N/A Internal clearances
The internal clearance between inner rotating magnets and containment shell depends on the wall thickness of the shell. However, a minimum clearance of 1 mm (0.040") will be provided in any case. This, together with wear resistant sleeve bearings, allows handling of fluid with solids.

Internal circulation, pressurized magnet end
When pump is in operation it generates eddy currents which heat up the containment shell and the pumpage in the magnet area. This heat is dissipated by internal circulation. The internal circulation flows from discharge, direct behind the impeller, through the magnet area and the pump shaft back to the impeller respectively discharge side. Injection holes respectively back vanes in the rear impeller wall create forced circulation. The effect of pressurizing the magnet end with the sleeve bearings gives an additional safety margin against flashing when handling boiling liquids.

N/A Construction
NMB/NML-pumps are single stage volute casing pumps with closed impellers, back-pull-out design, with end suction and top centerline discharge flange. Rigid support foot mounting is supplied as standard. Centerline mounted design is available on request. Capacity and flange to flange dimensions comply with EN 22858 (ISO 2858).

Containment shell, Disassembly
The containment shell is designed as a pressure vessel to separate the pumpage from the atmosphere only. The containment shell is not used as an additional bearing holder. No dynamic stress occurs. The containment shell is bolted to the bearing housing in a manner that allows removal of the bearing bracket (resp. of the drive motor for NMB-design), including outer magnets and ball bearings, without exposing the pumped liquid to the atmosphere.

Magnetic coupling
The single elements of the multipolar magnetic coupling are manufactured of a permanent magnet material "Cobalt-Samarium - Rare Earth" with unlimited lifetime. The magnets in the internal rotor are completely encapsulated; no contact with liquid occurs. Energy is transmitted to the hermetically sealed liquid end by a bank of external magnets passing motive force through the containment shell to a bank of internal magnets. Inner and outer magnet rings are locked together by magnetic power and work as a synchronous coupling. The inner magnet ring transmits the required torque directly to the impeller. Overload of the magnetic coupling and slipping will not effect demagnetization, if temperature is monitored by sufficient devices.

Casing drain
Complete drainage of casing and magnet end is possible through casing drain. No additional drain required.

Containment shell protection
The different clearances between the rotating outer magnets and stationary containment shell, and the rotating magnet holder and bearing bracket respectively, prevent rubbing of magnets on the containment shell in case of ball bearing failure.

NPSH-Conditions
Due to the internal circulation from discharge to discharge, no elevated temperature will re-enter the impeller eye. Handling of boiling liquids is possible without an increase of NPSH-required.

Balanced thrust loads
The thrust loads of the impellers are hydraulically balanced by impeller injection holes, respectively the back vanes.

Monitoring
Connection for temperature detection element for containment shell surface temperature is available as standard. Dry running protection and monitoring of ball bearings and containment shell temperature with the patented "MAG-SAFE" System is highly recommended.