Exam of Maintenance Management 2012
GLOBAL PRODUCTION ENGINEERING AND MANAGEMENT (GPEM)
Final assessment on Maintenance Management, by Marco Macchi, date 02-2011
Exercise #1 A Weibull analysis has been carried out on different components: the components under study are a pump and an electric motor (that is the motor needed in order to drive the pump); the analysis provides the reliability data for each component.
• The pump has the following data: scale factor α = 8000 hours and shape factor β = 1.
• The motor has the following data: scale factor α = 9000 hours and shape factor β = 1,8.
Based on these data:
• calculate the reliability of pump and motor at time t = 1000 hours;
• identify the stage of the life cycle of pump and motor;
• evaluate the reliability at time t = 1000 hours of a system made by one pump and one motor (system A) and the reliability of a system made by two pumps, each one with its own driving motor (system B); to this concern, you know that the pumping capacity provided by one pump is enough in order to satisfy the demand; moreover, the pumps and the motors have to be considered identical items for their perfomances
(i.e. reliability and pumping capacity).
Exercise #2 Assume that a FMECA team has defined the scale for the Occurence and the Severity based on the number of failures (Nf) and the mean down time (MDT), see the scales in the remainder.
Scale for the Occurrence O
O = 6 in case Nf > 20/year
O = 5 in case 16/year < Nf ≤ 20/year
O = 4 in case 12/year < Nf ≤ 16/year
O = 3 in case 8/year < Nf ≤ 12/year
O = 2 in case 4/year < Nf ≤ 8/year
O = 1 in case Nf ≤ 4/year
Scale for the Severity S
S = 6 in case MDT > 80 minutes / intervention
S = 5 in case 60 minutes / intervention < MDT ≤ 80 minutes / intervention
S = 4 in case 50 minutes / intervention < MDT ≤ 60 minutes / intervention
S = 3 in case 40 minutes / intervention < MDT ≤ 50 minutes / intervention
S = 2 in case MDT ≤ 40 minutes / intervention
S = 1 in case “the failure does not stop the
Final assessment on Maintenance Management, by Marco Macchi, date 02-2011
Exercise #1 A Weibull analysis has been carried out on different components: the components under study are a pump and an electric motor (that is the motor needed in order to drive the pump); the analysis provides the reliability data for each component.
• The pump has the following data: scale factor α = 8000 hours and shape factor β = 1.
• The motor has the following data: scale factor α = 9000 hours and shape factor β = 1,8.
Based on these data:
• calculate the reliability of pump and motor at time t = 1000 hours;
• identify the stage of the life cycle of pump and motor;
• evaluate the reliability at time t = 1000 hours of a system made by one pump and one motor (system A) and the reliability of a system made by two pumps, each one with its own driving motor (system B); to this concern, you know that the pumping capacity provided by one pump is enough in order to satisfy the demand; moreover, the pumps and the motors have to be considered identical items for their perfomances
(i.e. reliability and pumping capacity).
Exercise #2 Assume that a FMECA team has defined the scale for the Occurence and the Severity based on the number of failures (Nf) and the mean down time (MDT), see the scales in the remainder.
Scale for the Occurrence O
O = 6 in case Nf > 20/year
O = 5 in case 16/year < Nf ≤ 20/year
O = 4 in case 12/year < Nf ≤ 16/year
O = 3 in case 8/year < Nf ≤ 12/year
O = 2 in case 4/year < Nf ≤ 8/year
O = 1 in case Nf ≤ 4/year
Scale for the Severity S
S = 6 in case MDT > 80 minutes / intervention
S = 5 in case 60 minutes / intervention < MDT ≤ 80 minutes / intervention
S = 4 in case 50 minutes / intervention < MDT ≤ 60 minutes / intervention
S = 3 in case 40 minutes / intervention < MDT ≤ 50 minutes / intervention
S = 2 in case MDT ≤ 40 minutes / intervention
S = 1 in case “the failure does not stop the