How to repair the impeller of a Roots fan

The different problems of the journal, impeller and casing are repaired using brush plating, welding, thermal spraying and machining methods.
Measured after disassembling the bearing. Active wheel front journal 180 rear journal 180, driven wheel front journal 180 , rear journal 180, journal compound difference is too large, is the main reason for the vibration of the whole machine exceeds the standard.
Clean the oil with activation solution and clean with rust removing steel brush. Then clean with static electricity, and then use activation liquid to clean finally until the shaft warp is white. Brush plating with special pads to prevent the brush layer from falling off. Finally, brush plating is done with special fast brush plating. When brush plating, the impeller should keep rotating at the same speed to make the brush plating layer uniform.
Turning journal tolerance to 180, surface roughness 1.6
impellers
Repair by cast iron welding technique
Since the fan is used to transport synthetic raw material gas and semi-water gas, a large amount of coal tar is adhered to the impeller surface, attention must be paid to drilling small holes at both ends of the impeller to prevent the expansion of the closed gas inside the impeller from causing the impeller to crack. After 72 hours of heating, it is automatically cooled down to 20~30℃.
Impeller sealing line in the tapping M8 screw holes, are 6 M8 countersunk head bolts to increase the fusion of the welding layer and the impeller, due to long-term airflow scouring at both ends of the sealing line in addition to the form of rounded corners, welding repair for the right angle. Before welding flame heating welding parts to 150 ℃, using 308E welding rod store welding, thick 3 ~ 4mm. attention to welding, sandblasting on the protection of the spindle neck.
Remove rust by sand blasting until the surface is bright, cleanliness is up to Sa3 grade, and roughness is up to Rz25-100u m. The temperature of the working environment when sand blasting should be higher than the air temperature by more than 5℃, or the temperature of the substrate should be higher than the dew-point temperature of the atmosphere by more than 3℃.
Surface coating using arc spraying technology. The tip is melted using an electric arc generated between two wires, which can become the same or different. The molten metal droplets that have been melted are atomized by a beam of gas jet and sprayed onto the sandblasted basic surface to form a coating.
Turning impeller sealing line and end face (this process is carried out together with main journal turning).
Passed the G6.3 level of calibration of the dynamic weighing scale.