In industrial fields such as chemical engineering, pharmaceuticals, and environmental protection, solid particles contained in the medium are important factors affecting the stable operation of pump equipment. As a core equipment with leak-free sealing, the adaptability of shielded pumps to medium particles is directly related to system operation efficiency and equipment service life. This article will elaborate on the adaptation principle, selection points, and usage suggestions of shielded pumps and medium particles, providing professional references for industrial users.

I. Tolerance Mechanism of Shielded Pumps to Medium Particles

Shielded pumps adopt an integrated design of motor and pump body, isolating the motor rotor from the medium through a shield sleeve to achieve shaft seal-free sealing. Their ability to withstand medium particles mainly depends on two core components:

1. Bearing System: Shielded pumps mostly use sliding bearings （such as graphite-silicon carbide materials）with a bearing clearance usually between 0.1-0.3mm. When there are particles in the medium, excessively large particles will enter the bearing clearance, causing wear, jamming, or even bearing failure;

2. Impeller and Flow Channel: Particles will erode and wear the impeller blades, and may deposit in the flow channel, leading to reduced flow rate and increased energy consumption.

Generally, the particle size of the medium suitable for shielded pumps should be less than 1/2 of the bearing clearance, and the particle hardness should be lower than that of the impeller and bearing materials. For example, conventional shielded pumps can withstand soft particles with a particle size ≤0.1mm （such as resin particles）. For particles with a particle size of 0.2mm or more, special design is required to improve the equipment's tolerance.

II. Key Selection Criteria for Shielded Pumps When Medium Contains Particles

1. Clarify Particle Parameters: It is necessary to confirm the three key indicators of the particles in the medium in advance: particle size distribution, hardness, and concentration to provide a basis for selection. For example, for the 0.2mm particle size mentioned by the customer, a special shielded pump with a larger bearing clearance （0.3-0.5mm） or wear-resistant materials （such as silicon nitride bearings, duplex stainless steel impellers）should be selected;

2. Choose Special Design Models: For media containing particles, manufacturers usually provide “wear-resistant” or “special for particle-containing media” shielded pumps. Their optimized designs include: widened bearing clearance, wear-resistant coatings, reinforced impeller structure, additional filtering devices, etc.;

3. Support Auxiliary Systems: When the particle concentration is high or the particle size is close to the tolerance limit, a prefilter （filtration accuracy ≤0.1mm） or a clean mother liquor injection system (injecting clean mother liquor into the bearing cavity through a dosing pump to form a 'liquid film protection' to isolate particles from entering the bearing) can be equipped to further improve equipment stability.

III. Usage and Maintenance Suggestions

1. Regularly clean the prefilter to avoid insufficient medium supply caused by filter element blockage;

2. Monitor pump operation parameters （such as vibration, temperature, flow rate）. If abnormal fluctuations occur, promptly check whether they are caused by particle deposition or bearing wear;

3. Regularly replace lubricating oil （for oil-lubricated shielded pumps）or clean the bearing cavity （for self-lubricated shielded pumps） to reduce particle wear on the bearings;

4. Avoid sudden changes in medium temperature to prevent particle condensation and deposition in the flow channel.