(1) Lip filler
Due to the soft lip of the lip filler, it will expand laterally and tightly adhere to the retaining wall under the action of the medium pressure. This expanded filler can be used in compressed fillers, and relatively hard materials cannot be used. The disadvantage of lip packing is that its sealing effect is only unidirectional. Most of the lip packing used for valve stems is made of pure PTFE or filled PTFE. But some are made of fiber-reinforced rubber or leather. Mainly used in hydraulics. Most of the lip packing used as the valve stem is made into a V-shape. This is both easy to install and easy to expand.

(2) Extruded packing
The name of the extruded packing applies to packing such as O-rings. After the packing is installed, its side is squeezed, and the lateral preload force is maintained by the elastic deformation of the material. When the medium enters the packing cavity from the bottom, the packing moves to the gap between the valve stem and the support seat, thereby blocking the leakage path. When the pressure in the packing cavity drops again, the packing resumes its original shape.

(3) Thrust packing
The thrust packing consists of a packing ring or a gasket installed between the valve cover and the valve stem shoulder. The valve stem can move freely in the axial direction relative to the packing ring. The initial valve stem seal can be provided by an auxiliary shaft seal such as a shrinking packing, or a spring, which forces the valve stem shoulder against the thrust packing, and the subsequent medium pressure can force the valve stem shoulder to be tighter Contact with filler.

(4) Sealing of diaphragm valve stem
The diaphragm valve stem is sealed by a flexible and pressure-bearing valve cover, which connects the valve stem and the closing member. This kind of seal can prevent any medium from leaking to the atmosphere through the valve stem as long as the diaphragm does not fail. The material of the diaphragm varies according to the purpose of the valve. It can be stainless steel, plastic or rubber, etc.