15S Maintenance

Learning Objectives Explain the importance of maintenance in production systems Describe the range of maintenance activities Discuss preventative maintenance and the key issues associated with it Discuss breakdown maintenance and the key issues associated with it State how the Pareto phenomenon pertains to maintenance decisions

Introduction Maintenance Two basic categories All activities that maintain facilities and equipment in good working order so that a system can perform as intended Two basic categories Building and grounds Equipment maintenance

Goal of Maintenance To keep production systems in good working order at minimal cost

Maintenance Reasons Reasons for keeping equipment running Avoid production disruptions Avoid adding production costs Maintain high quality Avoid missed delivery dates

Breakdown Consequences Production capacity is reduced Orders are delayed No production Overhead continues Cost per unit increases Quality issues Product may be damaged Safety issues Injury to employees Injury to customers

Two Basic Options Reactive Maintenance: Breakdown maintenance Reactive approach; dealing with breakdowns or problems when they occur Proactive Maintenance: Preventive maintenance Proactive approach; reducing breakdowns through a program of lubrication, adjustment, cleaning, inspection, and replacement of worn parts

Total Maintenance Cost Figure 15S.1 Total Cost Cost Preventive maintenance cost Breakdown and repair cost Optimum Amount of preventive maintenance

Preventive Maintenance Preventive maintenance: goal is to reduce the incidence of breakdowns or failures in the plant or equipment to avoid the associated costs Preventive maintenance is periodic Result of planned inspections According to calendar After predetermined number of hours

Example 15S-1 Frequency of breakdowns If the average cost of a breakdown is $1,000, and the cost of preventative maintenance is $1,250 per month, should we use preventive maintenance? Number of breakdowns 1 2 3 Frequency of occurrence .20 .30 .40 .10

Example 15S-1 Solution Number of Breakdowns Frequency of Occurrence Expected number of 1 2 3 .20 .30 .40 .10 1.00 .80 1.40 Expected cost to repair = 1.4 breakdowns per month X $1000 = $1400 Preventive maintenance = $1250 PM results in savings of $150 per month

Predictive Maintenance An attempt to determine when best to perform preventive maintenance activities Total productive maintenance JIT approach where workers perform preventive maintenance on the machines they operate

Breakdown Programs Standby or backup equipment that can be quickly pressed into service Inventories of spare parts that can be installed as needed Operators who are able to perform minor repairs Repair people who are well trained and readily available to diagnose and correct problems with equipment

Replacement Trade-off decisions When is it time for replacement? Cost of replacement vs. cost of continued maintenance New equipment with new features vs. maintenance Installation of new equipment may cause disruptions Training costs of employees on new equipment Forecasts for demand on equipment may require new equipment capacity When is it time for replacement?