Problem

• One of NMTG’s reputed customers of India has faced an issue of Pinion-Shaft Assembly failure. After doing RCA (Root cause Analysis) by Maintenance Engineer & Service Engineer of NMTG in combined efforts, It was found that Pinion-Shaft Assembly was having Face Run-out & OD Run-out more than 300 µm after Installing Locking Assembly.
• Because of uneven Tightening/ Tightening with Allen key/ Tightening with Un-calibrated Torque wrench cause higher assembly run-out which should be reduced.

Solution

By jointly analyzing RCA, NMTG Service Engineer has immediately removed Previously Installed Locking Assembly & Started Installing it as per the guidelines followed as below.

• Shaft & Pinion bore should be cleaned properly (no dust particles).
• Applied Light coat oil into Pinion bore & onto Shaft where Locking Assembly is installed.
• Insert Locking Assembly into Pinion-Shaft Assembly & then Hand tightened all screws in diametric opposite sequence only.
• The full Tightening Torque has been divided by NMTG Service Engineer in seven numbers of passes.
• In first pass, Tightening was done in diametric opposite sequence by 1/7 revolution with help of Torque wrench & then checked Face run-out & OD run-out.
• Similarly this step was repeated until Full Tightening Torque is achieved by checking & maintaining Face & OD Run-out at each steps.
• Finally after Installation, less than 100 µm Run-out is achieved in Face & OD.

Conclusion

• By following proper Tightening & Installation procedure mentioned in NMTG Installation & Maintenance manual, proper Installation & Desired output can be achieved without failure.
• Always Use Calibrated Torque wrench for Tightening of Screws.
• Use of Allen key for Tightening is strictly prohibited.

NMTG is not only product manufacturer but also Solution provider