Transcript Document
Facility Maintenance Typical Job Categories for Maintenance Plant Maintenance Electricians Tinsmiths Welder s Pipe fitters Fire/emergency People Steam fitters Bricklayers Painters Glaziers Concrete Workers Carpenters Millwrights Machine Maintenance General Mechanics Machinists Sheet Metal Workers Welders Electronic Technician Computer Technicians Heavy Movers Window Washers Janitors Gardeners MAINTENANCE PROCEDURES Emergency Maintenance Preventative Maintenance CLASS EXERCISE - EMERGENCY STAND-BY CAPACITY A production line has 20 electric resistance welders It costs $40 per day to won each welder If one or two welders are down, replacement spares can be rented at $50 per day per machine If 3,4, or 5 welders are out, they can be rented but production slow downs result and the total cost is $100 per day per extra machine (rental + slow down) If 6 or more machines are out, the total cost (rental + slow down) is $500 per day per extra machine Objective: Calculate how many spare welders need to be purchased by your company to minimize the total operating costs. Emergency – Standby Capacity Probability Number of Machines will Out be broken: Total =100% Cost that to Rent Number of Machines of Order We have a line with 50 robot GMA welders The cost to do a preventative maintenance overhaul on each machine is $200/machine Average breakdown repair costs are $700/machine Objective: Calculate the cost if we elect to repair only when a machine breaks down. How much must we set aside each month? Probability of Breakdown as a function of months after overhaul of all machines. They Add to 100% 1.00 The months time the probability results in the partial expected time for failure. Since the partial probabilities add to 100%, the partial times add to the expect time for a failure = 8.42 months The cost of repair-on-breakdown then = ($700/machine) /(8.42 months) * 50 machines = $4157/month Thus, we better place $4157 in a fund every month if we decide to do repair-onbreakdown policy. We have a line with 50 robot GMA welders The cost to do a preventative maintenance overhaul on each machine is $200/machine Average breakdown repair costs are $700/machine Objective: Calculate if preventative maintenance should be done and if so what the schedule should be. Calculate Cost for Preventative Maintenance For every preventative maintenance overhaul we do it will cost: = $200/machine * 50 machines = $10,000 If we do a preventative maintenance every month, it will cost $10,000/month If we do a preventative maintenance every 2 months, it will cost $5,000/month, etc. Even though we do preventative maintenance, we can expect some breakdowns to occur anyway. We can calculate the number of expected breakdowns each month using the following equation. n P Bn N n Bn1P1 Bn2 P2 ......B1Pn1 1 Where: Bn = expected number of breakdowns N = number of machines Pn = probability of machine breakdown in period n B1 NP1 50(0.05) 2.50 That is, 2.5 breakdowns in the first month B2 N(P1 P2 ) B1P1 50(.05 .02) 2.50(.05) 3.63 That is, 3.63 breakdown in first 2 months Expected Cost = Ave. Number * $700/machine = 2.5 * $700 = $1750 Total Cost = Expected Cost + Prev. Maint. Cost = 1750 + 10000 = 11750 $4157