The Plastic Double Diaphragm Pump is an air-operated positive displacement pump engineered for handling corrosive chemicals, aggressive acids, and high-purity fluids without mechanical rotary seals. Driven by compressed air rather than electricity, it inherently prevents sparking, making it suitable for hazardous and explosive environments (ATEX-certified configurations available).
Working Principle
Compressed air is directed alternately by an internal air distribution valve to the back of two symmetrical diaphragms. As one diaphragm executes a discharge stroke (fluid displacement), the opposite diaphragm completes a suction stroke (fluid intake). Check valves (balls and seats) control directional flow, ensuring continuous fluid transfer with minimal pulsation.
Core Technical Advantages
• Sealless Design: Eliminates mechanical seals and packing glands, completely preventing typical leakage paths associated with centrifugal pumps.
• Run-Dry Capability: Can run dry indefinitely without generating excessive heat or damaging internal components.
• Variable Flow & Pressure: Discharge flow rate and pressure are easily adjusted simply by regulating the compressed air supply and inlet pressure.
• Self-Priming: Capable of dry suction lifts up to 5 meters (depending on pump size and elastomer configuration), reducing initial priming requirements.
• Solid-Handling: Flexible check valve geometry allows the passage of suspended solids and semi-viscous slurries without clogging.
Typical Handled Media
• Hydrochloric Acid (HCl), Sulfuric Acid (H2SO4), Nitric Acid (HNO3)
• Sodium Hydroxide (Caustic Soda, NaOH)
• Ferric Chloride, Polymers, and Coagulants
• Solvents, Inks, Paints, and Latex Emulsions
• Deionized Water and Plating Solutions
Typical Industries
• Chemical Processing & Distribution
• Industrial Wastewater Treatment & Effluent Dosing
• Electroplating, Surface Treatment & PCB Manufacturing
• Pulp & Paper Processing
• Food, Beverage & Pharmaceutical Secondary Utilities
Technical Specifications & Material Selection
Selecting the correct materials of construction is critical to prevent premature pump failure and chemical degradation.
Quick Technical Data Reference (Quick-Specs)
|
Specification Parameter |
Metric (SI) Standard |
Imperial (US) Standard |
|
Max Flow Rate |
Up to 1,060 LPM |
Up to 280 US GPM |
|
Max Discharge Pressure |
8.6 Bar |
125 PSI |
|
Port / Connection Size |
DN 8 to DN 80 |
1/4" to 3" (NPT / Flanged) |
|
Max Air Supply Pressure |
8.6 Bar |
125 PSI |
|
Operating Temperature Limit |
PP: up to 60°C PVDF: up to 100°C |
PP: up to 140°F PVDF: up to 212°F |
|
Dry Suction Lift (Max) |
Up to 4.5 Meters |
Up to 15 Feet |
|
Available Wetted Housings |
Polypropylene (PP), PVDF, Virgin PTFE |
|
|
Diaphragm Elastomers |
PTFE/Santoprene, Santoprene, Viton (FKM), EPDM |
Material Breakdown & Chemical Compatibility Matrix
|
Component |
Available Options |
Recommended Application / Limitation |
|
Pump Body (Housing) |
Polypropylene (PP) PVDF (Kynar) Virgin PTFE |
PP: General acids, caustics up to 60°C. PVDF: High-purity chemicals, strong oxidizers, higher temperature tolerance. PTFE: Extreme chemical resistance, ultra-pure applications. |
|
Diaphragms |
PTFE / Santoprene Backer Santoprene Viton (FKM) EPDM |
PTFE: Universal chemical resistance; flexing life is aided by a Santoprene backer. Santoprene: Excellent flex life for general water/waste applications. Viton: Hydrocarbons, oils, and aggressive solvents. EPDM: Dilute acids, ketones, and alcohols. |
|
Check Balls & Seats |
PTFE, PVDF, Stainless Steel, Acetal |
Match chemical compatibility of the fluid; PTFE balls standard for chemical duty. |
Application & Selection Guide
To specify the correct pump for your process loop, verify the following four operational parameters:
Chemical Compatibility:
Cross-reference your fluid concentration and operating temperature against our housing and elastomer material matrix.
