Working Principle
Compressed air is directed alternately by an internal pilot spool valve to two symmetrical air chambers, forcing the elastomeric diaphragms to reciprocate in tandem. One side discharges fluid while the opposite side draws fluid in. Check valves (balls and seats) control directional flow, ensuring continuous, pulse-mitigated fluid transfer without rotating shafts or dynamic mechanical seals.
Core Technical Advantages
• Seal-less Design: Eliminates mechanical seals prone to wear, preventing hazardous media leakage.
• Run-dry Capability: Operates safely against a closed discharge valve without thermal overload or component damage.
• Variable Operating Range: Adjusts flow rate and discharge head instantly via air pressure regulation (up to 8.6 bar / 125 psi).
• Shear-sensitive Handling: Low-shear pumping preserves the structural integrity of viscous or delicate fluids.
• Submersible Architecture: Can be fully submerged in the liquid medium when external components match chemical compatibility requirements.
Typical Handled Media
• Corrosive Acids & Bases: Hydrochloric acid (HCl), Sulfuric acid (H2SO4), Sodium Hydroxide (NaOH).
• Volatile Solvents: Acetone, Ethanol, Toluene.
• Effluents & Slurries: Chemical wastewater, metal hydroxides, ceramic slips.
• Viscous Fluids: Resins, glues, paints, and polymer emulsions.
Typical Industries & Proven Applications
• Chemical Processing & Distribution: Safe transfer of bulk hazardous acids.
• Water & Wastewater Treatment: Dosing polymer flocculants and handling chemical sludge.
• Electroplating & Metal Finishing: Recirculating corrosive acid baths (e.g., PVDF pumps continuously operating over 18 months in waste-acid lines without mechanical failure).
• Paint, Ink & Coating Manufacturing: Transferring high-viscosity resins and shear-sensitive pigmented coatings.
• Pulp, Paper & Textile Processing: Handling dyes, sizing agents, and caustic bleach solutions.
Technical Specifications & Material Selection
Standard Operating Parameters
|
Specification |
Metric Range |
Imperial Range |
|
Port Size Availability |
DN8 to DN80 |
1/4" to 3" |
|
Max. Flow Rate |
Up to 1,040 L/min |
275 GPM |
|
Max. Discharge Pressure |
8.6 bar |
125 psi |
|
Max. Suction Lift (Dry) |
3.0 m to 6.0 m |
10 ft to 20 ft |
|
Max. Particle Size |
1 mm to 9.5 mm |
0.04 in to 0.375 in |
|
Operating Temp. Limit (PP) |
0°C to 65°C |
32°F to 149°F |
|
Operating Temp. Limit (PVDF) |
-20°C to 104°C |
-4°F to 220°F |
Wetted Housing Options
• Polypropylene (PP): General-purpose chemical resistance; cost-effective for inorganic acids and caustics up to 65°C.
• PVDF (Polyvinylidene Fluoride): High mechanical strength and broad resistance against strong oxidizers, halogens, and aromatic solvents up to 104°C.
Elastomer Matrix (Diaphragms, Balls, Seats)
• PTFE (with backing): Universal chemical resistance; ideal for aggressive solvents and mixed chemical waste.
• Santoprene: Excellent abrasion resistance and flex life; suited for dilute acids and non-solvent wastewater.
• Viton (FKM): High resistance to hydrocarbons, oils, and concentrated acids at elevated temperatures.
• EPDM: Reliable performance for polar solvents, water-based solutions, and dilute caustics.
Application & Sizing Guide
Calculate Required Duty Point:
Match flow rate and total dynamic head (TDH) against the pump performance curve, accounting for pipe friction losses.
Verify Air Supply Capacity:
Ensure the plant air system supplies sufficient CFM at the target operating pressure. Air line diameter should match or exceed the pump air inlet port.
Assess Fluid Viscosity & Specific Gravity:
Fluids exceeding 5,000 cP require flooded suction and reduced cycle speeds to maintain volumetric efficiency. Adjust pressure calculations based on specific gravity relative to water (SG = 1.0).
