While well-maintained mining equipment is key for reliable operations, maintenance work itself is prone to risk. The nature and scale of mining systems by default enhances the presence of various commonly-known critical risks, eg, falling from height, handling/lifting, confined spaces, entanglement, stored energy or electricity during operations and maintenance.
Often however, solutions based on ongoing lessons learned serve as a ‘patchwork’ in the absence of those engineered from the outset. These ‘patchworks’ often result in significant inefficiencies and/or expenses in order to ensure safety along with the required maintenance. This has shaped a mindset that safety and efficiency are inherently in conflict with one other.
Absorbing costs
This traditional way of thinking had us all believe that an increased demand for safety leads to more complicated and time-consuming maintenance work; a cost that the industry finds increasingly difficult to absorb in these capital constrained and challenging economic times.
But is this really so? Does increased safety necessarily come at the expense of maintenance efficiency and is there not an approach that can achieve both objectives?
Right from the outset
The Takraf Group’s holistic and intelligent design approach, right from the outset of a project, takes cognizance of these traditional patchworks, transforming them into innovative solutions. While compromises may be the only option in the field, even during the design process, the cost and schedule impact of late design changes can result in a safe but inefficient patchwork.
This well-documented exponential curve, commonly referred to as the ‘cost of change’, directly translates into an imperative to support the early introduction of safe maintenance concepts even before project execution.
At the expense of the other
Leveraging its project and industry experience garnered over many years, the Group has developed numerous innovative solutions with the ambition of combining both safety and efficiency, where neither is achieved at the expense of the other. Furthermore, not only are products designed with a high level of configurability to enable the development of a solution tailored to plant requirements, but also with considerable maintenance flexibility to adapt the best concepts appropriate for each individual application.
Takraf’s In Pit Crushing & Conveying (IPCC) portfolio comprises fully-mobile, semi-mobile and fixed in-pit crushing stations, which can incorporate a variety of crushing solution types (ie, gyratory, cone, jaw, sizer), including the company’s proprietary range of sizer equipment. These crushing solutions are connected to a network of conveyors and spreaders (for waste) or stackers (for ore). For such equipment, a selection of four areas where Takraf can contribute most to maximizing both safety and efficiency of the maintenance of an operation is presented below.
Focus 1 – Avoid maintenance in the field
While maintenance in the field is the most established approach, this by default introduces various risks and inefficiencies. Field maintenance safety is often linked to long-term isolation of equipment, tight and limited ergonomic workspace, dusty/dirty environments, time pressure to continue operation, and exposure to weather conditions including temperature, rain and wind. While those conditions by themselves cause risks, their combination may entice individuals to opt for even riskier shortcuts.
Part of the Group’s solution is achieved by designing equipment for replacement of large maintenance modules as a whole, rather than individual components only. In combination with spare modules, this approach is unparalleled with regard to efficiency.
One common area for such a change is chutes. Chutes can be designed as being either modular or rotable. Modular chutes can generally be dismantled as a whole, while rotable chutes provide an additional engineered device for that purpose. Maintenance of chutes on the ground increases efficiency and mitigates various risks resulting from height, enclosed space and lifting activities.
Example 1 – Sizer hot-change: The hot-change arrangement can typically be provided for primary crushing applications, with primary sizers featuring travel sets for a safe, fast and efficient hot swap between an operational machine and a spare sizer on the same platform.
Example 2 – Checker type: Further expanding upon the hot-change concept, a checker-type arrangement can be provided for multiple machines in secondary or tertiary applications. In such an arrangement, multiple machines (eg, four or more) benefit from the hot-change efficiency of only one common spare sizer. For even greater efficiency, a bridge crane can be used that can handle entire sizers and, additionally, may serve for lifting operations within a dedicated maintenance and truck-loading bay.
