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Useful Maintenance Ratios

Ratios are extremely useful tools for effective management of the maintenance function.

They can be used to set targets, monitor results, assess discrepancies and analyze them according to the facts.

Here are the indications they can bring out:

  • Improved productivity in terms of time, resources and expenses;
  • Maintain and justify objectives for the maintenance department (budget monitoring);
  • Highlighting weak points;
  • Decision support when purchasing or renewing equipment.

Most measurement indices are determined from simple observations or compiled intervention reports (work orders, purchase orders, etc.).

The most commonly used are :

  • Contribution to operations (each index can be calculated by equipment, by department and globally)
    • Response time: Average time between breakdown and intervention
      • Average of: (hours of intervention – hours of failure)
    •  MTBF: mean time between failures
      • (Sum of uptime hours) / (Number of uptime periods)
    •  Do: operational availability
      • (MTBF x 100) / (MTBF + MTTR)
  •  Maintenance efficiency
    • MTTR: mean time through repair.
      • (Sum of repair times) / (number of malfunction periods)
  •   Overall efficiency
    • Downtime: estimated loss time
      • (Sum of downtime (production loss)) / (Sum of production time)
  •  Efficient use of maintenance personnel
    • Time allocation: between preventive and corrective maintenance tasks
      • (Preventive time) / (Maintenance time (%))
  •   Contribution to maintenance staff
    • Average salary
    • Absenteeism
    • Training costs per person
    • Turnover rate

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