JOHANNESBURG (miningweekly.com) – The world’s third-largest platinum producer Lonmin’s metal in process could increase by as much as 20 000 oz of platinum by September as a consequence of a matte run-out at its No 1 furnace earlier this month.

The company announced on June 15 that its No 1 furnace would remain closed for about a month following the incident.

An investigation had revealed that the matte run-out had been caused by a water leak in one of the lower copper cooling waffle units above one of the matte tappe blocks, the company reported on Wednesday.

This unit was being replaced and matte was expected to be tapped again within the previously announced estimate of 30 days, the company said.

The repair cost, in addition to the cost of running the three additional Pyromet furnaces, was about $4-million.

At the time of the incident, Lonmin had started up its three Pyromet furnaces to mitigate the impact of the shutdown on production.

These would remain operational until September, to assist the company in processing the majority of the concentrate inventory that was built up ahead of the smelter during the No 1 furnace shutdown, before the end of the 2009 financial year.

However, the shutdown would impact on the company’s ability to fully refine the remainder of this built-up metal in process during that period, Lonmin stated.

In February, the company said that platinum sales for the 2009 financial year were expected to be 700 000 oz.

The No 1 furnace is the largest of four at Lonmin’s Marikana operations and had given the company problems in the past.

In 2007, the miner announced that it would completely rebuild the furnace at a cost of R45-million – an exercise which would take 135 days, and 80 days longer than its initial expectations.

Lonmin also repaired the furnace during South Africa’s power crisis in the early part of 2008, followed by a one-week shutdown in June, after it detected a water leak.

The company rebuilt the furnace during the first quarter of the 2009 financial year.