Preventive maintenance is a schedule of planned maintenance actions aimed at the prevention of breakdowns and failures. The primary goal of preventive maintenance is to prevent the failure of equipment before it actually occurs. It is designed to preserve and enhance equipment reliability by replacing worn components before they actually fail.
Preventive maintenance generally refers to routine inspections, adjustments, lubrication and cleaning of fixed and movable equipment, machinery and appliances utilized in the daily operation of a facility. Performing regular routine preventive maintenance keeps equipment in good running order, reducing the possibility of equipment failure thus insuring and extending expected equipment life. Through regular preventive maintenance, potential problems can be detected early thus reducing down time and preventing more expensive repairs.
Purpose of Preventive Maintenance
- Minimize production loss from failures
- Prevent breakdown or failures
- Attempt to maximize performance of production equipment efficiently and regularly
- Increase reliability of the operating systems
Preventive maintenance activities
Repairs
- Repair activities are reactive.
- Breakdowns and malfunctions typically occur when equipment is in use.
- Standby machines and parts can speed repairs.
Preventive Maintenance (PM)
- Regularly scheduled inspections are performed.
- PM activities are performed before equipment fails.
- PM is usually performed during idle periods.
Principle – “Prevention is better than cure”
- Maximize production capacity – through high utilization of facility
- To achieve product quality and customer satisfaction through adjusted and serviced equipment
- Keep equipment safe and prevent safety hazards
- Minimize frequency and severity of interruptions
- Maximize useful life of equipment
The problem with this approach is that the mode of operation and system or plant-specific variables directly affects the normal operating life of machinery. The mean time between failures (MTBF) will not be the same for a pump that is handling water and one that is handling abrasive slurries. The normal result of using MTBF statistics to schedule maintenance is either unnecessary repairs or catastrophic failure. In the example, the pump may not need to be rebuilt after 14 months. Therefore the labor and material used to make the repair was wasted. The second option, use of preventive maintenance, is even more costly. If the pump fails before 14 months, we are forced to repair by using run-to-failure techniques. Analysis of maintenance costs has shown that a repair made in a reactive mode (i.e., after failure) will normally be three times greater than the same repair made on a scheduled basis.
All rotating machines need to be on a formal lubrication program with specific individuals assigned to the task of doing the lubricating. He should document how often he does it, what type of lubrication is needed, how much quantity is required in the equipment itself, and keep an inventory record of the different lubricants he needs.
Equipment specific PM procedures that include:
- Appropriate warnings or cautions relating to specific equipment
- Specific, clearly stated action steps for the performance of each PM task
- Special tools and equipment needed for PM performance
- Photographs and/or graphics showing key inspection or lubrication points
- Recommended frequency of the PM
- Information or data to be recorded during the performance of the PM
- References to applicable PM source materials
- Acceptance criteria and action to be taken upon out of specification results
Preventive maintenance is predetermined work performed to a schedule with the aim of preventing the wear and tear or sudden failure of equipment components. Preventive maintenance helps to:
- Decreases system downtime
- Improve system reliability
- Increases plant life
- Increases chances to get production incentive bonus
- Decrease cost of replacement
- Reduce injury
- Better quality products
- Protect assets and prolong the useful life of production equipment
- Better conservation of assets and increased life expectancy of assets, thereby eliminating premature replacement of machinery and equipment.