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Calculate the following:
1. The diameter of the piston
2. The Indicated power
3. The shaft power
4. The power of the electric motor required to drive the compressor
[0.005; 165.673; 9.373; 11.43; 13]
Activity 5.2
A double-acting, single stage air compressor Is required to deliver 5 kg of air
per minute at a pressure of 510 kPa. The temperature and pressure at the end
of the suction stroke are 21 ºC and 98 kPa respectively. The compressor runs
at 245 r/min and it has a clearance volume of 5% of the stroke volume. The
index for compression and expansion Is 1,33 and R for air is 0 ,287 kJ/kg.K. The
stroke length is 242 mm and the piston diameter Is 200 mm.
Calculate the following:
1. The swept volume
2. The volume 'V1'
3. The volume 'V3'
4. The volume 'V4'
5. The compressor power
[0.0076; 0.00798; 0.00038; 0.00313; 14.331]
Activity 5.3
A single stage, single-acting, reciprocating air compressor has a stroke
volume of 17,563 litres. The pressure at the outlet of the compressor is 395 kPa
while the inlet pressure is 99 kPa. The compressor has a clearance volume of
4,85% of the stroke volume and the index for compression and expansion is
1,32.
Calculate the following:
1. The volume 'V3'
2. The volume 'V1'
3. The volume V4·
4. The volumetric efficiency
5. The isothermal efficiency of the compressor
[0.017563; 0.000852; 0.018415; 0.00243; 91; 84.2]
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Activity 5.4
A single-acting, single stage air compressor takes in 1,8 m3 of air per minute at
a pressure of 120 kPa and 19 ºC. The speed or the compressor Is 360 r/min
and the delivery pressure is 820 kPa. The efficiency of the motor is 83% and
the compressor runs at a mechanical loss of 12%. The diameter to stroke ratio
Is 1:1,7. The characteristic gas constant for air is 0,268 kJ/kg.K and the
polytropic index is 1,32.
Calculate the following:
1. The indicated power
2. The cylinder diameter
3. The stroke length of the piston
4. The motor output power
5. The motor input power
[8.813; 155.3; 264; 10; 12]
Activity 5.5
A double-acting, single stage air compressor Is required to deliver 6,5 kg of air
per minute at a pressure of 510 kPa. The temperature and pressure at the end
of the suction stroke are 21 ºC and 98 kPa respectively. The compressor runs
at 245 r/min and it has a clearance volume of 5% of the stroke volume.
The Index for compression and expansion is 1,33 and R for air is 0 ,287 kJ/kg.K
The stroke length is 242 mm and the piston diameter is 200 mm.
Calculate the following:
1. The swept volume
2. The volume V1'
3. The volume V3'
4. The volume V4'
5. The compressor power
[0.0076; 0.00798; 0.00038; 0.00131; 18.631]
Activity 5.6
A single-stage, double-acting compressor must deliver 16 m3 of air every
minute. The compressor receives the air at 101,3 kPa and 20 ºC and delivers it
at a pressure of 900 kPa. The effective volume Is 0 ,94 of the swept volume,
and the speed of the compressor is 375 r/min. The index of compression is 1,3
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and the mechanical efficiency Is 79%.
Calculate the following:
1. The volumetric efficiency
2. The swept volume
3. The temperature of the delivered air
4. The power required to drive the compressor
[73.8; 0.0289; 485.05; 97.12]
Activity 5.7
A single cylinder, single-acting compressor takes In 56,4 m3 of air every hour.
The air is delivered at a pressure of 900 kPa after It is received at a pressure of
103 kPa and 22 °C. The compressor does not have a clearance volume and
the law of compression is PV1,35 = C. The stroke to bore ratio is 1,6 to 1 and the
speed is 350 r/min.
The electric motor experiences a power loss of 10% and the compressor
experiences a power loss of 12%. Air has a specific heat capacity of 0,287
kJ/kg.K.
Calculate the following.
1. The indicated power of the compressor
2. The bore diameter in mm
3. The stroke length In mm
4. The power rating of the motor used to drive the compressor in kW
[4.694; 0.002686; 128.8; 206.08; 5.93]
Self-Check
I am able to: Yes No
Describe solid, liquid and gaseous fuels
Describe the higher and lower calorific values of fuel
Calculate the minimum air required for complete combustion
Calculate the products of combustion
Describe the bomb calorimeter and the Orsat apparatus
If you have answered ‘no’ to any of the outcomes listed above, then speak to
your facilitator for guidance and further development.
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Learning Outcomes
On the completion of this module the student must be able to:
Describe the operation of the steam on the blades of an impulse turbine
Describe the operation of the steam on the blades of an reaction turbine
Describe the velocity diagram with all the velocity components
Calculate the work done on the blades
Describe the operation of the Watt, Porter and Hartnell types of governors
Calculate the maximum speeds
6.1 Introduction
A gas turbine, also called a combustion turbine, is a type of internal
combustion engine. It has an upstream rotating compressor
coupled to a downstream turbine, and a combustion chamber in
between.
6.2 Steam turbines
Turbine blades are of two basic types, blades and nozzles. Blades move
entirely due to the impact of steam on them and their profiles do not
converge. This results in a steam velocity drop and essentially no pressure drop
as steam moves through the blades.
Did you know?
A turbine composed of blades alternating with fixed nozzles is
called an impulse turbine, Curtis turbine, Rateau turbine or Brown-
Curtis turbine.
Nozzles
Nozzles appear similar to blades, but their profiles converge near the exit. This
results in a steam pressure drop and velocity increase as steam moves through
the nozzles. Nozzles are usually fixed to the stator.
Blades
Blades move entirely due to the impact of steam on them and their profiles do
not converge. This results in a steam velocity drop and essentially no pressure
drop as steam moves through the blades. Blades are usually fixed to the rotor.
Figure 6.1
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Condensing
Condensing turbines are most commonly found in electrical power plants.
These turbines receive steam from a boiler and exhaust it to a condenser. The
exhausted steam is at a pressure well below atmospheric, and is in a partially
condensed state, typically of a quality near 90%.
Casing
Single casing units are the most basic style where a single casing and shaft are
coupled to a generator.
