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NM Series

  • Overview
  • Features & Benefits
  • Specifications
  • Other Info

Overview

Dickow’s NM Series are sealless, single-stage, volute casing pumps with end suction and top centre-line discharge flange.  A static containment shell forms a closed system replacing double acting mechanical seals, along with external fluid reservoirs and the necessary control equipment.  NM-pumps therefore offer exceptional benefits to the chemical, petrochemical and allied industries and fulfill all environment protection regulations.  Dimensions and performance comply with EN 22858 (ISO 2858)

The NM series consists of a range of pump sizes and specifications with a maximum flow rate of 400 m³/hr and maximum differential head to 150 m.  The maximum operating temperature is 200°C for NML designs, and 240°C for NMB types.

The single elements of the multipolar magnet coupling are manufactured of Cobalt-Samarium with unlimited lifetime.  The magnets in the driven rotor are completely encapsulated and not in contact with liquid.  Power is transmitted to the hermetically sealed liquid end by a bank of external magnets.  Inner and outer magnet rings are locked together by magnet forces and work as a synchronous coupling.

The inner magnet ring transmits the required torque direct to the impeller.  Overload of the magnet coupling and slipping will not cause demagnetization if temperature monitoring is available.  Should an increase of motor power be required, i.e. when installing a larger impeller, the nominal power of coupling can be increased with additional magnets.  The maximum drive power of NM pumps is approximately 111 kW.

The internal clearance between rotor and containment shell is approximately 1.0 mm for standard containment shells.  This allows – together with wear-resistant SiC sleeve bearings – handling of solid containing fluids.

The drive shaft of NML pumps is carried by antifriction bearings, grease filled for lifetime and protected against the atmosphere by a lip seal.  The drive rotor of NMB pumps is mounted on the motor shaft so additional bearings, elastic coupling and coupling alignment are not required.

The pump shaft is carried by wetted sleeve bearings of pure Silicon Carbide with a diamond layer, providing limited dry-run capability.

Due to the internal circulation from discharge to discharge, there is no temperature elevation in the impeller eye.  Handling of boiling liquids is therefore possible and no increase of NPSH is required.

When fitted with suitable Ex-drive motors, the pumps can be applied in hazardous area Group II, Category 2.  The pumps meet the basic safety and health requirements of Explosion-proof Directive 94/9 EC and are suitable for plants with increased safety requirements.  For close coupled pumps (NMB variants) the containment shell temperature is limited when using Ex-motors.

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