How to choose packing for PVC regulating valve?

How to choose packing for PVC regulating valve?

In the past, the main consideration of packing choice of PVC valve is the working temperature of packing, when the temperature is lower than 200 degrees choose PTFE, when the temperature is higher than 200 degrees choose graphite. Now, when choosing the filler, we should not only consider the working temperature, but also consider the influence of the friction of the filler on the control process, such as return difference, sealing quality and service life.

The principle of filler selection is to minimize friction and prolong service life under the premise of leakage level.

The friction of graphite packing system is much greater than that of PTFE packing system, so PTFE system should be used as long as the temperature allows.

Summarize the key points of packing structure design and application:

1. Different packing box and packing structure are suitable for different applications. Reasonable selection of packing box and packing structure can reduce friction and prolong service life under the required sealing conditions.

Two, packing structure, packing layer and length is not the more the better, usually packing length is 1.5 times the stem diameter.

Three, improve the stem and packing box processing finish and surface accuracy is very important, PTFE packing, stem and packing box finish is not enough, will make the seal down, resulting in greater leakage.

4. The packing structure design should be able to automatically adjust the compression force, compensate for the decrease of the compression force caused by wear and tear, and be conducive to field maintenance and installation.

Five, improper installation of PVC regulating valve will cause uneven friction, such as horizontal installation of the stem weight on the lower horizontal line of the packing pressure, increase friction, and the upper horizontal line of the packing due to the reduction of compression force and make the sealing performance is poor.