Turbine efficiency
To maximize turbine efficiency, the steam is expanded, doing work, in a
number of stages. These stages are characterized by how the energy is
extracted from them and are known as either impulse or reaction turbines.
Most steam turbines use a mixture of the reaction and impulse designs: each
stage behaves as either one or the other, but the overall turbine uses both.
Typically, higher pressure sections are reaction type and lower pressure stages
are impulse type.
Figure 6.1 Turbine blade showing fixing dovetail
6.2.1 Impulse turbines
An impulse turbine has fixed nozzles that orient the steam flow into high speed
jets. These jets contain significant kinetic energy, which is converted into shaft
rotation by the bucket-like shaped rotor blades, as the steam jet changes
direction.
A pressure drop occurs across only the stationary blades, with a net increase in
steam velocity across the stage. As the steam flows through the nozzle its
pressure falls from inlet pressure to the exit pressure (atmospheric pressure, or
more usually, the condenser vacuum). Due to this high ratio of expansion of
steam, the steam leaves the nozzle with a very high velocity.
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The steam leaving the moving blades has a large portion of the maximum
velocity of the steam when leaving the nozzle. The loss of energy due to this
higher exit velocity is commonly called the carry over velocity or leaving loss.
6.2.2 Reaction turbines
In the reaction turbine, the rotor blades themselves are arranged to form
convergent nozzles. This type of turbine makes use of the reaction force
produced as the steam accelerates through the nozzles formed by the rotor.
Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the
stator as a jet that fills the entire circumference of the rotor. The steam then
changes direction and increases its speed relative to the speed of the blades.
A pressure drop occurs across both the stator and the rotor, with steam
accelerating through the stator and decelerating through the rotor, with no
net change in steam velocity across the stage but with a decrease in both
pressure and temperature, reflecting the work performed in the driving of the
rotor.
6.2.3 Speed control
The control of a turbine with a governor is essential, as turbines need to be run
up slowly to prevent damage and some applications (such as the generation
of alternating current electricity) require precise speed control.
Uncontrolled acceleration of the turbine rotor can lead to an over-speed trip,
which causes the nozzle valves that control the flow of steam to the turbine to
close.
Note:
If this fails then the turbine may continue accelerating until it breaks
apart, often catastrophically. Turbines are expensive to make,
requiring precision manufacture and special quality materials.
6.3 Thermodynamics of a steam turbine
The steam turbine operates on basic principles of thermodynamics using the
part 3-4 of the Rankine cycle shown in the adjoining diagram.
Superheated steam (or dry saturated steam, depending on application)
leaves the boiler at high temperature and high pressure. At entry to the
turbine, the steam gains kinetic energy by passing through a nozzle (a fixed
nozzle in an impulse type turbine or the fixed blades in a reaction type turbine).
When the steam leaves the nozzle it is moving at high velocity towards the
blades of the turbine rotor. A force is created on the blades due to the
pressure of the vapour on the blades causing them to move.
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A generator or other such device can be placed on the shaft, and the energy
that was in the steam can now be stored and used.
The steam leaves the turbine as a saturated vapour (or liquid-vapour mix
depending on application) at a lower temperature and pressure than it
entered with and is sent to the condenser to be cooled.
Note:
The first law enables us to find a formula for the rate at which work is
developed per unit mass.
Assuming there is no heat transfer to the surrounding environment and that the
changes in kinetic and potential energy are negligible compared to the
change in specific enthalpy we arrive at the following equation
Isentropic efficiency
To measure how well a turbine is performing we can look at
its isentropic efficiency.
This compares the actual performance of the turbine with the performance
that would be achieved by an ideal, isentropic, turbine.
When calculating this efficiency, heat lost to the surroundings is assumed to be
zero.
The starting pressure and temperature is the same for both the actual and the
ideal turbines, but at turbine exit the energy content ('specific enthalpy') for
the actual turbine is greater than that for the ideal turbine because of
irreversibility in the actual turbine.
The specific enthalpy is evaluated at the same pressure for the actual and
ideal turbines in order to give a good comparison between the two.
The isentropic efficiency is found by dividing the actual work by the ideal work.
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Figure 6.2 Large rotor with two turbines
6.3.1 Velocities on blade inlet
Figure 6.3 shows the how steam changes direction through the blade
imparting a force on the blade that causes it move in the direction indicated.
The steam has a velocity of Cai and an angle and the blade is moving at a
velocity U , then the velocity of the steam relative to the blade, Cri will be
obtained by compounding these two velocities as shown in the inlet velocity
triangle. See the velocity triangle Figure 6.4 (a) and the vector diagram Figure
6.4 (b).
The velocity Cwi is in the direction of the blade movement and is termed the
velocity of whirl at inlet.
Cfi is the velocity of flow and is along the axis of rotation.
Figure 6.3 Steam direction is changed
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Figure 6.4 (a) and (b) Inlet condition on blade. (a) Velocity triangle and
(b) Vector diagram
6.3.2 Velocities on blade exit
Figure 6.5 (a) shows the velocity triangle at the blade exit. As the steam passes
over the moving blade it changes direction and leaves the blade with an exit
relative velocity of Cre at an angle To the angle of direction.
The blade will be moving with a velocity U. Therefore the steam at exit has two
component velocities Cre and U. These velocities are compounded to give the
absolute velocity Cae.
Cwe is the velocity in line with the moving blades called the velocity of whirl at
exit and Cfe is termed the velocity of flow at exit and is in the direction of the
axis of rotation.
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Figure 6.5 (a) and (b) Outlet condition on blade. (a) Velocity triangle and
(b) Vector diagram
6.3.3 Work done on the blades
The combined vector diagram Figure 6.6 must be accurately drawn out with
the correct angles and to a suitable scale. From this, the relevant velocities are
obtained.
Figure 6.6 Combined vector diagram
Work done on blades:
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Force to change the velocity of whirl
The negative sign shows the force acts in the direction opposite to the rotation.
The reaction force has the same magnitude so this is the formula that we use.
The work done per second or power
Blade or diagram efficiency
Axial thrust is found by using the change in the velocity of flow:
Worked Example 6.1
A single-stage impulse turbine has an average blade speed of 300 m/s. The
gas leaves the turbine at an angle of 50º and the velocity coefficient is 0,75.
