Working Principle and Applications of Air-Operated Double Diaphragm Pumps
1. Working Principle
An air-operated double diaphragm pump (AODD) consists of two symmetric pump chambers. The central air distribution valve alternately feeds compressed air into the left and right air chambers, driving the diaphragms in reciprocating motion. As a diaphragm moves backward, negative pressure forms in the chamber and the inlet ball valve opens to draw fluid; as it moves forward, the inlet valve closes and the outlet valve opens to discharge. The two chambers alternate, producing an approximately continuous flow.
2. Key Advantages
- Strong self-priming: dry suction lift up to 4–7 m without priming — ideal for mobile operation and tank-truck unloading
- Can idle and run dry: running without media will not damage the pump — a capability centrifugal and gear pumps do not have
- Good media handling: transfers particle-laden slurry, high-viscosity coatings, jams and gels
- Intrinsically safe: powered by compressed air with no electrical parts — suitable for flammable and explosive environments
- Flow adjustable via air pressure, with automatic stall protection against a blocked outlet
3. Material Selection
Choose the body material by media corrosivity: aluminum suits general oils and water-based media; stainless steel (316L) suits strongly corrosive chemical media; PP and PVDF engineering plastics suit acids and alkalis. For diaphragms, nitrile (NBR) is oil-resistant, EPDM resists acids/alkalis, and PTFE offers the best temperature and corrosion resistance at a higher price — for example, a SKYLINK SA-series aluminum pump with a PTFE diaphragm balances versatility and corrosion resistance.
4. Typical Applications
Chemical plants transfer acid/alkali solvents and suspensions; coating shops circulate paints and coatings; wastewater treatment doses chemicals; ceramics and mining transfer slurries and glazes; food and pharmaceutical industries transfer hygienic viscous materials. Focus on three parameters when selecting: required flow (L/min), head/outlet pressure, and media viscosity and particle size.