Pumping systems perform many important functions in modern built environments. In addition to providing drinking water, they are used in fire protection systems, industrial processes and many types of HVAC installations. Pumps have electrical and mechanical components and are often subject to a high workload. Therefore, proper maintenance is very important.
Pumps are typically driven by electric motors, but use a combustion engine in some applications. While many performance problems affect the pump itself, malfunctions can also be the result of engine problems. When a building has low flow or other pumping problems, an inspection by a plumbing engineer is recommended to find the cause.
Upgrade your pumping system and improve performance.
Preventing impeller damage from cavitation
Cavitation is a hydraulic phenomenon where bubbles form in moving water due to a drop in pressure, and normally happens when water reaches the pump suction at low pressure. Although the bubbles may seem harmless, they produce small shock waves when they collapse and can seriously damage the pump's impellers over time.
One of the most common signs of cavitation is its characteristic sound, which gives the impression that the water flowing through the pump contains stones or marbles. In fact, the sound is caused by the shock waves from the collapsing bubbles.
Cavitation can be avoided with proper pump and piping selection, ensuring that water pressure never drops to the point where bubbles form. The location of the pump in a building also influences cavitation; pumps on upper floors are more likely to be affected, as water loses pressure as it flows upward toward the pump.
Preventing electrical problems in pumping systems
Even if the pump is in good condition and the piping is the correct diameter, problems with the electric motor can affect performance:
- Adequate voltage must be supplied to the motor, otherwise it will tend to overheat. Note that both overvoltage and undervoltage shorten the life of motors.
- In the case of three-phase motors, the voltage supply must have balanced phases. Voltage imbalance is also detrimental to motor performance and lifespan.
- The electrical protection of the motor must be suitable for the application. Consider that motors draw a high inrush current when they start, and protective devices must tolerate this current spike without tripping.
- If the pump uses a three-phase motor, it may be running in reverse due to an incorrect connection. However, this should not be a problem if the pumping system is installed by professionals. The rotation of a three-phase motor can be reversed simply by swapping two of the three live wires.
There are also cases in which the pump motor is working properly, but the unit is very old and inefficient, resulting in higher electricity costs. Significant savings are possible by upgrading to a NEMA Premium Efficiency motor, especially if the pumping system operates continuously.
Minimizing noise and vibration
A certain level of noise and vibration is inevitable when it comes to mechanical systems, and even well-maintained high-quality equipment produces them. However, when noise and vibration levels are excessive, they are a clear sign that the pumping system should be inspected and repaired.
As explained above, if the noise from your pumping system sounds like marbles in the water flow, cavitation is the most likely culprit. The problem must be resolved as quickly as possible to avoid serious damage to the pump impeller.
In pumping systems, a common cause of vibration is misalignment between the pump shaft and the motor shaft. Vibration can also be caused by pump or motor elements that are mechanically out of balance.
- Misalignment can be prevented or corrected with high-tech methods such as laser shaft alignment.
- Pump impellers can be balanced by removing material, typically by drilling. This leads to a uniform distribution of mass around the axis centerline.
- Note that impellers can become unbalanced due to physical damage, which is often the result of cavitation.
Vibration increases the forces experienced by many pumping system components, shortening their service life. Vibration problems worsen when the pumping system has worn bearings, as they are unable to provide adequate support for the rotating shaft.
Reducing the electricity consumption of pumping systems
A pumping system can function properly with low energy efficiency, but why pay higher electricity bills when you can have efficient pumps? As mentioned previously, significant savings are possible by replacing older motors with NEMA Premium Efficiency motors.
For even better results, you can add variable frequency drives (VFD) to control pump speed. Conventional pump control methods use valves to restrict or recirculate flow as needed, but this wastes pumping energy. On the other hand, speed control can provide adequate flow and pressure without control valves.
Professional MEP engineers can identify problems in the pumping system and propose the best solutions as well as energy efficiency measures to reduce pumping costs.