The blade inlet angle is 26 º and the gas flows at a rate of 48 kg/s through the
turbine. The relative exit velocity of the gas is 600 m/s.
1. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Use the diagram and determine the following:
2.1 the nozzle angle
2.2 the velocity of the gas leaving the nozzles
2.3 the velocity of the gas leaving the turbine
2.4 the blade outlet angle
2.5 the relative inlet velocity of the gas
2.6 the power developed by the turbine in MW
2.7 the axial thrust of the turbine in kN
Solution:
1.
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Figure 6.7
2.1 =
2.2 =
2.3 =
2.4 =
2.5 =
2.6 =
=
=
2.7 =
=
=
=
Worked Example 6.2
The velocity of steam leaving the nozzles of an impulse turbine is 900 m/s and
the nozzle angle is 20º. The blade velocity is 300 m/s and the velocity
coefficient of friction is 0,7. The blading is symmetrical and the mass flow of
the steam is 1,8 kg/s.
1. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Use the diagram and determine the following:
2.1 the blade inlet angle
2.2 the driving force on the wheel
2.3 the axial thrust
2.4 the diagram power
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2.5 the diagram efficiency
Solution:
1.
Figure 6.8 =
2.1 = =
2.2 =
2.3 =
=
=
2.4 =
=
=
=
2.5 =
=
= 68,89%
6.4 Governors
A governor, or speed limiter, is a device used to measure and regulate
the speed of a machine, such as an engine.
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Did you know?
A classic example is the centrifugal governor, also known as
the Watt or fly-ball governor, which uses weights mounted on
spring-loaded arms to determine how fast a shaft is spinning, and
then uses proportional control to regulate the shaft speed.
In steam turbines, the steam turbine governing is the procedure of monitoring
and controlling the flow rate of steam into the turbine with the objective of
maintaining its speed of rotation as constant. The flow rate of steam is
monitored and controlled by interposing valves between the boiler and the
turbine.
6.4.1 Centrifugal governors
These governors use centrifugal force to act on two balls with the same mass.
The governor types are:
The Watt governor
The Porter governor
The Proell governor
6.4.2 Watt governor
Power is supplied to the governor from the engine's output shaft by a belt or
chain connected to the lower belt wheel. The governor is connected to
a throttle valve that regulates the flow of working fluid (steam) supplying
the prime mover.
Note:
As the speed of the prime mover increases, the central spindle of
the governor rotates at a faster rate and the kinetic energy of the
balls increases.
This allows the two masses on lever arms to move outwards and upwards
against gravity. If the motion goes far enough, this motion causes the lever
arms to pull down on a thrust bearing, which moves a beam linkage, which
reduces the aperture of a throttle valve. Figure 6.10.
The rate of working-fluid entering the cylinder is thus reduced and the speed of
the prime mover is controlled, preventing over-speeding.
Mechanical stops may be used to limit the range of throttle motion, as seen
near the masses in the image at right.
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Figure 6.9 Watt governor
Read:
In 1787 Watt adopted the centrifugal governor and after it was
named "Watt's governor".
Figure 6.10 Action of a Watt governor
To eliminate the effect of the tension in the arm and reaction at the sleeve, we
Take moments resulting in the formula below. Figure 6.10.
The mass of a ball is m and the centrifugal force on it is F. The
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6.4.3 Porter governor
Figure 6.11 The Porter governor
For higher speeds, the porter governor is used. Figure 6.11 shows the added
mass on the moving sleeve. It is a Watt governor with this added central mass.
Figure 6.12 Action of a Porter governor
To eliminate the effect of the tension in the arm and reaction at the sleeve, we
Take moments resulting in the formula below. Figure 6.12.
The mass of a ball is m and the centrifugal force on it is F. M is the mass of the
central load.
()
6.4.4 Spring-controlled governors
The common types of spring loaded governors are:
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The Hartnell governor
The governor with spring connected balls
6.4.5 The Hartnell governor
There is a central spring which is initially compressed. This spring can be
adjusted to give any required equilibrium speed for a given ball radius.
Figure 6.13 The Hartnell governor
Taking moments about the fulcrum O. of the bell-crank lever, the formula
below is obtained.
Looking at Figure 6.14, M is the mass of the sleeve and P is the force acting on
the sleeve by the spring.
Figure 6.14 The action of the Hartnell governor
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6.4.6 Sensitivity and friction and respectively
If the maximum and minimum speeds of a governor is
and its mean speed is , then the sensitivity is defined as
If the friction between the sleeve and spindle is taken into account, then
Mg + f when the sleeve is rising and Mg – f when the sleeve is falling.
In controlling the force and stability there are the centripetal force of the balls
acting inward, the spring force, etc.
These forces are the controlling forces, and Figure 6.15 shows the curve for the
Porter governor. Figure 6.16 shows the curve for the Hartnell governor.
At any equilibrium speed, , the controlling force is equal and opposite to the
centrifugal force.
Figure 6.15 The force radius curve of a Porter governor
A governor is stable if, for each speed within the working range there is only
one radius of rotation for equilibrium. The ratio F/r must increase as increases.
For the Porter governor curve, the condition is satisfied.
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Figure 6.16 The force radius curve of a Hartnell governor
For the Hartnell governor, this condition is satisfied only if the straight line curve
intercepts the vertical axis below the origin. Figure 6.16.
Worked Example 6.3
A porter governor has 300 mm arms and the rotating balls each have a mass
of 1.8 kg. At a mean speed of 120 r/min, the arms make an angle of 30
degrees to the vertical.
Find the central dead load needed and the sensitivity of the governor if the
sleeve movement is 25 mm.
Solution
()
At the mean speed:
Dead load needed … M = 5.73 kg
√
When the sleeve rises 25 mm:
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√
Figure 6.17
When the sleeve falls 25 mm:
√
Activity 6.1
Steam with a velocity of 600 m/s enters an impulse turbine row of blades at
an angle of 25 º to the plane of rotation of the blades. There is a 10% loss in
relative velocity due to friction in the blades. The blade exit angle is 30º and
the mean blade speed is 255 m/s.
