Eliminate the Re-torque and Increase Mill Availability

T. Robinson, B. Widdows and J. Rosenberg

MetPlant 2019, September 9-10, Perth, Australia


Increasing mill availability is a key improvement to the productivity of most mine sites. Mills are often running at maximum capacity, consequently any downtime reduces the mine output. One of the most time- consuming maintenance processes is the mill relining exercise so Norbar Boltstress investigated ways to reduce the duration.

In 2009, the most common issues observed by the authors were un-planned shutdowns due to broken bolts. Typically, these caused 4 to 8 hours of un-planned downtime. There was an easy solution for this – ensuring the bolt tension is correct stops the bolts from breaking.

Over the next 10 years Norbar Boltstress built data records to show that not only could the failure modes be eradicated, one of the costliest processes could be removed; the re-torque. The re-torque often takes place 24 to 48 hours after the mill has been re-started following a reline. Mostly the re-torques take 4 to 8 hours, however once the grind out and re-charge of the mill is taken into consideration the lost production actually equates to 6 to 10 hours.

This poster aims to show the results of 10 years of testing and how this was applied to eliminate the re-torque.


T. Robinson, B. Widdows (1) and J. Rosenberg (2)

  1. Technical Sevices Manager, Norbar Torque Tools / Boltstress Ultrasonics Partnership
  2. Technical Services Representative, Norbar Torque Tools, Unit 2/22 Chullora Bend JANDAKOT WA, brendan.widdows@Norbar com.au
  3. Technical Services Representative, Norbar Torque Tools, Unit 4/55 Donaldson Rd ROCKLEA QLD, jeff.rosenberg@Norbar com.au


CEEC acknowledges and thanks AusIMM for organising MetPlant 2019. Proceedings can be downloaded from MetPlant 2019.