100% agree with Dale. If your installation practices are solid (torque specs, re-torque after 24 hrs operation, etc), you shouldn't be seeing breakages.
One question - are they liner bolts, or shell bolts?
Load monitoring fasteners can also be useful to help diagnose your issue if you're not having luck with existing visual inspections. There are a few different companies that make load monitoring fastener products. Some I'm familiar with are smart bolts, which are just a visual indicator of tension, and Copper State's LMF+ which is a Bluetooth solution. You'd probably only need a few around the circumference of the discharge end to work out if you've got issues with loosening.
You could also consider making sure you're tensioning the bolts properly using ultrasonic bolt tensioning. Just as a sanity check, I wouldn't do every bolt on every mill reline. I would strongly recommend this if you're replacing girth gear or shell fasteners, however.
Finally, it's unlikely to be your issue, but I have seen a batch of poor-quality fasteners lead to bolt breakages. Might be worth considering if you've ruled out all of the other potential root causes above.
Cheers,
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Ben Prior, MBA, BEng, CMRP
Project Manager
Core Asset Co
Brisbane, QLD, Australia
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Original Message:
Sent: 06-26-2024 08:00 AM
From: Dale Nicholson
Subject: Mill Bolts
The first step is to determine the failure mode. If they are fatigue failures, my approach would be much different than if they are overload failures. In the former case I would focus on installation practices and possibly implement a periodic visual check for loosening (using match-marks to make this possible), while in the latter case I would investigate design and operating parameters first.
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Dale Nicholson, PE, CMRP, CRL
Reliability Engineering Mgr
Evonik Corp
Original Message:
Sent: 06-25-2024 02:54 PM
From: Lesiba Moja
Subject: Mill Bolts
Greeting Reliability Professionals
How are you guys managing bolt breakages on your mills. Particularly on the Discharge end?
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Lesiba Moja
Reliability Coordinator
First Quantum Minerals
Solwezi WA
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