Frequently Asked Questions

An AODD pump is a positive displacement pump powered by compressed air. It uses two flexible diaphragms connected by a common shaft, driven back and forth by an air valve. When one diaphragm moves outward to push fluid out of the chamber, the other moves inward to draw fluid in — creating a continuous, smooth flow.

Key characteristics:

• No electricity — fully pneumatic, safe for explosive environments (ATEX zones)
• Self-priming — can lift fluid from below the pump level
• Can run dry — no damage when operating without fluid
• Infinitely variable flow — adjusted by air pressure and valve
• Handles solids — particles up to 6mm (varies by pump size)

AODD pumps are used in chemical processing, food & beverage, mining, painting, pharmaceuticals, water treatment, and many other industries.

The pumping cycle works as follows:

• Stroke 1: Compressed air enters the air valve and is directed behind diaphragm A. The air pressure pushes diaphragm A outward, forcing fluid out of chamber A through the discharge valve. Simultaneously, diaphragm B is pulled inward by the connecting shaft, creating a vacuum in chamber B that draws fluid in through the suction valve.
• Valve reversal: At the end of the stroke, the air valve automatically reverses the air flow — air now goes behind diaphragm B.
• Stroke 2: Diaphragm B pushes fluid out while diaphragm A draws fluid in. The cycle repeats.

The check valves (ball or flap type) ensure fluid flows in one direction only. BSK pumps use a patented ceramic air valve that reduces internal friction and ensures reliable valve reversal even at low air pressures.

AODD pumps excel where centrifugal pumps struggle:

However, AODD pumps are not ideal for very high flow rates (>1000 L/min) or very high pressure (>10 bar), where centrifugal pumps are more efficient.

• No electrical hazard: Pneumatic operation, safe for Zone 1/2 explosive environments
• Run dry without damage: Can operate with no fluid indefinitely
• Self-priming: Vertical suction lift up to 5m dry, 9m wet (varies by model)
• Variable flow & pressure: Simply adjust air supply — no VFD needed
• Handles wide viscosity range: From water-thin to 10,000 cP pastes
• Passes solids: Hard particles, slurries, and fibers without clogging
• Shear-sensitive: Gentle action preserves emulsions, food products, and live cultures
• Simple maintenance: Few moving parts, field-repairable in under 30 minutes
• Portable: Can be submerged or mounted on a cart
• Dead-head capable: Can be stopped against a closed discharge valve without damage

To recommend the optimal pump model, we need the following information:

• Fluid name & properties: Viscosity (cP), pH, solids content (%), specific gravity, temperature range
• Required flow rate: Liters/min or gallons/min at the discharge point
• Discharge head: Vertical height + horizontal pipe length + friction losses (in meters or bar)
• Suction conditions: Suction lift (dry or wet), flooded suction, or submerged
• Available compressed air: Pressure (bar/PSI) and air volume (m³/min or CFM)
• Material requirements: Chemical compatibility, food-grade (FDA), sanitary (3A), or ATEX
• Connection type: BSP, NPT, flanged, sanitary tri-clamp
• Operating cycle: Continuous duty, intermittent, or batch

Our engineering team will analyze your requirements and recommend the best pump model, size, and material configuration. Send us your application details for a personalized recommendation within 24 hours.

Pump size is primarily determined by the required flow rate. BSK AODD pumps are available in the following sizes:

Important: Always select a pump that can deliver 20-30% more flow than your minimum requirement. This allows you to throttle down for better diaphragm life and leaves headroom for viscosity increases or pipe scaling.

Diaphragm material depends on the fluid being pumped, temperature, and application:

Tip: PTFE has the best chemical resistance but the shortest flex life. For mildly corrosive fluids, Santoprene often provides a better cost-to-life ratio. Contact our engineers for a chemical compatibility check.

Higher viscosity = lower flow rate and higher air consumption. As a rule of thumb:

• 0-500 cP (water, thin chemicals): Minimal flow reduction, pump operates near rated capacity
• 500-2,000 cP (light oils, syrups): 10-20% flow reduction, may need larger pump
• 2,000-5,000 cP (paints, resins, adhesives): 30-50% flow reduction, size up one port size
• 5,000-10,000 cP (pastes, heavy slurries): Significant reduction, use largest practical pump with PTFE diaphragms

For viscous fluids, also consider: suction pipe diameter (should be same or larger than pump port), short suction line (minimize lift), and heated or insulated pipes if viscosity changes with temperature.

