Submersible pumps are units in which the motor and pump are hermetically sealed together and fully submerged in the fluid being pumped. By operating below the fluid surface they push fluid upward rather than pulling it — a fundamentally more efficient arrangement that eliminates suction-side cavitation risk and requires no priming.
History
The electric submersible pump was invented by Armais Arutunoff, an Armenian-born engineer and inventor who emigrated first to Germany and then to the United States. Arutunoff received his first patent for a submersible electric motor-and-pump unit in 1916 and founded REDA — Russian Electrical Dynamo of Arutunoff — in Bartlesville, Oklahoma in 1930, which became the first commercial manufacturer of electric submersible pumps, initially for oil well artificial lift. The technology was adapted for groundwater and sewage applications after the 1940s, when advances in moisture-resistant motor winding insulation and submersible-rated cable enabled reliable long-term submerged operation far beyond the oil well environment.
Operating Principle
The motor is housed in a sealed enclosure directly coupled to the pump section. When submerged, the motor windings are cooled by the surrounding fluid. An impeller (or multiple impellers in series) draws fluid in through the pump inlet — which is at the base or side of the unit — and discharges it upward through a riser pipe or column. Because the pump is below the fluid surface, there is no suction lift and no air-lock risk.
Pump Configurations
- Borehole (deep-well) submersible: Slender multistage centrifugal unit designed to fit inside a drilled borehole casing — for groundwater abstraction and water supply
- Sewage submersible: Wide-port, single or two-stage centrifugal with vortex or semi-open impeller — for raw sewage and sludge
- Drainage and dewatering: Portable unit for site drainage, flood control and construction dewatering
- Open-well submersible: Installed in open sumps, tanks or rivers — for irrigation, water transfer and process duty
- Slurry submersible: Heavy-duty open impeller with abrasion-resistant materials — for mining and dredging applications
Key Technical Parameters
- Flow rate (Q): 0.5 to 20,000 m³/h depending on unit size
- Total head (H): 5 to 1,000 m for borehole multistage configurations
- Motor power: 0.1 kW to 3,000 kW
- Submersion depth: Standard units rated to 20 to 50 m; deep-well units to 500 m
- Insulation class: Typically F or H with moisture-resistant encapsulation
- Cable: Requires submersible-rated cable — standard PVC cable is not suitable
Applications
- Groundwater abstraction for drinking water supply, irrigation and industrial use
- Municipal and industrial sewage lifting stations
- Construction site dewatering and mine water management
- Offshore oil production water injection wells
- Aquaculture and fish farm water circulation
- Flood and emergency drainage
- Fountain and ornamental water features
Advantages
- No suction lift limitation — operates at any depth
- No priming required — ready to operate immediately
- Quiet operation — motor noise is attenuated by the surrounding fluid
- Efficient — pushes fluid rather than pulling it, avoiding suction-related energy losses
- Compact installation — no above-ground pump house required for borehole units
- Suitable for operation in confined spaces, sumps and pits
Limitations
- Motor cooling depends on fluid flow past the motor body — reduced flow or stagnant operation can cause overheating
- Access for maintenance requires pulling the unit from the fluid — more complex than surface-mounted pumps
- Motor rewinds are specialist work; cable damage and seal failure are the most common faults
- Not suitable for fluids above the maximum rated temperature — motor insulation and seals set the limit
- Sand and grit ingestion in borehole duty causes impeller and wear-ring erosion over time
Selection Criteria
- Confirm static water level, maximum drawdown and required flow rate for borehole sizing
- Check borehole or sump diameter against the motor outside diameter — minimum clearance is required for motor cooling
- Specify impeller type for the fluid: vortex for raw sewage with solids, closed for clean water, open for slurry
- Verify motor insulation class and IP rating for the fluid temperature and chemistry
- Specify submersible cable cross-section for voltage drop over the cable length — long drops need upsized cable
- Install a dry-run protection sensor (level sensor or motor temperature monitor) to prevent motor burnout
Top 10 Manufacturers
- 1. Franklin Electric Co. (USA) — ~15% global market share; dominates the groundwater and water well submersible market
- 2. Grundfos A/S (Denmark) — ~12%; SP series borehole and Unilift sewage submersibles
- 3. Xylem / Flygt (USA / Sweden) — ~10%; Flygt brand is the global leader for wastewater submersibles
- 4. KSB SE (Germany) — ~8%; Amarex series for sewage and drainage submersibles
- 5. Ebara Corporation (Japan) — ~7%; submersibles for dewatering and irrigation across Asia
- 6. Sulzer Ltd. (Switzerland) — ~6%; submersible pumps for industrial and mining dewatering
- 7. Baker Hughes ESP Division (USA) — ~6%; electric submersible pumps for oil well production
- 8. SLB / OneSubsea (USA / France) — ~5%; subsea and ESP systems for offshore oil production
- 9. Wilo SE (Germany) — ~5%; submersible for drainage, sewage and building services
- 10. Pedrollo SpA (Italy) — ~4%; water well and irrigation submersibles for residential and agricultural markets