The HZSM / HZSMA-pumps are single or multi stage horizontal centrifugal pumps, combined with integrated side channel stage on discharge side, and permanent magnetic coupling. The containment shell forms a closed wetted end and separates the pumped liquid from the atmosphere.
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 shell is sealed against the atmosphere by a confined gasket.
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. The magnetic drives are designed for electric motors, direct on line starting. Should a subsequent increase of motor power be required, i.e. when installing a larger impeller, the nominal power of the magnetic coupling can be increased accordingly by an additional series of magnets. The maximum drive power is 150 kW at 2900 rpm (250 HP at 3500 rpm).
Suction- and discharge casing
The pump flanges of HZSM-pumps are provided principally in vertical top position to ensure a certain quantity of liquid in the pump which is necessary for priming empty suction pipes and lifting liquid from underground storage facilities. For obtaining low NPSH-value, the suction casing is designed in volute shape.
The HZSMA-pumps - for applications with flooded suction conditions - are provided with suction casings of end suction design to obtain further reduction of NPSH-values.
For lowering the NPSH-value, the impeller of the first stage is designed as a suction impeller with enlarged impeller eye.
The side channel stage is capable to evacuate the suction line and therefore, to self-prime if initially filled with operating liquid. In the priming phase the side channel pump works as a positive displacement pump.
The displacement effect is created by a rotating liquid ring which enters and exits the side channel in a piston fashion during each rotation. This is generated by an interrupter in the side channel which separates suction and pressure area. The piston effect conveys the gas from suction to discharge side. The priming stage works automatically; no auxiliary vent equipment required.
When pumping LPG, attention must be paid to gas entrainment by vapor bubbles. In practice, these pumps can pump this liquid-gas mixture without auxiliary device. Due to the increased pressure in the side channel stage, the gas bubbles turn into liquid phase again.
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.