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Wednesday, 18 February 2015

MAINTENANCE PRACTICE AND PROCEDURE

This post is based on plant maintenance, where we will try to understand the basic concept of maintenance. 

Let us understand, why we should read this post for ensuring the healthy maintenance system? 

Hence we must have to know the objective of this post.

Objective 

We will try to understand the following basic concept of a healthy maintenance system
  1. Requirement of Maintenance 
  2. Organizational Chart
  3. Type of Maintenance 
  4. Performance Measurement
One question i want to ask from my readers, why we are doing business? i am sure , your answer will be same that i am thinking and this is obviously money.

Requirement of Maintenance 

Each machine or equipment need maintenance for its complete life span , it might be possible that a particular machine need higher frequency of maintenance in it's starting time and at a time towards it's expiry time. Let us understand the need of maintenance by following points.
  1. For maintaining the productivity and efficiency of the equipment 
  2. For reducing the downtime of machine or equipment 
  3. Avoiding the loss in production 
  4. Improve the reliability of machines
  5. Improve the useful life span of machines 
  6. Maintaining the machine healthiness
  7. Improving the production capacity of unit by fixing the maintenance issues immediately weather errors are critical or non critical , as one non critical error might be the reason of a very critical and poisonous issue for a machine. 

Organizational chart

For better understanding the organizational chart, let us discuss one live example of organizational chart for a steel bar mill.

Type of Maintenance 

Maintenance could be classified in to five categories as mentioned below
  1. Breakdown or corrective Maintenance
  2. Preventive Maintenance
  3. Predictive or condition based Maintenance 
  4. Shutdown Maintenance
  5. DOM or Modification Maintenance 

Breakdown or corrective Maintenance

Breakdown maintenance as name suggested, repairing work would be start after machine failure. Machine is failed to perform its desired activities then corrective actions will be taken for restoring the capabilities of machine and such type of maintenance activity, those are carried out after failure of machine, comes under this category.

Let us understand the Breakdown maintenance advantage and disadvantage.

Advantage of Breakdown maintenance 

In fact there is no advantage of breakdown maintenance, but we may think one point as advantage for breakdown maintenance i.e. maintenance resources will be utilized only when that would be required.

Disadvantage of breakdown maintenance 

  • There will be no warning of failure hence it could be considered as Safety and environmental risk.
  • As breakdown normally occurs at wrong time from production point of view. Hence in order to reduce the repairing time, there might be possibilities of poor quality maintenance.
  • Rate of deterioration of machines will be higher in case of continuous breakdown maintenance.
  • There will be possibilities of consequential  failure hence repairing will be costly.
  • It is very difficult to plan and to execute according to plan in case of machine failure.
  • Downtime will be higher and production will be lost.
  • Spare consumption rate will be higher in Breakdown maintenance.
Such type of maintenance activities is only justified in small scale industries where machine down times / duration is not important but also they concentrate to consume less cost in maintenance.

Preventive Maintenance 

Preventive maintenance means the maintenance activities those are carried out for preventing the breakdown of machine because prevention is quite good as compared to cure. Preventive maintenance consist the some key activities as mentioned below
  • Cleaning activity 
  • Inspection or observations
  • Lubrication 
  • Servicing or overhauling 
We must note that if we are neglecting the observation, it may lead to a breakdown. We will have to note also the defect in machine and we must have to monitor that defect continuously and we will have to plan to resolve the issues earliest so that we may restore the healthiness of machine for achieving the business goal.

Advantage of preventive maintenance

There are following advantage by implementing the preventive maintenance.
  • Reduction in Breakdown 
  • Reduction in downtime 
  • Reduced the overtime wages of maintenance crew
  • Reduction in maintenance costing 
  • Reduction in spare consumption 
  • Maintenance work will be completed within time if we have planned the work properly in case of preventive maintenance activity.

Predictive maintenance 

Predictive maintenance is also called as condition based maintenance system. In such type of maintenance system, one experience professional will be needed to carry out the inspection work at machine. Engineer will monitor the behavior of machine continuously to decide the desired action timely. Conditioning monitoring team will have to prepare the observation of a particular machine. They use some key conditioning monitoring maintenance tools as mentioned below.
  • Dial testing indicators
  • Vibration analyzer
  • Temperature and resistance strain gauge 
  • Voltmeter and Ammeter 
  • Pressure gauge 
  • Audio gauge 

Advantage of predictive maintenance 

  • Allows shutdown before failure or severe damage.
  • Production could be modified to extend the unit life.
  • Maintenance could be planned.
  • Maintenance crew could be organized and Spare could be arranged.

Disadvantage of predictive maintenance 

Selection of the correct condition based monitoring technique.

Shut down maintenance 

Stopping entire plant or section of plant for executing major jobs, repairs or modifications those are observed during predictive, preventive maintenance or observed due to repeated failures.

Advantage of shutdown maintenance

  1.         Repetitive breakdown can be minimized or eliminated.
  2.         Increase in Machine reliability & availability.
  3.         Improvement in productivity and product quality

Disadvantage of shutdown maintenance

Loss of production
 

Maintenance Tactics



Maintenance costs

we may understand the costing in various case of maintenance activities with the help of following curve.
Lets us move towards next post " causes of hydraulic system overheating "

Keep reading ......

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