Centirfugal pump overhauling .centrifugal pump wear ring purpose, how wearing is attached, clearance measurement

Overhauling imp points: 
punch matching marks(parsies marks). Drain properly b4 opening pump. Renew gaskets and gland packing.
Checks 
1 check for corrosion, pitting and cavitation(repair using devcon or metal putty)
 2.check for thrust and shaft bearings for damages
3.check wear ring clearances with feeler gauges or vernier.
4. check shaft sleeve for wear.

5 check trueness of shaft by centering it on a lathe or rolling on ground
6 tight impeller on to the shaft with specified torque.
7. check shaft for scoring and damages and can be corrected by welding and turning in a lathe.
8.check for radial clearances, if the impeller is touching the casing marks will be there, slack bearings may be the reason
9. check gland packing location of shaft for wear excessive wear new packing sleeves to be fitted.
10. check for the working of latern ring and clean it.
11. examine the blades of impeller for wear or thinning down. 
Imp checks before starting- turn the shaft with hand, properly prime and do inching and then start and check amperage of the motor.