- Features & Benefits
- Other Info
Dickow’s NMW Series are a range of sealless, single-stage, volute casing pumps designed for handling thermal oil with a temperature range from 250 to 400°C without water cooling. The pumps have a maximum flow rate of 900 m³/hr and maximum differential head to 150 m. The capacity and casing dimensions comply with EN 22858 / ISO 2858. A static containment shell forms a closed system replacing double acting mechanical seals, along with external fluid reservoirs and the necessary control equipment.
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 transmissible power of the Cobalt Samarium coupling depends on the operating temperature of the magnets which should not exceed 250 °C. For applying the pumps at temperatures between 250 and 400 °C, the bearing housing is designed as a cooling device with cast-on fins. For high drive powers, an additional, external cooling loop is required.
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 KM pumps is approx. 170 kW.
The drive shaft of NMWR variants is carried by oil lubricated antifriction bearings, rated for 25,000 operating hours. The oil bath is protected against the atmosphere by a labyrinth seal. Oil level is controlled by a constant level oiler and an additional sight glass. The oil chamber is sealed against the magnetic coupling also by a labyrinth seal. NMWB versions have a close coupled design.
The pump shaft is carried by wetted sleeve bearings of pure Silicon Carbide with a diamond layer, providing limited dry-run capability.
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.