Miller Magazine Issue: 127 July 2020

51 COVER STORY MILLER / JULY 2020 a complex structure is observed, they can be grouped under three main methods applied 2 . A classification of maintenance activities is shown in Figure 1, and a sum- mary given below. Breakdown maintenance which is also called “reac- tive maintenance” is an emergency maintenance, is cor- rective and consequently unscheduled. It is carried out whenever a breakdown is faced. The problem is solved either in repairing or replacing the problematic element. Planned maintenance is scheduled, and depending on the strategy, technology and present situation reports, one of the three planned methods may apply. One is “Protective maintenance (PM)” which is also called “preventive maintenance (PM) ,and “proactive main- tenance (PM)” to point out its precautionary character, or “periodical maintenance (PM)” to emphasize that it is scheduled having daily, weekly, monthly, yearly main- tenance periods. “Predictive maintenance (PdM)” mak- ing use of measurements and monitoring to predict the eventual breakdown times for taking precautions before such breakdowns occur is the other strategy which may be decided for. “Revision” is a case when maintenance is not sufficient anymore to maintain the functionality and extend the life of equipment and parts. Redundancy is not a direct maintenance method, but a supporting activity to make maintenance and replace- ment possible. Predictive maintenance (PdM) is a new approach and has in application briefly 3 phases [1], [2]: • Measurement phase, where critical points for measurement are identified, measurements are performed using NDT methods like oil analysis, temperature analysis through infrared thermography, ultrasonic test, vibration analysis, noise analysis, measurement of pressure and current differences, and also visual in- spection. • Analysis, where results of the mea- surements are analysed and failure source is determined. • Repair, where fault is evaluated and necessary repair is carried out. This phase should also include a “planning” sub-phase. A concept not mentioned among maintenance methods above is “au- tonomous maintenance”. It is not a direct method comparable to the de- scribed ones, but is an application to emphasize the degree of operational sufficiency. In autonomous mainte- nance, the equipment operator car- ries out some of the maintenance activities by himself/herself. For planned maintenance, a strategy, a schedule and an execution program and method is inevitable. Planned maintenance cannot be performed like breakdown, and needs a sophisticated maintenance management strat- egy to guide, control and evaluate maintenance activi- ties. Companies generally try to establish an “Efficient Maintenance System” to be able to manage mainte- nance. Elements of an efficient maintenance system would be maintenance policy, materials control, work order system, equipment records, maintenance (both sched- uled and unscheduled), work planning and scheduling, control of incomplete tasks and prior system, evaluation of maintenance in order to achieve maintenance goals such as minimizing time loss, maintenance cost, stop- ping time and wearing of equipment 3 . The concept of Total Productive Maintenance (TPM) presents a proved, efficient, and well defined philos- ophy, methodology and technique to establish such a system. It includes technically the planning, monitoring, evaluating, management and development elements of an efficient system. TPM needs well definitions, continuous and reliable information (and data depending upon the maintenance type) and analysis, both technical and managerial, to be able to yield effective results. So, a master plan is necessary for establishing TPM; a Figure 1: Classification of Maintenance Activities Source: Ahmet Yalcinkaya, Etkin Bakım Sistemi, Konya, 2013 (from Ilhan Or, Total Productive Maintenance Management)