Improving efficiency
of existing pump systems by Amy Stone*
As expenses increase and the markets get even more volatile, everyone is looking to cut costs. While there are many ways to reduce expenses, this article will focus on improving efficiency of existing pump systems. Variable frequency drives are a great tool for optimizing hydraulic systems.
TECHNICAL GURU
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ariable frequency/speed drives, or VFDs/VSDs, are often coupled with water pumps and air blowers to reduce/increase the motor speed while optimizing flow and pressure to intersect the system needs to the pump or blower’s best efficiency point. For many years, many people have oversized their pumps and blowers with the intention of using a valve to create artificial head pressure, moving the system curve far away from the pumps best efficiency point. A VFD works by manipulating the incoming frequency provided to the motor that it is controlling. This manipulation of frequency also changes the pressure and flow characteristics of the pump or blower. Some VFDs also have an internal transformer which allows it to convert single phase power to three phase power in the smaller horsepower applications. A very important piece to consider when adding a drive to your system is the type of motor that the pumps have. Not all motors can be used with a VFD. The motor must be rated for 3-phase voltages and inverter duty. If the equipment is not rated for inverter duty applications, it will prematurely fail from overheating the windings in the motor.
Water pumps Even though this has been an accepted practice that saves in acquisition costs, it translates into wasted energy, electrical expense, and undue wear and tear on the equipment. Using a throttling valve to control flow and create pressure also creates turbulence at the outlet of the pump which can create cavitation conditions that wear down valve bodies and significantly reduce their service life. Cavitation in pumps happens on the suction side and often occurs in higher speed motors (3500 RPM) in suction lift applications operating far to the right hand side of the curve, AUGUST - SEPTEMBER 2020
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