Canned motor pumps
The canned motor pump is an integral, compact unit without shaft seal. This type of pump combines the rotating part of the pump hydraulics with the rotating part of the motor on a common shaft. The pump shaft is completely enclosed by a tightly welded rotor lining that separates the rotor assembly from the stator of the drive motor. This design principle eliminates the need for shaft seals (e.g. mechanical seals or shaft bushings) and prevents leakage. Therefore, canned motor pumps are also called 'sealless' or 'hermetically sealed'.
Function of the canned motor pump
The rotor is held by two identical, medium-lubricated, hydraulic slide - bearings (e.g. made of SiC 30 high-performance ceramics) that allow the rotor to float without any contact during operation. If the axial forces are neutralized in addition by suitable axial thrust balancing (e.g. the HERMETIC ZART ® technology - Zero Axial and Radial Thrust), the entire rotor runs contact-free and thus completely wear-free. This allows plant operators to achieve an extraordinarily high MTBF (Mean Time Between Failures), i.e. high availability with extremely long service life resulting in years of exceptionally low life cycle costs.
Structure of a single stage canned motor pump
Canned motor pump technology is often used when critical media (toxic or carcinogenic) must be conveyed or when extreme operating parameters (e.g. low-temperature applications down to -160 °C, high-pressure pumps up to 1200 bar system pressure, high-temperature versions for pumped media of up to 450 °C) need to be implemented.
The reason: In addition to the motor can as a hermetically sealed component, the special, pressure-resistant motor housing represents a second safety containment that reliably prevents the pumped medium from leaking into the environment even in case of an accident. For this reason, liquid gases with high vapor pressures that otherwise require complex shaft seal systems are a typical application for canned motor pump technology.
With the so-called 'in-tank' application, this hermetically sealed pump is increasingly opening up a new field of application: thanks to its absolutely sealed second safety casing (the motor housing), the pump complete with motor is immersed in a tank. The design principle eliminates the otherwise necessary long shafts with their potential sources of failure such as additional slide bearings and increased vibrations. At the same time, the long service life of these pumps eliminates the need for time-consuming maintenance and repairs as the pump would have to be removed from the tank.
Range of typical applications for canned motor pumps
- high temperature applications
- cryo applications
- toxic and carcinogenic media
- supercritical gases
- LPG applications (ethylene, propylene)
- melts / liquids with high boiling point (eg. sulfur)
- water-glycol mixtures
- heat transfer media (oils)
- refrigerants (e.g., CO2 R744, NH3 R717, etc.)
Cryo applications (low temperature) up to -160 °C
Standard version for environmentally harmful pumped media
Technical features of canned motor pumps
- Delivery rate up to 1.600 m³/h
- Delivery head up to 2.300 m (7.546 ft)
- Viscosity up to 300 mm²/sec
- Pressure up to 1.200 bar
- Temperature from -160°C till +450°C (-253°F till +842°F)
High-temperature version for media up to 450 °C
Benefits of canned motor pumps
- hermtically sealed / sealless
- different versions possible:
- high pressure
- high temperature
- different types of installation possible:
- single stage / multi stage
- chilled / heated
'In-tank' applications, submersible pumps