In a diaphragm pump, the reciprocating member is a flexible diaphragm of metal, plastic, or rubber. This eliminates the need for packing or seals exposed to the liquid being pumped, a great advantage when handling toxic or corrosive liquids. A diaphragm pump is a positive displacement pump that uses a combination of the reciprocating action of a rubber or teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of pump is also called membrane pump. It handles small to moderate amounts of liquid, up to about 100 gal/min, and can develop pressures in excess of 100 atm. There are three main types of diaphragm pump In the first type, the diaphragm is sealed with one side in the fluid to be pumped, and the other in air or hydraulic fluid. The diaphragm is flexed, causing the volume of the pump chamber to increase and decrease. A pair of non-return check valves prevent reverse flow of the fluid. The second type of diaphragm pump works with volumetric positive displacement, but differs that the prime mover of the diaphragm is neither oil nor air; but is electro-mechanical working through a crank/ geared motor drive. The third type of diaphragm pump has one or more unsealed diaphragms with the fluid to be pumped on both sides. The diaphragms again are flexed, causing the volume to change.