Grinding out performance when it comes to relines

When it comes to a successful reline, the efficiency of the event does not just revolve around the completion of the reline. There is a world of data analysis before, during, and after the reline that has now become the accepted common standard. Whether it’s calculating workflows and resources, execution tracking, end time forecasting, selecting the right mill liner, evaluating ideal scenarios and liner sequencing, or even planning for contingencies, putting in the time upfront aids in mitigating potential downtime and helps with optimization efforts.

Living in a digital world means everything can be analyzed if the right data has been collected. When the data is combined with the right expertise, improvement opportunities can be identified, and the most efficient course of action can be mapped out for ideal situation as well as for when unforeseen circumstances throw a bottleneck into the equation.

Ensuring safety during shutdown

Ensuring the safety of reline crews during the shutdown process has continued to be a substantial challenge for any mine site reline. Handling and maneuvering heavy parts such as new and worn liners is a constant concern to the safety of reline crew members. Removing and handling worn mill liners requires the right tooling as well as people trained to use them in the right manner. Tool management programs and inspections are vital to ensure safety. Periodic checklist inspections, ensuring the right safety accessories, proper equipment operation, having standby tooling, and standardized crew trainings should all be fundamental activities both before and during a reline event.

One often overlooked challenge with these types of activities, is the psychological safety of the reline crew. Relining can be an extremely dangerous activity, especially if the crews are new or do not have to perform a reline frequently. Unplanned stops due to safety issues or an accident can be costly for both the mine and the personnel, which is why companies often focus their attention on identifying how accidents can be either fully prevented or how their effects can be mitigated if something unforeseen were to occur. Solutions vary from having experts in designated positions and cross training with new technicians to engaging in regular safety conversations to maintain and reinforce safety. In these types of situations, where every minute counts, continuing to monitor the surrounding environment as well as evaluating the mental health of the reline crews, all help ensure personnel are sent home without running into harm.

Planning the work and working the plan

A second element to consider is preparation. Incomplete preparation is a definite challenge for many mine site relines. There are multiple activities in the planning stage of a reline that if not done properly, can lead to a lack of efficiency during the execution phase or even lead to an unplanned stop and higher downtime. Planning the scope of work is critical to define the time, resources, processes, tooling, equipment, safety gear, communication plan, and contingency plan. A mill reline can still technically succeed if any of these are missed during the execution stage, but the increased threat of safety incidents due to a lack of preparation is what must be avoided. Planning for a shutdown as well as all the associated resources often begins months before the actual shutdown and reline. With most mines today operating in remote locations and facing difficulties in retaining knowledgeable staff, finding personnel comfortable and trained to plan and perform a mill reline can be a challenge.

Choosing the right reline option

When it comes to selecting a reline crew, there are quite a range of choices. Each option offers some advantages as well disadvantages so carefully evaluating the choices is important.

In-house

In the case of an in-house reline, although certainly the cheapest and most readily accessible option, one major disadvantage is that crews may not be specialized in this type of a shutdown event. This can lead to increased downtime compared to other approaches. Typical mining operations may execute only a handful of shutdowns in a given year, so in-house crews may not be performing these activities with any kind of frequency. This can lead to inefficiencies or even injuries as crews reacquaint themselves with the process. More specialized teams who only perform shutdowns and relines may manage 20 to 40 shutdowns yearly, helping them to work more quickly and safely based on their experience.   

Local or national general contractor

Being a local or national reline team (often general contractors) carries the advantage of decreased travel time to the mine site, leading to faster emergency response time as compared to other approaches. The leading disadvantage is that local or national contractors are not specialized, due to their team being composed of mainly shutdown maintenance workers, often with only a few experienced mill reline personnel. These types of contractors typically handle many different types of projects outside of relines, and so may handle mill shutdowns and reline events only infrequently. Their lack of experience may expose the team to an increased risk of accidents or delays due to crews not being as familiar with the process and potential pitfalls as more specialized teams.

Dedicated regional or global reline company

When considering a regional or global reline team that is dedicated only to handling reline events, you can rest assured that they will arrive equipped with best practices and experience. They are reline experts who will efficiently complete the job with good quality, procedures and processes, applying their expertise. The other side of the coin is that as they are only focused on the actual reline and are being measured against KPIs dealing with the speed of the actual reline, opportunities to take additional time to inspect anomalies or issues during the reline may be overlooked or not even considered.

As these types of teams are not involved with liner selection, or the manufacture of liners and parts, they may not notice abnormal wear patterns or other signals that could be caught or flagged by reline teams with access to OEM expertise on mill structure or wear parts. Without a holistic outlook on the relining process, they may struggle to coordinate the many teams involved in the event such as inspections teams, wear part experts, service teams and routine maintenance work that needs to be conducted in parallel with the reline.

Major OEM mill and liner supplier with reline expertise

Being a major mill supplier or a liner manufacturer, opens the door to additional advantages beyond reline speed and safety. By selecting a manufacturer who plans and performs relines but also designs the liners, the site can benefit from a more effective approach. As manufacturers of mills, liners and spares thoroughly understand the liner specifications, wear patterns as well as the maintenance work that can be done while the mill is in planned shutdown mode, they can better manage the various activities needed. Being able to provide additional related services during a reline event can be a major advantage in terms of coordinating the entire process.

Often a project manager from the OEM can be involved to coordinate the planning and pre-staging before the shutdown takes place, to ensure all parts are available and placed correctly to be sure that not a minute is lost once the mill is shutdown. During the liner removal stages, certified inspectors can examine the worn liners to look for wear issues and make recommendations for the next reline event. For example, if certain lifters are showing more wear than others, it may be possible to plan ahead with a more robust or thicker liner in that region to compensate. This may allow the mill to run for a longer time in the future and stretch out the period between relines, allowing the plant to produce more before needing to replace wear parts. Service work can also be coordinated, for example to allow for the changing out of a worn seal or other part. Having all these offerings coordinated by the same supplier can eliminate miscommunication, resulting in a faster and smoother shutdown.

Time and motion studies for continuous improvement

The last advantage of involving an OEM supplier and reliner to manage the entire reline event is that they can have the tools and resources to continually improve on the overall process. One method that can have a major impact on improving the efficiency of a shutdown and relining project is the power of a SMED analysis. A single minute exchange of dies (SMED) study is a time and motion analysis tool that records the entire shutdown process in video. It captures details such as delays, critical tasks, liner sequences, tooling, wears managements, and crew skills. This allows shutdown experts to review and identify specific areas where they can improve. Identifying each and every delay, determining its cause and then looking at why it happened and how it can be avoided in the future can end up saving hours of downtime for the next reline.

Often, after a SMED has been conducted and improvement opportunities identified, a new shutdown plan is developed with a revised timeline target aimed at further reducing downtime. Bundling an entire reline project under a long-term service agreement such as Metso’s Life Cycle Services can also bring further benefits. Usually signed for three to five years, clauses can be built into the contract to ensure continuous improvement for the time taken to reline with a bonus for succeeding and penalties for not meeting the agreed shutdown and reline times.

Bringing everything together

Reline events can seem like straightforward projects but in fact involve safety, planning considerations, the choice of reliner as well as looking at whether it makes sense to partner with a supplier with a longer-term service agreement and aim for continuous reline improvement. Tools such as time and motion analysis as well as looking at solutions to get more wear life from current liners through design changes, or even operational changes, can all be important factors when optimizing a concentrator plant’s overall grinding performance.