BSK AODD pumps are self-priming and can achieve the following suction lifts:

• Dry lift: Up to 4-5 meters (pump starts dry and pulls fluid up)
• Wet lift: Up to 7-9 meters (pump is pre-wetted/primed)

Actual lift depends on:

• Air pressure available (higher air pressure = better suction)
• Fluid viscosity (thicker fluid = lower lift capability)
• Suction pipe diameter and length (use shortest, widest pipe possible)
• Altitude (at high altitude, reduced atmospheric pressure lowers lift)

For lifts over 4 meters, we recommend flooded suction (pump below fluid level) for best performance and diaphragm life.

BSK AODD pumps normally operate between 2-7 bar (30-100 PSI) compressed air supply. The key advantage of BSK pumps:

• Ultra-low start pressure: 0.6 bar — BSK's patented ceramic air valve allows the pump to start and operate at pressures as low as 0.6 bar, where most competitor pumps require 1.5-2 bar minimum
• Optimal operating range: 3-6 bar — Best balance of flow rate, energy consumption, and diaphragm life
• Maximum: 8 bar — Do not exceed 8 bar air supply to prevent damage

The low start pressure is particularly valuable in:

• Facilities with limited or aging air compressor capacity
• Remote locations with long air supply lines (pressure drop)
• Energy-saving applications where reduced air pressure lowers operating cost

The maximum discharge pressure equals the air supply pressure (minus minimal internal losses). For standard BSK pumps:

• Standard models: Max 6-8 bar discharge pressure
• High-pressure models: Up to 15-16 bar (using dual-pump or booster configuration)

Note: Discharge pressure is determined by the system resistance (pipe friction + vertical head + nozzle/back pressure). The pump will cycle slower as discharge pressure increases, and will stall (stop) when discharge pressure equals air supply pressure.

For applications requiring pressures above 8 bar, consider our high-pressure AODD pump models with reinforced diaphragms and specialized air valve design.

Air consumption depends on pump size and operating conditions. Approximate consumption at 4 bar air supply:

BSK's ceramic air valve saves up to 30% air consumption compared to conventional metal air valves, due to reduced friction and more efficient air distribution. This translates directly to lower energy costs for your air compressor.

To minimize air consumption: use the lowest air pressure that still meets your flow/head requirements, keep air lines clean, and ensure the muffler is not blocked.

Yes. AODD pumps can run dry indefinitely without damage. This is one of their key advantages over centrifugal pumps, which suffer seal damage within minutes of dry running.

However, prolonged dry running will accelerate diaphragm wear due to the flexing action without the cooling and lubricating effect of the fluid. We recommend installing a liquid level sensor or timer to shut off the air supply when the fluid source is empty.

Yes, BSK AODD pumps can be submerged provided that:

• The air exhaust is routed above the fluid level (use extended exhaust hose/pipe)
• The fluid is compatible with the pump's external materials (body, bolts, fasteners)
• Stainless steel hardware is used for submerged applications

This makes AODD pumps excellent for sump pumping, underground tank transfer, and barrel emptying applications.

Yes, flow rate can be controlled by several methods:

• Air pressure adjustment: The simplest method — increase air pressure for more flow, decrease for less. Use a manual air regulator or electronic pressure regulator for automated control.
• Air valve speed control: Install a needle valve in the air supply line to restrict air volume while maintaining pressure.
• Discharge valve throttling: A ball valve on the discharge side can restrict flow. AODD pumps can dead-head (pump against a closed discharge) without damage.
• Cycle control: For batch dosing, use a solenoid valve on the air supply controlled by a timer or PLC.

Important: Do NOT throttle the suction side — this causes cavitation and accelerates diaphragm wear.

