Main parts of a diaphragm valve are, body, bonnet and a flexible diaphragm. Diaphragm is lifted up when the valve is opened and the diaphragm is tightly pressed against the bottom of valve, when it is closed. Diaphragm valves are classified as: 1. weir type and 2. Straight through type. In weir type diaphragm valve relatively low thrust and shut off stroke is required. This gives longer life for diaphragm. Weir type diaphragm valve is commonly used. Straight through type diaphragm valve is suitable for handling slurries, viscous liquids, fibrous suspensions. In some diaphragm valves, the diaphragm is not fully lifted up of the weir, so accurate control of small flow becomes possible. Diaphragm is made either from rubber, neoprene or buna. It is available in size 3 mm to as large as 600 mm. It can be used up to 20 kg/cm2 pressure and 2200 C temperature. Material of construction for diaphragm valve can be cast iron, stainless steel, and  corrosion resistant alloys.