Canned motor pumps are characterised 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.
Canned motor pumps guarantee maximum safety for man and the environment in the various production processes of the chemical industry. Often designed for extreme conditions, they are used whenever liquids and gases have to be pumped at extreme temperatures and under potentially hazardous conditions. The pumps offer complete reliability – even at the highest pressures and performance levels. They are used whenever conventional technologies reach their limits. High system pressures, large temperature fluctuations, media that is extremely difficult to convey – HERMETIC pumps were developed for such extreme conditions.
The second hermetically-sealed containment shell of the canned motor pumps offers completely reliable protection against undesired leakage from the pumps. Also, the canned motor design (which has been well-established for decades) completely avoids the need for shaft seals, conventional bearings and couplings. The result is a high level of
operational reliability, hardly any wear and, consequently, a high MTBR (“Mean Time Between Repairs”) value.
Canned motor pumps are preferred in the chemical and petrochemical industry, but also for simple pumping tasks, such as circulating pumps in industrial refrigeration equipment.
In general, the following media are conveyed: aggressive, toxic, explosive, hot, cryogenic, malodorous, volatile, flammable or carcinogenic substances – in brief, media that represent an environmental and health hazard.