What are the differences between canned motor pumps, magnetic pumps and centrifugal pumps?

Pumps, as common dynamic equipment in industrial production, are now being used in increasingly demanding scenarios. Due to the absence of a shaft seal, the canned motor pump can achieve no leakage, and thus its use in chemical plants is becoming increasingly common. Some people ask, then in what aspects do canned motor pumps, magnetic pumps and centrifugal pumps differ? In this issue, we will focus on this for everyone.

The sealed or leak-free structure of the canned motor pump makes it suitable for pumping flammable, valuable, corrosive and toxic liquids. Because the canned motor pump is non-leaking, it is helpful for flammable liquid systems. It has more prominent economic benefits for precious and corrosive liquids.

The differences of canned motor pumps

1. The motor and water pump are integrated in structure, and the water pump and the motor are coaxially connected.

2. The inner side of the stator and the outer side of the rotor of the motor are equipped with shielding sleeves, and the inner side of the shielding sleeve is connected to the pump.

3. The installation methods are divided into horizontal and vertical types

4. The motor has eliminated the cooling fan. The motor is cooled by the circulating medium between the stator and rotor, and the surface of the motor frame is cooled at the same time.

The advantages of canned motor pumps

Fully enclosed. There is no dynamic seal in the structure, only a static seal at the pump casing. Therefore, it can achieve no leakage and is particularly suitable for transporting flammable, explosive, precious liquids, as well as toxic, corrosive and radioactive liquids.

2. Each of the rotor and stator is equipped with a shielding sleeve to prevent the motor rotor and stator from coming into contact with the material. Even if the shielding sleeve breaks, there will be no risk of external leakage.

3. Compact structure and small floor space. The pump and the motor are integrated as a whole, and there is no need to align the center during disassembly and assembly. It has low requirements for the base and foundation, and requires less daily maintenance work and low maintenance costs.

4. It operates smoothly with low noise and does not require lubricating oil. As there are no rolling bearings or motor fans, no lubricating oil needs to be added and the noise is low.

5. Wide range of applications. It can meet the requirements of various working conditions such as high temperature, high pressure, low temperature and high melting point.

The disadvantages of canned motor pumps

1. As the canned motor pump uses sliding bearings and is lubricated by the medium being conveyed, media with poor lubricity are not suitable for transportation by the canned motor pump. Generally, the viscosity of the medium suitable for canned motor pumps is 0.1 to 20 MPa.s.

2. The efficiency of canned motor pumps is usually lower than that of single-end face mechanical seal centrifugal pumps, but roughly equivalent to that of double-end face mechanical seal centrifugal pumps.

3. If the canned motor pump operates for a long time at a low flow rate, its efficiency will be relatively low, which can lead to heat generation, evaporation of the liquid, and dry running of the pump, thereby damaging the sliding bearings.

Application scenarios of canned motor pumps

1. In situations where the pressure conditions are abnormal. When the pressure on the suction side of the pump is relatively high and the difference between the pressure on the discharge side is relatively small, if a stuffing box is used, it will be subjected to additional stress.

2. Situations where a high degree of vacuum needs to be maintained. If a stuffing box is used, when the shaft is slightly eccentric or worn, air will enter through the stuffing box.

3. In situations where vacuum and pressure operations alternate. Stuffing boxes or sealing structures used for ordinary vacuum operation cannot be used for operation under pressure.

4. Situations where valuable liquids are handled. The liquid has caused considerable economic losses.

5. Situations where toxic liquids are handled. And the threat to life. If a stuffing box is adopted, a considerable amount of valuable substances will be lost each year due to leakage. If a stuffing box is used, the leakage of toxic liquids will cause harm to human health.

6. In situations where explosive gases occur. Although flammable liquids such as gasoline, kerosene and jet fuel can be transported by a centrifugal pump with a rotary seal connected to an explosion-proof motor, leaked liquids and liquids that have turned into vapor will make the entire site an explosive hazard.

7. In situations where radioactive liquids are handled. Radioactive liquids are not allowed to leak from the stuffing box. In addition, the materials of many fillers cannot be in long-term contact with radioactive liquids.

8. In situations where corrosive liquids are handled. In addition to local corrosion caused by the leakage of the stuffing box, the process flow equipment may also be eroded by the vapor generated from the leakage of corrosive liquids.

9. Situations where hazardous liquids are handled. When harmful gases such as foul odors are produced due to the leakage of the stuffing box, it will lead to a bad situation where operation cannot be carried out.

10. In situations where liquids are prone to reaction. If a canned motor pump is used, the liquid will not solidify due to contamination by air, moisture, packing, lubricants or other substances, nor will it crystallize or cause other hazards.