The TSURUMI NK4-22 is a portable submersible dewatering pump from Tsurumi's NK series, with a 50 mm discharge and a 2.2 kW single-phase motor. The NK series is Tsurumi's line of larger-output portable drainage pumps: although they run on single-phase power, their wear parts are made of abrasion-resistant materials, giving durability equivalent to three-phase drainage pumps. The slim body fits into confined spaces, making the NK4-22 well suited to pumping rain water, groundwater and sand-laden water on sites, in basements and in sumps where no three-phase supply is available.
Selection note: the NK4-22 is a dewatering pump, not a sewage or slurry pump. Its solids passage is only 8.5 mm, so it is not suitable for sewage containing fibrous matter, settled sludge or dense sand slurry (Tsurumi's NKZ construction slurry pump is a different series from NK). The Hong Kong and international standard version has a 50 mm hose coupling; the US-market version has an 80 mm (3-inch NPT) discharge and different specifications. For lower head and flow requirements, consider the 1.5 kW NK3-15 from the same series.
Key features
- 2.2 kW single-phase motor: no three-phase supply needed. Capacitor-start, capacitor-run, continuous-duty dry-type induction motor with class F insulation.
- Top-discharge, side-flow design: the semi-built-in top discharge keeps the motor cooled even when it runs exposed to air, and reduces the pump's overall diameter for installation in confined spaces.
- Abrasion-resistant construction: a ductile cast-iron semi-vortex impeller with a synthetic rubber casing, suited to sand-carrying water.
- Double inside mechanical seals: silicon carbide (SiC) faces running in an oil chamber, with Tsurumi's Oil Lifter to keep the seals lubricated even when the oil level drops, plus a V-ring / oil seal.
- Built-in circle thermal protector (CTP): cuts power automatically on overheating or overload.
- Anti-wicking cable entry and cable clip: limits water creeping along the cable cores into the motor and holds the cable securely.
Applications
- Construction sites: excavation, basement and standing-water drainage
- Sumps and confined spaces: the slim body fits smaller pits
- Storms and flooding: emergency removal of rain and flood water
- Raw water transfer: pumping raw water from rivers or lakes (not for potable water)
Suitable liquids are rain water, groundwater and sand-carrying water at 0–40 °C. Do not pump seawater, salt water, oil, chemicals, corrosive liquids, organic solvents, flammable or explosive liquids, or liquids above 40 °C.
Performance
At 50 Hz, the 24.0 m maximum head is the head at near-zero flow, and the 0.525 m³/min (525 L/min, about 31.5 m³/h) maximum capacity is the end point of the performance curve. The two do not occur together: actual flow falls as total head (static head plus hose friction loss) rises, so select the pump from the performance curve using your site's total head. At 60 Hz the figures are 26.0 m and 0.495 m³/min (495 L/min); these are for reference only, as the Hong Kong supply is 50 Hz.
