Patent attributes
A liquid pump control system for dry run avoidance and re-prime detection. Pump dry run conditions can be detected with improved sensitivity by measuring pump cycle speed. Pump cycle speed is determined from sensors including pressure sensors, diaphragm end of stroke indicators, check valve movement sensors, and other techniques. A controller closes a valve to reduce pump cycle speed by reducing drive air pressure or by deadheading the pump liquid outlet. When the pump re-primes, the valve is opened, pump cycle speed increases, and pumping volume flow rate increases until a dry run condition is again encountered. Time delays can be introduced to delay shutting down or restarting the pump, for example to give a liquid source tank time to refill. The improved control sensitivity provides improved shut-down and re-start performance, reducing wear on the pump and reducing wasted drive air and energy consumption.
