Diaphragm Pumps

Diaphragm Pumps

Air-operated double diaphragm (AODD) pumps transfer liquids using two flexible diaphragms alternately pressurised and exhausted by compressed air. The design makes them inherently self-priming, capable of running dry without damage, and suitable for abrasive, viscous, and chemically aggressive fluids that would damage standard centrifugal pumps. AIMS Industrial supplies AODD pumps in a range of materials for industrial fluid transfer applications.

How AODD Pumps Work

Two pumping chambers, each sealed by a flexible diaphragm connected to a central shaft, alternate between pressurisation and exhaust cycles driven by the compressed air valve. When one chamber is pressurised, its diaphragm displaces liquid through the outlet ball valves; simultaneously, the opposite chamber is on the suction stroke, drawing liquid in through its inlet ball valves. The result is a smooth, near-continuous flow with self-priming capability from dry. The absence of rotating seals, impellers, or close-clearance components makes AODD pumps tolerant of solids, abrasives, and chemically aggressive fluids that would quickly destroy alternative pump types.

Material Selection

Pump body, diaphragm, and ball valve materials must be compatible with the fluid being pumped. Common configurations:

• Polypropylene body, PTFE diaphragms: Broad chemical resistance including most acids, alkalis, and solvents. The standard for industrial chemical transfer.
• PVDF body: For highly aggressive fluids where polypropylene is insufficient — concentrated solvents, oxidising acids.
• Aluminium body, neoprene diaphragms: Economical option for water, mild chemicals, and non-corrosive fluids. Not suitable for strong acids or solvents.
• Stainless steel (316L): Food-grade and pharmaceutical fluid transfer, aqueous solutions, and applications where contamination from plastic pump components is unacceptable.

Flow Rate and Air Consumption

AODD pump output is controlled by adjusting the compressed air supply pressure and flow. Maximum flow rate and discharge head are set by pump size and air pressure. Air consumption is significant — AODD pumps are less efficient than electric centrifugal pumps for continuous high-volume transfer. They are best suited to batch transfer, drum emptying, and applications where their chemical resistance and handling capability justify the air consumption.

Maintenance and Common Issues

AODD pumps are relatively low-maintenance — the primary wear components are the diaphragms and ball valves. Diaphragm failure (cracking or puncture) results in the pumped fluid entering the air exhaust stream. Ball valve wear causes reduced pump efficiency and flow rate as the valves no longer seat cleanly. Both are straightforward to replace with a pump service kit. Freezing in cold conditions (the expanding air causes significant temperature drop at the exhaust) can cause ice formation in the air valve in cold environments — air line heating or insulation resolves this without altering the pump itself.

Order Diaphragm Pumps from AIMS

AIMS Industrial supplies AODD pumps for industrial chemical and fluid transfer. For material selection advice based on your specific fluid, contact our team.