The Air Operated Double Diaphragm pump is illustrated on the right. This pump uses a very simple valve system to move the DIAPHRAGM ROD. The flexible diaphragms (shown in white here) are round disks attached at each end of the Diaphragm Rod.

The PILOT SPOOL (the middle of the three horizontal rods) is pushed back and forth whenever the Diaphragm Rod reaches the end of its throw. The Pilot Spool allows air to move the Air Distribution Valve (the top rod in this drawing) back and forth.

The AIR DISTRIBUTION ROD controls air flow to the left or right air chamber, reversing on each stroke.

The four BALL VALVES are free-floating and operated by pressure differences in the pumped liquid. Flapper valves are also commonly used. In the pump shown, liquid flow is from the bottom to the top.

Sanitary Double Diaphragm pumps, often made of plastic and/or stainless steel, are used in the food industry to pump everything from sliced fruit, to sausage, to chocolate.

See also Diaphragm Pumps.

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