Australian Mining speaks to comminution expert, Peter Erlynne, about how plant operators can get the best run from their crushers and avoid unnecessary downtime.
Peter Erlynne, a comminution consultant with Weir Minerals, has over 40 years of experience in comminution, both in Australia and internationally.
He says one of the challenges that all mineral processing operations face when trying to optimise the efficiency of their crushers is the question of who controls the crusher: production or maintenance?
“The answer is almost always production,” he says. “That’s because throughput pays the bills.”
But it’s not always easy to get the balance right between having production dictate the operation and practicing good maintenance.
Erlynne says processing plants need to have the right strategy in place and know the implications of their equipment not being operational.
A successful maintenance strategy starts by measuring the equipment availability.
“Measuring the machines’ availability will tell you whether your maintenance and operational practices are appropriate for your machines,” Erlynne says.
“If you are measuring the availability of a single piece of equipment, such as a crusher, you should be targeting a figure that sees the machine operating at least 95 per cent of the time.
“If you measure that and it’s less than 95 per cent, there are operational practices that could be improved.”
The next step is to check the feed stream of material to the plant to make sure the crusher is being fed correctly.
“Is your plant feeding the crusher correctly? Is the material presented to the crusher appropriately, so it does not all fall on one side of the machine? Are there oversized rocks that block the feed to the machine?” Erlynne asks.
“All of those things need to be looked at in order to analyse the feed stream and feed direction.
“In addition to that, have a look at the discharge area and the downstream equipment – is the discharge area always clear? Discharge conveyors and hoppers form part of the system, and when you’re measuring availability, you need to know downstream equipment is all online too.”
After measuring availability and feed, it comes down to regular maintenance to avoid the risk of unnecessary downtime.
“Many plants have a crusher or a crushing system with a part/equipment that is difficult to access, and difficult to access areas are generally those that are neglected during regular maintenance,” he says.
“Make sure that access to the equipment is easy and safe, and that there are enough access platforms.
“As an example, Weir Minerals’ Trio TP crushers make a point of easy access to all parts inside the machine that requires maintenance.”
According to Erlynne, using maintenance checklists is the best way of ensuring that the maintenance routine is embedded into the plants’ work practices.
“You want to make sure that you‘ve got something to measure your maintenance by. For example, did you look at the feed plate on your last shutdown? Do you have enough spares?” he says.
Weir Minerals provides ready-to-use maintenance checklists in manuals for their Trio range of crushers.
Erlynne says having a maintenance manual might seem like a basic thing, but having a manual available to the maintenance team can avoid bad practices.
“Manuals and checklists remain important on a plant, particularly for machines that have been in operation for years; where the original people trained to use and maintain these machines have moved on, very likely without passing on the knowledge to the new team,” he continues.
And finally, Erlynne suggests to make sure there’s an appropriate stock level of wear and replacement parts available on the site.
“Take into consideration the supplier’s lead time when planning the appropriate levels of spares stock and do not buy wear parts from unreliable suppliers,” he says.
“Replicated parts can look like genuine parts, but you can never know if they were manufactured appropriately for the operation of your machine.
“Replicators often make small modifications to spare parts, which can adversely affect other parts of the machine. So get the right parts, get them at the right time and know that they were designed for that machine.”
When requested by a customer, specialists from Weir Minerals can carry out site surveys to offer solutions for machine optimisation.
Erlynne says if the efficiency of an existing crusher can be increased by even 1 per cent, a site is effectively increasing its output by 1 per cent for free, every hour of every day, 365 days a year.
“When our team surveys a site, we spend a couple of days there and observe the machine, and then we can report back and suggest the areas that should be looked at,” Erlynne says.
To demonstrate how well-maintained crushers can improve the overall efficiency of the comminution process, Erlynne uses an example from Westgold Resources’ Bluebird mine site in Western Australia.
“The customer had concerns regarding production restrictions caused by pebble loads in their mill circuit. Pebble crushing is considered one of the most demanding crushing applications as the pebbles are very hard and the system generally has a high percentage of tramp metal,” says Erlynne.
“To take the pebble load off the mill, a Trio TC51 cone crusher was installed in the mill circuit. This was complemented by a support structure, including isolation frame, drive motor, ancillary lubrication and hydraulic systems and control system.
“With the new arrangement, the pebble load on the mill was decreased, thus increasing plant production. The return on investment for the Bluebird site was realised in only 35 days from the date of commissioning and increased production by 20-30 tonnes per hour.”
There’s no limit to what you can do to get better performance from your crushers, Erlynne says.
“There’s always room for improvement. If you’ve got 95 per cent availability, why wouldn’t you have 96 per cent?” he concludes.
This article also appears in the May edition of Australian Mining.