Problems and Selection of Ball Valves for Molecular Sieves
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In chemical processes, there is a dryer equipped with molecular sieves, which is used to dry process gases. This dryer needs to be regenerated periodically, and compressed air is used for this purpose. The current problem is that the valves in the regeneration pipeline either cannot be closed completely or cannot be opened fully. These valves are ball valves; the valve seats are made of PTFE material, while the valve balls are made of stainless steel. The operating temperature is 70 degrees, and the operating pressure is 4 bar. Upon disassembling the valves, it was found that there was a small amount of molecular sieve powder on the valve seats. I wonder if anyone among you has encountered similar problems on site – what could be the cause, and how can it be resolved? Thank you.
The powder can get stuck on the valve seat; PTFE is a soft seal, which results in poor sealing, so it is recommended to use a wear-resistant hard seal.
It is unreasonable to choose soft seals; moreover, could you tell me which manufacturers’ ball valves you have selected? The problem with you must be that the powder has gotten into the spring chamber behind the valve seat. Your control switch likely has a time requirement; in mild cases this leads to delays, while in more severe cases it causes sticking, eventually preventing the switch from functioning.
In fact, we need to trace it back to the source – why is there so much powder? We’ve been using the molecular sieves in our compressed air dryers for seven or eight years now, and there’s very little powder produced.
For molecular screening valves, pneumatic quick-opening globe valves with a hard seal are generally used; there is no risk of poor sealing due to dust, unless the quality of the valve is substandard.
Use hard-sealed, wear-resistant ball valves from imported brands. Fors in the United States, KACE in the United States, Walker in the United States, Prolide in Germany. All have performance.
Relatively simple check valves or filters
Domestic ball valves, with modest specifications, can also be used; for example, the FBV valve by Biwei, and the NEWAY valve by Nuowei