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1. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Use the diagram and determine the following:
2.1 the inlet angle of the blade
2.2 the exit angle of the gas from the turbine
2.3 the power developed by the turbine
2.4 the diagram efficiency
2.5 the axial thrust per kilogram of steam
[300; 725; 240; 455; 425; 0.934; 222]
Activity 6.2
The nozzles of an impulse turbine supply 5 kg of gas at an angle of 19º every
second. The gas leaves the nozzle at a speed of 1 000 m/s. The mean blade
is 475 m/s and the outlet angle of the moving blades is 23º. There is a 9,5%
frictional loss in the relative part of the blades.
1. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Determine the following from the diagram:
2.1 the inlet angle of the moving blade
2.2 the exit angle of the gas
2.3 the driving force on the wheel in kN
2.4 the axial thrust on the wheel in N
2.5 the power developed by the turbine in MW
[35; 90; 4.725; 625; 2.244; 515.85]
Activity 6.3
An impulse turbine has a blade ring which is 1,91 m in diameter and it rotates
at 3 500 r/min. The blade speed is 0,35 of the steam velocity leaving the
nozzles, which are inclined at 20º to the plane of the wheel. The velocity
coefficient of friction is 0,9 and there is no axial thrust.
1. Calculate the blade velocity of the turbine in m/s
2. Calculate the velocity of the steam leaving the nozzles
3. Use scale 1 cm = 50 m/s and construct a velocity diagram (landscape)
and enter all the values (m/s) onto the diagram.
4. Use the diagram and determine the following:
4.1 The diagram efficiency
4.2 The power developed per kilogram of steam per second
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[350; 700; 38; 117; 115; 390; 590; 312]
Activity 6.4
5 000 kg of steam per hour, leaves the nozzles of an impulse turbine at a
velocity of 1 000 m/s and at an angle of 20º to the plane of the wheel. The
steam leaves the turbine at 85º to the plane of the wheel. The inlet angle of
the moving blade is 35º and the outlet angle is 30º. The wheel rotates at 11
000 r/min.
Use a scale of 1 cm = 50 m/s and construct a velocity diagram (landscape)
and enter all the values (m/s) onto the diagram.
[85; 20; 30; 35; 965; 340; 275.5]
Activity 6.5
12 kg of gas flows into an impulse turbine every minute, at a velocity of 600
m/s making an angle of 28º to the plane of rotation. The absolute outlet
velocity of the gas is axial to the turbine shaft. The velocity of the blades is
240 m/s and the coefficient of friction is 0,85.
1. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Use the diagram and determine the following:
2.1 the inlet angle of the moving blade
2.2 the outlet angle of the moving blade
2.3 the velocity at which the gas leaves the turbine
2.4 the angle at which the gas leaves the turbine
2.5 the power generated in the turbine
2.6 the turbine efficiency
2.7 the axial thrust
[44; 33; 155; 90; 18.6; 70.67; 25]
Activity 6.6
Gas leaves a single-stage impulse turbine at an angle of 41º. Friction over the
blading causes a 10% loss in velocity. The relative velocity of the gas at the
inlet to the blades is 350 m/s at an angle of 30 º. The blade experiences a
peripheral velocity of 175 m/s when 50 kg of gas flows through the turbine
every second.
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1. Use a scale of 1 cm = 25 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
2. Determine the following from the diagram:
2.1 the nozzle angle
2.2 the nozzle velocity
2.3 the exit angle of the moving blades
2.4 the axial thrust
2.5 the power developed
[315; 20; 510; 19; 3.625; 5.25]
Activity 6.7
The blades of a single-stage impulse turbine has a mean diameter of 960 mm.
100 kW of power develops at a speed of 4 755 r/min. The gas discharges in
an axial direction and the coefficient of friction is 0,87. Both blade angles are
30º each to the plane of rotation.
1. Calculate the blade velocity in m/s
2. Use a scale of 1 cm = 50 m/s and construct a velocity diagram
(landscape) and enter all the values (m/s) onto the diagram
3. Determine the following from the diagram:
3.1 the nozzle angle
3.2 the mass flow of gas in kg/s
3.3 the diagram efficiency
3.4 State the volume and enthalpy of 1 kg of steam which has a
temperature of 500 ºC and a pressure of 0,5 MPa.
[239; 17; 0.816; 85.6; 0.7108; 3484]
Activity 6.8
In a Hartnell governor the length of the ball arm is 190 mm. The sleeve arm is
140 mm and the mass of each ball is 2.7 kg. The distance of the pivot of each
bell-crank lever from the axis of rotation is 170 mm and the speed, when the
ball arm is vertical, is 300 r/min. The speed is to increase 0.6 % for a lift of 12
mm of the sleeve.
1. Neglecting the dead load on the sleeve, find the necessary stiffness of
the spring.
2. Find the initial required compression.
[0.0804; 1230; 1364; 11160; 0.11]
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Activity 6.9
1. Define the sensitivity, stability and isochronism as applied to governors.
2. For isochronism, the equilibrium speed remains constant for all radii of
rotation.
3. Describe equilibrium speed.
Activity 6.10
1. A spring controlled governor has two balls, each with a mass of 2.3 kg.
The mean speed is to be 500 r/min and the variation is 2 %.
2. The extreme radii of the path of the balls are 110 mm and 85 mm. Find the
controlling force at the balls in each case.
3. If the effect of friction is 45 N at each ball, find the highest and lowest
speeds.
[721.5; 514.5; 525; 468]
Self-Check
I am able to: Yes No
Describe the operation of the steam on the blades of an impulse
turbine
Describe the operation of the steam on the blades of an
reaction turbine
Describe the velocity diagram with all the velocity components
Calculate the work done on the blades
Describe the operation of the Watt, Porter and Hartnell types of
governors
Calculate the maximum speeds
If you have answered ‘no’ to any of the outcomes listed above, then speak to
your facilitator for guidance and further development.
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Learning Outcomes
On the completion of this module the student must be able to:
Describe the condition that boilers and pressure vessels should be kept in
Describe documentation required in order to operate a boiler
Describe how boiler documentation is obtained
Describe the procedure to be taken before changes are performed on a
boiler
7.1 Introduction
Below are extracts from the factories act relevant to the work
covered in this course.
7.2 General requirements
(1) Any person who manufactures, imports, sells, offers or supplies any
pressure equipment described in these Regulations for use in the
Republic shall ensure that such equipment complies with these
Regulations.
