How To Repair And Replace The Worn Parts Of Sanitary Centrifugal Pumps

Sanitary Centrifugal Pump Parts wear diagnosis and repair and replacement

(1) Repair after gear wear
The wear parts of the gear are mainly the meshing of the teeth, the involute working surface and the planes at both ends of the gear. When the wear is slight, the tooth surface can be repaired with an oil stone, and the two ends can be flat and polished on a flat plate. When the gear tooth surface is severely worn, a new gear should be replaced. If only the two ends of the gear are worn, it can be ground and polished on a surface grinder. After the replacement gear is surveyed, its module m=3, number of teeth z=12, tooth angle α=20°, tooth top height coefficient f0=1, tooth positive displacement coefficient x1=x2=0.5, the geometric dimensions of each part are calculated as follows.
Pitch circle diameter: d=mz=3x12=36(mm)
Tooth top height: ha=m(f0+x)=3x(l+0.5)=4.5(mm)
Tooth root height: hf[=m(f0+c-x)=3x(l+0.25-0.5)=2.25(mm)
Tooth total height: h=ha+hf=4.5+2.25=6.75(mm)
Tooth top circle diameter: da=d+2ha=36+2x4.5=45(mm)
Fixed chord tooth thickness: sxn=m(π/2*cos2a+xsin2a)=3x(1.387+0.6428x0.5)=5.125(mm)
Tooth height for measuring fixed chordal tooth thickness: hxn=m(π/8*sin2a+xsin2a)=3x(0.7476x0.117x0.5)=2.42(mm)
Module m3 displacement coefficient x0.5
Tooth profile angle o20°Fixed chordal tooth thickness sxn5.12
Tooth top height coefficient f1Fixed chordal tooth thickness measurement of maximum tooth height hxn2.42
Tooth number z12

(2) Repair after shaft wear
The wear of the shaft in the sanitary centrifugal pump is mainly due to the friction wear between the two ends of the shaft and the supporting needle rollers, which reduces the shaft diameter. If it is a slight wear, the diameter of the shaft at this part can be increased by plating a layer of hard chrome to repair the shaft. If the shaft is seriously worn, it should be remade with 45 steel or 40cr steel. After rough and fine turning of the shaft blank, the bearing part should be heat treated to a hardness of hrc60-65, and then ground to make the surface roughness ra of the bearing mating part not greater than 0.32μm; the roundness and cylindricity tolerance of the shaft is 0.005mm; the surface roughness ra of the gear mating part should be h7/h6 and not greater than 0.63μm.

(3) Maintenance after pump body wear
The inner surface wear of the pump body is mainly the arc-shaped working surface of the oil suction section. If there is slight wear, it can be used after grinding and deburring with an oilstone. The pump body is formed by cast iron casting blanks. When there is severe wear, new parts should be replaced. If the two end faces of the gear inside the pump are repaired by grinding, the width of the pump body should also be changed to be equal to the size removed by grinding at both ends of the gear. The two end faces of the reprocessed pump body should meet the technical requirements.

(4) Repair after wear of the two end covers
The end covers of sanitary centrifugal pumps are made of cast iron. If they are slightly worn, they can be ground and smoothed on a flat plate. If they are seriously worn, they should be ground and smoothed on a surface grinder. The contact between the end cover and the pump body after grinding should not be less than 85%. The flatness tolerance, the verticality tolerance of the end face to the center line of the hole, the parallelism tolerance of the two end faces and the parallelism tolerance of the center lines of the two shaft holes are all 0.01 mm. The surface roughness ra after grinding should not be greater than 1.25 μm.

(5) Repair and replacement of needle roller bearings for pumps
After the parts in the pump are repaired, the bearing needle rollers should be replaced. The requirements for needle rollers are: the dimensional error of the diameter of all needle rollers should not exceed 0.003 mm, the length tolerance is 0.1 mm, and the clearance with the shaft should be around 0.01 mm; when assembling the needle rollers, they should fill the bearing shell according to the quantity requirements, and the needle rollers should be arranged parallel to each other.