The TSURUMI KRS45.5 is a heavy-duty submersible dewatering pump from Tsurumi's KRS series (officially classed as a general construction pump). It has a 100 mm (4-inch) discharge and a 5.5 kW 4-pole three-phase motor. With a semi-open ductile-iron impeller, a grey cast-iron body and a low-speed motor, it is built for excavation dewatering, tunnel work and storm or flood drainage, and handles stormwater, groundwater, wash water and sand-carrying water with solids up to 12 mm. Dry weight is 100 kg (50 Hz, excluding cable).
Selection note: the KRS45.5 is a dewatering pump, not a slurry pump. It has no agitator and no high-chrome wear parts, so it is not suitable for settled sludge, dense sand slurry, desilting or dredging. For that duty, choose the KRD35.5, KRD47.5 or KRD611 slurry pumps, which have a high-chrome impeller and an agitator.
Key features
- Top-discharge, side-flow design: the motor stays cooled even when partly exposed, and the slim body fits confined spaces. Keep at least 155 mm of water for continuous running and do not run it dry for long periods.
- Double inside mechanical seals: silicon carbide (SiC) faces on both the upper and lower seals, running in an isolated oil chamber. A nitrile lip seal acts as a dust seal to protect the mechanical seal from abrasive particles.
- Tsurumi's original Oil Lifter: keeps the seal faces lubricated and cooled even when the oil level drops to about one third of normal.
- Built-in circle thermal protector (CTP): cuts the motor circuit directly on overheating or overcurrent.
- Anti-wicking cable entry: blocks water from creeping along the cable by capillary action if the sheath is damaged or the cable end is submerged; a cable clamp provides strain relief.
- Low-speed 4-pole motor: continuous-duty dry-type induction motor, IP68, insulation class F, 1,500 min⁻¹ synchronous speed at 50 Hz, paired with a cast-iron body for long service life.
- Double-shielded ball bearings: deep-groove C3 bearings, permanently lubricated.
Applications
- Construction sites: excavation and basement dewatering, temporary drainage for foundation works
- Tunnels, bridges and dams: civil engineering site drainage
- Storms and flooding: stormwater and emergency flood drainage
- Temporary drainage: provisional sewage drainage during works
Performance
Read from Tsurumi's official 50 Hz performance curve (1,500 min⁻¹ synchronous speed), the KRS45.5 reaches a maximum head of about 20 m and a maximum capacity of about 2.0 m³/min (about 2,000 L/min). The maximum head is the head at near-zero flow; the maximum capacity is the end point of the curve, where the head is only about 2 m. The two do not occur together: actual flow falls as total head (static head plus hose friction loss) rises. Tsurumi does not publish exact figures for this model, so treat these curve readings as a guide; select the pump from the performance curve using your site's total head, or ask the Hong Kong agent for the model datasheet. For more flow, consider the 150 mm KRS67.5 or KRS611.