Optimize Suction Piping:
Minimize suction lift distance and piping elbows to prevent cavitation and air-binding.
Manufacturing Quality & Quality Control
Injection Molding Integrity: Pump bodies are molded using multi-cavity presses with virgin engineering thermoplastics, eliminating internal voids.
Dimensional Verification: Critical fluid pathways and mating surfaces are inspected using CMM (Coordinate Measuring Machines) to maintain sealing tolerances.
Pneumatic Spool Machining: Air valve spools and sleeves are machined to sub-micron tolerances for low-friction shifting, preventing stall during low-flow operation.
Factory Testing: 100% of manufactured units undergo dry pneumatic testing and wet-prime testing for flow verification and leak detection prior to packaging.
Compliance: ISO 9001 certified production facility; CE compliant; ATEX-certified configurations available for Zone 1 and Zone 2 hazardous environments.
Supplier Assessment & Manufacturing Strength
In-House Tooling:
Direct control over plastic injection molds ensures consistent wall thickness and part interchangeability.
Traceability:
Raw material batch numbers and elastomer compound test reports are archived for every production run.
Inventory Management:
Standard catalog pumps and high-turnover replacement parts (diaphragms, air valve kits) are stocked for rapid dispatch.
Engineering Support:
Direct engineering access for custom port configurations, pulsation dampeners, and skid-mounting integration.
RFQ & Inquiry Guidelines
Please provide the following parameters when submitting an inquiry to accelerate technical review:
Fluid Name & Concentration: (e.g., 30% Hydrochloric Acid, Used Motor Oil, Polymer Emulsion)
Fluid Temperature: Operating and maximum cleaning temperatures (°C or °F)
Required Flow Rate: (LPM or GPM) and Discharge Pressure (bar or psi)
Suction Condition: Flooded suction, suction lift height, or drum transfer
Material Requirements: Housing material (PP/PVDF) and Elastomer option (PTFE/Viton/Santoprene)
Quantity & Logistics: Annual forecast, sample requirements, or destination port for freight calculation.
Frequently Asked Questions
Q: Can a plastic AODD pump run dry without damaging internal components?
A: Yes. The seal-less, friction-face-free design allows dry running without generating destructive thermal heat. However, prolonged dry running at maximum cycle speed accelerates edge wear on elastomers and check valve seats.
Q: What causes an AODD pump to stall or fail to cycle?
A: Stalling is typically caused by insufficient inlet air pressure, contaminated air valve spools, or solid debris lodged beneath check valve balls. Inspect the pilot valve assembly and flush the fluid chambers if particulate accumulation occurs.
Q: How do I choose between Polypropylene (PP) and PVDF housing materials?
A: Choose Polypropylene for standard chemical transfer, water treatment, and operating temperatures below 65°C. Choose PVDF for aggressive media containing strong oxidizers, halogens, or temperatures up to 104°C.
Q: Are PTFE diaphragms suitable for high suction lift applications?
A: PTFE has lower intrinsic elasticity than elastomers like Santoprene, which slightly reduces dry-prime suction lift capability. For high suction lift requirements, a composite configuration utilizing an elastomer backup layer paired with PTFE is recommended to maintain flexibility and seal integrity.
Q: How is the flow rate adjusted on an air-operated double diaphragm pump?
A: Flow rate is adjusted by regulating the incoming air supply pressure and volume via a pressure regulator or needle valve to alter pump strokes per minute. Restricting the fluid discharge line also stops or slows the pump safely without motor damage.
Q: What is the typical service life of diaphragms, and what factors affect it?
A: Diaphragm lifespan depends on chemical compatibility, operating discharge pressure, cycle speed, and abrasive solid content. Under proper operating parameters with compatible media, PTFE and high-grade elastomer diaphragms achieve millions of cycles. Inspect wear components annually or based on recorded operating hours.
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