Required Flow Rate (GPM / LPM):
Plot your required duty point on the pump performance curve. Ensure the operating point sits in the middle 60% of the curve to maximize diaphragm lifespan.
Total Dynamic Head (TDH):
Calculate static discharge head, friction losses in piping, and backpressure from downstream filtration or injection points.
Air Supply Availability:
Verify your facility compressed air system can deliver clean, dry air at the required pressure and volume (SCFM).
Manufacturing Quality & Testing Standards
Every pump undergoes rigorous multi-stage quality control before leaving our facility to ensure zero-defect field installation.
CNC Machining Tolerances: Injection-molded and CNC-machined plastic components maintain dimensional stability within plus/minus 0.02 mm to prevent internal air bypass and leakage.
Air Valve Assembly: Precision-lapped spool valves are assembled in cleanroom environments to eliminate premature stalling caused by particulate contamination.
100% Factory Wet Testing: Every assembled pump undergoes dry-run and water-test verification for suction lift, air consumption, pressure holding, and flow rate consistency.
Traceability: Raw material batch numbers and elastomer compound certificates are recorded against individual pump serial numbers for complete QA traceability.
Certifications: ISO 9001:2015 quality management system compliant; ATEX Zone 1/2 compliant configurations available for explosive atmospheres.
Supplier Evaluation for B2B Sourcing
When sourcing plastic diaphragm pumps for OEM integration or plant maintenance, evaluate suppliers against these operational benchmarks:
Spare Parts Interchangeability: Ensure internal wear parts (diaphragms, balls, seats, air valve kits) are dimensionally interchangeable with major global brands to simplify local maintenance inventories.
Lead Times & Stocking Programs: Standard plastic pump models (PP/PVDF with PTFE diaphragms) ship within 3 to 7 business days for standard catalog items.
Engineering Support: Direct access to engineering support for custom fluid loops, performance curve analysis, and retrofitting.
Warranty & Technical Backing: Supported by a 12-month manufacturing defect warranty backed by direct engineering troubleshooting.
Frequently Asked Questions
Q: What causes an air-operated double diaphragm pump to stall or fail to cycle?
A: Stalling is typically caused by low incoming air pressure, exhausted or contaminated air distribution spools, or icing of the air valve due to high moisture content and rapid air expansion. Ensure your system utilizes an air filter-regulator-lubricator (FRL) with a functional moisture separator.
Q: Can a plastic diaphragm pump handle abrasive slurries containing solid particles?
A: Yes, provided the solid size does not exceed the pump's maximum particle passage limit (ranging from 1 mm to 9.4 mm depending on port size). Elastomer check balls and flexible diaphragms absorb impact energy, reducing wear when handling abrasive mineral slurries or wastewater grit compared to centrifugal impellers.
Q: What is the maximum dry suction lift for a 2-inch polypropylene diaphragm pump?
A: Under optimal conditions with clean, pliable PTFE or Santoprene diaphragms and wetted internal surfaces, a standard 2-inch plastic pump achieves a dry suction lift of approximately 3 to 4 meters. Priming performance decreases if internal check valves are dry or worn.
Q: How do I choose between Polypropylene (PP) and PVDF housing materials?
A: Choose Polypropylene for general chemical transfer, water treatment chemicals, and mild acids up to 60°C due to its cost-effectiveness. Choose PVDF when operating temperatures exceed 60°C, or when handling strong oxidizers, high-purity deionized water, and aggressive halogens that degrade polypropylene.
Q: Are your plastic double diaphragm pumps interchangeable with Wilden, Sandpiper, or Yamada models?
A: Our pumps are engineered with identical port-to-port dimensions, mounting footprints, and hydraulic performance profiles to major industry standards, allowing direct drop-in replacement without modifying existing pipework or baseplates.
Q: What information is required to get an accurate technical quotation and delivery timeline?
A: Please provide:
Fluid name, concentration, and operating temperature.
Required flow rate (LPM or GPM) and discharge pressure.
Suction conditions (flooded suction vs. dry lift height).
Required wetted materials (body and elastomers).
Destination port for shipping calculation.
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