Instructions on the centrifugal pump mouth ring

     The function of the centrifugal pump mouth ring is to form a narrow and tortuous channel between the impeller and the pump casing to increase the flow resistance of the medium and reduce the leakage of the medium. The setting of the centrifugal pump mouth ring also plays a role in protecting the main parts on the pump from wear. After the mouth ring is worn, it can be repaired or replaced with a new ring to restore the normal assembly clearance, which is economical and easy to repair.

    The structural forms of the centrifugal pump port ring usually include radial clearance ring type, double ring stepped type, double ring labyrinth type and axial clearance type. The integrity of the centrifugal pump mouth ring and the radial clearance between it and the impeller should be checked first when disassembling the pump. If the centrifugal pump port ring has grooves and other defects or is broken or the gap exceeds the specified value, the new port ring should be replaced or the original port ring should be repaired by welding.

    During the operation of the centrifugal pump, the corresponding circumference of the centrifugal pump port ring and the impeller are worn at the same time, which causes the gap to increase beyond the specified value, because the inner diameter of the new port ring should be prepared according to the outer diameter of the impeller inlet, and the gap between the impeller and the centrifugal pump port ring the provisions of the radial clearance. In the repair process, this gap should be made smaller in order to improve the working efficiency of the pump and prolong the service life.

    The material of the mouth ring can generally be made of gray cast iron HT200, tin bronze or tin bronze-bearing alloy (Babbitt). For the copper ring with bearing alloy hanging, when the gap is too large, it is only necessary to re-hang the alloy, and the new ring needs to be replaced.

    When the original alloy wear is not large and there is no peeling or falling off, it can be repaired by repair welding. Repair welding steps are as follows:

    ① Wash and activate it with 5% hydrochloric acid.

    ②Put it into the caustic soda solution with a temperature of 90°C and a mass fraction of 10% for 10 minutes, and then put it into clean water at 90°C for cleaning.

    ③ Repair welding alloy. Preheat the mouth ring to about 100°C, properly melt the original alloy on the mouth ring with gas welding, pre-cast the welding rod with the same grade of alloy as the original alloy, and evenly surfacing along the circumference or longitudinal direction of the centrifugal pump mouth ring ( Do not re-solder repeatedly). After welding, it can be machined to the required standard size.

    If the alloy peels off, falls off or wears too much to be repaired by repair welding, the alloy should be re-cast.

    After the new mouth ring is installed, it should be checked whether the clearance between it and the impeller meets the requirements of Table 1. At the same time, it is necessary to check whether there is friction between the two. The method is to coat the rotor with red lead powder, and then turn the rotor. If the mouth ring is stained with red lead powder, it must be repaired.