The performance of the mechanical seal of a mixed-flow pump directly determines the service life of the pump. The mechanical seal of a mixed-flow pump, also known as an end face seal, has a pair of end faces perpendicular to the rotating shaft. Under the action of fluid pressure and external mechanical elastic compensation, the end faces adhere to each other through the auxiliary seal and slide relatively, thus avoiding leakage of the fluid inside the mixed-flow pump and leakage of the fluid outside the pump.

　　One of the reasons for poor mechanical seal performance of mixed-flow pumps:

　　During trial operation, the pump was started without pre-filling the pump with water or supplying water from the outside, or the pump was operated without water during use.

　　Inspection method: Disassemble the pump for inspection. Check the damage to the mechanical seal.

　　Characteristics: Cracks in the mechanical seal rotor or stator ring, or melting marks on the rubber seal.

　　Solution: Replace the mechanical seal and cultivate correct operating methods.

　Another reason for poor mechanical seal performance of mixed-flow pumps:

　　The mechanical seal is too tight or too loose.

　　Inspection method: Disassemble the pump for inspection and investigate the damage to the mechanical seal.

　　Characteristics: Partial wear or scratches on the wear surface of the mechanical seal rotor and stator rings (only semicircular part) or some lines (circles) drawn by dirt on the two contact surfaces. Generally, when the pump starts or leaks, if it is only for debugging operation, the two contact surfaces of the rotor and stator rings may not have scratches and abrasions. Check the shaft clearance.

　　Solution: Check the rotor and stator rings of the mechanical seal. If there is no wear or scratches, readjust the equipment. If the rotor and stator rings of the mechanical seal are worn or scratched, replace the mechanical seal with a new one. Check if the sleeve length meets the requirements, or if the bellows or O-rings of the mechanical seal are too loose, too large, or do not meet the specifications. Check the cause of the large shaft clearance. If the bearing is damaged, replace the bearing; if there is an error in the relevant dimensions of the bearing cover, suspension, shaft, etc., replace the parts with incorrect dimensions.

　　So how to improve the mechanical efficiency of mixed-flow pumps?

　　1. Reduce bearing wear

　　2. Reduce packing wear

　　(1) Select appropriate packing according to the pump's purpose and working environment;

　　(2) Maintain the appropriate tightness of the packing gland.

　　3. Reduce frictional losses in the mixed-flow pump.

　　Internal loss includes:

　　Frictional loss between the water flow and the surface of the pump body and pump cover;

　　Frictional loss between the water flow and the impeller surface on both sides of the high and low pressure impellers;

　　Frictional loss between the mating surfaces of the rotating parts inside the pump.

To reduce frictional losses, for the first two items, if the surface roughness of the parts is large, they can be polished and then coated. Depending on the size of the area, epoxy resin or other easily coated and wear-resistant materials can be used for coating treatment; if the impeller surface is partially damaged due to cavitation, it should be derusted and then coated. If the area is small, it can be repaired by welding and polishing.

If you encounter other problems that cannot be easily solved during the reuse of the mixed-flow pump, please feel free to contact us.