(1) lip packing.Labiform packing: due to its flexible lip pads, the expanded packing can be used in compression packing and cannot be made of relatively hard materials.The drawback of labial packing is that its sealing effect is only unidirectional.Most lip packing for stem is made of pure teflon or filled teflon.But some are made of rubber or leather reinforced with fibre.It is mainly used in hydraulic pressure.Most are v-shaped with lip packing for stem.This is easy to install and extend.
(2) extruded packing.The name of extruded packing is applicable to packing of O - ring type.When the packing material is installed, its side is squeezed and its lateral preload is maintained by elastic deformation of the material.When the media enters the packing chamber from the bottom, the packing moves towards the gap between the stem and the support seat, thus blocking the leak path.When the packing chamber pressure drops again, the packing returns to its original shape.
(3) thrust filler.The thrust packing consists of a packing ring or a gasket arranged between the cover and the stem shoulder. The stem can move freely relative to the packing ring.The starting stem seal may be supplied by an auxiliary shaft seal such as a retractable packing, or by a spring which forces the stem shoulder against the thrust packing and forces the stem shoulder to come into closer contact with the packing.
(4) the sealing diaphragm valve stem of the diaphragm valve stem is sealed by a flexible and pressurized cover that connects the stem to the closing member.This seal prevents any media from leaking into the atmosphere through the stem as long as the diaphragm does not fail.The materials of the diaphragm vary according to the use of the valve, available in stainless steel, plastic or rubber, etc.