy: PTFE material cannot withstand temperatures of 200 degrees; in my opinion, even temperatures around 100 degrees require caution. The mechanical properties of plastics decrease at high temperatures, and they also deform.
Obviously, only graphite can be used; it is recommended to use a metal-graphite wound gasket with a lining ring. If PTFE is to be used over a long period of time, it is best not to expose it to temperatures above 140 degrees, even though it is claimed to be a high-temperature resistant composite material! ! !
The maximum operating temperature of modified PTFE is 200 degrees, and it is generally not used at temperatures exceeding 150 degrees. In contrast, the maximum operating temperature of ordinary PTFE is only 100 degrees, with actual usage temperatures not exceeding 80 degrees. The maximum operating temperature for flexible graphite can reach 650 degrees, whereas that for LZ is 200 degrees; using flexible graphite provides great reliability (generally, gaskets made of 304 steel combined with flexible graphite are used). For specific details, refer to the provisions of HG/T20606-2009D.
This question can be very simple or it can become complicated. First of all, the operating conditions aren’t that severe; to be honest, either PTFE-woven packers or graphite fiber-woven packers can be used. Many people don’t seem to understand why PTFE woven packing cannot withstand temperatures of 200 degrees; in fact, PTFE woven packing can handle temperatures up to 250 degrees without any problems. However, if you’re worried, I recommend using PTFE-graphite permeable woven gaskets, which contain both PTFE and graphite – excellent choice. Of course, the friction coefficient of PTFE is lower than that of graphite. These packing materials are quite inexpensive. When using packing materials, it’s best not to focus too much on the price; choosing the right product is what will serve you in the long run.
There are many types of PTFE; the reinforced variants can withstand temperatures of up to 260 degrees, while ordinary versions can handle around 120 degrees. Therefore, in the owner’s case, caution is needed when dealing with temperatures of 200 degrees. Metal-flexible graphite gaskets can withstand temperatures of up to 600 degrees, so there should be no problem with them. There are also rubber-asbestos gaskets that can handle temperatures below 300 degrees, but they aren’t used very often
Do not trust the idea of using PTFE at high temperatures; no professional manufacturer would use PTFE in place of graphite at high temperatures. Although books state that PTFE can be used at high temperatures, its normal operating temperature is below 80 degrees. When the temperature rises, the fatigue strength decreases and the lifespan shortens