Desmi Rotan HD51EM-1U2B2 Internal Gear Pump with Nord SK20-100L/4 Motor

Desmi Rotan HD51EM-1U2B2 Internal Gear Pump with Nord SK20-100L/4 Gear Motor

The Desmi Rotan HD51EM-1U2B2 is an industrial-duty positive displacement internal gear pump designed for high-viscosity, non-corrosive liquids in severe physical situations. The unit is built around a very strong cast iron shell (GG 25) and has a 50 mm (2-inch) inline suction and discharge port configuration designated as “E”.

The specialized pump assembly is directly attached to a superior NORD Drivesystems SK20-100L/4 Gear Motor for the high torque, low RPM input speeds needed to keep continuous volumetric efficiency without fluid shearing. The pumping parts have a real back pull-out structure that means quick service without having to damage the pipework or detach the primary motor alignment. This results in a large reduction in operating downtime in naval engine rooms and industrial facilities.

Model Details

• Pump Model: HD51EM-1U2B2
• Gear Motor Model: SK20-100L/4
• Brand: DESMI A/S (Denmark) / NORD Drivesystems (Germany)

Main Features

1. True Back Pull-Out Design: Permits complete disassembly of internal gear elements without breaking physical pipe flanges or removing the gear motor from its baseplate, facilitating routine machinery inspections.
2. High Viscosity Volumetric Efficiency Optimized to exploit tight internal tolerances, volumetric performance actually improves with thicker fluid viscosities up to 250,000 cSt, providing a steady, non-pulsating flow.
3. Heavy Duty Material Composition: Made from high-density Cast Iron GG 25, with a hardened 16 MnCr 5 idler pin and bronze bushings, for cyclic structural loads and thermal expansion up to 250 °C.
4. NORD Helical Gear Motor Match: Optimized coupling with the 4-pole SK20 motor, producing the high starting and running torque profiles required to shear through viscous or cold fluid columns at first start.
5. Bi-Directional Pumping Flexibility: Full capacity flow operations can be performed in both clockwise (CW) and counter-clockwise (CCW) directions by simply reversing the phase rotation on the electric motor terminal box.

Applications

• Marine & Shipbuilding: Transfer of heavy fuel oil (HFO), marine diesel oil (MDO), lube oil distribution, sludge stripping, and oily water separation systems.
• Petroleum and Bitumen Plants: Pumping asphalt, pitch, bitumen additives, raw crude fractions, and base lubricating oils.
• Chemical & Process Industries: Transport of polymers, polyols, soap stocks, fatty acids, resins, and liquid lacquers.
• Food Processing: Bulk processing transfer of highly viscous food items such as chocolate mass, molasses, maltose, and fats.

Equipment Compatibility

• The Desmi Rotan HD51 assembly fits standard industrial baseplates and is widely used across high-viscosity transfer skids.
• Compatible Competitor Footprints: Viking Pump Universal Series (Size H/HL Internal Gear), Tuthill GlobalGear Series (Model GG050), Roper Pump 3600 Series.
• Part Number Cross-References: HD51EM, ROTAN-HD51-1U2B2, SK20-100L/4-HD51.

Engineer’s Insight:

1. Risk of cavitation during cold start. If you are pumping a very viscous medium (cold lube oil or fuel oil for example), the resistance in the suction line might easily cause cavitation. Always select a bigger size of suction pipework than the pump port DN50 to reduce the friction losses.
2. Internal vs External Lubrication: As the ‘U’ version, internal bearings depend only on the pumped medium for cooling and lubrication. Hence, dry running must be avoided at any cost. If left dry even for a short amount of time, the bronze idler bushing will quickly gall and seize on the hardened pin. Before commissioning, install a dry-running protection switch or charge the pump casing manually.
3. Axial Clearance Adjustment: The axial clearance of the rotor can be adjusted using the adjustment screw on the rear bearing cap to compensate for the volumetric slip that develops due to abrasive wear over time. Tightening this clearance improves pump efficiency without the need to replace the internal gears.