water pump shaft sets definition and function protection pump shaft auxiliary sealing guidance and positioning transfer load hardware electromechanical

1. Definition and Function

The pump shaft sleeve is a cylindrical component that fits over the pump shaft, with the following main functions:

- Protecting the pump shaft: As a vulnerable component, the shaft sleeve takes the place of the pump shaft to bear friction and wear, reducing the risk of damage to the pump shaft and extending its service life. For example, in slurry pumps, the shaft sleeve prevents the shaft from being eroded by the slurry.

- Auxiliary Sealing: Compatible with the sealing element, preventing leakage of media within the pump, such as the shaft sleeve of a self-priming centrifugal pump working in conjunction with the sealing element to prevent liquid from leaking out.

- Guidance and Positioning: Guiding the pump shaft's rotation to ensure its accurate motion trajectory, and simultaneously determining the pump shaft's position during installation to ensure the relative position accuracy between the various components.

- Load transmission: bearing the partial force generated by the pump shaft rotation and transmitting it to the transmission system to maintain stability.

Section Two: Common Materials and Their Properties

- Metal Material

- 45 steel: After tempering treatment, it has good comprehensive mechanical properties, moderate strength and toughness, and low cost. It is often used in ordinary pumps with general wear resistance and corrosion resistance requirements.

- Stainless steel (such as 304, 316): Strong corrosion resistance, can be used in working conditions with corrosive media (such as acid and alkali solutions, seawater, etc.), 316 stainless steel has better corrosion resistance than 304, suitable for more severe corrosion environments.

- Alloy steel: By adding alloy elements (such as chromium, molybdenum, vanadium, etc.), it has high strength, high hardness, good wear resistance and heat resistance, suitable for pumps in harsh conditions such as heavy loads and high temperatures.

- Non-metallic materials

- Silicon carbide: High hardness, excellent wear resistance, strong corrosion resistance, low friction coefficient, often used in high-performance requirements such as magnetic pumps, but it is more brittle, attention should be paid to avoid external force impact.

- Polytetrafluoroethylene (PTFE): It has excellent chemical stability, corrosion resistance, a low coefficient of friction, and good self-lubrication properties, which can be used in environments with chemical corrosion and low friction requirements. However, its mechanical strength is relatively low.

Section Three: Key Points of Structural Design

- Dimensions accuracy: The inner diameter of the shaft sleeve and the outer diameter of the pump shaft are highly accurate in fit, typically with clearances or interference fits. Clearance fits are convenient for installation and disassembly, ensuring that the shaft sleeve and shaft can rotate relative to each other with flexibility. Interference fits are firmly connected, effectively transmitting torque. The outer diameter dimensions must be compatible with the related components of the pump body.

- Shape and Structure: Some shaft sleeves are equipped with positioning steps to accurately position the shaft in the pump; sealing grooves can be installed to enhance the sealing effect; some high-temperature melt gear pump shaft sleeve inner hole walls are equipped with guide grooves, and side walls are equipped with return grooves, realizing the self-lubrication cycle of the melt, reducing wear.

Fourthly, Failure Forms and Causes

- Wearing

- Lack of lubrication: If the lubricating oil is not added in time or of poor quality, it cannot form an effective lubrication film, resulting in dry friction or boundary friction between the shaft sleeve and the shaft. If the lubricant is not changed for a long time, it can lead to performance degradation and exacerbate wear.

- Media Scouring: When transporting media containing solid particles (e.g., sand grains), the particles continuously scour the surface of the shaft sleeve, causing abrasive wear. This is common in slurry pumps and sand pumping systems.

- Assembly issues: The deviation in the concentricity between the shaft and the shaft sleeve is large, leading to uneven force distribution during the rotation of the shaft sleeve and exacerbating local wear; improper installation tightening force can cause deformation of the shaft sleeve if too strong, or instability of the connection if too weak, both of which can lead to wear.

- Corrosion: When the pumping medium is corrosive (such as acidic and alkaline liquids in the chemical industry), if the material of the shaft sleeve is not sufficiently corrosion-resistant, surface corrosion will occur, which can destroy the tissue structure, reduce the strength, and promote each other with wear, accelerating the damage.


- External force impact: During transportation, when assembly or disassembly is being performed, or when a hard object is struck in a medium, the shaft sleeve is subjected to external forces that exceed its bearing limit, resulting in cracking.