How to extend the service life of the valve packing
WATO Wuhan Weituo Fluid Equipment Control Equipment Co., Ltd
The valve is a control component in the fluid delivery system, with the functions of cut-off, regulation, diversion, prevention of backflow, pressure stabilization, diversion or overflow pressure relief. Valves for fluid control systems, from the most simple cut-off valve to a very complex automatic control system used in a variety of valves, its varieties and specifications quite a wide range.
In the valve design or use experience, the lift valve packing is mostly asbestos packing or graphite packing or PTFE V packing, but these kinds of packing are limited by the number of valve opening and closing, that is, with the increase of the number of valve opening and closing, the packing will wear and the gap will gradually increase, and the valve will leak from the packing to a certain number of times (according to statistics, no more than 2000 times). After leakage, the packing gland needs to be pressed again. This scheme is suitable for the number of valve opening and closing occasions.
If the valve open and close frequently, (such as a year open and close 500000 times), which will undoubtedly increase the use of the valve, maintenance costs. Is there a design that can seal the valve after 100-2 million times? The answer is yes.
One way is to add a gasket under the packing and add a spring under the gasket (the preload of the spring needs to be calculated). When the packing is worn, due to the action of the spring, the packing will be re-compressed to make it sealed. At present, this method can only reach 50-1 million times of opening and closing without leakage through use inspection. It requires the user to re-press the packing gland during annual overhaul, which can only reduce normal maintenance.
Another way is to use hydraulic and pneumatic sealing technology to change the original valve design idea, use the cylinder seal slip ring at the packing, and increase the O-ring (need to calculate the friction force and seal pressure to determine the number of slip ring and O-ring). This method can be used to open and close 2 million times without leakage, but the O-ring seal is aging, the use time is only 5 years, and the cost is high.
