How To Extend The Service Life Of Valve Packing

The valve is a control component in the fluid conveying system, which has the functions of cut-off, regulation, diversion, prevention of backflow, stabilization, diversion or overflow and pressure relief. Valves used in fluid control systems, ranging from the simplest shut-off valves to the various valves used in extremely complex automatic control systems, have a wide variety and specifications.

In the valve design or use experience, the packing of the lift valve is mostly asbestos packing or graphite packing or PTFE V-type packing, but these kinds of packing are limited by the number of valve opening and closing, which is the number of opening and closing of the valve. If it increases, the packing will wear out and the gap will gradually increase. After a certain number of times (according to statistics, it will not exceed 2000 times) the valve will leak from the packing. After the leak, it is necessary to re-press the packing gland. This scheme is suitable for occasions where the valve is not opened and closed frequently.

If the valve is opened and closed frequently (such as 500,000 opening and closing times a year), this will undoubtedly increase the use and maintenance costs of the valve. Is there a design that can still seal after the valve is opened and closed 1 to 2 million times? The answer is yes.

One way is to add a washer under the packing and a spring under the washer (the pre-tightening force of the spring needs to be calculated). When the packing is worn out, due to the action of the spring, the packing will be re-compressed to seal it. At present, this method can only reach 500,000 to 1 million times of opening and closing without leakage. The user needs to re-press the packing gland during the annual overhaul, which can only reduce the usual maintenance.

Another way is to use hydraulic and pneumatic sealing technology to change the original valve design thinking, use the oil cylinder seal slip ring at the packing, and add an O-ring seal (it is necessary to calculate the friction force and the seal specific pressure to determine the slip ring and O The number of type sealing rings). Through the use of this method, it can achieve 2 million times of opening and closing without leakage, but the O-ring seal has to be aged, the use time is only 5 years, and the cost is high.