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Pumps

Why use pumps?
Types of pumps
Pumping tips

Why use pumps?

The running cost of a pump is many times its initial cost – selecting an efficient pumping system can save your business money.

Pumps are widely used in many industries to transfer fluids, for heat transfer or processing, and to provide the motive force in hydraulic systems. In the manufacturing sector, pumps represent approximately 27% of the electricity used by motors. In the commercial sector, pumps are primarily used in air conditioning systems to provide water for heat transfer.

Since they serve such diverse needs, pump sizes range from fractions of a kilowatt to several thousand kilowatts. In addition to an extensive range of pump sizes, there are also several different types of pumps.

Pump reliability is often critical. In cooling systems, pump failure can result in equipment overheating and catastrophic damage. In lubrication systems, inadequate pump performance can destroy equipment. In many situations, pump downtime can cause a substantial loss in productivity.

Types of pumps

Although pumps are available in a wide range of types, sizes, and materials, they can be broadly classified into two categories – positive displacement and centrifugal.
Within these classifications there are many different sub-categories of pumps.

Positive displacement pumps

These pumps pressurize fluid with a collapsing volume action. Essentially they squeeze fluid through the system with each piston stroke or shaft rotation.

Centrifugal pumps

Centrifugal pumps work by adding kinetic energy to a fluid using a spinning impeller. As the fluid slows in the diffuser section of the pump, the kinetic energy of the fluid is converted into a pressure increase.

Which pump?

Centrifugal pumps are more common due to their simple and safe operation, low maintenance requirements, and characteristically long operating lives. They typically suffer less wear and require fewer part replacements than positive displacement pumps. Although the packing and mechanical seals must be replaced periodically, these tasks usually only require minor downtime.

Centrifugal pumps can also operate over a broad range of conditions and have a low risk of catastrophic damage due to improper valve positioning. These pumps also offer the best opportunities for energy savings.

Pumping tips

Design systems with lower capacity and total head requirements
Designing a system so that it runs at the lowest practical flow rate will reduce dynamic head and pump energy requirements.

The most challenging aspect of the design process is cost-effectively matching pipe size, pump and motor characteristics to the needs of the system. This process is often complicated by wide variations in flow and pressure requirements. Designing your system to meet requirements during ‘worst case’ conditions can lead to specifying equipment that is oversized for normal operation. And using larger than necessary pipes and pumps increases material, installation, and operating costs. Operating energy cost benefits will accrue from:

• Pumping at lower rates
• Maximising pipe diameter and minimising length
• Minimising elbows (use radial bends) and eliminating large or abrupt changes in pipe diameter
• Minimising use of throttling valves
• Locating equipment/systems to reduce static head

The design process is a balance between meeting the overall system needs, capital costs and operating costs.

Select the most efficient pump type and size at the start
Carefully considering pump selection and efficiency when selecting pumps will help ensure that increased operating costs are avoided.

Use high efficiency motors for pump drives

You can directly improve the efficiency of your pump system by increasing the efficiency of the motor - see the high efficiency motors section.

Use two or more smaller pumps instead of one larger pump
This lets you reduce the system capacity by turning off pumps, which can provide significant energy savings. Designs need to take into account varying system curves at different operating points to make sure you select the appropriate pump.

Regularly maintain your system

Although centrifugal pumps are widely used due to their low maintenance requirements, as with all machinery, they do require periodic maintenance

Common maintenance tasks on centrifugal pumps include:

Bearing lubrication and replacement

• Packing tightening and replacement
• Mechanical seal replacement
• Wear ring replacement
• Impeller replacement
• Pump/motor alignment
• Motor repair or replacement

In addition you should carry out regular maintenance of your total system to avoid increased pressure requirements (due to fouling, blocked strainers etc).

Further information

Find out how to reduce your energy costs, by contacting Synergy's Energy Consultants. Just email us at energyreview@synergyenergy.com.au or call 1300 859 333.
For more information on energy efficiency in your business visit the Sustainable Energy Development Office at http://www1.sedo.energy.wa.gov.au