The role of the liner from the ring sets
  In the valve applications, the bushing within the valve cover, wrapped around the stem, generally DU oil-free bushing PTFE or graphite and other corrosion-resistant materials for sealing effect.

supplement

Role: to protect the shaft, seat hole, do not send DX oil-free bushing Health and wear; shock absorption, noise reduction; reduced to reduce the demolition and maintenance;

Material: an import THORPLAS can be considered under;

Use: no grease, dry running;

Installation: interference fit

Oil-free bushings, as the name implies, do not add lubricating oil JDB graphite copper sleeve and grease, in the use and maintenance of convenience, cost savings, time, cost;
Several types:
Now there are many in the market, there are three:
1, the metal matrix, usually copper lead, the surface of a hole, the hole by adding grease; rely on a large number of holes in the grease to support the operation, in fact, a long time also need to refuel;
2, composite bushings, one is the steel back + copper + PTFE Teflon, the other is the steel back + copper + POM POM; are pressed molding; inner lining material by the bushing to achieve operation, but it is Thin, fragile, the pressure can not afford;
3, non-metallic self-lubricating bushings: the real self-lubricating; nylon, Teflon,

 Oil-free bushing, said that the improvement of copper is in the design of the time, if the light load we will choose copper sets and oil-free bushings,
The majority of oil-free bushings are steel plates, with sintered spherical bronze powder in the middle, and some other materials, such as polytetrafluoroethylene (PTFE) and lead, are sprayed on the surface. Friction coefficient is small, wear-resistant and engage in a good non-corrosive oil lubrication characteristics. Used for a variety of mechanical sliding parts, such as printing presses, textile machines, fitness pallet truck. Some bushings are specially engineered to withstand high speeds, but can not withstand heavy loads.
Oil-free bearings in general when I design are low-load low-speed 1000 turn to use.