B2Gold Masbate Mine increased mill uptime with unique lining design and improved throughput by 33%
At the B2Gold Masbate Mine in the Philippines, grinding efficiency is the top priority and the SAG mill is the key to achieving it. In 2017, B2Gold raised the annual production target from 6 to 8 million tons while setting out to maintain the same 2.4 complete mill relines per year. This meant that the existing Poly-Met lining had to be replaced with a lining more than capable of handling the higher wear rate.
“We knew that we needed a steel lining. But because it is so heavy, we didn’t want to use it for the whole lining. Metso then came up with a hybrid concept by combining several materials such as steel, Poly-Met, rubber and ceramics to keep the weight down because excessive weight burns and consumes your mill power for no real gain. Less weight protects your bearings and your driveline. It also allows you to get higher throughput without adding extra mill weight,” says Jason Ives, Senior Maintenance/Mill Advisor at B2Gold Masbate.
By combining different materials, the individual liner components could be positioned in high, medium and low impact grinding zones. It enabled the use of high-profile heavy-duty steel lifter bars in the high wear zones and prevented overloading trunnion bearing capacity. Metso’s capability in supplying a unique mill lining design with several materials, a well-defined optimization plan and a regular presence on site also made the choice of supplier much easier to make. In addition, by rolling all these elements into a Metso Life Cycle Services (LCS) contract, it made the decision easier for the mine to proceed with the project.
The first lining was installed in February 2019. To accommodate Metso’s heavy-duty liner in the 32’x14’ SAG mill, a Metso field services team from Indonesia was deployed to re-drill a larger liner bolt hole diameter in accordance with Metso OEM metallic liner fastening standards.
“Metso is the only one who can supply the mill lining solution we want, and they can provide engineering back up. We want the whole package – from the mill lining design, engineering team and service team, together with a competitive price – and these factors determined our choice of supplier. Others simply do not have that in depth engineering knowledge design team,” explains Jason. But technical knowledge or innovative products would amount to nothing if service quality is sub-par. “We want to be able to ask specific questions and get a quick response. They certainly do follow up very closely and respond promptly. I am very pleased.”
Exceeding the target
The mill lining in use is still the initial design, but the results have started to show.
“We thought four million tons was a lot because previously, we were lucky to get three. However, we have experienced significant improvements in wear life on most parts of the lining. Everything except the shell lining have exceeded the targets with a wear life of more than 4 million tons. That’s a distinct advantage already seen with just the first set of liners,” notes Jason.
Most parts of the lining lasted for 4.6 million tons which works out to about seven months. Data and statistics from the first set of liners were subsequently studied. This has allowed design changes and improvements to be implemented with the next set of liners to be installed in April 2020. One challenge that the team is working on is the shell plates as the first set did not meet the targets. Ultimately, the goal is to push the wear life of the shell liners up to 2.3 million tons; this way, the wear life will be balanced with the other lining, but with one additional change out.
While the performance of the shell plates so far has not been satisfactory, Jason believes that Metso’s constant communication with them makes things easier. “They have followed up regularly on the wear rate and as soon as they discovered the wear, they came up with an improvement plan. The team knows mill linings very well, and they are backed up by a great engineering team. They have been supportive, and we trust that they will solve the challenge.”
An LCS contract for mill lining - fewer stops and more profit
Mill linings are normally long transactions. The benefit of design changes will not show until the next set of liners is installed and in use. Knowing that they’re both invested in the long run as partners, Masbate Mine’s long-term LCS contract with Metso provides both parties with the opportunity to collaborate on continuous improvements and growth. As a result, Masbate Mine is looking to further solidify this relationship and Jason is optimistic about the future.
“There won’t be much difference this year but come next year, we will reach our goal. We might have the same cost as last year, but that is actually good. The goal for 2020 is 4.6 million tons for the whole lining, which means seven months in between relines. We’ll make one liner change next year and two liner changes in 2021. So, this means that every other year, we will only need to make one reline. That is great!” says Jason.
Masbate Mine focuses on cost-per-ton. One reline equates to three days of lost production, so fewer maintenance stops will have a greater impact on profitability. Savings will also be achieved both on increased uptime and a lower cost for the linings and reline crew.
With the new lining solution and LCS contract in place, the resulting additional uptime has had an immediate positive impact on Masbate’s bottom line. “Even if we must stop for other maintenance it will still be shorter, maybe 36 hours instead of 72. One less reline every year means an additional revenue of USD 0.08 per ton and when the overall business objectives are taken into consideration, our revenue has increased. It also reduces the reline cost, as we don’t need that lining and we don’t have to plan for a reline crew to come in to do the reline,” explains Jason.
Why settle for four million tonnes if we can have five?
The B2Gold Masbate Mine and Metso have a close relationship and long-term goals are set according to the LCS mill lining supply contract. As one of its deliverables, Metso scans and monitors the wear rate of the liners regularly such that the mill lining design is optimized fully to correspond with current operating conditions.
“We need to follow the wear pattern closely and truly understand the customer’s targets to be able to optimize the mill lining design. We cooperate very closely with B2Gold Masbate Mine, so these challenges push us even harder to find newer and better solutions to increase our customer’s profitability.” says Henry Carroll, Regional Product Manager at Metso.
Jason agrees: “I am always pushing for better results. From a business perspective, why should I settle for four million tons if I can have five million? The lining may have exceeded the initial target, but it shows that anything is possible. I believe in Metso; they know mill linings. And if anyone can push the target up to five million, it’s them.”