The function of the hole in the pump shaft of a shielded pump

The function of medium cooling and flushing the bearings.

The shaft should be cooled.

The main reason is medium cooling. The working principle and characteristics of shielded pumps: With the development of the chemical industry and an increasing awareness of environmental and safety issues, the requirements for pumps used in the chemical sector are also rising. In some applications, there is a demand for pumps that are completely leak-free, and this requirement has contributed to the advancement of shielded pump technology. Due to the lack of a shaft seal, shielded pumps can achieve complete leaklessness, which has led to their increasing use in chemical processing plants. A shielded pump combines the pump and the motor together; the rotor of the motor and the impeller of the pump are mounted on the same shaft. A shielding sleeve is used to separate the rotor from the stator of the motor. The rotor rotates within the medium being transported, with power being transmitted to it through the magnetic field of the stator. Furthermore, the manufacturing of shielded pumps is not complex; their hydraulic sections can be designed and manufactured according to the structural types commonly used in centrifugal pumps as well as relevant standard specifications. 1 Advantages and disadvantages of canned pumps 1.1 Advantages of canned pumps (1) Fully enclosed. There are no dynamic seals in the structure; only static seals are present at the pump’s casing, which enables complete leak prevention. This makes it particularly suitable for transporting flammable, explosive, valuable liquids, as well as toxic, corrosive, and radioactive liquids. (2) High safety. Both the rotor and the stator are equipped with shielding sleeves to prevent them from coming into contact with the material; even if these shielding sleeves are damaged, there is no risk of external leakage. (3) Compact structure with low floor area. The pump and motor are integrated; no centering is required for disassembly or assembly. It has low requirements for the base and foundation, requires little routine maintenance, and results in low maintenance costs. (4) It operates smoothly, with low noise, and requires no lubricant. Since there are no rolling bearings or motor fans, no lubricant is required, and it produces low noise. (5) Wide range of applications. It can meet the requirements for various operating conditions such as high temperature, high pressure, low temperature, and high melting point. 1.2 Disadvantages of shielded pumps (1) Since shielded pumps use sliding bearings and are lubricated by the medium being transported, media with poor lubricity are not suitable for transportation using shielded pumps. Generally, the viscosity suitable for the medium in shielded pumps is 0.1 to 20 mPa·s. (2) The efficiency of shielded pumps is usually lower than that of centrifugal pumps with single-end mechanical seals, but it is roughly comparable to that of centrifugal pumps with double-end mechanical seals. (3) Operating for long periods at low flow rates results in lower efficiency of the shielded pump, which leads to heating and vaporization of the liquid, causing the pump to run dry and thus damaging the sliding bearings. 2 Types and application ranges of canned pumps Based on factors such as the temperature, pressure, viscosity of the liquid being transported, and the presence of particles, canned pumps can be classified into the following types: (1) Basic type: The temperature of the medium being transported does not exceed 120°C, and the head does not exceed 150 m. All other types of shielded pumps can be obtained by modifying and improving the basic model. (2) Reverse circulation type: In this type of shielded pump, the flow direction of the liquid used for bearing lubrication, cooling, and motor cooling is exactly the opposite of that in the basic type. Its main feature is that it is less prone to cavitation, making it particularly suitable for transporting liquids that are easy to vaporize, such as liquefied petroleum gas and chloromethane. (3) High-temperature type: The maximum temperature of the medium being transported is generally 350°C, the maximum flow rate is 300 m3/h, and the maximum head is 115 m. It is suitable for high-temperature liquids such as heat transfer oils and hot water. (4) High-melting-point type: The pump and motor are equipped with jackets, which significantly improves the heat resistance of the motor. Suitable for high-melting-point liquids, with a maximum temperature of up to 250°C. Steam or a liquid at a certain temperature can be introduced into the jacket to prevent crystallization of liquids with high melting points. (5) High-pressure type: The casing of a high-pressure type shielded pump is a high-pressure vessel, enabling the pump to withstand very high system pressures. To support the shield sleeve under internal high pressure, the stator coils can be used to bear the pressure. (6) Self-priming type: When the suction pipe is not filled with liquid, the pump expels fluid through automatic vacuum creation, making it suitable for drawing liquid from underground containers. (7) Multi-stage type: Equipped with multiple impellers, suitable for high-head fluid transfer, with a maximum head of up to 400 m. (8) Slurry type: Suitable for transporting liquids mixed with a large amount of slurry. 3 Points to consider when selecting a canned pump. In summary, the use of canned pumps ensures complete leakage prevention, effectively avoiding environmental pollution and material loss. As long as the right model is selected and the operating conditions remain stable, there is little need for maintenance during normal operation. Shielded pumps are the ideal choice for transporting flammable, explosive, corrosive, and valuable liquids

Shielded pumps are self-lubricating; the purpose of the holes is to allow the medium being transported to enter the bearings for lubrication. They also serve a cooling function, but their primary role is still lubrication

Some of Haimi’s pump models feature a hollow shaft, which is mainly used in applications involving easily vaporizable media, presumably to enhance pressure through the auxiliary impeller

Its function is to provide lubrication and cooling. The hollow shaft serves as a circulation loop, allowing the fluid inside the pump to circulate, carry away heat, and provide effective lubrication.

This is a type of canned pump, of the internal shaft circulation type, and it is designed for preventing fluid leakage

Its purpose is to guide the medium to the low-pressure area.

Shielded pumps can generally be classified into: basic type, reverse circulation type, high-temperature type, slurry type, etc. Their flushing methods are different. The so-called flushing refers to the lubrication and cooling of graphite bearings using their own medium. Loop! ! !