Mechanical Seal
Seal functioning refine operations and reduce wear and tear, almost all the gear and bearings require continuous lubrication. And to ensure the presence of lubricant around the components that move and keep the lubricating fluid not to go out and keep dirt and dust do not get into the system it is necessary to seal. The function of the seal are:
- Keeping lubricant leakage (lubrication).
- Keep dirt and other materials get into the system.
- Provides fluid restrictions that are not mixed.
- More flexible with moving parts and does not leak.
- Coat the uneven surface.
- Component is not quickly broken.
Figure 3.18 Seal lubricant leakage prevention
Figure 3.19 Kinds of types of seals
Seal classified into two parts:
1. Static Seal, used on the surface that there is no movement on the two surfaces are coated. Which includes Static seals are: O-ring seals, gaskets and liquid gaskets.
2. Dynamic Seal, Dynamic seal wear on moving parts between the surface of one with the other. While that includes Dynamic seal are: O-ring seals, lip seals, Duo Cone seals and packing rings.
1. O-rings
An O-ring is a ring forms a very soft material made from natural or synthetic rubber or plastic. In its user O-ring is usually compressed between two surfaces as seals, O-rings are often used as a static seal which functions the same as the gasket. For insulation in applications of high pressure above 5500 kPa (800 psi) O-ring is often added to the back-up ring to prevent leakage caused by the gap between the two surfaces.
Pressure back-up ring is usually made of a plastic material that serves to prolong the life of the O-ring. At the time of installation O-ring seal, make sure all surfaces are clean from dirt and dust. Check the O-ring seal from dirt, dust, scratches (screth) and other defects that would cause leaks.
Figure 3.20 O-ring
2. Lip seal
Lip seal is a dynamic seal types that are widely used in the construction heavy equipment. Lip seals bearing all kinds of operating conditions and prevents operation of the machine is not due to the heat caused by friction or also prevent mixing of lubricants or fluids. Lip Seal also resist displacement movement between the two components is limited. Lip seals are relatively easily removed at the time of repair or replacement of components.
Figure 3.21 Lip seal
Radial lip type seal is a lip seal and Dirt excluding lip seals. Dirt excluding lip seals are used to clean the dirt in the cylinder. Radial lip seals are used to prevent leaks in the rotation shaft and is made with an assortment of shapes and sizes tailored to application installation. Internal lip seal has a lip seal on the inside diameter. External radial lip seal has a lip seal on the outer diameter of the seal.
Radial lip seals withstand shaft surface with a liquid pressure and a garter spring. Garter spring pressing the seal lip when the fluid pressure is low. In actual operation seal aided by a thin layer of oil between the lip seal and the shaft, this in order to lubricate the lip seal and prevent leaks.
Figure 3.22 Duo cone seal
3. Duo Cone Seal
Duo cone seal made to keep the dirt does not get into the system and keep the lubricating fluid leak in a large area. Duo cone seal should be able to withstand rust longer with a little more care duo cone seal can withstand shaft crookedness, end play and load suddenly. Duo cone seal consists of two rings which are usually made of rubber, mounted on two metal retaining ring groove.
Rubber rings cooperate with metal rings serve as a seal. Rubber ring as well as a cushion for metal rings and keeping the surface flatness when the shaft rotates during machine operation. Surface smoothness metal rings together with the oil viscosity coats the shaft.
