Peristaltic Metering Pump

Peristaltic metering pumps deliver precise chemical dosing in municipal water and wastewater treatment by compressing flexible tubing with rotating rollers to create positive displacement flow. The pump head contains multiple rollers that sequentially compress and release the tubing, creating a peristaltic wave that moves fluid without contamination. These pumps typically achieve flow rates from 0.1 to 50 GPH with accuracy within ±1% of set point, making them ideal for low-flow chemical feed applications like polymer, chlorine, and pH adjustment chemicals. The primary trade-off is tubing replacement costs and limited flow capacity compared to diaphragm pumps.

• Chemical Feed Systems (Polymer, Coagulant, pH Adjustment): Peristaltic pumps excel in feeding liquid polymers, aluminum sulfate, and sodium hypochlorite at 0.1-50 GPH rates. Selected for their ability to handle viscous polymers without shearing and corrosive chemicals without seal degradation. Typically installed with suction lines from chemical storage tanks and discharge to rapid mix chambers or contact basins.
• Laboratory Sample Transfer: Used in plant laboratories for precise sample metering and reagent addition during jar testing and analytical procedures. Flow rates typically 0.01-5 GPH. Chosen for contamination-free operation and easy tube changeover between different chemicals.
• Low-Flow Chemical Dosing: Ideal for small treatment plants (0.5-5 MGD) requiring precise chlorine residual control or corrosion inhibitor addition at 0.5-10 GPH. Selected over diaphragm pumps for better accuracy at low flows and simplified maintenance in remote locations.

Daily Operations: Operators monitor flow rates via stroke counters or flow meters, checking for consistent pulsing action. Tubing inspection for wear, cracks, or swelling occurs during routine rounds. Flow adjustments made through VFD controls, with typical accuracy within ±2% of setpoint when properly calibrated.

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Maintenance: Tubing replacement every 6-18 months depending on chemical service and operating pressure. Requires basic hand tools and 15-30 minutes downtime. Safety glasses and chemical-resistant gloves mandatory when handling chemical-contacted tubing. Most maintenance performed by plant operators without specialized training.

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Troubleshooting: Primary failure mode is tubing rupture, indicated by loss of discharge pressure or visible chemical leakage. Reduced flow often signals tubing fatigue or rotor bearing wear. Typical tubing service life: 2000-6000 hours for hypochlorite service, 4000-8000 hours for polymer applications.

• Pump Head Assembly: Houses the rotor with compression shoes/rollers that squeeze the tubing. Cast iron or stainless steel construction for municipal durability. Size determines maximum tubing diameter (typically 1/4" to 1" ID for municipal applications).
• Flexible Tubing: Heart of the system - typically Norprene, Viton, or EPDM depending on chemical compatibility. Wall thickness affects pressure rating (up to 100 PSI). Tubing life varies from 500-8000 hours based on chemical and operating pressure.
• Variable Speed Drive: Controls flow rate through RPM adjustment, typically 1-200 RPM range. AC or DC motors with 4-20mA input for automated control integration.
• Tube Fitting System: Quick-disconnect fittings allow rapid tubing replacement. Barbed or compression fittings sized to match tubing ID, typically 1/4" to 1" for municipal flows.

• Flow Rate Range: 0.001 to 264 GPH (0.00004 to 17 GPM) typical for municipal applications. Most common range 0.1-50 GPH for chemical feed systems.
• Discharge Pressure: Up to 150 PSI maximum for standard models; high-pressure versions reach 300 PSI. Municipal applications typically require 50-100 PSI to overcome static head and injection pressure.
• Accuracy: ±1% of set point under steady conditions; ±2% with varying suction conditions. Repeatability typically ±0.5% for quality units (Watson-Marlow, Grundfos, ProMinent).
• Turndown Ratio: 1000:1 standard, enabling precise control from 0.1% to 100% capacity without valve throttling.
• Tube Life: 1,000-8,000 hours depending on chemical compatibility and operating pressure. EPDM tubes typical for chlorine solutions; Viton for aggressive chemicals.
• Power Requirements: 1/4 to 2 HP motors standard. Variable frequency drives recommended for flow modulation.
• Suction Lift: Up to 25 feet dry suction capability; 6-10 feet practical limit with viscous chemicals.
• Temperature Range: 32°F to 104°F ambient; chemical temperature up to 140°F with proper tube selection.
• Viscosity Range: Up to 10,000 cP; performance decreases significantly above 1,000 cP.

• 1. What maximum flow rate and turndown ratio are required? Need daily chemical usage data and peak/minimum demand ratios. Undersizing by 25% means inadequate treatment during peak flows. Oversizing reduces accuracy at low flows. Requires 24-hour demand profiles and seasonal variations.
• 2. What discharge pressure must the pump overcome? Calculate static head plus friction losses plus injection pressure (typically 5-15 PSI). Underestimating by 20 PSI results in inadequate flow delivery. Need accurate piping layout, elevation drawings, and injection point pressures.
• 3. Which tube material provides adequate chemical compatibility and service life? Chemical compatibility charts show EPDM fails with chlorine dioxide; Viton required. Wrong material selection causes tube failure in weeks versus months. Need complete chemical inventory including pH, concentration, and temperature.
• 4. What control signal integration is needed? 4-20mA analog most common; Modbus/Ethernet for SCADA integration. Lack of proper control integration prevents automatic dosing adjustments. Requires control system architecture documentation and communication protocols.

• Division 40-48: Process Integration
• Section 46 13 16 - Chemical Feed Pumps
• Primary section for peristaltic metering pumps in water treatment chemical feed systems.

• Material/Equipment Verification: Verify tube material compatibility with specific chemicals, Confirm IP65 rating for outdoor installations, Check calibration certificates and flow accuracy specs
• Installation Requirements: 120/240V power with NEMA 4X enclosures, Mounting height considerations for suction lift limitations, Chemical containment and secondary spill protection
• Field Challenges: Tube replacement scheduling and inventory management, Calibration drift requiring frequent verification, Pulsation dampening for sensitive downstream equipment
• Coordination Issues: SCADA integration protocols vary by manufacturer, Lead times: 8-12 weeks for standard models, 16+ weeks for custom configurations

• Watson-Marlow - Qdos series (municipal standard), particularly Qdos 30 for 0.1-30 GPH applications
• ProMinent - Dulco Flex series, DF4a models popular for polymer feed
• Grundfos - DDA and DDC series for municipal chemical dosing
• Blue-White Industries - Flex-Pro A4V series, cost-effective option for smaller plants
• All maintain strong municipal references and local service networks

• Diaphragm metering pumps - Better for high-pressure applications (>150 PSI), similar accuracy, higher maintenance. Cost: 15-25% less initially.
• Progressive cavity pumps - Higher flow rates (>50 GPH), continuous flow, more complex maintenance.
• Magnetic drive pumps with VFDs - Lower cost for high-flow applications (>100 GPH), less precise dosing control.

Stock spare tube sets for each pump - tube life varies dramatically by chemical type and concentration. Establish service contracts with manufacturers for calibration and tube replacement rather than training operators. Consider dual-pump configurations for critical applications like chlorine feed. Negotiate volume pricing for tube replacements across multiple installations. Watson-Marlow and ProMinent offer excellent field service support in most regions.