The diaphragm pump has been developed for handling corrosive liquids and those containing suspensions of abrasive solids. It is in two sections separated by a diaphragm. In one section a piston or plunger operates in a cylinder in which a non-corrosive fluid is displaced. The movement of the fluid is transmitted by means of flexible diaphragm to the liquid to be pumped. The only moving parts of the pump that are in contact with the liquid are the valves, and these can be specially designed to handle the material. In some cases the movement of the diaphragm is produced by direct mechanical action, or the diaphragm may be air actuated.

Mechanical Operated Diaphragm Pumps: 

Simple and robust crank mechanism/ spring-return mechanical diaphragm pump, Low cost due to reduced number of components, Use mechanically-actuated diaphragm to combine the characteristics of a plunger pump (linear flow rate) with the sealing advantages of a diaphragm pump, Suitable for batching operation, minimum maintenance required.

Hydraulic Operated Diaphragm Pumps : 

Hydraulic actuated diaphragm head. A double PTFE diaphragm hermetically separates the wetted area from the hydraulic chamber.

During the discharge stroke the diaphragm is balanced by the hydraulic liquid only. During the suction stroke the diaphragm operation is aided by the mechanical coupling. This combined principle offers an extraordinary suction lift capability of the pump.

(a) Single Diaphragm Pumps :A single diaphragm separates the wetted area from the hydraulic chamber. During the discharge stroke the diaphragm is balanced by the hydraulic liquid only.

(b) Double Diaphragm Pumps : When the liquid being pumped is highly corrosive, the backup diaphragm will keep the liquid out of pump body in the primary diaphragm, allowing the diaphragm to be replaced before the pump is damaged

(c) Sandwich Diaphragm Pumps :It's two identical diaphragms mounted together and operating as one piece. Since either diaphragm is capable of full pump performance, each is the backup of the other. Should one fail, operation continues without interruption on the other, there is no leakage or air sucked into the process and no mixing of the process fluid with the hydraulic oil. A pressure gauge reading between the diaphragms monitors the diaphragm conditions, no pressure indicates the diaphragms are okay while pressure indicates that the pump is operating on one diaphragm. "Sandwich" diaphragms have very long live years even in continuous operation