The most widely used method of grease application is through pressure fittings. These pressure fittings can be screwed directly into the bearing housing. When grease is applied under pressure at the top, a ball check valve opens and allows the grease to flow into the bearing area. When pressure is removed, the valve closes to seal the bearing against dirt and prevent leakage which may arise from back-pressure in the bearing. Pressure fittings are available in a number of different designs to accommodate various applications.
Pressure fittings more effectively protect bearings against the entry of foreign particles.
More efficient lubrication can be expected from pressure systems because grease waste is kept to a minimum. Centralized Grease Systems Centralized grease systems are far more reliable and economical than the various hand-greasing methods previously described. Even more important, centralized grease systems eliminate the potential for injury associated with hand-operated systems and facilitate the delivery of grease to bearings and fittings which are normally difficult or dangerous to access. Automatic centralized systems supply grease in metered amounts to many different locations. Basically, automatic systems consist of a pump which builds up the required pressure to force grease through metering valves, lines, and flexible-hose connections to all bearing points requiring lubrication.