Section 6.1.1 - Centrifugal Pump Bearings: Cooling

Cooling   A water-cooled oil sump utilizes a plain or finned tube that runs through the oil
sump. Cooling water is circulated through the tube, conducting heat from the oil (Figure 6).
Some designs use a separate water jacket that bolts to the outside of the oil sump to draw
heat from the oil through the bearing housing wall into the water jacket. Tube style heat
exchangers are preferable because they are easier to disassemble and clean any mineral
deposits, or even replace, than are jackets.Water cooling is not effective nor is it applied
on oil mist or grease-lubricated systems.

Air-cooling is becoming more popular as cooling water is in limited supply or of poor
quality in many parts of the world. It is also less expensive to operate. In its simplest form,
a fan is mounted on the shaft on the outboard side of the bearing housing to direct air over
the bearing frame toward the pump, thus creating forced convection of heat from the bearing
frame. Sometimes a heat deflector is also utilized which is a finned disc mounted on
the shaft between the seal chamber and the bearing housing (Figure 7). This device conducts
heat from the shaft before it reaches the bearing housing, absorbs heat radiated

from the seal chamber and also creates forced convection in the seal chamber area. Air-
cooling can be used on sump oil, oil mist and grease-lubricated bearing systems.

External lubricating oil systems incorporate either an oil-to-water or oil-to-air heat
exchanger. The oil-to-water heat exchanger is a tube-type system with the lubricating oil
on the tube side and the water on the shell side. Small oil-to-air heat exchangers consist
of an electric motor driven fan, forcing convection over a coil of finned tubes containing the
circulating oil. Larger systems utilize a large radiator and fan much like you would see on
a diesel engine.

Cooling   A water-cooled oil sump utilizes a plain or finned tube that runs through the oil
sump. Cooling water is circulated through the tube, conducting heat from the oil (Figure 6).
Some designs use a separate water jacket that bolts to the outside of the oil sump to draw
heat from the oil through the bearing housing wall into the water jacket. Tube style heat
exchangers are preferable because they are easier to disassemble and clean any mineral
deposits, or even replace, than are jackets.Water cooling is not effective nor is it applied
on oil mist or grease-lubricated systems.

Air-cooling is becoming more popular as cooling water is in limited supply or of poor
quality in many parts of the world. It is also less expensive to operate. In its simplest form,
a fan is mounted on the shaft on the outboard side of the bearing housing to direct air over
the bearing frame toward the pump, thus creating forced convection of heat from the bearing
frame. Sometimes a heat deflector is also utilized which is...