MAINTENANCE ENGINEERING

What is Maintenance ? The combination of all technical and associated administrative actions intended to retain or restore an item into a state in which it can perform its required function. This required function might be defined as stated condition.

IMPORTANCE OF MAINTENANCE Production capacity: Machines idled by breakdowns cannot produce, thus the capacity of the system is reduced. Production costs: Labor costs per unit rise because of idle labor due to machine breakdowns. When machine malfunctions result in scrap, unit labor and material costs increase. Besides, cost of maintenance which includes such costs as costs of providing repair facilities, repair crews, preventive maintenance inspections, spare parts and stand by machines will increase as machines break down frequently. Product and service quality: Poorly maintained equipments produce low quality products. Equipments that have not been properly maintained have frequent break downs and cannot provide adequate service to customers. For example, air craft fleets of the airline, railway and road transport services not maintained well can result in poor service to customers. Employee or customer safety: Worn-out equipment is likely to fail at any moment and these failures can cause injuries to the workers, working on those equipments. Products such as two wheelers and automobiles, if not serviced periodically, can break down suddenly and cause injuries to the stress. Customer satisfaction: When production equipments break own, products often can not be produced according to the master production schedules, due to work stoppages. This will lead to delayed deliveries of products to the customers.

OBJECTIVE OF MAINTENANCE Minimizing the loss of productive time because of equipment failure (i.e. minimizing idle time of equipment due to break down). Minimizing the repair time and repair cost. Minimizing the loss due to production stoppages. Efficient use of maintenance personnel and equipments. Prolonging the life of capital assets by minimizing the rate of wear and tear. To keep all productive assets in good working conditions. To maximize efficiency and economy in production through optimum use of facilities. To minimize accidents through regular inspection and repair of safety devices. To minimize the total maintenance cost which includes the cost of repair, cost of preventive maintenance and inventory carrying costs, due to spare parts inventory. To improve the quality of products and to improve productivity.

TYPES OF MAINTENANCE SYSTEM Planned (Work organized and carried with forethought, control and record) Unplanned (Emergency maintenance work caused by unforeseen damage and accidents) Preventive maintenance (Work intended to preserve an asset, to prevent failure and to delete incipient faults) Corrective maintenance (Work intended to restore an asset, to the acceptable standard) Running maintenance (Asset is in operation) Shutdown maintenance (Asset is out of service) Breakdown maintenance (Work implemented after failure but based on advance planning) Scheduled Maintenance Reliability-based Maintenance Repair Replacement Overhaul Conditioned-based Maintenance

BREAKDOWN MAINTENANCE (BM) Breakdown maintenance is maintenance performed on equipment that has broken down and is unusable. It is based on a breakdown maintenance trigger. It may be either planned or it can be unplanned. LIMITATION OF BM : Unpredictability  – which result in either labour or materials being unavailable – therefore delay in time taken for a repair, increasing equipment downtime – can result in unnecessarily expensive charges that may have been avoided – can also affect budgets and cost planning Equipment not maximised  – reduces the lifespan of the unit – the equipment won’t fulfill its potential or return on investment. Indirect costs  – equipment downtime/ unreliable equipment causing negative effects on reputations, safety and the ability to run a business efficiently and productively – inefficient use of employee time.

PLANNED MAINTENANCE (PM) The planned maintenance is an organized type of maintenance, which takes care of other aspects such as control and records required for this type of work. Method : First of all, a work study has to be carried out to decide the periodicity/ frequency of the maintenance work. Time study can also suggest the ways and means of devising optimal maintenance schedules for the given system. Features : The work is planned beforehand to avoid random failures. It decides ‘Who’ will carry-out 'what‘ maintenance work, by 'when’. Specific instructions for each type of equipment have to be provided in greater detail . The type of maintenance job will depend upon the nature of equipment and its working conditions.

SCHEDULED MAINTENANCE (SM) In this type of maintenance work, the actual maintenance program is scheduled in consultation with the production department, so that the relevant equipment is made available for maintenance work. Method : The frequency of such maintenance work is pre-determined from experiences. In this way, the where and when of the maintenance work can be approximated by most efficient use of the idle time of equipment. Features : It utilizes the idle time of the equipment effectively. This also helps the maintenance department to use their manpower effectively. The specialists for a particular work can also be made available during the maintenance period as the schedule is known in advance. Though scheduled maintenance is costly compared to breakdown maintenance, the availability of equipment is enhanced.

PREVENTIVE MAINTENANCE Preventive maintenance is the utilization of planned and coordinated inspections, adjustments, repairs and replacements needed in maintaining an equipment or plant. Features : Detection of any condition that may cause machine failure before such breakdown occurs. This makes it possible to plan and schedule the maintenance work without interruption in production schedule and thus improves the availability of equipment. A systematic and extensive inspection of each item of equipment (or the critical parts) is made at predetermined intervals. Method : Routine attention: This involves maintenance activities that take regular care of the machines or assets. These activities are designed to preserve the assets of the organization at a given standard of maintenance, which conforms to its financial and operating policies. Routine servicing includes cleaning, oiling, and adjusting.

PREVENTIVE MAINTENANCE Contd.. Method : Routine examination : Routine examinations are carried out to identify dormant faults or items prone to failure. This type of preventive maintenance work helps to detect faults before they can actually occur. Preventive replacement : The preventive maintenance work comprises preventive replacement of parts and components that have a definite life. Such type of replacements help to avoid emergency situations and prolonged downtime and risk of hazards associated with sudden breakdowns. Inspection measurements : Inspection measurements comprise jobs of preventive maintenance that aim at identifying the degradation rate of items, and such other items which are at unacceptable service conditions. This type of maintenance work requires many costly instruments and laboratory testing facilities

MAINTAINABILITY It is expressed as the probability that an item will remain in a serviceable condition for a given period of time. Maintainability is also expressed in terms of the minimum cost of maintenance as well as the accuracy of the maintenance function.

MAINTAINABILITY Contd… Mean Time to Repair (MTTR) : The parameter for expressing the maintainability i.e. how much time is required to restore the equipment/ system to its working condition. Failure Rate (FR) or Mean Time Between Failures (MTBF) : The parameters expressing reliability, which is defined as the probability that an asset or a system will operate satisfactorily for a pre-determined period of time, under the working conditions for which it was designed.