Technical specifications
TSURUMI NK4-22 technical specifications (50 Hz)
| Item | Specification |
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| General |
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| Model | NK4-22 |
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| Series | NK (portable dewatering pump) |
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| Discharge bore | 50 mm |
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| Discharge connection | Hose coupling (standard); male threaded coupling for pipe connection available on special request |
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| Hydraulic performance |
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| Max. head (at zero flow) | 24.0 m (60 Hz: 26.0 m) |
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| Max. capacity (curve end point) | 0.525 m³/min (525 L/min, about 31.5 m³/h) (60 Hz: 0.495 m³/min) |
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| Solids passage | 8.5 mm |
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| Electrical |
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| Motor output | 2.2 kW |
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| Motor | Dry-type induction motor, 2-pole, continuous-duty rated, insulation class F |
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| Synchronous speed | 3,000 min⁻¹ (50 Hz) / 3,600 min⁻¹ (60 Hz) |
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| Power supply | Single-phase (voltage as per nameplate) |
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| Starting method | Capacitor start + capacitor run |
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| Motor protection | Built-in circle thermal protector (CTP) |
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| Power cable | 10 m, chloroprene rubber sheath |
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| Seals and bearings |
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| Shaft seal | Double inside mechanical seals, silicon carbide (SiC) faces, with Oil Lifter |
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| V-ring / oil seal | Nitrile butadiene rubber (NBR) |
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| Lubricant | Turbine oil ISO VG32 (non-additive), 270 ml |
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| Bearings | Shielded ball bearings |
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| Materials |
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| Impeller | Semi-vortex, ductile cast iron |
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| Pump casing | Synthetic rubber |
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| Shaft | 403 stainless steel |
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| Liquid limits |
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| Liquid | Rain water, groundwater, sand-carrying water |
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| Liquid temperature | 0–40 °C |
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| Min. water level for continuous running | 80 mm |
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| Dimensions and weight |
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| Dry weight (excl. cable) | 29 kg |
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| Overall height | 614 mm |
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Sources: Tsurumi single-phase portable pumps catalogue (IB101), KTV/KTVE/NK operation manual (B-10276) and Tsurumi Hong Kong NK series page. Voltage and rated current of the Hong Kong supply version are as per the nameplate.
NK series comparison
Tsurumi NK series model comparison (50 Hz)
| Model | Discharge | Power | Max. head | Max. capacity | Dry weight |
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| NK3-15 | 50 mm | 1.5 kW | 20.0 m | 420 L/min | 29 kg |
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| NK4-22 (this product) | 50 mm | 2.2 kW | 24.0 m | 525 L/min | 29 kg |
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Tsurumi also offers the NK4-22L, with an 80 mm discharge and a high-chromium cast-iron semi-open impeller (18 m max. head and 0.8 m³/min max. capacity at 50 Hz). Contact us if you need it.
What's in the box
- NK4-22 pump with 10 m cable × 1
- Operation manual × 1
Optional accessories
- 50 mm discharge hose and hose band (sold separately).
- Male threaded discharge coupling for pipe connection (special order).
- Dedicated earth-leakage circuit breaker and thermal overload relay (installed by the user to suit the site supply).
Safety and installation
- Electrical connection must be made by a registered electrical worker in line with local regulations, with a dedicated earth-leakage circuit breaker, a thermal overload relay and a secure earth. Never earth the pump to a gas pipe, water pipe, lightning rod or telephone earth.
- Keep the supply voltage within ±5% of the nameplate voltage. When running from a generator, do not power other equipment from the same generator.
- Never run the pump dry, below 80 mm (the minimum water level for continuous running) or against a closed gate valve.
- Carry and lift the pump by its handle, never by the cable, and do not start it while it is suspended.
- Secure the discharge hose so it cannot whip. If the pump could be buried in sediment, stand it on a firm base such as a concrete block.
- The pump is neither dust-proof nor explosion-proof: do not use it where toxic, corrosive or explosive gas may be present. Never run it while anyone is in the pool or sump.
- The pump surface may be hot during and after operation.
- The pump restarts automatically when power returns after an outage. Switch off the power before maintenance, after a power cut and during long idle periods.
- Not for use with potable water.
Wear parts and routine checks
- Parts for periodic replacement: mechanical seal (when the oil turns milky), lubricant, packing and O-rings (at every disassembly or inspection), V-ring (when worn or at disassembly) and shaft sleeve (when worn). Mechanical seal inspection and replacement should be done by a dealer or Tsurumi service.
- Daily: check that operating current is at or below the rated current and that voltage is within ±5% of the nameplate.
- Monthly: measure insulation resistance; it should be at least 1 MΩ (reference for a new pump: 20 MΩ or more).
- Oil: inspect every 6 months or 3,000 hours; change the VG32 turbine oil every 12 months or 6,000 hours, whichever comes first.
- Overhaul every 2 to 5 years depending on use, even if there are no problems.
- If the pump is left in water, run it at least once a week to prevent it from seizing.
