What is Pump Bearing Lubrication?
Horizontal centrifugal pump bearings may be lubricated with either grease or oil. Vertical pump bearings may be lubricated by the water being pumped (product water), an external source of water, oil, or less-commonly grease.
All horizontal centrifugal pumps are equipped with roller-element bearings. Even close-coupled pumps have bearings that must be lubricated since the motors supplied with close-coupled pumps must be lubricated periodically. Pump bearings may be lubricated either with grease or oil depending on the bearing arrangement designed by the pump manufacturer and the preferences of the pump operator.
Oil Lubrication in Horizontal Centrifugal Pumps
Horizontal centrifugal pump bearings that are oil-lubricated may employ either the ring-oil method or the oil-bath or oil-flood method. In the ring-oil method of bearing lubrication the bearings themselves do not descend into the oil. Instead, they ride just above the oil, and oil is lifted out of the oil reservoir by a ring attached to the pump shaft. The ring then transfers the oil to the bearing.
In the oil-bath or oil-flood method, the lower race of the bearing runs partially submerged in oil.
While the ring-oil method is considered to be a superior design in that it allows for better heat dissipation, the oil-bath method is sometimes preferred because it is less susceptible to failure and more forgiving.
Vertical Pump Bearing Lubrication
Vertical turbine pumps have sleeve-type bearings that are usually lubricated by the water the pump is pumping. However, in cases where the water being pumped is not suitable to use for bearing lubrication or where the pump bearings require lubrication prior to the pump starting (pre-lube), the pump shaft and bearings can be enclosed in a tube, and the bearings can be lubricated either by an external source of water or by oil that is drip-fed into the tube through the pump stuffing box.