Pump Vibration Monitoring Basics

Posted by eliteinternet on April 20th, 2021

Pumps do a lot of work for mankind. They get water clean. They fill our swimming pools. They get gasoline from one place to the next. They’re kind of everywhere, it seems! Yet, when the pumps don’t work, that’s when we’re in big trouble.

Vibration test equipment can help. This equipment consists of sensors and computers that measure how the pump is doing by means of its vibration. The vibration can be measured as a frequency, like sound, and that report is read by a digital device.

If a problem pops up, according to the vibration sensors for pumps, then the computer alerts the correct people (foreman, tech, owner, etc.). If only other processes could be so automatic!

This can make machine vibration and pump vibration difficult. How can one company make technology that is able to measure the vibration of so many different types of pumps? Luckily, one firm, STI Vibration Monitoring, Inc. (www.stiweb.com) answers the call.

Most pumps can operate from 450 to 3,600 CPM (7.5 to 60 Hz) depending on site pumping requirements, available horsepower, drive, and gearing. General-purpose accelerometers (those with an output of 100 mV/g) are adequate for these mid-band frequencies.

However, pump faults can cause vibrations across a wide frequency range. Accelerometers should be selected based on the faults and ranges of interest.

Many pump vibrations are directly related to the running speed of the pump (or multiples of the running speed) and the motor drive system. These vibrations occur in the mid-to high-frequency range of 450 to 60,000 CPM (7.5 to 1,000 Hz).

These examples include harmonics of a drive motor and pump running speed and vane/impeller pass frequency.

Many destructive system faults appear at very low frequencies and can be identified by accelerometers, which sense problematic vibrations. In other words, if the pump is acting funny, you’re going to hear about it.

Motion in terms of acceleration is very low at these frequencies. When low amplitude vibrations are measured near the electronic noise floor of the sensor, or monitoring instrument, the signal-to-noise ratio can corrupt the real signal.

There can be a lot of complications. It’s better to protect the pump with vibration monitoring equipment.