SDG – Technologies


The mine’s Compressor no 8, a 15 MW compressor, was flagged as the mine’s worst performing asset. The compressor had a history of frequent breakdowns, including gearbox and motor failures, resulting in high repair and maintenance costs. 


A new high turndown LRS with stainless electrodes and a MillSafeStart Condition Monitoring, Protection and Control system were installed and commissioned in December 2018. The dipper movement were controlled with a VSD. The new LRS electrolyte mixture was made with purified(RO)  water and  tuned to minimize the damaging starting torque spikes.


  1. The airgap torque spike measured when the shorting contactor closes reduced from 161% prior to installation, to 52% after installation of the LRS. Similarly, the equivalent shock load spike came down from 226% to 64%, which is a significant improvement and well within the allowable design limits. 
  2. The TDR increased from 17:1 which was measured in March 2018 to 72:1.
  3. The improved starter performance enables a wider temperature range for safe start-up – between 22°C and 47°C.
  4. Improved start-up torque control  and less boiling at the end of the start-up cycle
  5. The LRS start-up performance is also monitored during each start-up which enable timeous problem identification before it results in costly breakdowns and repairs. .
  6. The mines appointed project manager Alan Northcote commented. “The No 8 compressor was the mines worst performing asset and is now the best performing asset’. 

Torque graphs before and after:

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LRS & Safe Start Documents

Datasheet for Advanced LRS
Advanced LRS Protection Overview
Testing of an LRS on a grinding mill – Typical Results
Safer Starting – Engineering Background
LRS Maintenance Manual
Datasheet for Cooler
List of installations