- Features & Benefits
- Other Info
Dickow’s PRM Series are end suction, top discharge, single stage, radial split volute casing pumps of back-pull-out design with closed impellers. The mechanical design complies with API 685. A static containment shell forms a closed system replacing double acting mechanical seals, along with external fluid reservoirs and the necessary control equipment. PRM-pumps therefore offer exceptional benefits to the chemical, petrochemical and allied industries and fulfil all environment protection regulations.
The PRM series consists of a range of heavy duty pumps with a maximum flow rate of 900 m³/hr and maximum differential head to 150 m. The equipment (including auxiliaries) is designed for a minimum service life of 20 years (excluding normal wear parts) and an uninterrupted operation of at least 3 years. The PRMW version is designed for handling heat transfer fluids up to 400°C with an air cooler limiting the fluid temperature in the magnet area to 250°C. The PRM b version has a heating jacket for handling fluids with melting temperature above ambient.
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 PRM pumps is approx. 260 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 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.
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.