(2) Any person who erects or installs any pressure equipment for use in the
Republic shall ensure, as far as is reasonably practicable, that it is
erected or installed in a safe manner and without risk to health and
safety when properly used.
(3) All pressure equipment for use in the Republic shall be categorized and
submitted to the applicable conformance assessments of SANS 347 in
addition to the requirements of the relevant health and safety standard
incorporated into these Regulations under section 44 of the Act.
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7.3 Duties of manufacturers
(1) The manufacturer shall have an obligation to ensure that all equipment
designed and manufactured for use in the Republic shall be conformity
assessed and subjected to the requirements set out in SANS 347.
(2) Subject to the requirements set out in the relevant health and safety
standard incorporated into these Regulations under section 44 of the
Act, the manufacturer shall ensure that the pressure equipment as
manufactured, modified, inspected, tested or repaired is safe and
without risks to health when properly used.
(3) Subject to the requirements of this regulation a manufacturer shall issue
a certificate of manufacture for all pressure equipment supplied, with a
verification signature by an approved inspection authority when so
required.
(4) Subject to the requirements of this regulation a manufacturer shall
comply with any other duty assigned to the manufacturer in these
Regulations.
(5) A manufacturer who determines that pressure equipment in use has a
latent defect shall advise the chief inspector in writing forthwith thereof
and of measures being taken to correct the defect.
7.4 Duties of users
(1) The user shall ensure that the pressure equipment is operated and
maintained within its design and operating parameters.
(2) The user shall, subject to the relevant health and safety standard
incorporated into these Regulations under section 44 of the Act –
(a) provide the manufacturer, repairer or modifier with
comprehensive information of the operating or intended
operating conditions of the pressure equipment, including the
characteristics of the fluid and operating parameters of other
connected pressure equipment, where reasonably practicable;
(b) ensure pressure equipment has a certificate, issued by the
manufacturer, including a verification signature by an approved
inspection authority when required, which certifies that the
pressure equipment has been designed and manufactured in
accordance with the relevant health and safety standard
incorporated into these Regulations under section 44 of the Act;
(c) ensure pressure equipment has a certificate issued by the repairer
or modifier, including a verification signature by an approved
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inspection authority when required, which certifies that the
pressure equipment has been modified or repaired in accordance
with the relevant health and safety standard incorporated into
these Regulations under section 44 of the Act;
(d) ensure that pressure equipment has a certificate issued by an
approved inspection authority before commissioning, where
applicable; and
(e) ensure that a gas system has a valid certificate issued by an
authorised person.
7.5 Approval and duties of approved inspection authority
(1) Only an organisation holding an approval certificate from the chief
inspector shall perform the duties of an approved inspection authority
within the scope of accreditation.
(2) An application for approval in terms of sub-regulation (1) shall include
the applicant’s proof of accreditation prescribed by paragraph (a) or
(b) of sub-regulation (3), including full contact details and address.
(3) The chief inspector’s approval –
(a) of inspection bodies operating in the Republic shall be subject to
the submission of an accreditation certificate issued by the
accreditation authority in accordance with the requirements of
SANS/ISO 17020 and SANS 10227: Provided that the chief inspector
may set additional requirements before granting approval; or
(b) of foreign inspection bodies shall be subject to the submission of
an accreditation certificate issued by an International Laboratory
Accreditation Cooperation (ILAC) or an International
Accreditation Forum (IAF), Mutual Recognition Arrangement
signatory in accordance with the requirements of ISO/IEC 17020:
Provided that –
(i) the foreign inspection body shall ensure compliance with all
the duties assigned to an approved domestic inspection
authority in terms of these Regulations and within their scope
of accreditation together with the applicable health and
safety standards; and
(ii) the chief inspector may set additional requirements before
granting approval.
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(4) Imported pressure equipment stamped by an ASME authorised
manufacturer in compliance with the full ASME Code of Construction
shall be deemed to meet the requirements of these Regulations.
(5) In the event of a dispute of a technical or safety issue, which could not
be reasonably resolved between an approved inspection authority and
any interested party, including the user, modifier, repairer or
manufacturer, an interested party may refer the case to the chief
inspector in writing for arbitration, setting out the full details of the
dispute.
(6) Upon receiving such a dispute in terms of sub regulation (5), the chief
inspector may appoint an arbitrator mutually agreed upon between the
parties.
(7) A case referred to the chief inspector in terms of sub regulation (5) shall
be investigated and arbitrated within a maximum of 90 days.
(8) An approved inspection authority shall ensure compliance with all the
duties assigned to an approved inspection authority in these Regulations
within its scope of accreditation and the relevant health and safety
standard.
7.6 Registration of a steam generator
(1) No user may use a steam generator unless such user is in possession of a
certificate of registration issued in terms of sub-regulation (3) for that
steam generator.
(2) Application for registration to use a steam generator shall be made prior
to use to the provincial director in the form of Annexure 2, including
copies of a certificate from the manufacturer and from the approved
inspection authority after installation prior to commissioning: Provided
that this sub-regulation shall not apply in respect of the re-erection of a
steam generator on the same premises.
(3) On receipt of an application for registration in terms of sub-regulation (1),
the provincial director shall forward that application to an inspector who
may issue a certificate of registration in the form of Part C of Annexure 2
in respect of that steam generator, subject to the conditions that may
be specified on the certificate.
(4) Any user of a steam generator for which a certificate of registration has
been issued shall cause the certificate of registration to be made
available on request to an inspector or an approved inspection
authority.
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(5) A user shall, within seven days after discovering that the certificate of
registration has been lost, defaced or destroyed, apply to the provincial
director in the form of Part A of Annexure 2 for the issue of a duplicate
certificate, and affix the fee of R100,00 in the form of un-cancelled
revenue stamps to such an application.
(6) On receipt of an application in terms of sub-regulation (5), the provincial
director shall issue the duplicate certificate if he or she is satisfied that the
original certificate has been lost, defaced or destroyed.
(7) A user of a steam generator shall immediately notify the provincial
director in writing when –
(a) such steam generator is no longer in use;
(b) the right of control over the use of the steam generator is
transferred by the user to any other user; or
(c) the user moves the steam generator to premises other than the
premises reflected on its certificate of registration.
