Portable Tank Mixers

Portable tank mixers are temporary mixing systems designed to maintain solids suspension and promote chemical reactions in municipal treatment basins during maintenance, startup, or emergency conditions. These units typically consist of a submersible propeller or impeller mounted on a portable frame that can be quickly deployed into tanks, basins, or temporary holding areas. Most portable mixers range from 1-15 HP and can effectively mix volumes up to 2 million gallons with proper positioning. The key trade-off is limited mixing intensity compared to permanent installations, requiring careful placement and potentially multiple units for larger basins to achieve adequate turnover rates.

• Chemical Feed Tank Mixing: Portable mixers maintain polymer solutions in 50-500 gallon day tanks at clarifier and belt press facilities. They prevent stratification and settling that reduces polymer effectiveness by 20-30%. Connected via quick-disconnect flanges, operators move units between tanks as needed rather than installing fixed mixers on every tank.

• Emergency Mixing Operations: During fixed mixer failures, portable units maintain critical processes like lime slurry mixing or alum feed preparation. 5-15 HP units handle most municipal chemical tanks, with deployment within 30 minutes preventing process upsets.

• Temporary Basin Mixing: Construction projects and seasonal lagoon turnover require temporary mixing. Units with 20-50 foot cables reach basin bottoms, providing 0.5-2.0 HP per 1000 gallons for effective turnover in detention basins and equalization tanks.

• Biosolids Holding Tank Mixing: Portable mixers prevent settling in 10,000-50,000 gallon holding tanks before dewatering, maintaining 3-5% solids concentration uniformity essential for consistent belt press performance.

Daily Operations: Operators verify proper rotation direction and check for unusual vibration or noise during routine rounds. Amperage monitoring identifies loading changes indicating settling or process upsets. Most units run continuously, but polymer tank mixers cycle with feed pumps. Visual confirmation of adequate mixing patterns through tank observation ports prevents dead zones.

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Maintenance: Monthly bearing lubrication and quarterly seal inspection prevent 80% of failures. Annual impeller inspection identifies wear or damage. Lifting equipment required for units over 50 pounds; confined space entry procedures needed for tank-mounted repairs. Basic mechanical skills sufficient for routine maintenance, but seal replacement requires millwright-level experience.

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Troubleshooting: Excessive vibration indicates impeller damage or shaft misalignment, typically developing over 2-4 weeks. Motor overheating suggests bearing failure or impeller fouling. Seal leakage creates oil sheens requiring immediate shutdown. Typical service life ranges 8-12 years with proper maintenance, with seals requiring replacement every 3-5 years in continuous service applications.

• Impeller Assembly: Hydrofoil or pitched-blade designs in 316SS, ranging 12-36 inches diameter. Hydrofoil impellers provide 3:1 flow-to-power advantage for bulk mixing, while pitched-blade handles higher viscosity applications. Selection based on tank geometry and fluid properties.

• Motor/Gearbox Unit: TEFC motors from 0.5-15 HP with helical gear reducers achieving 35-180 RPM output speeds. IP65 rated housings standard for wet environments. Gear ratios selected for optimal tip speed of 8-12 ft/sec in municipal applications.

• Mounting System: Portable bridge mounts, clamp-on brackets, or weighted base assemblies. Adjustable shaft lengths from 3-50 feet accommodate varying liquid levels. Quick-release mechanisms enable rapid repositioning between tanks.

• Shaft and Seals: 316SS shafts with mechanical seals rated for continuous submersion. Shaft deflection calculations critical for lengths exceeding 15 feet to prevent bearing failure and seal damage.

• Tank Geometry & Volume: Tank diameter: 10-200 feet typical for municipal applications; Tank depth: 8-40 feet operating range; Volume capacity: 50,000-10,000,000 gallons; Liquid level variation: 2-15 feet operational range

• Mixing Performance Parameters: Turnover rate: 1-3 complete tank volumes per hour; Velocity gradient (G): 20-100 sec⁻¹ for flocculation, 200-800 sec⁻¹ for rapid mix; Thrust output: 50-2,000 lbf depending on tank size; Power density: 0.5-10 HP per million gallons typical

• Equipment Specifications: Motor power: 1-50 HP standard range; Propeller diameter: 24-96 inches; Operating depth: 3-30 feet below surface; Positioning angle: 5-15 degrees from horizontal optimal; Cable length: 50-200 feet standard; Thrust-to-power ratio: 40-80 lbf/HP for efficient units

• Operational Requirements: Continuous duty rating required; Variable speed capability: 50-100% of rated RPM; Remote monitoring capability for flow, power, vibration

• What mixing intensity is required for the specific process application? Threshold: G-values of 20-50 sec⁻¹ for flocculation vs. 200-500 sec⁻¹ for chemical mixing. Wrong selection leads to either inadequate mixing (poor treatment) or excessive shear (floc breakup). Need: process requirements, detention time, chemical dosing rates.

• How will the mixer be positioned and repositioned within the tank? Threshold: Fixed mounting vs. portable deployment affects coverage area (typically 3-5 tank diameters effective mixing radius). Wrong choice results in dead zones or excessive equipment costs. Need: tank configuration, access limitations, operational flexibility requirements.

• What power and thrust combination optimizes energy efficiency? Threshold: Thrust-to-power ratios below 40 lbf/HP indicate inefficient units; above 80 lbf/HP may compromise durability. Poor selection increases operating costs 20-40%. Need: tank geometry, required turnover rate, energy cost analysis.

• What level of process control and monitoring is necessary? Threshold: Basic on/off vs. variable speed with remote monitoring affects operational flexibility and energy consumption (potential 15-30% savings). Under-specification limits optimization; over-specification increases capital costs unnecessarily. Need: plant automation level, staffing, energy management goals.

• Primary: 46 13 16 - Portable Water Treatment Equipment Mixers

• Secondary considerations: 40 45 13 (Water Treatment Clarifiers) when integrated with settling processes

• 46 07 13 (Packaged Water Treatment Plants) for complete system specifications

• Material/Equipment Verification: Verify 316SS wetted parts for municipal wastewater; Confirm IP68 motor ratings for submersible units; Check cable length specifications (typically 50-100 ft standard)

• Installation Requirements: Crane access for deployment/retrieval (units typically 200-800 lbs); Adequate electrical service (480V/3-phase common); Lifting hardware rated 2x equipment weight

• Field Challenges: Seasonal deployment timing; Debris fouling of propellers; Cable management in active basins

• Coordination Issues: 8-12 week lead times typical; Electrical contractor coordination for temporary connections

• Xylem (Flygt) - Model 4640 series submersible mixers, widely used in municipal lagoons and basins

• Grundfos - CRI series portable mixers, popular for temporary applications and pilot studies

• Sulzer - ABS Robusta portable mixers, common in Canadian municipal markets

• KSB - Amaprop series, gaining traction in smaller municipal facilities under 5 MGD

• Fixed Submersible Mixers - Preferred for permanent installations, 20-30% lower lifecycle cost but require basin modifications ($15K-25K vs $8K-15K portable)

• Surface Aerators - Better for oxygen transfer applications, similar capital cost but higher energy consumption

• Jet Mixing Systems - Effective for deep basins >15 feet, higher installation cost but no moving parts in basin, preferred where maintenance access is limited

Establish relationships with equipment rental companies - many municipalities rent portable mixers seasonally rather than purchasing. Consider standardizing on one manufacturer's quick-connect systems to simplify operations. For emergency applications, maintain spare propellers on-site; prop damage from debris is the most common failure mode. Negotiate rental-to-purchase agreements for units that see extended use beyond initial temporary applications.