Catch problems early to avoid pump failure.
by Rob Fusco
August 7, 2019

Modern pumping systems typically include alarms that alert operators when a malfunction occurs. However, by practicing predictive maintenance, potential problems can be caught before they become major issues. Integrate a remote monitoring system with the right sensors and data logging functionality to prevent high-level equipment failure, extend pump life and minimize station downtime.

pump failures that can be predicted

Advantages of Remote Monitoring

Managing a stormwater or sewer pump station can be challenging. Unexpected events such as fast-moving storms, heavy rains, lightning and power outages are unpredictable. During these times, an unexpected pump failure can make it difficult to take fast enough action to avoid a spill. Remote monitoring of pumping stations provides operators with real-time alerts on failures, which maximizes pumps’ best efficiency points (BEP) and reduces overflows and spills. (See the sidebar at the end of this article: Types of Vibration)

Monitoring systems also safeguard from costs associated with fines from overflow and flooded wells, cleanup and downtime. If a pump fails, the callout system immediately sends an alert, so personnel can diagnose the pump failure and take corrective action to get the well back online before a spill occurs. In addition, having a remote monitoring system reduces maintenance and travel costs because it prevents the need to regularly drive to remote sites to check if pumps are functioning properly.

Predicting Equipment Failures

In theory, a well-designed pumping system should continue performing effectively for years. However, the reality is that many different operating conditions can cut a system’s life short.

A pump laboring under the handicap of a clogged intake, suction loss or cavitation stresses parts of the system and can cause it to fail prematurely. Bearing wear, dead head, dry pump and impeller jams can all cause premature motor and pump failure, which can lead to overflows and station shutdown.

Using sensors and data logging are keys to performing predictive maintenance, preventing unscheduled shutdowns and optimizing the pumps’ BEP. Here are five ways to get more out of the pumps and water/wastewater equipment by using sensors and remote monitoring technology.

Remote MonitoringImage 1. Remote monitoring systems monitor the pressure on the discharge and intake sides of the pump. (Images courtesy of Sensaphone)

1. Monitor Vibration

Fortunately, critical and auxiliary pumping systems usually give hints they are damaged and about to fail. Every rotating machine has its own vibration characteristics, and when a part starts going bad, those characteristics change.

If the seals or bearings on a pump begin to fail or if an impeller breaks, vibration increases. Although this change would not be noticeable to the human eye or ear, it is easily detected by a vibration sensor installed on the pump. The sensor “listens” to the pump’s acoustics to detect imbalances, providing early warning of issues arising within the pump.

Vibration sensors measure the vibration velocity (severity of vibration) of a machine from 0 to 25 millimeters per second (mm/s) root mean square amplitude (rms) over the frequency range 10 to 1,000 hertz (Hz). An output of 4 milliamps (mA) will correspond to 0 mm/sec (no vibration) and an output of 20 mA corresponds to 25 mm/sec (intense vibration).

Each vibration sensor communicates its frequency readings in real time to the remote monitoring system. The system can be set to “alarm” when an out-of-limit value is detected. This allows for time to take the action required to prevent catastrophic failure, secondary damage and downtime.

Many remote monitoring systems function as data loggers because they record and store all sensor data, which personnel can access and view at any time. When vibration sensors are integrated, they capture vibration readings at set time intervals, which can be viewed in real time and analyzed for trends that indicate a failure is imminent.

remote monitoring system dashboardImage 2. A remote monitoring system’s dashboard shows total flow output from the pump in gallons from a pulse count flow meter.

2. Monitor Pressure

If a pump is running, it has pressure. Monitoring this pressure is a key way to understand the characteristics of the pump and increase its life cycle. The more flow, the less pressure on the discharge, whereas low flow will show a higher pressure on the discharge. Pressure sensors help identify key problems that can prevent the pump from running within its BEP.

Ideally, a pump should not operate at flows ±10 percent of its BEP.

When a pump is not running at BEP, motor temperature rises, and bearings, seals and impellers have more stress, reducing service life. This can lead to premature failure of the pumping system. It is also useful to have a pressure sensor on the suction side: the difference in pressure is proportional to the total head. It is ideal to have pressure sensors on both sides of the pump.

Pressure sensors also monitor pump discharge, so they can alert if a pump shuts down for a long period of time or pressure drops from lack of suction. Pressure alarms allow users to take action to prevent the pumps from running dry if suction is lost for any reason.