(8) A certificate of registration issued in terms of sub-regulation (3)
shall lapse –
(a) upon the transfer of the right of control over the use of the steam
generator to another user; or
(b) when a steam generator is removed from the premises reflected
on its certificate of registration.
7.7 Pressure equipment marking
(1) Every manufacturer of pressure equipment shall cause the pressure
equipment to be marked in accordance with the relevant health and
safety standard incorporated into these Regulations under section 44 of
the Act.
(2) Every manufacturer shall cause a data plate to be permanently fixed in
a conspicuous place to any steam generator or pressure vessel with the
following minimum particulars:
(a) Name of manufacturer;
(b) country of origin;
(c) year of manufacture;
(d) manufacturer’s serial number;
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(e) reference number, date and edition of the health and safety
standard;
(f) design pressure in units of Pascal;
(g) design temperature for both minimum and maximum in degrees
Celsius;
(h) capacity in cubic metres;
(i) unique mark of an approved inspection authority as applicable;
and
(j) the hazard category in accordance with the requirements of
SANS 347.
(3) In the case of composite pressure equipment the following information
shall be included in addition to that referred to in sub-regulation (2):
(a) The resin system of the corrosion barrier/lining;
(b) the resin system of the structural wall; and
(c) the name and specific gravity of the medium for which the vessel
was designed.
(4) No person may remove a marking or data plate referred to in this
regulation or wilfully damage or alter the particulars marked thereon,
except as provided in this regulation.
(5) A user shall ensure that any modification that changes the original
design conditions is identified by affixing an additional data plate.
(6) A user shall ensure that a data plate is affixed to any steam generator or
pressure vessel that has been re-certified: Provided that where the
manufacturer is unknown, the user responsible for the re-certification
shall be deemed to be the manufacturer.
7.8 Pressure and safety accessories
(1) No user may require or permit pressure equipment to be used unless it is
provided with all the pressure and safety accessories required by the
relevant health and safety standard which is incorporated into these
Regulations under section 44 of the Act and used in the design,
construction and manufacture of such pressure equipment: Provided
that alternative safety accessories other than those required by the
standard may be fitted with the written approval of an approved
inspection authority.
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(2) In the absence of a requirement referred to in sub regulation (1) in the
relevant health and safety standard which is incorporated into these
Regulations under section 44 of the Act and used in the design,
construction and manufacture of such pressure equipment, safety
accessories shall be provided by the user as required by the approved
inspection authority and those safety accessories shall be so selected,
arranged and installed as to be safe for the particular purpose for which
the pressure equipment is to be used.
(3) Every user of a steam generator or pressure vessel shall ensure that the
steam generator or pressure vessel in use is fitted with at least one
pressure measuring device.
(4) Every user of a steam generator or pressure vessel shall ensure that the
steam generator or pressure vessel in use is fitted with at least one safety
valve and that safety valve is kept locked, sealed or otherwise rendered
inaccessible to any un-authorised person.
(5) The number and capacity of the safety valve referred to in sub-
regulation (4) shall comply with the requirements of the design standard
for the steam generator or pressure vessel or as required in terms of sub-
regulation (2).
(6) Every user shall ensure that the automatic controls and indicators of a
steam generator, pressure vessel or piping are arranged, installed,
maintained and operated in accordance with the relevant health and
safety standard which is incorporated into these Regulations under
section 44 of the Act and used in the design and manufacture of the
steam generator, pressure vessel or pressurized system: Provided that in
the absence of such provisions, where automatic controls and indicators
are installed, they shall be selected, arranged and installed subject to
the written approval of an approved inspection authority.
7.9 Inspection and test
(1) Subject to the requirements of the relevant health and safety standard
incorporated into these Regulations under section 44 of the Act, the user
shall cause –
(a) steam generators or pressure vessels, including pressure and safety
accessories, after they are installed or re-installed and before they
are commissioned, to be subjected to a witnessed internal and
external inspection of a hydraulic pressure test to 1,25 times the
design pressure by an approved inspection authority: Provided
that Category I equipment as categorized in terms of SANS 347
may be inspected, tested and witnessed by the user: Provided
further that the user may, subject to the written approval of an
approved inspection authority, dispense with the internal
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inspection and hydraulic pressure test where it could have an
adverse effect on the operation or integrity of the pressure
equipment;
(b) piping to be inspected and tested by the manufacturer after
manufacture, installation, modification or repair and before
commissioning in accordance with the relevant health and safety
standard incorporated into these Regulations under section 44 of
the Act, and, where applicable, to be witnessed by an approved
inspection authority: Provided that Category I equipment as
categorized in terms of SANS 347 may be inspected, tested and
witnessed by the user;
(c) every fire-tube steam generator to be subjected to an external
inspection every 12 months and a witnessed hydraulic test and
crack detection of critical welds every 36 months, by an approved
inspection authority for in-service inspection appointed by the user
in writing;
(d) every pressure vessel and steam generator, excluding those
referred to in sub-regulation (3), to be subjected to an internal and
external inspection and a hydraulic test to a pressure of 1,25 times
the design pressure by an approved inspection authority for in-
service inspection appointed by the user in writing, at intervals not
exceeding 36 months: Provided that Category I equipment as
categorized in terms of SANS 347 may be inspected and tested by
the user: Provided further that where the pressure equipment is not
subject to deterioration processes, the user may dispense with the
internal inspection and hydraulic pressure test, subject to a
maximum period of nine years for that pressure vessel or steam
generator and written approval by an approved inspection
authority: Provided further that the chief inspector may require a
specific steam generator or pressure vessel to be inspected or
tested more frequently; and
(e) all piping and pipelines to be inspected and tested in accordance
with the relevant in-service health and safety standard: Provided
that where the health and safety standard does not prescribe in-
service inspections and test intervals, such intervals shall be
determined by a risk-based inspection applying sound engineering
practice: Provided further that such inspection and test for
Category II equipment and higher as categorized in terms of SANS
347 shall be performed by a competent person referred to in
regulation 1 of the General Machinery Regulations, 1988.
(2) Where it is impracticable to use a liquid for the hydraulic pressure test
referred to in sub regulation (1)(d) or (e), the test may, subject to the
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prior written approval of an approved inspection authority, be carried
out with an inert gas to a pressure of 1,1 times the design pressure:
Provided that, where reasonably practicable, the test shall be preceded
by an internal inspection and any conditions and precautionary
measures determined by the user and approved by the approved
inspection authority.
