Plant maintenance

• Maintenance is defined as that function of production management concerned with the day to day problem of keeping the physical plant in good operating condition.

• Maintenance management is concerned with the direction and organisation of resources in order to control (improve) the availability and performance of the industrial plants to some specified level.

• Plant maintenance is concerned with actions taken by the plant user to maintain an existing system and facilities or to restore it to an operating condition.

Maintainability• Is concerned with those actions taken by a system

and facilities during development so that the system or facilities when installed and operated can be maintained with ease.

• Maintainability means design for ease of maintenance. It is the characteristic of system design which determines the ability of a system to be retained in or restored to an effective operational condition. It is concerned with the system’s down time. It include aspects such as:– Incorporation of fail safe features– Tolerance which allows for wear through machine life– Selection of materials that ensure minimum failure due

to fatigue and friction

• Reliability is defined as the probability of a plant to give satisfactory performance in a particular period of time under specified conditions. The time between failures is called MTBF

• Availability is the percentage of time the machine will be available for operation

• Availability = Mean Time Between failures(MTBF) MTBF + Mean Time for Repairs(MTR)

Scope

• Primary functions

• Secondary functions:– Plant protection ( including fire fighting)– Waste disposal– Pollution and noise reduction– Sanitorial services– Storekeeping, accounting etc.

Categories • Breakdown Maintenance ( Corrective

maintenance)• Preventive maintenance(PM)– Lubrication & Inspection

• Predictive maintenance ( Condition monitoring)– Is a form of PM– by tracing the performance of the machine over its

operating life, deterioration that can occur at various intervals of time is predicted. Early symptoms of failure are identified and proper maintenance measures developed.

PM

• Is repairing of the machine at planned intervals so that sudden breakdowns could be prevented and costly downtime avoided. This work is generally done when the shop can spare the machine for repairs, generally during off shift hours, Sundays and holidays.– Lubrication and Inspection are two constituents

of PM

Advantages of PM

• Greater safety to workers• Reduction in production down time• Lesser expenditure on repairs due to fewer

repetitive and large scale repairs• Less spare parts• Prolongs the life of the machine• Maintains quality and continuity of production

Disadvantages of PM• High control on records and analysis, planning

& scheduling• Monitoring of parameters like temperature,

lubrication, noise, corrosion ,leaks etc are high. The equipments to do that also are costly.

• Optimum PM is required, hence correct judgement is needed. Too much or too little is not good.