System design oversight

After replacing the pump motor controller for the second time, we decided to find out what caused the controller to burn up. After operating for several days, we noticed excessive motor current on the controller. While we had the pump down for inspection, the customer technician removed and cleaned the filter screen. To continue our test we started the pump and the motor current was back to normal. What we learned was as the clogged filter screen increased the back pressure on the pump. To maintain the correct flow (pump speed) caused an increase in motor current to overcome the increased backpressure from the clogged filter screen. The motor current feedback was not included in the system diagnostics and the operators had not indication of the impending failure. The systems integrator undertook two improvement actions. (1) Increase the frequency at which all filter screens received cleaning and maintenance and (2) Brought the motor current value into an alarm to warn (predictive) the operators when a drive controller motor current was approaching and unsafe value. Why did the system integrator perform this work? Driven by the customer, the contract was written to require the system integrator to support the system for a pre-determined period of time after the system acceptance test.
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