Page 427 - Intro Predictive Maintenance

418 An Introduction to Predictive Maintenance

too often not subjected to the same quality assurance and reliability tests as parts that
are put into new equipment.

Parts Use. Replacing parts at preplanned preventive maintenance intervals, rather
than waiting until a failure occurs, will obviously terminate that part’s useful life
before failure and therefore require more parts. This is part of the trade-off between
parts, labor, and downtime, of which the cost of parts will usually be the smallest com-
ponent. It must, however, be controlled.

Initial Costs. Given the time-value of money and inflation that causes a dollar spent
today to be worth more than a dollar spent or received tomorrow, it should be recog-
nized that the investment in preventive maintenance is made earlier than when those
costs would be incurred if equipment were run until failure. Even though the cost will
be incurred earlier, and may even be larger than corrective maintenance costs would
be, the benefits in terms of equipment availability should be substantially greater from
doing preventive tasks.

Access to Equipment. One of the major challenges when production is at a high rate
is for maintenance to gain access to equipment in order to perform preventive main-
tenance tasks. This access will be required more frequently than it is with breakdown-
driven maintenance. A good program requires the support of production, with
immediate notification of any potential problems and a willingness to coordinate
equipment availability for inspections and necessary tasks.

The reasons for and against doing preventive maintenance are summarized in the fol-
lowing list. The disadvantages are most pronounced with fixed-interval maintenance
tasks. Reactive and condition-monitoring tasks both emphasize the positive and reduce
the negatives.

Advantages
• Can be performed when convenient
• Increases equipment uptime
• Generates maximum production revenue
• Standardizes procedures, times, and costs
• Minimizes parts inventory
• Cuts overtime
• Balances workload
• Reduces need for standby equipment
• Improves safety and pollution control
• Facilitates packaging tasks and contracts
• Schedules resources on hand
• Stimulates pre-action instead of reaction
• Indicates support to user
• Ensures consistent quality
• Promotes cost–benefit optimization