What is the sealing structure of the valve stem of a flat gate valve

Flat gate valves have the advantages of good sealing performance, long service life, small opening torque, and short structural length. Therefore, they have been widely used in petroleum, chemical, long-distance pipelines, oil terminals, and tank farms. However, during long-term use, medium leakage may occur at the valve stem seal, which is difficult to handle on site, resulting in the normal operation of the valve being affected.

The valve stem seal of the flat gate valve is a combination structure of self sealing and injection sealing grease packing. Its main material is tetrafluoroethylene molding filler and fiber containing colloidal sealing grease. The formed packing has an upper, middle, and lower structure, which is installed in two groups of upper and lower parts inside the valve stem packing box, forming two independent sealing chamber groups. The sealing grease packing is injected between the valve stem packing box and the upper and lower PTFE combination packing through the sealing grease filling plug in the middle of the packing box (Figure 1).

When the medium in the valve chamber is pressurized, the medium drives the lower packing group to move upwards, the lower packing group drives the sealing grease to move upwards, and the sealing grease is compressed to form a valve stem seal.