PUMPS
at the well head in a separate electrical box. It is imperative that the system be connected to an acceptable grounding system. A surge arrestor works by redirecting the power surge and sending it to ground. This surge will take the path of least resistance. If the grounding system has higher resistance than other devices in the system, the surge will flow to those components and cause damage. The National Electric Code suggests that the resistance in a grounding system should be no more than 25 ohms. For systems with sensitive electronic controls like a variable frequency drive, the resistance to ground should be approximately 5 ohms for proper operation and protection.
SAND AND SEDIMENT Sand and particulates are one of the greatest enemies of rotating
Abrasives create wear on the surface of impeller and damage components. Sand and particulates are among the biggest dangers to rotating equipment.
THERE ARE SEVERAL ASPECTS OF POWER QUALITY AS WELL AS UNEXPECTED POWER EVENTS THAT CAN SEVERELY HAMPER THE OPERATION OF A SUBMERSIBLE MOTOR.
For detection of and protection from these power quality issues, the use of an advanced motor protection device is recommended. These types of devices are available from several suppliers and in most cases will not only monitor the system for power issues, but they will also stop the motor when significant problems are detected. An advanced motor protection device may also record voltage and current in real time and either store this data or send it to a cloud server. Additional advanced motor protection device functions may include monitoring for loss of phase, phase sequence change, motor temperature, power factor and more.
Surges and lightning. An unexpected increase in transient voltage can be caused by changes or malfunctions within the power grid, an individual system or by a lightning strike. These voltage spikes are often random and difficult to predict and can wreak havoc on an unprotected pump motor.
Things to consider: Surge arrestors are a critical, and in many places mandatory, component in helping to prevent catastrophic equipment failure due to grid or system surges. A surge arrestor should be mounted as close to the motor as practical. The location is usually in the pump panel, but sometimes it is placed
14 Irrigation TODAY | Winter 2024
equipment. Sand and gravel are common in aquifers and it is difficult to prevent these particulates from entering a well. Turbulence created from the running pump can also stir up and suck in debris that settles on the bottom of the well. Once these materials enter the pump, they are set in motion at high speed through the impellers. These particles act as abrasives to the metal and can wear away at components over time. This can result in loss of efficiency and even cause the pump to seize.
Things to consider: Typical limits for sand content in domestic well water according to the National Ground Water Association should not exceed 2.5mg/l. Screens and gravel pack or sand filters should be installed in the well to prevent excessive sand inclusion and prolong the life of the pump.
By taking the time to assess and plan for each of these risk factors, in addition to the fundamentals of proper pump sizing, you can help to ensure the longest and most efficient operation life for your pump.
is a technical sales engineer for Grundfos, Brookshire, Texas.
is a market development manager for digital and controls for Grundfos, Brookshire, Texas.
Brookshire, Texas.
irrigationtoday.org
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