Operations assignment
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Brock University *
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5P07
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Industrial Engineering
Date
Feb 20, 2024
Type
docx
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17.7 What is the overall reliability that bank loans will be processed accurately if
each of the five clerks shown in the chart has the reliability shown?
Reliability R
s
= First step:
1-(.95*.95) = 0.0975 ……….(a)
Second step:
1-.95 = 0.05 ………..(b)
Third step:
1-.95 =0.05 ………..(b)
Total probability of failure: 1 – (a*b*c) = 0.99975
Total probability of the system: .95 * 0.99975 = 0.94976
17.13 Rick Wing, a salesperson for Wave Soldering Systems, Inc. (WSSI), has
provided you with a proposal for improving the temperature control on your present
machine. The machine uses a hot-air knife to cleanly remove excess solder from
printed circuit boards; this is a great concept, but the hot-air temperature control
lacks reliability. According to Wing, engineers at WSSI have improved the reliability
of the critical temperature controls. The new system still has four sensitive
integrated circuits controlling the temperature, but the new machine has a backup
for each. The four integrated circuits have reliabilities of .90, .92, .94, and .96. The
four backup circuits all have a reliability of .90.
a) What is the reliability of the new temperature controller?
b) If you pay a premium, Wing says he can improve all four of the backup units
to .93. What is the reliability of this option?
R
s (total reliability of the system) = [0.90 + {(1-0.90)*0.90}] * [0.92 + {(1-0.92)
*0.90}] * [0.94 + {(1-0.94)*0.9}] * [0.96 + {(1-
0.96)*0.90}] = 0.9723
.90
.90
.90
.90
.96
.94
.92
.90
.93
.93
.93
.93
R
s
(total
reliability of the system) =
[0.90 +
{(1-0.90)*0.93}] * [0.92 + {(1-0.92)
*0.93}] * [0.94 + {(1-0.94)*0.93}] * [0.96
{(1-
0.96)*0.93}] = 0.9805
17.14 As VP for operations at Méndez-Piñero Engineering, you must decide which
product design, A or B, has the higher reliability. B is designed with backup units for
components R3 and R4. What is the reliability of each design
Reliability R
s
(Product design A) =
0.99*0.95*0.998*0.995 = 0.934
Reliability R
s
(Product design B) = 0.99 *
0.95 * [ 0.985 + {(1- 0.985) * 0.95] *[0.99 + {(1-
0.99) * 0.99}] = 0.94
17.21 The fire department has a number of failures with its oxygen masks and is
evaluating the possibility of outsourcing preventive maintenance to the
manufacturer. Because of the risk associated with a failure, the cost of each failure
is estimated at $2,000. The current maintenance policy (with station employees
performing maintenance) has yielded the following history:
This manufacturer will guarantee repairs on all failures as part of a service contract.
The cost of this service is $5,000 per year.
a.
What is the expected number of annual breakdowns with station employees
performing maintenance?
b.
What is the cost of the current maintenance policy?
c.
What is the more economical policy?
Answer: Number of
Number of years in
Frequency
Expected breakdowns
.96
.94
.92
.90
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