Run a Mill on a Loco Battery

It was May 2011, at a Gold Process Plant in proximity to Nelspruit and Barberton. One of the grinding SAG Ball Mills tripped on motor over-temperature. Fault finding on the Synchronous motor pointed to excitation failure, confirmed by a test of the exciter circuit.

We had a production problem - it would take more than a week to have this repaired. I found a solution and after sharing and agreement from the team, they fetched a spare 8 Ton Loco battery and charger from the mine entrance, matched copper area panel wiring, a circuit breaker, and a multi-meter. We selected the correct amount of cells to match the nameplate voltage/amps of the faulty equipment and arranged for it to be connected according to traced and marked panel wiring. It was done under my supervision with excellent team input.

In quick time the exciter was stripped off and ready for the OEM to collect. A few hours later, the Mill was started and ran like a clock with optimal excitation for the period awaiting delivery of the rewound exciter combination - actual was 5 days. The battery charger was kept connected in close proximity to the battery. Demand from the battery was only about 5 amps at 50 Volt = 250 Watt at optimal rheostat setting from the 800 Amp-Hour battery.

The moral of the story is, the manager, upon visiting remarked, "I have never seen an Engineer running a total Mill on a Loco Traction Battery"! Estimated savings, was no less than R 800 000.

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