Submersible Vertical Turbine Pump

Submersible vertical turbine pumps move large volumes of water from wells, reservoirs, or wet wells by using multiple impeller stages housed within a submerged motor assembly. The motor drives a vertical shaft connected to stacked impellers that progressively increase pressure through each stage. These pumps typically achieve 75-85% wire-to-water efficiency in municipal applications, handling flows from 100 to 5,000 GPM with heads up to 800 feet. The key trade-off is higher upfront cost and complex maintenance requiring specialized lifting equipment, but they offer reliable operation in variable water levels without priming issues.

• Raw Water Intake Pumping: Installed in intake wells or wet wells, these pumps lift raw water from depths of 50-200 feet to treatment plant headworks. Selected for high-head capability (150-400 feet TDH) and space efficiency in confined intake structures.

• High Service Pumping: Located in clearwells or finished water reservoirs, pumping treated water to distribution systems. Chosen for reliable operation at variable flows (200-2,500 GPM) and heads up to 300 feet.

• Backwash Water Supply: Positioned in filter backwash storage tanks, providing high-pressure water (40-60 PSI) for filter cleaning cycles. Selected for rapid startup capability and consistent pressure delivery.

• Sludge Return Pumping: Installed in secondary clarifier hoppers or RAS wells, returning activated sludge to aeration basins. Chosen for solids-handling capability and submerged operation eliminating priming issues.

Daily Operations: Operators monitor motor amperage, discharge pressure, and flow rates through SCADA systems. Key parameters include vibration levels (typically <0.3 IPS), motor temperature, and seal water flow. Adjustments focus on variable frequency drive settings to match system demand while maintaining minimum flow requirements to prevent overheating.

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Maintenance: Quarterly inspections include checking motor insulation resistance (>10 megohms), verifying check valve operation, and monitoring bearing wear through vibration analysis. Annual maintenance requires crane access for pump removal, typically 8-hour procedures requiring confined space entry permits and electrical lockout. Technicians need rigging certification and electrical troubleshooting skills.

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Troubleshooting: Common failures include seal deterioration (indicated by increasing motor temperature), impeller wear (reduced flow at constant speed), and bearing failure (increasing vibration). Warning signs include motor current fluctuations, unusual noise transmission through column pipe, and declining pump efficiency. Typical service life ranges 15-20 years with proper maintenance, though motors may require rewinding at 10-year intervals.

• Pump Bowl Assembly: Multi-stage diffuser bowls (typically 3-8 stages) housing bronze or stainless steel impellers. Materials selection based on water quality - bronze for potable water, 316SS for wastewater. Stage count determines head capability, with each stage adding 40-80 feet TDH.

• Submersible Motor: Enclosed squirrel-cage induction motor (10-200 HP range) with water-filled or oil-filled design. Water-filled motors provide better heat dissipation for continuous duty.

• Column Pipe and Shaft: Steel column pipe (6-16 inch diameter) housing drive shaft connecting motor to pump. Shaft materials typically 416SS with bronze bearings. Length varies from 25-300 feet based on installation depth and pump setting.

• Discharge Head: Cast iron or steel assembly containing check valve, isolation valve, and pressure gauge connections. Includes shaft seal and bearing assembly. Sized to match column pipe diameter and system pressure requirements.

• Flow Rate: 50-15,000 GPM typical range for municipal applications. Raw water intake: 200-8,000 GPM. High service: 100-5,000 GPM. Effluent discharge: 150-12,000 GPM.

• Total Dynamic Head (TDH): 20-800 feet typical. Static lift: 10-400 feet. Friction losses: 5-150 feet. System pressure requirements: 30-250 feet.

• Pump Setting Depth: 15-300 feet below static water level. Minimum submergence: 3-15 feet above pump intake. Well diameter constraints: 6-36 inch casings.

• Motor Power: 5-500 HP range. Efficiency targets: 75-85% at design point. NPSHR: 5-25 feet depending on specific speed.

• Materials: Cast iron/bronze for potable water. 316SS for aggressive environments. Duplex stainless for high-chloride applications.

• Performance Curves: Steep vs. flat curve selection based on system characteristics. Minimum continuous flow: 20-30% of design capacity.

• Electrical: 480V/4160V three-phase. Variable frequency drive compatibility required for most applications. Motor cooling requirements: 1-3 fps minimum velocity past motor.

• What is the required pump setting depth and available NPSH? Critical threshold: Minimum 3 feet submergence above intake, 5+ feet preferred. Insufficient submergence causes cavitation, reduced capacity, and premature wear.

• What motor cooling velocity can the system provide? Minimum 1 fps past motor required, 3+ fps preferred for motors >25 HP. Inadequate cooling causes thermal trips and shortened motor life.

• Should the design use single large pump or multiple smaller units? Threshold: >2,000 GPM typically justifies duplex installation. Single pump risks total system failure; multiple pumps provide redundancy but increase complexity and cost.

• What head-capacity curve shape matches the system curve? Steep curves for constant-head systems; flat curves for variable-demand applications. Mismatched curves cause efficiency losses and control problems.

• Division 40 - Process Integration

• Section 40 23 00 - Process Pumps - Primary specification for submersible vertical turbine pumps in water/wastewater treatment

• May reference Section 33 21 00 (Water Supply Wells) for well-specific requirements and Section 40 20 00 (Process Piping) for discharge piping integration

• Material/Equipment Verification: Verify 316SS wetted parts for wastewater service, confirm motor enclosure ratings (NEMA 6P minimum), check impeller materials match application requirements

• Installation Requirements: Crane access for pump removal/installation, guide rail system design and anchoring, electrical connections above high water level

• Field Challenges: Wet well dimensional constraints during retrofit, electrical conduit routing in confined spaces, pump alignment with guide rails

• Coordination Issues: Structural engineer for guide rail supports, electrical contractor for motor control center integration, lead times: 12-16 weeks for standard models, 20+ weeks for custom configurations

• Grundfos: SP series submersible pumps, widely used in municipal lift stations 50-2000 GPM range

• Xylem (Flygt): NP series, proven in wastewater applications up to 5000 GPM

• KSB: UPA series for clean water, Amarex for wastewater service

• Pentair Myers: VRS series, cost-effective option for smaller municipal systems under 500 GPM

• Horizontal Split-Case Pumps: Preferred for high-flow applications (>3000 GPM) with better efficiency but require dry pit installation. Cost: 15-20% less than submersible.

• Vertical Lineshaft Pumps: Better for deep wet wells (>30 ft) but higher maintenance complexity.

• Horizontal End-Suction: Most economical for smaller flows (<500 GPM) with reliable prime source. Cost advantage: 30-40% less than submersible systems.

Pump Selection: Oversize discharge connections by one pipe size - reduces friction losses and simplifies maintenance access. Manufacturer Relations: Establish preferred vendor relationships for faster technical support and parts availability. Cost Savings: Specify standard motor voltages (460V) and avoid custom impeller trims. Consider buying spare pumps during initial procurement for volume discounts rather than emergency replacement pricing.