(3) Where an inspection or test carried out in terms of sub regulation (1)(c),
(d) and (e) reveals any weakness or defect whereby the safety of
persons may be endangered, the weakness or defect shall be reported
forthwith to the user by the person carrying out the inspection or test and
the user shall forthwith cease the use of the pressure equipment until
such weakness or defect has been rectified to the satisfaction of the
person who carried out the inspection and the approved inspection
authority concerned in cases of modifications or repairs, as the case
may be, or the steam generator, pressure vessel or storage vessel has
been re-rated to the satisfaction of the approved inspection authority.
7.10 Records
(1) Every user of pressure equipment shall keep a record, which shall be
open for inspection by an inspector, in which the certificate of
manufacture, and the results, after manufacturing, of all inspections,
tests, modifications and repairs shall be recorded.
(2) When pressure equipment is sold, the manufacturer shall ensure that it is
accompanied, where relevant, with instructions for the user, containing
all the necessary safety information relating to -
(a) mounting, including the assembling of different pieces of pressure
equipment;
(b) putting into service; and
(c) maintenance, including checks by the user:
Provided that those instructions shall cover information affixed to
the pressure equipment in accordance with these Regulations and
the relevant health and safety standard incorporated into these
Regulations by section 44 of the Act, with the exception of serial
identification, and be accompanied, where appropriate, by
technical documents, drawings and diagrams that are necessary
for a full understanding of the instructions: Provided further that, if
appropriate, the instructions shall also refer to hazards arising from
misuse of the pressure equipment.
(3) The manufacturer shall keep the original manufacturing records of the
pressure equipment for a minimum period of 12 years.
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7.11 Introduction to boiler and pressure vessels
Below are extracts from the Boiler and pressure vessels act relevant to the work
covered in this course.
GENERAL 2.
(1) Except as provided in subsection
(2) this Act and the regulations apply to all boilers, pressure vessels, power
plants, heating plants and pressure plants and fuel-burning equipment.
(3) This Act and the regulations do not apply to
(a) a boiler having a boiler rating of 10 kilowatts or less in capacity which
forms the whole or part of a power plant;
(b) a boiler having a boiler rating of 20 kilowatts or less in capacity, installed
in a heating plant;
(c) a boiler that is intended to be used in connection with a hot water
heating system and that has no valves or other obstructions to prevent
circulation between the boiler and the expansion tank, but only if the
expansion tank is fully vented to the atmosphere;
(d) a pressure vessel of 152 millimetres or less in internal diameter;
(e) a pressure vessel which is used for the storage of hot water and has an
internal diameter of 610 millimetres or less;
(f) a pressure vessel operating at and with relief valves set at 103
kilopascals or less;
(g) a pressure vessel intended to be installed in a closed hot water heating
system having a working pressure of 207 kilopascals or less and having
an internal diameter of 610 millimetres or less; or
(h) any pressure piping system and machinery and equipment ancillary
thereto by which refrigerants are vaporized, compressed and liquefied
in the refrigerating cycle and that has a capacity of 10.5 kilowatts or
less. 1981, c.4, s.2; 1986, c.8, s.2; 1988, c.13, s.1; 2015,c.36,s.10
(4) Civil Service Act R.S.P.E.I. 1988, Cap. C-8
(1) In accordance with the Civil Service Act R.S.P.E.I. 1988, Cap. C-8, there
shall be appointed a chief inspector and such other inspectors as may
be required for the purposes of this Act and the regulations.
(2) Where the chief inspector is given any power or duty under this Act or
the regulations, the chief inspector may authorize an inspector or other
person to exercise or perform that power or duty upon such conditions
or in such circumstances as the chief inspector prescribes and
thereupon that power or duty may be exercised or performed by the
inspector or other person so authorized in addition to the chief
inspector. 1981,c.4,s.3; 1994,c.4,s.2 {eff.} July 14/94; 2012(2nd),c.2,s.2. 4.
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Where any calculation is made with respect to the application of this
Act or the regulations, the calculation shall be made and determined
in accordance with the regulations. 1981,c.4,s.4.
FITTINGS 10.
(1) Any person who intends to construct in the province a fitting in connection
with any boiler, pressure vessel or pressure piping system, shall apply to the
chief inspector to register the fitting in accordance with the regulations.
(2) Where an inspector is satisfied that the application forms are properly
completed, the fitting shall be registered and the applicant notified
accordingly.
(3) No person shall commence construction of any fitting in the province
unless the fitting has been registered in accordance with the regulations.
1981, c.4, s.10. 11. Any person who brings into the province a new or used
fitting that has not been registered in accordance with the regulations shall
apply for registration of the fitting. 1981,c.4,s.11. 12.
(1) Where a person wishes to make any change to the manner or method of
constructing a fitting that is registered in accordance with the regulations,
the person shall apply to the chief inspector to register the change.
(2) Where an inspector is satisfied that the application forms are properly
completed, the change to the fitting shall be registered and the applicant
notified accordingly.
(3) Where the design of a fitting is changed, no person shall commence
construction in accordance with the change unless the change is
registered in accordance with the regulations. 1981,c.4,s.12;
2012(2nd),c.2,s.5. 13.
(1) Where a fitting has been registered in accordance with the regulations
and the chief inspector determines that the fitting
(a) is not safe; or
(b) does not meet or no longer meets the requirements of the regulations,
the chief inspector shall give notice in writing to the person who
registered the fitting that from a date specified in the notice, the fitting
described therein shall not be constructed in the province in
connection with a boiler, pressure vessel or pressure piping system.
(2) Upon receipt of a notice referred to in subsection
(1) the person who registered the fitting shall forward copies of the notice to
every person who is permitted to construct the fitting referred to in the
notice.
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(3) No person shall construct a fitting in the province contrary to a notice
referred to in subsection (1).
(4) No person shall use, sell or otherwise dispose of any fitting in the province
that is intended for use in connection with a boiler, pressure vessel or
pressure piping system.
BOILER AND PRESSURE VESSEL IDENTIFICATION
14. Before an inspector issues the first certificate of inspection with respect to
any boiler or pressure vessel the inspector shall ensure that the boiler or
pressure vessel is stamped with an identification number. 1981,c.4,s.14;
2012(2nd),c.2,s.6.
