QUESTION 1:
GRINDING TOOLS AND BITS
1.1 Name FOUR
aspects that you must consider when selecting a grinding stone. (4)
1.2 You are busy
grinding and you find that the grinding wheel becomes clogged
up with small metal particles. What is
the cause and how would you rectify
this problem? (2)
1.3
Write brief definitions for EACH of the following
terms in your own words:
1.3.1 Red hardness (1)
1.3.2 Abrasive resistance (1)
1.4 Define toughness. (1)
1.5 You are
required to sharpen an 10 mm drill bit to drill a hole into a mild steel
plate. At what drill cutting angle would
you grind the bit? (1)
[10]
QUESTION 2:
BEARINGS
|
2.1 FIGURE 2.1 shows a drawing of a ball
bearing. Name the parts that are
indicated by the letters A to C, in your
ANSWER BOOK.
FIGURE 2.1
(3)
2.2 Give TWO
reasons why plain journal bearings are used on heavy industrial
machines instead of anti-friction
bearings (2)
2.3 Explain FOUR
common types of damage on a bearing. (4)
2.4 The job of the
maintenance fitter is to ensure that all the machines in the
workshop are in peak condition and in
good running order. The job thus
requires the fitter to inspect, remove,
maintain and replace bearings.
. 2.4.1 During the daily inspection, how can
the fitter check if the bearings
are functioning correctly? (1)
2.4.2
List TWO items of equipment or tools that a fitter would need to
remove roller bearings from the
shaft. (2)
2.4.3
Give TWO advantages of using rolling bearings. (2)
2.4.4
On inspection of the ball bearings, it is found that there are
indentations/grooves made into
the bearing raceways. What could
the likely cause be? (1)
[15]
QUESTION 3: BRAKES
AND CLUTCHES
3.1 Koos is given a file with instructions to
do maintenance on clutches. In the
file, there are documents detailing what
Koos must do.
List TWO types of documents that Koos
can expect to find. (2)
3.2 Clutches are
divided into four categories. Name any TWO. (2)
3.3 Name THREE
parts in the hydraulic clutch system that you should examine
for leaks. (3)
3.4 Explain the
braking action of an electromagnetic brake. (3)
3.5Tabu must
inspect a clutch assembly of a motor vehicle. Name TWO parts
that he is expected to examine for wear
and whether they are operating
correctly. (2)
3.6 Briefly
explain the reasons for having a maintenance schedule. (3)
[15]
QUESTION 4: DIRECT
DRIVES
4.1 Name TWO
advantages of the direct drive. (2)
4.2 A maintenance
fitter is working on the gearbox of a pastry mixing machine.
He/She realises that there is an axial
misalignment at the flange coupling
between the motor and the gearbox.
What TWO measuring instruments will
he/she need to re-align the motor with
the gearbox? (2)
4.3 Explain the
difference between a permanent coupling and a flexible coupling. (2)
4.4 The diagram
below shows a sketch of a spider coupling. Name the parts
listed as 4.4.1 – 4.4.3.
(3)
The choice of couplings is determined by
its purpose and its use.
Complete the sentences by identifying the
coupling with its purpose by
correctly matching COLUMN B with COLUMN A.
Write only the letter (A - C)
next to the question number (4.6.1 - 4.6.3)
in the ANSWER BOOK
COLUMN A
|
COLUMN B
|
4.5.1 A universal coupling can
be
used when …
4.5.2 An Oldham coupling can
be used when …
4.5.3 A rubber belt coupling
can be used when …
|
A misalignment, shock and
vibration can be taken up
between shafts
B the angles of the axis of the
shafts vary between 90°
and180°
C there is a small variation in
the axial alignment
between the two shafts
|
(3)
4.6 Briefly
describe what you would check on a drive coupling during a monthly
service. (3)
[15]
QUESTION 5: DYNAMIC
SEALS IN MACHINES AND EQUIPMENT
5.1 What is the
purpose of a seal? (1)
5.2 Name THREE
types of dynamic seals and state the use of each type of seal. (6)
5.3 What is the
difference between a static seal and a dynamic seal? (2)
5.4 Illustrate, by
means of a neat section drawing, how an O-ring is used as a
static seal. Show clearly how the O-ring
is fitted in a square groove in the
body and how the cover compresses the O
-ring to seal. (3)
5.5 Choose a
description from COLUMN B that matches a description in
COLUMN A. Write only the letter (A - C)
next to the question number
(5.5.1 - 5.5.3) in the ANSWER BOOK.
