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Peristaltic Pumps Compared to Air Operated Double Diaphragm Pumps
Comparison of pump application and designs
Industrial hose pumps and air-operated double-diaphragm pumps are used fro transferring a variety of liquids. This page compares the two designs and highlights advantages of the peristaltic design for general industry, chemical processing, food and beverage applications
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The first advantage is solids. Particles that foul or wear AODD check valves — gray water, black water, reclaimed acid, water-treatment slurry — pass through a hose pump because it has no check valves. Hard, gelatinous or fibrous, the resilient hose and its connectors are the only components in contact with the liquid pumped.
Comparison of Pump Designs
An AODD increases and decreases the volume of two pump chambers. Liquid comes in through a one-way check and leaves through another. Those checks set direction and they eventually wear out. Compressed air drives a piston that flexes the diaphragms. Diaphragms also wear — they have a flex count to failure.
A peristaltic pump has no check valves. Flow direction is the direction the hose is pinched. Fluid is trapped between two or more pinch points and walked from inlet to outlet.
Both diaphragms and hoses are wear parts. Diaphragms last X flexes; hoses last X compressions. AODD wear speeds up in cavitation: the diaphragms keep flexing on empty chambers and vapor-bubble collapse can damage the both the diaphragms and check valves. A hose pump does not cavitate the same way. The hose is never pinched 100%. Under high vacuum it just stays closed.
Cavitation is common. A plugged inlet strainer is the usual cause. Viscous liquid and undersized pipe can do it too — asking for more liquid than the suction line can deliver.
On fluids that wear check valves, the hose pump stays on line longer. A hose swap is faster than an AODD rebuild, which matters when the liquid hazardous.
An AODD also needs clean, dry compressed air. A hose pump usually uses an electric motor. Hydraulic or air motors exist for hazardous areas. Making instrument-quality air costs more than an electric motor.
Flow Control
An AODD pumps flow rate tracks air pressure versus discharge pressure. More air or less back-pressure and the pump speeds up. Holding a steady rate means extra air and liquid valves. An electric hose pump moves a fixed volume per turn. A VFD gives at least a 4:1 turndown without requiring extra valves.
That is why hose pumps are used to meter chlorine and fluoride in water treatment. Harsh chemistry plus a known displacement is a better fit than an AODD pump.
Low shear is the other food-plant reason. Juice, syrup, sauce and puree can be damaged by check-valve shear; the hose does not impart shear.
So: better runtime on solids, no cavitation, cheaper energy than plant air, and a repeatable flow rate you can set with a VFD. Those are hose pump advantages for hazardous liquids, shear-sensitive products and anything with particulate in it.