Technical specifications
TSURUMI KRS45.5 technical specifications (50 Hz)
| Item | Specification |
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| General |
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| Model | KRS45.5 (North American model KRS2-B4) |
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| Series | KRS (general construction pump, heavy-duty submersible dewatering) |
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| Discharge bore | 100 mm (4 in) |
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| Discharge connection | Hose coupling (standard) |
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| Hydraulic performance |
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| Max. head (at zero flow) | approx. 20 m (from official curve) |
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| Max. capacity (curve end point) | approx. 2.0 m³/min (approx. 2,000 L/min, from official curve) |
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| Max. solids size | 12 mm |
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| Electrical |
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| Motor output | 5.5 kW |
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| Motor | Continuous-duty dry-type induction motor, 4-pole, IP68, insulation class F |
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| Speed | 1,500 min⁻¹ synchronous (50 Hz) |
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| Power supply | 3-phase 50 Hz (voltage as per nameplate) |
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| Starting method | Direct-on-line (DOL); star-delta on special request |
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| Motor protection | Built-in circle thermal protector (CTP) |
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| Cable | 8 m, chloroprene rubber sheath |
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| Seals and bearings |
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| Shaft seal | Double inside mechanical seals, SiC + SiC upper and lower faces, oil-lubricated, with Oil Lifter |
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| Oil seal | Nitrile rubber lip seal (dust seal) |
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| Lubricant | Turbine oil ISO VG32, 1,850 ml |
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| Bearings | Double-shielded deep-groove ball bearings (C3), permanently lubricated |
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| Materials |
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| Impeller | Semi-open, ductile cast iron |
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| Pump casing, suction cover | Grey cast iron |
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| Motor frame | Grey cast iron |
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| Shaft | 420 stainless steel |
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| Liquid limits |
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| Liquid | Stormwater, groundwater, wash water and sand-carrying water |
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| Liquid temperature | 0–40 °C |
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| Dimensions and weight |
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| Dry weight (excl. cable) | 100 kg |
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| Dimensions (L × W × H) | 364 × 346 × 747 mm |
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| Min. water level for continuous running | 155 mm |
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Sources: Tsurumi KRS/KRD series catalogue (IB111) and the Tsurumi KRS45.5 specification sheet (KRS-05). Figures are for the 50 Hz version; voltage, rated current and cable size of the Hong Kong supply version are as per the nameplate and confirmation from the Hong Kong agent.
KRS series comparison: 100–200 mm
Tsurumi KRS series model comparison (50 Hz; "approx." values are read from the official curves)
| Model | Discharge | Power | Max. head | Max. capacity | Max. solids |
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| KRS45.5 (this product) | 100 mm | 5.5 kW | approx. 20 m | approx. 2,000 L/min | 12 mm |
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| KRS67.5 | 150 mm | 7.5 kW | approx. 19 m | approx. 2,850 L/min | 20 mm |
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| KRS611 | 150 mm | 11 kW | approx. 22 m | approx. 3,650 L/min | 20 mm |
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| KRS811 | 200 mm | 11 kW | 17.5 m | 5,500 L/min | 30 mm |
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What's in the box
- KRS45.5 pump with attached 8 m cable × 1
- Hose coupling × 1
Optional accessories
- Male threaded coupling (Tsurumi option, in place of the standard hose coupling).
- Float switch. On a three-phase pump it must switch a control-panel contactor, never the motor directly.
- Motor overload protector or control panel, set to the nameplate rated current.
- Special factory builds on request: high-temperature liquid version (60–80 °C) and star-delta starting.
Safety and installation
- Lift the pump by its handle with a chain or shackle rated for about 100 kg or more. Never lift it by the cable or the hose.
- Electrical connection must be made by a registered electrical worker in line with the Hong Kong wiring regulations, with earth-leakage protection. Set the overload relay to the nameplate rated current.
- Check rotation before first use: at start-up the pump body should kick anticlockwise when viewed from above. If it turns the wrong way, have an electrician swap two phases. Do not hold the handle while checking.
- After the built-in motor protector trips, the motor restarts automatically once it cools. Always isolate and lock off the power before inspection or servicing.
- Stand the pump on a firm or raised base so it does not sink into silt.
- Keep the water level at 155 mm or above for continuous running and avoid prolonged dry running.
- Use only for stormwater, groundwater, wash water and sand-carrying water at 0–40 °C. The standard model is not seawater-resistant; do not pump seawater or brackish water, flammable, oily or chemical liquids, or hot liquids.
Wear parts and routine checks
- Main wear parts: impeller, suction cover, mechanical seals and oil seal. With long running in sandy water, the impeller and suction cover gradually wear and flow drops.
- Regularly check the oil condition in the oil chamber (turbine oil ISO VG32, 1,850 ml) and the clearance between the impeller and the suction cover. If the oil is cloudy or contains water, have the shaft seals inspected promptly.