BSK offers five body materials to match different fluids and environments:

PTFE (Teflon) — choose when:

• Pumping strong acids (sulfuric, hydrochloric, nitric), strong alkalis, or aggressive solvents
• High chemical purity is required (semiconductor, pharmaceutical)
• Temperature exceeds 80°C
• Fluid is incompatible with any elastomer

Santoprene — choose when:

• Fluid is mildly corrosive or neutral (water-based, mild acids/bases, food products)
• Longer diaphragm life is important (Santoprene flex life is 2-3x longer than PTFE)
• Cost is a factor (Santoprene is more economical)
• Food-grade certification is needed (FDA-compliant grades available)

BSK also offers PTFE-backed Santoprene composite diaphragms, which combine the chemical resistance of PTFE (fluid side) with the flex life of Santoprene (air side). This is the best choice for most chemical applications.

Rule: If PP handles your fluid, use it. Upgrade to PVDF only when PP is not compatible or temperature exceeds 70°C.

Yes. BSK offers sanitary-grade AODD pumps certified for food and beverage applications:

• Stainless steel 316L body with electropolished surface finish (Ra ≤ 0.8 μm)
• Tri-clamp sanitary connections for easy CIP (Clean-in-Place) cleaning
• Food-grade diaphragms: FDA-compliant Santoprene or PTFE
• No dead legs: Designed for complete drainage and cleaning
• Certificate options: FDA material compliance, CE marking

Typical food applications: dairy (milk, cream, yogurt), beverages (wine, beer, juice), sauces and condiments, edible oils, chocolate and confectionery, CIP chemical transfer.

Yes. Since AODD pumps are powered by compressed air (no electricity), they are inherently safe for explosive atmospheres. BSK pumps are suitable for:

• ATEX Zone 1 & Zone 2 — explosive gas atmospheres
• ATEX Zone 21 & Zone 22 — explosive dust atmospheres

For ATEX compliance, ensure:

• Pump body and hardware are conductive (metallic body, not plastic) and properly grounded
• PTFE diaphragms with conductive carbon additive are used for plastic-body pumps
• Air exhaust is routed to a safe area (exhaust may contain fluid vapor)

Diaphragm life depends on operating conditions. Typical ranges:

Factors that reduce diaphragm life:

• High operating pressure (>6 bar)
• Elevated fluid temperature (approaching material limit)
• Abrasive particles in fluid
• Frequent cavitation (suction lift too high)
• Rapid cycling (excessive air pressure for the application)

Tip: Replace diaphragms in pairs (both sides at the same time) for balanced performance. A spare diaphragm kit should always be kept on hand.

Common causes and solutions:

• Use the lowest effective air pressure: If 3 bar achieves the required flow, don't run at 6 bar. Every 1 bar reduction saves ~15% air volume.
• Size the pump correctly: An oversized pump running throttled wastes air. A correctly sized pump at full speed is more efficient.
• Maintain the air valve: A worn or dirty air valve wastes air. Clean and lubricate (if applicable) regularly.
• Keep the muffler clean: A blocked muffler creates back-pressure that increases air consumption.
• BSK ceramic air valve: BSK's patented ceramic air valve reduces internal friction, saving up to 30% air compared to conventional metal valves.
• Install an air shut-off valve: Use a level switch or timer to automatically stop the pump when not needed, instead of letting it run continuously.

This is a common symptom with several possible causes:

• Both diaphragms ruptured: Air is passing through the diaphragms to the fluid side. Replace both diaphragms immediately.
• Valve balls stuck or missing: Check balls and seats in the fluid chambers. Clean out debris or replace worn parts.
• Air valve malfunction: The air valve may be short-cycling. Disassemble, clean, and check O-rings.
• Suction line air leak: Check all suction connections for leaks. Even a small air leak prevents priming.
• Suction lift too high: If fluid level has dropped, the pump may not be able to lift it. Lower the pump or raise the fluid source.

BSK recommends keeping the following spare parts inventory:

• Diaphragm kit (2 diaphragms + O-rings) — the #1 wear item
• Valve ball kit (4 balls + 4 seats) — second most common wear item
• Air valve repair kit (O-rings, gaskets, pilot valve)
• Muffler — inexpensive, prevents back-pressure issues

For critical applications (24/7 operation), keep a complete spare pump ready for swap-out. All BSK pumps use a modular design — most repairs can be completed in under 30 minutes with basic hand tools (Allen wrench, socket set).