COLUMN A
|
COLUMN B
|
5.5.1 A reciprocating seal is used …
5.5.2 An O-ring is used …
5.5.3 A face seal is used …
|
A for
light – duty places
B for
rotary action
C for
pistons or rods
|
(3)
[15]
QUESTION 6: HEAT
EXCHANGERS AND PRESSURE VESSELS
6.1 Identify TWO
methods that you would apply to test for leaks in pressure
vessels. (2)
6.2 Heat
exchangers use THREE types of flow layouts for the fluid or air flowing
inside and outside the pipes
or plates. Name them. (3)
6.3 State THREE
factors to consider when cleaning tubes of heat exchangers. (3)
6.4 A heat exchanger consists of a bundle of tubes or
pipes that are used to
transfer
heat from one medium to another within a system. Name ONE of the
coolants
that can be used in the system. (1)
6.5 Give TWO examples of items used in our daily lives
that can be classified as heat
exchangers. (2)
6.6 Name any TWO control mechanisms that you would use
to adjust the
pressure
in a pressure vessel. (2)
6.7 It is important that all the pressure gauges used
on pressure vessels be correctly
calibrated. List TWO reasons why this is such an important statement. (2)
[15]
QUESTION 7: LUBRICATION
7.1 Lubrication can be grouped into three categories.
Name any TWO. (2)
7.2 Name any TWO of the main parts of a lubrication
system. (2)
7.3 Study the following sequence of operations, and
the consequences of not
following
the sequence when doing maintenance on lubricating systems.
Choose an
item from COLUMN B that matches an item in COLUMN A. Write
only the
letter (A – E) next to the question number (7.3.1 – 7.3.5) in the
ANSWER
BOOK
COLUMN A
(CORRECT PROCEDURE)
|
COLUMN B
(RESULT OF WRONG
PROCEDURE)
|
7.3.1 Complete all the electrical
and
mechanical lockout
procedures
7.3.2 Gather all the necessary tools
and
equipment for the
maintenance of lubricating systems
7.3.3 Clean the lubricating system
7.3.4 Check that the work has been done
properly and that the lubricating
systems are working properly
7.3.5 Remove the lubricator from the machine as shown in
the instruction book
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A if the assembly is dirty, you
may not be
able to see any damage
B if you do not follow the instructions
in the
book, you may make a
mistake and
damage the lubricator
C if you do not isolate the machine
electrically and mechanically,
someone who
does not know you
are working
on it may start the
machine and
cause an accident
and injury
D if you do not have all the tools
and
equipment ready, it can
cause
delays when doing the work
E if the maintenance has not
been
properly done, the parts
will not be
lubricated, causing
the machine
to break down
|
. (5 × 1) (5)
7.1 State THREE possible causes of each of the
following lubrication systemsfaults:
7.1.1
The temperature of the machine is too high (3)
7.1.2
The color of the oil has become darker (3)
[15]
TOTAL: 100
Memo
QUESTION 1:
GRINDING TOOLS AND BITS
1.1
- Grit size
- The strength of the bond
- The grade
- The grain spacing or structure (4)
1.2 Cause:
The soft material becomes imbedded into the grinding wheel.
Rectify:
The wheel needs to be dressed with a grinding wheel dresser. (2)
1.3
1.3.1 Allows the cutting tool to stay hard at high cutting temperatures (1)
1.3.2 Allows the cutting tool to
resist being worn away during the cutting
process. (1)
1.4 A cutting tool
must have a certain amount of toughness to make it less brittle. (1)
1.5 Any angle from
the RANGE: 110° to 120° (It’s correct if given as 118°) (1)
[10]
QUESTION 2:
BEARINGS
2.1 A Inner Ring or inner Race
B Cage
C Outer Ring or
outer Race (3)
2.2 ANY TWO of
the following
·
It can carry heavy loads
·
It operates very quietly
·
It is cheaper to operate
·
It can be replaced when worn
·
It is strongly made
·
It can operate for long periods without breaking
down due to fatigue. (2)
2.3 ANY FOUR
·
Flaking of
metal on the outer race
·
Micro-cracks on the surfaces of the inner and outer
races
·
Grooves on the races and balls or rollers
·
Corrosion on all parts of the bearing
·
Wear on the balls or rollers
·
Burn holes on the races and rollers or bearings (4)
2.4.1 ANY ONE
·
Listen to the sound of the bearings.: noisy bearings
·
Measure the temperature: hot bearings
·
Check the lubricant: Oil and grease (1)
2.4.2 ANY TWO
of the following
Bearing removal equipment:
·
Bearing puller
·
Impact puller
·
Hydraulic puller
·
Puller plate
·
Screw puller
·
Hammer and bearing removal collar.
·
Bearing heater (2)
2.4.3 ANY TWO
·
Generate very little fiction.
·
Use less space
·
Easy to replace
·
Can support axial and radial loads
·
Can support heavy loads for short
periods. (2)
2.4.4 ANY ONE of the following
·
The bearing was misaligned
·
The bearing was fitted the wrong why round.
·
Bearing mounted out of square.
