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.
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.
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.
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.
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.