I R R I G AT I O N
flow systems like drip, spray or mist irrigation. All positive displacement pumps require a pressure relief valve downstream of the pump to protect the mainline.
Protection or control equipment
Controls for irrigation pumping equipment fall into two groups: 1. prime mover (engine or motor) protection 2. protection of the irrigation system. A variety of pressure, temperature and water level sensing devices are available. They are usually fully automatic and are designed to override the manual control if anything happens which could damage the pumping unit or irrigation system. 1. Prime mover protection Diesel engines running unattended should be protected against any failure of the pressure lubrication system, water cooling system or belt drive components, as applicable. Electric motors are usually protected by sensing current rises or temperature
rises, thus detecting electrical overloads. Both types of prime mover should also be protected against overloads resulting from a change in delivery conditions. For example, a pipe failure with rotodynamic pump system will result in a large increase in power demand, beyond that which can safely be met by the prime mover. 2.
Distribution system protection
Pipelines usually break because of too much pressure. If a pipe breaks, then there is a risk of pump damage. Crop losses around the break are also likely. A pressure-sensing device to stop the pump avoids both of these possible outcomes. Pipeline protection can also be achieved by monitoring the pump output and taking care in the manual operation of valves, that is, closing and opening them slowly.
Efficiency and cost
The selection of a pump, prime mover and piping to provide the best operating efficiency for your system will result in lower power costs. Good design also results in a longer component life, further reducing operating costs through lower maintenance costs. Good design and correct pump selection will also assist you to use your water effectively. The first place to begin looking at improving efficiency is at the pump. As the pump is a major energy consumer, any improvement in its efficiency reduces the cost of operating the system. However, other factors should also be considered. Further savings may be found in improved pump operation and maintenance and by the selection of system components (such as pipe diameters, valves and fittings) which do not add excessive head losses. â– This article is adapted from a paper from the NSW DPI and is used with permission.
With the ever-rising cost of power and the need to use water effectively, the overall efficiency of a pumping system will continue to be of major importance to farmers.
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pump industry | November 2013 | Issue 5
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