Working Principle

An air operated double diaphragm pump has two diaphragms. These diaphragms are connected by a shaft in the center section. The diaphragms are working as separation wall between the air and the liquid. The air valve is located In the center section of the diaphragm pump.

The air valve directs the compressed air to the back of diaphragm number one. This way, diaphragm number one moves away from the center section. This diaphragm causes a press stroke moving liquid out of the pump. At the same time diaphragm number two is performing a suction stroke. The air behind diaphragm number two is being pushed out to the atmosphere. Atmospheric pressure pushes the liquid to the suction side. The suction ball valve is being pushed away off its seat. This allows the fluid to flow along the ball valve into the liquid chamber. When the pressurized diaphragm number one has reached the end of its stroke, the movement of the air is switched from diaphragm number one to the back of diaphragm number two by the air valve. The compressed air pushes diaphragm number two away from the center block. Doing so, diaphragm number one is pulled toward the center block. In pump chamber number two the discharge ball valve is pushed off its seat. In pump chamber number one the opposite occurs. Upon completion of the stroke the air valve leads the air again to the back of diaphragm number one and restarts the cycle as described above.

DIAPHRAGM MATERIALS AND OPERATION TEMPERATURES

Material Maximum Minimum
Neoprene

It is resistant to the vegetable oils. Its abrasion resistant is very good. The fluids like acids, esters, ketones can cause damages to the material of construction and therefore they are not recommended.
90 0C -22 0C
Buna-N

It is generally used for oils. It is very durable to the transfer of water and hydraulic oil.
87 0C -22 0C
EPDM

It is durable to chemicals. It is not durable to oil and solvents. It has moderate resistance to the alcohols and ketones.
138 0C -40 0C
Teflon

It is generally used for heavy chemicals and acids. It features good resistance. It is suitable for heat transfer at elevated temperatures.
100 0C -35 0C
Viton

It has very good resistance to acids, oils and solvents.
175 0C -40 0C
Santopren

It is resistant to weak and medium acids. It features good abrasion resistance.
135 0C -40 0C
Polypropylene

It is resistant to chemicals. It is usually preferred for food, chemicals and cosmetic products.
82 0C 0 0C
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