Canned Motor Pumps as Process Pumps in Heat Transfer Services
28 January 2008 16:10
Heat transfer processing with its thermal fluids on mineral or synthetic basis up to +450°C is covering a wide range in production services for chemical and petrochemical industry.
The process pump is considered as the heart of the heat transfer process as the pump itself has to withstand special stress during operation.
The relatively low pressure in the heat transfer process corresponds to the differential head of the process pumps which one has to circulate against the resulting friction losses in the tubes, fittings, vessel and heat exchanger.
On the other side the pumps for heat transfer services have to handle higher flow rates than compared to vapour-operated systems.
The selection of the suitable transfer pump related to the specification is depending on:
- The specific heat transfer oil in service
- Operating temperature
- Protection for environment and employees
- Efficiency
The installation of canned motor pumps with its standby pump guarantees the long-time plant reliability.
Sealless centrifugal pumps have been increasingly used in the chemical and petrochemical industry for higher temperatures or heavy duty services. There are two options for seal-less design: Canned motor pumps and magnetic drive pumps.
Design and manufacturing of heat transfer pumps is executed by companies which have a long-time experience for such processes. One of these companies is HERMETIC-Pumpen GmbH. This company is generally selecting canned motor pumps for heat transfer services at high temperatures that requires special care:
Advantages of canned motor pumps for heat transfer services at higher temperatures:
- Real secondary containment: even in the seldom event of stator liner defect, there is no leakage to ambient: thus 100% leakage free design
- Thanks to the absence of any mechanical seals or roller bearings, there are no cost intensive wear parts included. This allows optimised MTBF-values (Mean Time Between Failure), reduced maintenance costs and longer life-time
- No lubrication and sealing liquid required: Thanks to the seal-less design with its product lubricated hydrodynamic slide bearings there is no need for costly loop system for lubrication and cooling.
- Due to its closed coupled design no shaft alignment is required. Coupling and coupling protection is not necessary as well as large base plates
- All heat transfer pumps are equipped with centerline-mounted pump casings in order to follow any increase in higher temperatures
- Low noise level: the absence of any noise design parts as coupling, roller bearing or ventilating fan allows lowest noise levels far below the usual level
For canned motor pumps there are two different design characteristics available for high temperature applications:
- Canned motor pumps with external cooling with the so-called H-winding (max. 120°C winding temperature) for maximum liquid temperature up to +450°C
- Canned motor pumps without external cooling with the so-called C-winding (ceramic winding) for a maximum liquid temperature up to 380°C.
The pump range CNPK is used when cooling medium is available, such as cooling water. If there is no cooling liquid available the pump range CNP (with ceramic winding) can be used by dissipating part of the created heat via the rips on the motor through natural convection to the atmosphere.
For more information on this company:
HERMETIC - Hermetically Sealed Centrifugal Pumps
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