Monitor Energy Consumption & System Variables

Measuring the energy consumption of a pumping system can be very simple. Simply installing a meter in front of the main line that supplies power to the entire pumping system will show the power consumption of all electrical components in the system, such as motors, controllers and valves.

Another important feature of system-wide energy monitoring is that it can show how energy usage changes over time. A system that follows a production cycle may have fixed periods when it consumes the most energy and idle periods when it consumes the least energy. The best thing that electricity meters can do to reduce energy costs is to allow us to stagger the production cycles of machines so that they consume the lowest energy at different times. This doesn't actually reduce energy consumption, but it can lower energy costs by reducing peak usage.

Planning Strategy

A better approach is to install sensors, test points, and instrumentation in critical areas to monitor the condition of the entire system. The critical data provided by these sensors can be used in many ways. First, sensors can display flow, pressure, temperature and other parameters in real time. Secondly, this data can be used to automate machine control, thus avoiding the human error that can come with manual control. Third, data can be accumulated over time to show operating trends.

Real-time monitoring - Establish set points for sensors so they can trigger alarms when thresholds are exceeded. For example, an indication of low pressure in the pump suction line can sound an alarm to prevent fluid from vaporizing in the pump. If there is no response within a specified time, the control shuts down the pump to prevent damage. Similar control schemes can also be used for sensors that sound alarm signals in the event of high temperatures or high vibrations.

Automation to control machines - There is a natural progression from using sensors to monitor set points to using sensors to directly control machines. For example, if a machine uses a split case centrifugal pump to circulate cooling water, a temperature sensor can send a signal to a controller that regulates the flow. The controller can change the speed of the motor driving the pump or change valve action to match the split case centrifugal pump's flow to cooling needs. Ultimately the purpose of reducing energy consumption is achieved.

Sensors also enable predictive maintenance. If a machine fails due to a clogged filter, a technician or mechanic must first ensure the machine is shut down and then lock/tag the machine so the filter can be safely cleaned or replaced. This is an example of reactive maintenance - taking action to correct a fault after it occurs, without prior warning. Filters need to be replaced regularly, but relying on standard time periods may not be effective.

In this case, the water passing through the filter may be more contaminated than expected and for a longer period of time. Therefore, the filter element should be replaced before the planned time. On the other hand, changing filters on a schedule can be wasteful. If the water passing through the filter is unusually clean for an extended period of time, the filter may need to be replaced weeks later than scheduled.

The crux of the matter is that using sensors to monitor the pressure differential across the filter can show exactly when the filter needs to be replaced. In fact, differential pressure readings can also be used at the next level, predictive maintenance.

Data collection over time - Going back to our recently commissioned system, once everything is powered up, adjusted and fine-tuned, the sensors provide baseline readings of all pressure, flow, temperature, vibration and other operating parameters. Later, we can compare the current reading to the best-case value to determine how worn the components are or how much the system has changed (such as a clogged filter).<

Future readings will eventually deviate from the baseline value set at startup. When readings drift beyond predetermined limits, it may indicate impending failure, or at least the need for intervention. This is predictive maintenance - alerting operators before a failure is imminent.

A common example is that we install vibration sensors (accelerometers) at the bearing locations (or bearing seats) of centrifugal split case pumps and motors. Normal wear and tear of rotating machinery or pump operation outside the parameters set by the manufacturer can cause changes in the frequency or amplitude of rotational vibration, often manifesting as an increase in vibration amplitude. Experts can examine vibration signals at startup to determine if they are acceptable and specify critical values that indicate a need for attention. These values can be programmed into the control software to send an alarm signal when the sensor output reaches critical limits.

On startup, the accelerometer provides a vibration baseline value that can be saved in control memory. When real-time values eventually reach predetermined limits, the machine controls alert the operator that the situation needs to be evaluated. Of course, sudden severe changes in vibration can also alert operators to potential failures.

Technicians responding to both alarms may discover a simple fault, such as a loose mounting bolt, which may cause the pump or motor to move out of center. Re-centering the unit and tightening all mounting bolts may be the only actions needed. After the system restarts, real-time vibration readings will show whether the problem has been corrected. However, if the pump or motor bearings are damaged, further corrective action may still be required. But again, because the sensors provide early warning of potential problems, they can be assessed and downtime postponed until the end of a shift, when a shutdown is planned, or when production is moved to other pumps or systems.

More than just Automation & Reliability

Sensors are strategically placed throughout the system and are often used to provide automated control, support operations and predictive maintenance. And they can also take a closer look at how the system is operating so they can optimize it, making the overall system more energy efficient.

In fact, applying this strategy to an existing system can reduce energy consumption by exposing pumps or components that have significant room for improvement.