Principle and structural characteristics of shielded electric pumps from Shandong Luchen Pump Industry

1. Principle

The shielded pump utilizes a single shaft to connect the rotor of the motor and the impeller of the piston metering pump, which are then shielded by a shielding sleeve. The stator of the motor surrounds the shielding sleeve, which is made of metal, allowing power to be transmitted to the rotor through a magnetic field. The entire rotor operates within the pumped liquid. The ends of the shield are sealed statically using flanges or welded structures. The shielding sleeve is essentially a pressure vessel. The inner surface of the stator and the outer surface of the rotor are equipped with stator and rotor shielding sleeves made of corrosion-resistant metal sheets. Their respective end faces are welded with corrosion-resistant metal sheets to separate them from the pumped liquid, protecting the stator winding core and rotor core from corrosion. In addition to the shielding sleeve, there is another component, the circulation tube, which uses the pumped liquid to lubricate and cool the bearings and sometimes the motor. The axial force balance method of the shielded pump typically employs an automatic thrust balance device, or sometimes a radial vane mounted on the back of the impeller, known as a back impeller thrust balance mechanism. 2. Advantages and Disadvantages of Shielded Pumps Advantages of Shielded Pumps 　　　① Fully enclosed. Structurally, there is no dynamic seal, only a static seal at the pump housing, allowing for complete leak-free operation, especially suitable for conveying flammable, explosive, valuable liquids, as well as toxic, corrosive, and radioactive liquids. 　　　② High safety. Each rotor and stator has a shielding sleeve, preventing the motor rotor and stator from coming into contact with the material. Even if the shielding sleeve ruptures, there is no risk of external leakage. 　　　③ Compact structure and small footprint. The pump and motor are integrated, eliminating the need for centering during disassembly and assembly. The requirements for the base and foundation are low, and the daily maintenance workload and maintenance costs are low. 　　　④ Smooth operation, low noise, and no need for lubricating oil. Since there are no rolling bearings or motor fans, lubricating oil is not required, and the noise level is low. ⑤ Wide range of applications. It can meet the requirements for various working conditions such as high temperature, high pressure, low temperature, and high melting point. Disadvantages of Shielded Pumps 　　　① Due to the use of sliding bearings and lubrication with the medium being pumped, shielded pumps are not suitable for conveying media with poor lubricity. Generally, the viscosity of the medium suitable for shielded pumps is 0.1-20mPa·s. 　　　② The efficiency of shielded pumps is usually lower than that of single-end mechanical seal centrifugal pumps, but roughly comparable to that of double-end mechanical seal centrifugal pumps. 　　　③ Long-term operation at low flow rates can reduce the efficiency of shielded pumps, leading to heating, evaporation of the liquid, and causing the pump to run dry, thereby damaging the sliding bearings.