The plant has three small cooling towers. All of them had over-temperature problems last summer, so the mechanics spent considerable time on them. They addressed various issues ranging from scale buildup to pump impeller deterioration.
The towers, which also operate in winter, are equipped with flow meters that provide a low flow alarm. An instrument tech has calibrated the flow meters, yet the flow readings are below operating specifications. The mechanics are saying the cause must be low voltage.
Where do you start?
The mechanics may be correct about an electrical issue, but it would be the frequency not the voltage. If supply voltage at the motors is low, the motors will run hotter not slower.
If these are on variable speed drives (VSDs), adjusting the drives is the obvious solution. Take “As Found” flow measurements, noting the drive settings. Then, take new flow measurements after increasing the motor speed (assuming it’s not already at maximum).
If these are across the line connected, you just need to prove it’s not an electrical problem. Use a power analyzer to check the frequency and other characteristics. You can look for waveform anomalies, low power factor, and other issues that may need correcting, but they aren’t affecting the speed of the motor. If the frequency is correct, so is the motor speed.
