Canned Motor Pump

Description

Canned motor pumps are characterized by a compact, integrated unit without mechanical seal. The motor and pump form a unit with the rotor and the impeller fitted onto a common shaft. The rotor is guided by two identical, liquid-lubricated slide bearings. The stator winding of the motor is separated from the rotor chamber by means of a thin stator liner. In conjunction with the hydraulic section of the pump, the rotor chamber itself provides a combined cavity which needs to be filled with liquid to be conveyed prior to the start-up of the pump. The heat losses of the motor are dissipated by a partial flow between the rotor and the stator. At the same time, the partial flow lubricates both slide bearings in the rotor chamber. Both the stator liner, which is a hermetically sealed component, and the motor casing are used as safety containments. Because of that, canned motor pumps always ensure highest safety level when conveying dangerous, toxic, explosive and valuable liquids.

Function

CN - The partial flow for cooling the motor and lubricating the slide bearings will be deverted at the periphery of the impeller and, after having passed through the motor, is recirculated through the hollow shaft to the suction side of the impeller. This design is suitable for the delivery of uncritical liquids at low vapour pressures.

CNF - The partial flow for cooling the motor and lubricating the slide bearings will be diverted at the periphery of the impeller and, after having passed through the motor, is recirculated to the discharge side. An auxiliary impeller is used to overcome the hydraulic losses encountered along the way. The recirculation of the partial flow towards discharge side ensures that the heated motor cooling flow has sufficient excess pressure above the boiling point of the pumped liquid during re-entry into the pump. This pump design can be used for liquefied gases with an extremely steep vapour pressure curve.

CNK - The liquid is delivered from the suction side through the impeller to the discharge side. A thermal barrier avoids the direct heat transfer from the pump to the motor part. The motor heat losses are dissipated by a secondary cooling / lubricating circuit via a separate heat exchanger. This cooling / lubricating circuit also supplies the slide bearings. Thus the liquids at temperatures up to +400 °C can be conveyed while the secondary cooling cycle is at a lower temperature level. This construction is also suitable for conveying polluted or particle-containing liquids. If applicable, pure process liquid needs to be injected into the motor circuit.

Fields of application

CN - For the delivery of aggressive, toxic, explosive, precious, inflammable, radioactive and slightly volatile liquids e. g. sulfuric acid, nitric acid, hydrofluoric acid, hydrocyanic acid, ethanoic acid, formic acid, NaOH, KOH, D2 O solvent, etc.

CNF - Liquefied gases, e. g. ammonia, freons, carbon dioxide, amines, propane, butane, vinyl chloride, ethylene oxide, chlorine, phosgene, propylene, carbon bisulphide, hydrocarbon, diphenyl (> 250 °C) etc.

CNK - For the delivery of hot organic heat transfer oil, as well as heating bath liquids. This design can also be used for aggressive, toxic, explosive, precious, inflammable, radioactive and slightly volatile liquids.