Canned motor pump principle and structure feature
1, and shield pump of principle and structure features
General centrifugal pump of drive is through coupling will pump of impeller axis and electric axis phase connection, makes impeller and motor with rotating and work, and shield pump is a no sealed pump, pump and drive motor are was sealed in a was pump sent media full of pressure container within, this pressure container only static sealed, and by a wire group to provides rotating magnetic field and drive rotor. This abolishes the traditional centrifugal pump with rotary shaft seal, it can be done without leakage.
of canned motor pump and motor pump together, the rotor of the motor and the pump impeller is fixed on the same shaft, use shielded motor between the rotor and the stator, rotor running in a transmission medium, its power through the stator magnetic field to the rotor.  
in addition, canned motor pump manufacturing is not complicated, centrifugal pump with hydraulic end can usually structure type and related standards to design and manufacture.
2 and the advantages and disadvantages of canned motor pump  
2.1 shield
pumps advantages (1) closed. No dynamic seal on the structure, only static seal in the pump casing, so can be done without leakage, particularly suitable for transporting flammable, explosive, valuable liquid and toxic, corrosive and radioactive liquids.
(2) safety. Rotor and stator of a shield the rotor and the stator is not in contact with the material, even shielding rupture, and no risk of external leakage.
(3) compact occupies less. Pump and motor is a whole disassembly is not required to find dead center. Basic requirements of the base and low, and less routine maintenance work, maintenance costs low.
(4), stable running, low noise, do not need to add oil. Because there were no rolling bearing and motor fans, there was no need to lubricate, and low noise.
(5) using a wide range of. High temperature, high pressure, low temperature, high melting point can meet the requirements of.
2.2 disadvantages of canned motor pump
(1) because of the sliding bearing of canned motor pump and lubricated with medium to be transported, so the media should not be used as Shield poor lubrication pump. Generally suitable for shielding the viscosity of the pumped medium as 0.1~20mPa.s.
(2) shielded single mechanical seal for pump efficiency is usually lower than the centrifugal pump, with double mechanical seals of centrifugal pumps roughly equivalent.
(3) in the case of small flow operation for a long time, shield pump efficiency is low, can cause fever, so that the liquid evaporates, causing pump dry transfer, thereby damaging the bearing.
3, shield pump type and scope of
according to the temperature of the liquid, pressure, viscosity and particle-free condition, shield pump can be divided into the following types:
medium temperature-up to 120 ℃, head of not more than 150m. A variety of other types of canned motor pump can be based on the Basic, variant and after the improvement.
(2) reverse circulation
this type of canned motor pump for bearing lubrication, cooling and motor cooling liquid flow direction and basic-just the opposite. Its main feature is less susceptible to cavitation, particularly suitable for easy vaporization of liquid transportation, such as liquefied petroleum gas, Methyl chloride, etc.
General transmission medium temperature up to 350 ° c, highest flow 300m3/h, head up to 115m, for thermal oil and hot water and other high temperature liquids.
(4)-high melting point jacket
pump and motor, motor resistance can be greatly improved. Suitable for high melting point liquid, temperature of up to 250 ℃. Steaming in the jacket or the temperature of the liquid and prevent high melting point liquid crystals.
(5) type
high-voltage canned pump shell is a high pressure container, can withstand the high pressure of the pump. In order to support the shield in an internal high pressure, stator coils can be used under pressure.
suction tube is not full of liquid, by automatically pumping the pump discharge, adapted from underground extraction liquid in the container.
(7) multi-stage
with complex impeller for high lift transmission fluid, maximum lift of 400m.
for delivery of liquid mixed with a lot of mud.
4, shield pump considerations for selection of
General shielded pumps are used for part of the liquid to cool the motor, and ring gaps are small, so the liquid must be clean. To convey a wide range of liquid mixtures, if they produce precipitation, coke or gum, the first selection of canned motor pump (non-mud) may plug shielded space, cooling and lubrication of the pump, leading to burning graphite bearings and motor.
shield pump circulating cooling tubes generally have when when the ambient temperature is below the freezing point of pumped liquid, it tube freezing measures should be adopted to ensure convenient pump to start.
at boot time should strictly abide by the export of canned motor pump valve and the inlet valve open order, stops the pump outlet valve first, turn down when pump stops working and then, to close the inlet valve and close the outlet valve.
in short, shield pump without leakage, effectively avoid pollution and loss of material, as long as the selection is correct, changes in operating conditions, without exception, under normal operating conditions, there is hardly any maintenance work. Canned motor pump is transporting flammable, explosive, corrosive, ideal as a valuable liquid pump.

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