Mining companies are facing great pressure to minimize their operation costs so that they can remain afloat in the unpredictable mining industry. Reducing plant downtime is quite critical when it comes to minimizing operation costs; that’s why proper plant maintenance becomes very important.
Mining remains one of the most hazardous occupations worldwide. Selection of optimal maintenance strategy is increasingly important in this industry. However, the degree of importance of selecting a suitable maintenance strategy is different in various mineral processing plants. In continuous plants, the issue of selecting suitable maintenance strategy is more critical than other systems, because failure of processing plant leads to stoppage of mineral processing.
While the implementation of a maintenance strategy should suit the specific conditions and constraints of a specific company, it is highly advisable to have a cost analysis model that will help to select corrective or preventive maintenance.
The following are different maintenance strategies that can be adopted to ensure minimum to zero machine downtime during mining operations.
Emergency maintenance (EM)
This alternative maintenance strategy is also named as fire-fighting maintenance, failure-based maintenance or breakdown maintenance. When the emergency maintenance strategy is applied, maintenance is not implemented until failure occurs. In fact, maintenance is done when a machine is failed and there is no endeavour to trim down the number of failures.
Time-based maintenance (TBM)
In TBM, maintenance is performed at fixed time gaps, whether a problem is obvious or not, to shun failure of the items while the system operates. According to reliability characteristics of machinery, maintenance is planned and performed periodically to decrease frequent and unexpected failure. This maintenance strategy is called time-based preventive maintenance, where the term ‘time’ may refer to calendar time, operating time or age.
For implementation of time-based preventive maintenance, a decision support system is needed, and it is often difficult to explain the most effective maintenance intervals because of lacking sufficient historical data. In many cases when TBM strategies are used, most machines are maintained with a significance amount of useful life remaining. This often leads to redundant maintenance, even deterioration of machines if incorrect maintenance is implemented.
Condition-based maintenance (CBM)
CBM is a maintenance strategy that recommends maintenance actions based on the information collected through condition monitoring and its goal is often to improve the plant’s reliability, availability, or its associated life cycle costs. In CBM, maintenance decision is made depending on the measured data from a set of sensors system when using the CBM strategy. To date a number of monitoring techniques are already attainable such as vibration monitoring, lubricating analysis, and ultrasonic testing.
The monitored data of machinery parameters could tell engineers whether the situation is normal, allowing the maintenance staff to perform essential maintenance before failure occurs. This maintenance strategy is often designed for rotating and reciprocating machines, e.g., turbines, centrifugal pumps and compressors. However, it should be noted that limitations and deficiency in data coverage and quality reduce the effectiveness and exactness of the CBM strategy.
Total productive maintenance (TPM)
TPM is one of plant maintenance strategies that aim to increase availability and reliability of production machines. It is a maintenance programme philosophy which is similar in nature to total quality management (TQM) in several aspects, including the total commitment of upper-level management to the TPM programme, employees must be empowered to take enterprises and corrective actions, and continuity and long-term strategy is needed as TPM is a continuous process. It can be considered as the medical science of machines. TPM is a maintenance programme which involves a newly defined concept for maintaining plants and equipment.
The purpose of the TPM programme is to markedly increase production while, at the same time, increasing employee morale and job satisfaction. TPM brings maintenance into focus as a necessary and vitally important part of the business. It is no longer regarded as a non-profit activity. Down time for maintenance is scheduled as a part of the mining day and, in some cases, as an integral part of the mining process. The purpose is to hold emergency and unscheduled maintenance to a minimum.
Design out maintenance (DOM)
In DOM, the goal is to minimise the effect of failures and in fact to remove the cause of maintenance. Although it is an engineering design problem, yet it is often a responsibility of maintenance department. This is preferred for items of high maintenance cost that are due to poor maintenance, poor design or poor design outside design specifications.
If there are recurrent faults of the same type occurring after a system is commissioned and put into service, then the maintenance staff should carry out investigation on the root causes of the problem and re-design the system if suitable to eliminate the problem. It is aimed to improve the design in order to make maintenance easier or even eliminated.