Contact us to order spare part kits for your specific pump model.

For heavy-duty applications (abrasive slurries, high temperature, continuous duty), shorten intervals by 50%.

BSK has been manufacturing AODD pumps for over 30 years. Our key differentiators:

• Patented ceramic air valve: Reduces friction by 60% vs. metal valves. Result: lower start pressure (0.6 bar), 30% less air consumption, and longer valve life.
• Ultra-low 0.6 bar start pressure: Most competitors need 1.5-2 bar. BSK pumps start and run reliably even with weak or distant air supply.
• 30% energy savings: The ceramic valve's efficiency translates directly to lower compressor electricity costs. At scale, this saves thousands of dollars annually.
• 3-day standard delivery: In-stock models ship within 3 business days. Custom configurations in 7-15 days.
• Full material range: Aluminum, SS316, cast iron, PP, PVDF — with PTFE, Santoprene, Viton, and Nitrile diaphragms.
• OEM/ODM capability: Custom branding, colors, packaging, and special configurations for distributors and OEM partners.
• 30+ years manufacturing experience: Proven reliability across chemical, food, mining, and painting industries worldwide.

Traditional pneumatic diaphragm pumps use metal-on-metal air valves with higher friction. This means they need more air pressure to overcome the valve's internal resistance before the pump can cycle — typically 1.5 to 2 bar minimum.

BSK's patented ceramic air valve solves this problem:

• Ceramic material has a much lower coefficient of friction than metal
• The ceramic surfaces are precision-lapped for smooth sliding contact
• Reduced friction means the valve can shift with less air pressure force
• Result: the pump starts and cycles reliably at just 0.6 bar

Additional benefits of the ceramic valve:

• No lubrication needed: Ceramic is self-lubricating
• Longer life: Ceramic wears much slower than metal
• Resists contamination: Smoother surface repels dirt and moisture
• Corrosion resistant: Unlike metal, ceramic doesn't rust

Shipping options:

• Sea freight: Most economical for large orders (15-35 days to most ports)
• Air freight: For urgent orders (5-10 days)
• Express courier: DHL/FedEx/UPS for small pumps and spare parts (3-7 days)

We handle all export documentation, including commercial invoice, packing list, and Certificate of Origin. FOB, CIF, and DDP terms available.

• Standard warranty: 12 months from date of shipment, covering manufacturing defects
• Extended warranty: Available for an additional fee — up to 24 months
• Wear parts: Diaphragms, valve balls, and seats are consumables and are not covered under warranty (but can be replaced using spare part kits)
• Exclusions: Damage from misuse (over-pressure, incompatible fluids, improper installation), normal wear, and unauthorized modifications

All pumps are 100% factory-tested before shipment — including air pressure test, leak test, and cycling test. Each pump ships with a test report and operation manual.

Yes, BSK offers comprehensive OEM/ODM services for distributors and brand owners:

• Custom branding: Logo engraving or printing on pump body
• Custom colors: Match your brand color (anodized aluminum or painted finish)
• Private label packaging: Custom-designed boxes with your brand
• Custom nameplates: With your company name, model number, and specifications
• Special configurations: Custom thread types (BSP/NPT/flanged), port sizes, or mounting options
• Custom material combinations: Non-standard body/diaphragm/valve combinations

Minimum order quantity (MOQ): Typically 10-50 units depending on customization level. Contact our OEM team to discuss your requirements.

Yes. BSK provides lifetime technical support for all pump models:

• Installation guidance: Detailed manuals, wiring/piping diagrams, and video guides
• Remote troubleshooting: Email/WhatsApp/phone support for diagnosing issues
• Spare parts identification: Send us your pump model and serial number — we'll provide the exact parts you need
• Maintenance training: On-site or video training for your maintenance team (for bulk orders)
• Custom application engineering: Our engineers can help optimize your pumping system, recommend accessories, and suggest efficiency improvements

Support channels: linda@bskfluid.com | WhatsApp: +86-134-3105-8937 | Online contact form