Order the Video Training Program
This dynamic video training program shows you how to optimize the performance of your pump systems to achieve remarkable energy savings. You'll get practical information on:
Developed specifically for pump, engineering, and systems professionals, this 60-minute, professionally-produced video comes with an instructor's manual and three participant workbooks. Use this program as self-guided instruction or in an instructor-led, four to six hour training session.
Design systems with lower capacity and total head requirements. Do not assume these requirements are fixed.
Flow capacity, for example, can be reduced through use of lower velocity in heat exchangers and elimination of open bypass lines. Total head requirements can be reduced by: lowering process static gage, pressure, minimizing elevation rise from suction tank to discharge tank, reducing static elevation change by use of siphons, lowering spray nozzle velocities, lowering friction losses through use of larger pipes and low-loss fittings, and eliminating throttle valves.
Avoid allowing for excessive margin of error in capacity and/or total head. It typically will be less expensive to add pumping capacity later if requirements increase.
Small differences in efficiency between pumps are not as important as knowing and adjusting to the service conditions. Energy savings may be as high as 20% if pumps are sized based on reasonable system heads and capacity requirements. Savings result from operating at a more efficient point on the pump curve, and in some cases, this also avoids the need to throttle pump capacity or operate at a higher capacity than necessary.
Despite the tendency to emphasize initial cost, you will save in the long run by selecting the most efficient pump type and size at the onset.
The choice of a pump depends on the service needed from the pump. Considerations are flow and head requirements, inlet pressure or net positive suction head available, and the type of liquid to be pumped. Maximum attainable efficiency of a centrifugal pump is influenced by the designer's selection of pump rotating speed as it relates to "specific speed." Purchasers need to be aware of this, as well as the decision criteria for determining the type of pump to use.
Use variable-speed drives to avoid losses from throttle valves and bypass lines, except when the system is designed with high static heads.
In such instances, extra concern must be shown when calculating the savings, since the pump affinity laws cannot be used without regard to the change of pump (and motor) efficiency along the system curve. Take care to ensure that the operating point of the pumps remains within the allowable/recommended limits specified by the pump manufacturer.
Use two or more smaller pumps instead of one larger pump so that excess pump capacity can be turned off.
Two pumps can be operated in parallel during peak demand periods, with one pump operating by itself during lower demand periods. Energy savings result from running each pump at a more efficient operating point and avoiding the need to throttle a large pump during low demand. An alternative is to use one variable-speed pump and one constant-speed pump.
Use pumps operating as turbines to recover pressure energy that would otherwise be wasted.
Practically all centrifugal pumps will perform as turbines when operated in reverse. A hydraulic power recovery turbine can recover pressure energy when used to drive a generator, or assist the driver of a pump or a compressor.
Maintain pumps and all system components in virtually new condition to avoid efficiency loss.
Wear is a significant cause of decreased pump efficiency. Bearings must be properly lubricated and replaced before they fail. Shaft seals also require consistent maintenance to avoid premature mechanical failures. Most important is the renewal of internal wearing ring clearance and the smoothness of impeller and casing waterways.