·
Too much pressure on the sides of the
bearing raceways: too much
axial thrust. (1)
[15]
QUESTION 3: BRAKES
AND CLUTCHES
3.1 ANY TWO of the following
·
Maintenance schedule
·
Engineering drawing
·
Manufacturer 's manual/specifications for the
clutch system (2)
3.2 ANY TWO of the following
·
Positive clutches
·
Friction clutches
·
Centrifugal clutches
·
Hydraulic clutches (2)
3.3
·
The master cylinder
·
The slave cylinder
·
The clutch fluid lines (3)
3.4
·
When the electricity is flowing, the
electromagnetic solenoid uses a
magnetic force
·
To pull the two levers in towards it which keeps
the springs
attached to the top of the
levers open
·
The open springs keep the brake shoes, which are
positioned on each
side of a shaft, away from the shaft while
it is turning (3)
3.5 ANY TWO
of the following;
·
Clutch plates
·
Pressure plate
·
Flywheel
·
thrust collar (bearing) (2)
3.6
·
Maintenance schedules must
be in place to ensure proper procedures and
implementation of preventative maintenance
plans.
·
To do planned maintenance
to ensure smooth running of plant.
·
Early failure is attributed
to inadequate handling or maintenance
(3)
[15]
QUESTION 4: DIRECT
DRIVES
4.1 ANY TWO
·
It reduces the forces on
the bearings, which makes them last longer.
·
It reduces the wear on
different parts of the coupling.
·
It reduces the chance of
the seals breaking or becoming damaged.
·
It reduces the amount of
vibration in the machine casing and bearing
housings.
(2)
4.2 ANY TWO of the following;
·
Feeler gauge
·
Dial gauge
·
Taper feeler gauge.
(2)
4.3
·
Permanent couplings are
used where the shaft needs to be in a straight
line when in use and where
no flexibility is required between the
components. (1)
·
Flexible couplings are used where the shafts
are not in a straight line with
each other. This is achieved by the
flexibility of the coupling.
(1)
4.4
4.4.1 Driving hub (1)
4.4.2
Moulded rubber spider (1)
4.4.3
Driven hub (1)
4.5
4.5.1 A Universal coupling is used when the
angles of the axis of the
shafts varies between 90° and 180°. (1)
4.5.2 An Oldham coupling can be used when
there is a small variation
in the axial alignment between the
two shafts. (1)
4.5.3 A Rubber Belt coupling can be used when
misalignment, shock
and vibration can be taken up between shafts. (1)
4.6
·
Check clearance between
flanges.
·
Check for any loose
components e.g. (bolts)
·
Check alignment of shafts (3)
[15
QUESTION 5:
DYNAMIC SEALS IN MACHINES AND EQUIPMENT
5.1 The
purpose of a seal is to prevent the leakage of the liquids, fluids and
grease
in the system and it prevent entry of foreign material.
(1)
5.2
·
Reciprocating seals (1)
Are
used on parts that move up and down or sideways. (1)
·
Rotary seals (1)
Are used
for equipment in which one part moves and the other remains (1)
stationary.
·
Compressing seals (1)
Are used
between two parts on assemblies when one part is stationary
and the
other part both rotates and moves axially. (1)
5.3 Static
seal- static means stationary: this means that any seal that is used on
parts
that are not moving is classified as static seals.
Dynamic means moving: this means that
any seal that is used on moving
parts of a machine is classified as dynamic
seals. (2)
5.4
|
Show the cover plate.
|
1
|
|
Show the O-rings in groove.
|
1
|
|
Show the body with groove.
|
1
|
|
total
|
3
|
(3)
5.5
5.1.1 A Reciprocating seal
is used for pistons or rods (1)
5.1.2 An O-ring is used for
light duty places (1)
5.1.3 A Face seal is used
for rotary action (1)
[15]
QUESTION 6: HEAT
EXCHANGERS AND PRESSURE VESSELS
6.1 ANY
TWO
·
Vacuum test
·
Dye test
·
Pressure test
(2)
6.2
·
Parallel layout
·
Counter layout
·
Cross layout
(3)
6.3
·
The amount of workspace available –cleaning
must often be done in
confined spaces.
·
The tube configuration
–U-tubes in a shell and tube heat exchanger may
limit the choice of cleaning techniques.
·
The kind and amount of
deposits – different approaches are required for
cleaning heavy accumulations of mud and debris than for removing
light scale build up (3)
6.4
·
Water
·
Oil (1)
6.5 ANY TWO
·
Oil heater
·
Air conditioners
·
Refrigerators
·
Car radiators (2)
6.6
·
Pressure
regulator
·
Valves (2)
6.7
·
The readings
taken on gauges must be correct at all times.
·
Incorrect
readings may lead to unsafe conditions. (2)
QUESTION 7: LUBRICATION
7.1 ANY TWO
·
Liquid
·
Semi- liquid
·
Solid (2)
7.2 ANY TWO of the
following
·
Pump
·
Filter
·
Container /
reservoir (2)
7.3
7.3.1 C (1)
7.3.2 D (1)
7.3.3 A (1)
7.3.4 E (1)
7.3.5 B (1)
7.4
7.4.1
·
Incorrect
lubricants (1)
·
Lubricants that
have broken down chemically (1)
·
Dirty lubricants (1)
·
Abnormal friction
or wear (1)
ANY THREE
7.4.2
·
Oil has
overheated (1)
·
Dirt and
impurities in the oil (1)
·
Wrong lubricants
have been used (1)
[15]
TOTAL: 100
