Air-Operated Double Diaphragm (AODD) pumps are the workhorse choice for feeding filter presses with corrosive, abrasive, or shear-sensitive slurries. Unlike centrifugal pumps that struggle with high-solids fluids, AODD pumps self-prime up to 8 m of vertical lift, handle solids up to 9.5 mm in diameter, and run dry without damage — which makes them ideal for the start-stop cycles of a filter press feed line.
How AODD Pumps Work
An AODD pump uses compressed air alternately pushing two flexible diaphragms back and forth through a center shaft. As one diaphragm pushes fluid out the discharge port, the other draws fresh slurry through a check ball valve. There are no rotating seals, no impellers, and no metal-on-metal contact between the wetted parts — only the diaphragms and ball valves touch the slurry.
This seal-less design is why AODD pumps tolerate the conditions that destroy other pumps: closing dead-head against a fully-loaded filter press, running dry between feed cycles, and pumping abrasive tailings without seal failure. Typical flow ranges are 0.5 to 60 m³/h with discharge pressures matching the air supply (usually 4-7 bar / 60-100 psi).
When AODD Beats Centrifugal or Screw Pumps
Choose AODD when your slurry meets one or more of these conditions: solids content above 30%, abrasive particles, corrosive chemistry (acid, alkali, solvents), explosion-risk environment (compressed air drive is intrinsically safe), or frequent dry-running cycles. For continuous high-volume duty above 60 m³/h or when you need higher pressure (8+ bar), ceramic piston pumps are usually a better fit. For high-viscosity sludge transfer, see progressing cavity pumps.
Common Applications
- Mining tailings dewatering — handles abrasive slurry without impeller wear (see mining filter press solutions)
- Chemical & fine chemicals — PTFE diaphragm options for strong acids, solvents, and corrosive intermediates
- Pharmaceutical clarification — sanitary 316L stainless construction available
- Food & beverage — food-grade EPDM or PTFE diaphragms certified for direct contact
- Municipal wastewater — handles sludge with rags, grit, and variable solids without clogging
Specifications & Customization Options
- Body materials: Cast aluminum, stainless steel 304/316L, PP, PVDF
- Diaphragm options: Buna-N, EPDM, Viton, PTFE, Santoprene
- Flow capacity: 0.5 – 60 m³/h (custom configurations to 100 m³/h)
- Max particle size: Up to 9.5 mm
- Inlet/outlet: 1/2″ to 3″ connections, flange or BSP/NPT thread
- Operating pressure: 4-8.6 bar driven by 7 bar air supply
FAQs
How do I size an AODD pump for my filter press? Match the pump’s discharge pressure to your filter press’s design operating pressure (commonly 4-6 bar for chamber and 6-8 bar for membrane presses). Then select a flow rate that fills the press chambers within 30-60% of the filtration cycle time.
Why does my AODD pump stall against the filter press? Stalling is normal and intended — it’s how AODD pumps “tell” the operator the press is full. Confirm the inlet air pressure is at least 1 bar above the press operating pressure to keep the pump cycling until the cake is fully formed.
What’s the typical service life of the diaphragms? With food-grade or chemical-grade Senjie diaphragms, expect 5-8 million cycles (roughly 1-3 years of continuous duty depending on chemistry and abrasion).
Need a quote or selection help? Contact Senjie’s engineering team with your slurry chemistry, solids content, target flow rate, and filter press model — we’ll size the right AODD pump from our diaphragm pump catalog.