Activity 7.1
1. Every user shall cause his/her pressure vessel to undergo an internal
inspection and a hydraulic test before commissioning. Who must do the
inspection and test?
2. A vessel under pressure may not be used unless they are at all times
maintained in a clean and safe order. From what must it be kept clean
and free?
3. No person shall use a boiler unless he/she is possession of what?
4. Regulation C99 of the factories act, refers to the returns of boilers. Name
six different occasions when a written notification and approval must be
sought from the inspector.
5. Define the term pressure vessel as given in the vessels under pressure
regulation.
6. Define the terms as given in the Vessels under pressure regulations: Modify
and repair.
7. Every boiler and pressure vessel shall be fitted with a data plate securely
fixed to the shell, in a conspicuous place. What particulars shall be on this
plate?
8. Of what changes in the status of a boiler must you forthwith notify the
provincial director?
9. What must you do if you intend to modify your boiler?
10. With reference to boilers, what shall cause the certificate of certification
to lapse?
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Self-Check
I am able to: Yes No
Describe the condition that boilers and pressure vessels should
be kept in
Describe documentation required in order to operate a boiler
Describe how boiler documentation is obtained
Describe the procedure to be taken before changes are
performed on a boiler
If you have answered ‘no’ to any of the outcomes listed above, then speak to
your facilitator for guidance and further development.
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TaPbalesotf CExamination Papers
NOVEMBER 2014
NATIONAL CERTIFICATE
POWER MACHINES N5
(8190035)
26 November 2014 (Y-Paper)
13:00 – 16:00
REQUIREMENTS:
Steam Tables (BOE 173)
Superheated Steam Tables (Appendix to BOE 173)
Calculators may be used.
This question paper consists of 5 pages and a formula sheet of 3 pages.
DEPARTMENT OF HIGHER EDUCATION AND TRAINING
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REPUBLIC OF SOUTH AFRICA
NATIONAL CERTIFICATE
POWER MACHINES N5
TIME: 3 HOURS
MARKS: 100
__________________________________________________________________
INSTRUCTIONS AND INFORMATION
1. Answer ALL the questions.
2. Read ALL the questions carefully
3. Number the answers according to the numbering system used in this question
paper.
4. Write neatly and legibly.
___________________________________________________________________
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QUESTION 1:
1.1 State THREE advantages of a condenser. (6)
1.2 Every hour a surface condenser processes 6 500 kg exhaust steam,
which has a dryness fraction of 0,83. Air leakage into the condenser is at
a rate of 1 ,2 kg/1 000 kg of steam. The air pump suction pipe and the
condensate have a temperature of 31 ºC each. The barometer and
vacuum gauge reading is 760 mm Hg and 662 mm Hg respectively. The
temperature of the cooling water is increased by 21 ºC after it passes
through the condenser. The specific heat capacity of the water is 4 187
kJ/kg.K and R for air is 0,288 kJ kg K.
Calculate the following:
1.2.1 The mass of cooling water required by the condenser every minute (8)
1.2.2 The capacity of the air pump in m3/min (6)
[20]
QUESTION 2:
2.1 A certain gas has a density of 1,28 kg/m3 at 200 kPa and 267ºC. The law
PV1,29=C is used to expand 0,7 kg of this gas to 2,5 time its original
volume, from 200 kPa and 267ºC.
Calculate the following: (3)
2.1.1 The characteristic gas constant
2.1.2 The original and final volume of the gas (6)
2.1.3 The final pressure of the gas (3)
2.1.4 The final temperature of the gas (3)
2.1.5 The work done during the expansion (3)
2.2 State the function of a governor. (2)
[20]
QUESTION 3:
Gas leaves a single-stage impulse turbine at an angle of 41 º. Friction
over the blading causes a 10% loss in velocity. The relative velocity of the
gas at the inlet to the blades is 350 m/s at an angle of 30°. The blade
experiences a peripheral velocity of 175 m/s, when 50 kg of gas flows
through the turbine every second.
3.1 Use a scale of 1 cm = 25 m/s and construct a velocity diagram in the (11)
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ANSWER BOOK. Enter ALL the values (m/s) onto the diagram.
NB: NO marks will be awarded if the values (m/s) are NOT entered onto
the diagram and if the diagram is NOT constructed to the given scale.
HINT: Use the answer page in the landscape format to construct the
diagram.
3.2 Determine the following from the diagram:
3.2.1 The nozzle angle (1)
3.2.2 The nozzle velocity (1)
3.2.3 The exit angle of the moving blades (1)
3.2.4 The axial thrust (3)
3.2.5 The power developed (3)
[20]
QUESTION 4:
4.1 18,04 kg of air is used for the complete combustion of a kilogram of fuel. (18)
The fuel has the following composition:
Carbon = 87%
Hydrogen = 2,5%
Sulphur = 1%
The balance of the fuel is non-combustible
Calculate the percentages of the products of combustion.
4.2 Regulation C112 provides for the access and inspection openings of (2)
boilers.
Name TWO reasons for these openings.
[20]
QUESTION 5:
5.1 A single-stage, double-acting, compressor must deliver 16 m3 of air every
minute. The compressor receives the air at 101,3 kPa and 20 ºC and
delivers it at a pressure of 900 kPa. The effective volume is 0,94 of the
swept volume, and the speed of the compressor is 375 r/min. The index
of compression is 1 ,3 and the mechanical efficiency is 79%.
Calculate the following:
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5.1.1 The volumetric efficiency (3)
5.1.2 The swept volume (4)
5.1.3 The temperature of the delivered air (3)
5.1.4 The power required to drive the compressor (6)
5.2 Regulation C97.7 refers.
State the hydraulic test pressure for the following boilers:
5.2.1 Boilers which do NOT exceed the working gauge pressure of 500
kPa.
5.2.2 Boilers which exceed the working gauge pressure of 500 kPa.
(2 x 2) (4)
[20]
TOTAL: 100
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Marking Guidelines
NOVEMBER 2014
NATIONAL CERTIFICATE
POWER MACHINES N5
(8190035)
26 November 2014 (Y-Paper)
13:00 – 16:00
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