Masbate Gold Project reduces downtime through mill head replacement

Mill head design causing excessive downtime 

The Masbate Gold Project’s operations are comprised of a large conventional open-pit mine feeding ore to a process plant consisting of crushing, grinding and a carbon-in-leach (CIL) process step. Crushing is performed in a single stage using a jaw crusher. The grinding circuit consists of a SAG mill and two parallel ball mills, each in a closed circuit with hydrocyclones.

In 2015, the mine began having issues with bolt breakage on one of their ball mill heads. The breakage originated from the Trunnion to Head connection and worsened with time. Masbate enlisted several engineering firms to provide advice on the breakage issue, however they were unable to resolve the problem due to the specific design of the mill head. With bolts at the Trunnion to Head connection continually breaking and resulting in unwanted downtime and lost production, the mine decided to act by replacing the mill head rather than continue to suffer downtime on the mill.

Results: Higher availability and less service stoppages

In May of 2016, Metso was awarded the contract to manufacture the replacement head, this time with an integral trunnion to replace the bolted joint. The service contract was then later won by Metso’s Surabaya, Indonesia Field Services department. When it came time to install the new Mill Head, Metso Surabaya sent two service engineers and lead mechanical fitters to the site to work in conjunction with Masbate’s own mechanical fitters. They were responsible for carrying out the installation and commissioning.

The Metso team provided specialized skills and worked alongside the Masbate maintenance team to complete the head change out project on schedule, within budget and without safety incidents. The combined effort minimized lost production. Since the installation, the mine has not had any issues with the newly installed head, allowing them to improve the mill’s availability by reducing unplanned service stoppages. As a result, Metso has been awarded a second identical mill head order at the mine site.

Grinding mill expertise

As an OEM supplier for grinding mills with over 3000 global installations worldwide, Metso has access to a vast amount of knowledge through its engineered services groups. With the existing head coming from a third party supplier, Metso engineers worked in conjunction with the third party’s engineering group using general arrangement drawings to reference some key information such as weights and general head characteristics for the 5.3 m x 7.8 m ball mill.  Designing the head with an integral trunnion required considerable reverse engineering of the existing parts while adhering to the strict tolerances needed to replace the existing head.

“I believe the dedication and attention to detail that we’ve shown and given has really helped cement our good working relationship” added Matt Wesson, Regional Product Manager – ETO Sales and Services for Asia Pacific. “This is reflected in one way by us being trusted to further expand on our supply of Wears and Spares on site as well as ongoing Field Services work and audit opportunities that we never had previously.”

Another key factor in ensuring that the installation went smoothly was the provision of a complete installation crew flown in from Surabaya who worked alongside the mine’s own crews throughout the installation process.

Jason Ives, Senior Maintenance Advisor summed up the experience of working with Metso on the project “The Engineering support and prompt responses Masbate Gold Project received from Metso during the entire process from assessment through to delivery was excellent.  The utilization of Metso’s Field Services team from Surabaya was also an excellent choice for the installation of the new head, the team is extremely professional with a good attitude to job completion and safety.”