After determining the pressure change, convert it to feet of water, the usual pressure

unit used on pump curves. This is sometimes called feet of head. They are the

same. Multiply the PSI times 2.3 to convert to feet of water. For example, our

example pump had a pressure change of 10 PSI. This is:

10 PSI x 2.3 = 23 feet of water

The final step is to use the manufacturer's pump curve to determine what flow rate

the pump will provide working at that pressure change. Using Figure 3-14 as an

example, the 23 feet of pressure change across the pump indicates a flow rate of

about 30 gallons per minute.

NOTE

While this method is reasonably accurate, it is not perfect. As

the pump impeller wears, flow rates will decline. If the pump

is moving glycols or oils, there may be a considerable deviation

from the published pump curve. If the flow rate is 50% higher

or lower than the design flow rate, consult the fluid manufacturer

for the correction factor.

FIGURE 3-14

A Typical Pump

Curve

The motors of wet rotor pumps never require lubrication. External motor pumps

should be checked at every inspection. If there is no way to determine lubricant

levels, a regular schedule for adding oil should be established, to avoid over-oiling

the motor.

**INSPECTION**

79

3.1 INSPECTION PROCEDURES