By that time the stator may have suffered substantial damage. These devices sense the presence or absence of flow by noting changes in electric power by the pump motor. However, the power dip caused by run dry conditions is short lived and difficult to capture. The reason is that running dry causes such rapid heat buildup. The fluid film lubricating the interface between the stator and rotor quickly evaporates.
Friction increases within seconds after loss of fluid.
Soon the heat build up in the stator can causes the rubber to revert, making it gummy, further increasing friction. Pressure Monitors Pressure monitors use pressure to determine flow conditions. This method is simple and straightforward, with the advantage that you can monitor high pressure with the same device. Positive displacement pumps should always be fitted with over-pressure protection. The motor fuses may blow, but it is equally probable that a pipe fitting will burst.