Controlling Pressure While Greasing Bearings

These seven quick pointers for managing pressure when regreasing bearings are excepts from Noria's Machinery Lubrication Level I training course.

Shut-off Grease Fitting Prevents over-pressurization during greasing. Shuts off flow at 50-110 psi. When pressure relieves grease flow can resume.

Relief-type Vent Plugs These fittings are installed in the vent (purge) port. They are pressure-relief valves with cracking pressure of 1-5 psi.

• Slowly pump grease into bearings over a period of three to five seconds per normal shot of grease (0.1 ounces, or 2.8 grams). Increase or decrease time to adjust for larger or smaller volume output per shot. Using a quick lever action could blowout seals and may not allow the grease to distribute correctly within the bearing.

• Discontinue greasing when you feel or observe abnormal back pressure. The pressure limit varies by application.

• If back pressure is high, the passageway may be blocked with caked thickener.

• Grease guns can produce over 15,000 psi while lip seals can fail at 500 psi. There is also a risk of collapsing shields and grease getting onto windings in electric motors.

• If risk is high, consider installing pressure relief fittings on grease guns or use pressure relief-type grease fittings.

• It is possible to install pressure gauges on some grease guns.

• If risk is high, avoid use of pneumatic-type grease guns.