The diaphragm isolates liquids from the internal workings of the pump and the outside atmosphere, preventing internal leakage and contamination. But if the diaphragm ruptures, it can damage the pump and downstream machinery as well. To prevent most such accidents, engineers at Wanner Engineering Inc., Minneapolis (hydracell.com/frames/frame-Home.html) developed a diaphragm-displacement-limitation device (DDLD) for their Hydra-Cell pumps. It protects against partially or completely blocked inlet pipes or filters, inadequate fluid fluids that are too viscous, and that cause excessive vacuum DDLD prevents hydraulic overfill even vacuum conditions. Flow rates to 37 gpm (0.4 to 128 l pm) and pressures 2,500 psi (170 bar).