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TEST
Semester 1, 2011
SCHOOL OF: AEROSPACE, MECHANICAL AND
MANUFACTURING ENGINEERING
SYLLABUS NO. & TITLE: MANU 1051RISK MANAGEMENT AND
FEASIBILITY
DATE:
TIME: 6:00 pm (EST)
DURATION OF TEST: Two (2) hours.
TEST PAPER DETAILS:
Number of pages: 6 (including cover sheet)
Number of questions: 3
INSTRUCTIONS:
1. Answer ALL questions.
2. Paper is marked out of 90, i.e. 30 marks for each
question.
3. Final score will be scaled to 30% of total in course
4. Open book test.
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Question 1
A large complex commercial centre is keen to provide most
reliable power supply
system to its tenants. The centre has four gas turbines each of
capacity 10 MWbut their reliability is different. The gas turbines
are connected to the main grid byswitches in standby mode. Table 1
shows the Weibull factors of the gas turbines.The demand for power
varies as a normal distribution N (22 MW, 12 MW) with aminimum
guaranteed power availability to be mean value or more.
Assumeperfect switching.
What is the best combination of operating these gas turbines at
different demandlevels?
Table 1 Weibull factors for gas turbines
Entity
Gas turbine 1 1.6 85
Gas turbine 2 1.7 80
Gas turbine 3 1.4 75
Gas turbine 4 1.5 80
(30 marks)
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Question 2
An electronic firm is trying to decide whether or not to
manufacture a new
communication device. The decision to produce the device means
an investmentof $5 million, and the demand for such a device is not
known.
If the demand is high, the company expects a return of $2.0
million each year.
If the demand is moderate, the return will be $1.6 million each
year.
A light demand means a return of $0.8 million each year.
It is estimated that the probability of a light demand is 0.1,
and the probability of ahigh demand is 0.5.
The minimum acceptable rate of return is 10%.
The lifecycle time is 4 years.
What is your conclusion?(30 marks)
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Question 3
Freight train brake systems have not changed in basic operation
since the 1930's.
They are controlled and actuated by compressed air.
Each power unit (locomotive) has an air compressor that supplies
air for the entiretrain's braking system. A feed valve in the
locomotive regulates the desiredpressure that is supplied to
remainder the train. This pressure must be at least 70psi (although
most modern systems use 90 psi). A "brakepipe" runs the full
lengthof the train. The brakepipe carries the compressed air from
the control unit to therest of the train. Unlike truck brakes (and
passenger train brakes for that matter)this single source of air
carries both the air that powers the brakes as well as thesignal to
control them.
Flexible hose carries the Brakepipe between Cars
Each rail car has its own brake system. The brake components
include a brakecylinder, brake shoes, a dual air reservoir, and a
control or AB valve. The ABvalve is used to route air from the
reservoirs (auxiliary and emergency) to thebrake cylinder. The
brake cylinders are connected through rods, levers and
slackadjusters to the brake shoes. While these components are
similar to truck brakestheir operation is very different. Unlike
truck brakes, train brakes are normally off,or unapplied. The
spring in the brake chamber is used as a return device to pullthe
brake shoe away from the wheel and allow the wheel to roll freely.
So, in orderto apply the brakes, air must be ported from the
reservoir to the brake chamber.
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Gas reservoir on each carriage
There are several ways the engineer can apply braking to the
train. He selects thetype of braking depending on the nature of the
stop desired.
The service brake is the type of brake application normally used
for braking. Thislevel of braking is achieved with a 6psi to a
26psi reduction in the brake pipepressure. When the AB valve senses
the difference in pressure air is ported fromthe reservoir to the
brake chamber. Air pressure acts against the diaphragm andbrakes
are applied. Braking with the Service Brakes offers up to 75% of a
train'sEmergency Brake capability.
Brake shoes
Develop the failure mode, effect and criticality analysis for
operation of the pressand the mitigation measures to the
failures.
(30 marks)
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