Focus 2 – Engineered flexibility
There should only be one way in a situation: the safe way. However, the safest way to maintain a piece of equipment is not always easy to envision or understand at the design stage – in particular, for equipment standardized for multiple mines. This very much depends on actual restraints in the field, situational conditions, blocked procedures, individual experience and established site-wide procedures. Again, the risk of shortcuts arises when apparently efficient methods are not pre-engineered and assessed but chosen in the field.
Assuming we have a broken pick (tooth) in a typical primary sizer application, depending on the preference and wear condition of the remaining picks and segments, different maintenance concepts may be the most favorable method for either safety or efficiency in this scenario. As such, Takraf’s sizer design foresees the realization of any or all of the following on the same sizer as required:
- Radially replace only the one broken pick
- Radially replace only the one affected segment
- Replace entire roll without exposing the bearings to dirt (offsite maintenance)
- Replace entire sizer – hot-change as explained above in Focus 1 (offsite maintenance)
To some extent, the objective of time-efficient maintenance and the resulting reduction of time-related risk exposure do correlate. Flexibility in design allows for making best use of this trend. On a case-by-case basis, breaking points can be identified, which give preference to certain maintenance tasks depending on the conditions. For the previous broken pick(s) example, the procedure related to a roll change may turn out to be the safest but also the most efficient way if two or more segments are affected. Having no procedure or design provision for either would force the use of a riskier practice in one case or the other.
Focus 3 – Delay of maintenance cycles
The safest and most efficient maintenance task is one that does not need to be performed at all. While a maintenance-free IPCC system will remain a utopia, delaying recurring maintenance tasks is a realistic goal that can be achieved through solid and holistic design. However, this approach requires careful balancing of matters on a case-by-case basis. As an example, thicker wear plates would likely last longer on average, but would obviously impact plant design and result in either more or heavier pieces for each replacement.
Takraf’s sizer range is designed from the outset with maintenance in mind. Superior durability, abrasion resistance segments and a special roll design resulting in excellent intake behavior reduce wear and the subsequent demand for maintenance. Additionally, a hard facing, such as tungsten carbide on the crushing pick(s) (tooth) can be provided to maximize the lifetime of wear parts subject to high abrasion.
For transfer areas, the careful design of areas exposed to material wear can significantly delay the demand for maintenance. The Discrete Element Method (DEM) helps to identify and improve areas exposed to increased wear. Such special measures include solutions that delay major maintenance activities on chutes such as rock-boxes with wear-adjustable liners or even wear plates that can be inspected and replaced without even entering into the chute body.
Focus 4 – Engineered maintenance solutions in the field
Conducting maintenance on belt conveyors requires maintenance in the field. This involves the replacement of worn or damaged idlers, work that is especially challenging on steep slopes, in tunnels or on the elevated structures so typical of mining sites. The belt needs to be lifted and the idler(s) replaced. Idlers can run into thousands on long overland conveyors and have a single part weight of about 50kg or more.
Steep slopes make it almost impossible for a maintenance crew to reach an area, not even considering safety yet. The issue of limited space becomes critical in tunnels and the work has to be conducted manually. Enlarging a tunnel’s size in order to conduct maintenance more effectively, as well as for greater safety and access reasons, is not feasible due to the significant costs incurred.
However, despite these challenges, worn or damaged idlers need to be replaced as soon as possible in order to maintain efficiency and reduce operating costs, as well as to avoid the risk of any further damage to equipment or the potential outbreak of fire.
Takraf’’s maintenance cart was therefore developed to ensure both the safety of personnel and the efficient replacement of idlers. The cart can access any location along a conveyor belt in the shortest possible time and in the safest manner. Equipped with a number of solutions that enable the safe and efficient replacement of idlers in both the top and return strand of a belt conveyor in less than 15 minutes, the cart is fitted with a belt-lifting device that safely lifts the belt away from the idler in need of replacement.
By adopting a holistic maintenance philosophy, which considers all factors and touchpoints, there is no need for a compromise.
