Peristaltic Metering Pumps

Peristaltic metering pumps deliver precise chemical dosing in municipal water and wastewater treatment by squeezing flexible tubing with rotating rollers to create positive displacement flow. The pump head contains a rotor with multiple rollers that compress and release the tubing in sequence, creating suction and discharge without fluid contact with mechanical components. These pumps typically achieve flow rates from 0.01 to 50 GPH with accuracy within ±1% of setpoint, making them ideal for polymer, coagulant, and disinfectant feed applications. The primary trade-off is frequent tubing replacement every 3-12 months depending on chemical compatibility and operating pressure.

• Chemical Feed Systems (Coagulants/Flocculants): Peristaltic pumps dose polymer solutions at 0.1-5 GPM in water treatment plants. Selected for their ability to handle viscous polymers without shearing, maintaining chemical effectiveness. Connected downstream of polymer makeup systems, upstream of flash mixers or flocculation basins.

• Sodium Hypochlorite Dosing: Used for disinfection at flows of 0.05-2 GPM in smaller plants (0.5-10 MGD). Chosen because tubing replacement eliminates valve/seal corrosion issues common with hypochlorite. Installed after clearwells, upstream of contact basins or distribution systems.

• pH Adjustment Chemical Feed: Doses caustic soda or acid at 0.1-3 GPM for pH correction. Selected for precise flow control and ability to handle corrosive chemicals without metallic contact. Positioned upstream of filtration or downstream of lime softening processes.

• Phosphoric Acid Feed (Corrosion Control): Delivers orthophosphate at 0.02-0.5 GPM for distribution system corrosion control, chosen for accuracy at low flow rates and chemical compatibility.

Daily Operations: Operators monitor flow rates via digital displays and verify chemical feed rates against plant demand. Flow adjustments made through VFD speed control or stroke length settings. Visual inspection of tubing for wear, cracking, or chemical attack performed during routine rounds. Pump typically requires minimal daily attention compared to diaphragm pumps.

​

Maintenance: Tubing replacement every 6-12 months depending on chemical and operating hours. Requires basic hand tools and 15-30 minutes per pump. PPE includes chemical-resistant gloves and safety glasses when handling feed chemicals. Rotor bearing lubrication annually. No specialized skills required - maintenance technician level adequate for all routine service.

​

Troubleshooting: Primary failure mode is tubing fatigue causing flow loss or chemical leaks. Warning signs include erratic flow readings, visible tubing deformation, or chemical staining around pump head. Typical service life 3-5 years for pump head, 10+ years for drive components. Flow calibration verification recommended quarterly using graduated cylinder method.

• Pump Head/Rotor Assembly: Houses rotating mechanism with adjustable rollers or shoes that compress tubing. Typically cast iron or stainless steel construction, sized for 0.02-10 GPM municipal applications. Selection based on required flow rate and chemical compatibility.

• Peristaltic Tubing: Flexible tube (typically Norprene, Viton, or EPDM) that carries fluid. Wall thickness ranges 1/8" to 1/2" for municipal flows. Material selection critical for chemical compatibility and service life (6-12 months typical).

• Variable Speed Drive: Controls pump speed for flow adjustment, typically 0-100% capacity. Standard VFD or servo motor options available. Sizing based on required turndown ratio and flow precision requirements.

• Occlusion Adjustment: Mechanism to set compression level of tubing, affecting flow rate and tube life. Proper setting critical - too tight causes premature failure, too loose reduces accuracy.

• Pulsation Dampener: Smooths inherent pulsating flow, particularly important for analytical instrumentation downstream.

• Flow Rate Range: 0.001-50 GPH (0.0038-189 L/hr) for typical municipal chemical feed applications. Most installations use 0.1-10 GPH range for polymer, sodium hypochlorite, and pH adjustment chemicals.

• Discharge Pressure: Up to 100 PSI (690 kPa) maximum, with most municipal applications requiring 20-60 PSI (138-414 kPa) to overcome static head and injection point pressure.

• Turndown Ratio: 100:1 minimum, with premium units achieving 1000:1 for precise low-dose applications like fluoride or coagulant aid feeding.

• Accuracy: ±1% of setpoint under steady conditions, ±2% with viscosity variations. Critical for compliance chemicals like fluoride (±0.1 mg/L tolerance).

• Tube Life: 1,000-8,000 hours depending on chemical compatibility and operating pressure. Viton tubes last 3,000-5,000 hours with sodium hypochlorite; EPDM tubes achieve 5,000-8,000 hours with alum or polymer.

• Suction Lift: 10 feet (3 m) maximum practical lift, though 6 feet (1.8 m) recommended for consistent priming with viscous chemicals.

• Viscosity Range: Up to 10,000 cP, making them ideal for polymer solutions (typically 100-1,000 cP) and liquid alum (50-200 cP).

• What chemical concentration and viscosity will be pumped? Polymer solutions above 1,000 cP require larger tube bore (≥1/2") and reduced operating speed (<50% maximum RPM). Wrong tube selection leads to premature failure and flow rate degradation within 500-1,000 hours instead of rated 3,000+ hours.

• What turndown ratio is required for process control? Applications requiring <10% of maximum flow (10:1 turndown) need premium controllers with pulse dampening. Standard units lose accuracy below 20% flow, causing chemical overdosing and compliance issues.

• What is the total dynamic head and required injection pressure? Systems exceeding 80 PSI discharge pressure require reinforced tubing and reduced flow capacity (30-50% derating). Undersized pumps cavitate and lose prime, while oversized units operate inefficiently at low turndown ratios.

• How critical is chemical feed interruption to process compliance? Fluoride, disinfectant, and pH control applications require duplex pump systems with automatic switchover. Single pump failures can cause immediate permit violations and public health risks.

• MasterFormat 40 05 23 - Chemical Feed Pumps - Primary section for peristaltic metering pumps in water treatment chemical feed systems

• Also applicable under 40 05 13 (Metering Pumps) for general chemical dosing applications

• Material/Equipment Verification: Verify tube material compatibility with specific chemicals (Viton for chlorine compounds, EPDM for caustics), Confirm IP65 rating for outdoor installations

• Installation Requirements: 120V single-phase power standard; verify electrical classification for chemical areas, Mounting height considerations for suction lift limitations (typically 6-8 feet maximum)

• Field Challenges: Tube replacement access - ensure 18" clearance minimum, Calibration requires graduated cylinder and stopwatch

• Coordination Issues: Lead times typically 6-8 weeks for standard models, 12+ weeks for explosion-proof versions

• Watson-Marlow: Qdos series (Models 30, 60, 120) - widely used for polymer and chemical dosing at 0.1-50 MGD plants

• ProMinent: Dulco Flex series - popular for chlorine dioxide and phosphate applications

• Verder: VF series peristaltic pumps for abrasive slurries and lime milk

• Cole-Parmer: Masterflex L/S series for smaller municipal facilities and pilot testing applications

• Diaphragm metering pumps cost 20-30% less initially but require more maintenance for abrasive chemicals

• Progressive cavity pumps handle higher viscosities better but cost 40-60% more

• Gear pumps offer precise flow control for non-abrasive applications at similar costs

• Peristaltic pumps excel for corrosive/abrasive chemicals where contamination-free pumping justifies 15-25% higher operating costs versus diaphragm alternatives

Establish tube replacement schedules based on actual runtime hours, not calendar time - tubes in intermittent service last significantly longer. Maintain spare tube assemblies on-site; field replacement takes 10-15 minutes versus days for factory service. Negotiate annual service contracts with local distributors for facilities with 6+ pumps. Consider manufacturer training programs for maintenance staff to reduce service call costs.