The pumps are designed to be lightweight, robust and durable, making them suitable for use in the harsh environments. They include an air valve that cools the motor when the pump runs dry, a water cut that prevents leakage through the power cable, a thermal contact that protects the motor from overheating, double mechanical shaft seals in the oil bath, essential for a long life span in tough applications and a rubber strainer that improves the shock resistance. Grindex's Mini and Solid pumps, for example, have external oil plugs so they do not need to be disassembled to check the oil. The Solid sludge pump comes with a polyurethane impeller and pump housing that provides high wear resistance when pumping abrasive media. The Solid pump can run in water containing relatively abrasive solids and handle solids up to the size of 38 mm.