Steam Turbines A Flashcards
1
Q
Why are most steam turbines covered in insulation?
A
To retain heat and protect personnel.
Insulation is also known as lagging.
2
Q
As it relates to steam turbines, what is lagging?
A
Insulation
This is the insulation around the exterior of the steam turbine, used to reduce heat loss and protect personnel.
3
Q
As it relates to steam turbines, what is a sentinel valve?
A
A safety valve that makes a whistling noise when an overpressure condition is sensed.
This valve blows off excess pressure in a steam turbine.
4
Q
What causes a sentinel valve to blow?
A
Excess steam pressure.
5
Q
True or false: A sentinel valve is designed as a warning device, as well as a way to relieve or reduce pressure within the steam turbine.
A
False
The sentinel valve is an audible warning device only, and doesn’t relieve any steam pressure within the turbine.
6
Q
What kind of temperatures would one expect to see in the lubrication and hydraulic systems used on steam turbines?
A
Up to 120℃
Contact with any of the parts or with the steam or oil from a ruptured line could cause serious burns.
7
Q
What type of oil system in a steam turbine can reach pressures in excess of 2500 psi?
A
The jacking and hydraulic oil systems.
8
Q
True or false: Steam leaks can be invisible.
A
True
Dry steam is invisible to the naked eye.
9
Q
What two advanced tools are used for leak detection on steam turbines?
A
- infrared thermography
- ultrasonic acoustic equipment
Never use your hand or any body part to check for leaks.
10
Q
What two basic tools can be used to detect steam leaks on a turbine?
A
- stick with a rag
- piece of cardboard
NeverNever use your hand or any body part to check for leaks.
11
Q
Steam turbines are equipped with an emergency trip mechanism to shut off the steam in the event of ______.
A
overspeed
If an overspeed condition occurs while the turbine is in operation, immediately evacuate the building.
12
Q
Inspection and testing of the trip mechanism should be done only with the steam turbine _______.
A
unloaded (uncoupled)
13
Q
What four piping systems must be blocked in before work can proceed on a steam turbine?
A
- steam supply
- jacking oil
- lubrication oil
- hydraulic oil
This is in addition to LOTO of all electrical, mechanical and potential energy.
14
Q
True or false: Ensure that you check for radiation levels when working on a steam turbine at a nuclear reactor.
A
True
15
Q
True or false: A steam turbine is a type of external combustion engine.
A
True
It is a heat engine that obtains its heat from fuel consumed outside the turbine cylinder.
16
Q
Which one of Newton’s Laws applies to steam turbines?
A
Newton’s Third Law
For every action, there is an equal and opposite reaction.
17
Q
Define Newton’s Third Law.
A
For every action, there is an equal and opposite reaction.
18
Q
What is an example of Newton’s Thrid Law in action inside of a steam turbine?
A
The steam velocity (kinetic) energy imparting mechanical (kinetic) energy as it accelerates through the rotor blades, pushing back on the blades as it leaves.
This causes the blades to move in the opposite direction to the steam as it leaves the blades.
19
Q
This type of steam is steam that has been heated to temperatures above the its vapour point.
A
Superheated steam
This steam has absorbed additional latent heat.
20
Q
This type of steam is steam that is at a pressure and temperature where condesning of steam is occuring (boiling, water, fog).
A
Wet steam
This is steam that has shifted from the sensible heat stage to the latent heat stage.
21
Q
This type of steam is steam that has no condensation present.
A
Dry steam
This is the type of steam that is desireable in steam turbines.
22
Q
What type of steam is desireable for powering turbines?
A
Dry steam
Steam that has no condensation present.
23
Q
What Priniciple describes the change from potential energy to kinetic energy that takes place in a steam turbine as the steam flows through the nozzles?
A
Bernoulli’s Prinicple.
An increase in the velocity (kinetic energy) of a fluid occurs simultaneously with a decrease in pressure (potential energy).
24
Q
Steam turbines are divided into what two operational types?
A
- Impulse type.
- Reaction type.
These are based off of the shape of their blades.
25
Small steam turbines tend to use the ____ principle.
impulse
26
Large steam turbines tend to use the ____ principle.
reaction
27
This style of steam turbine blade is not symmetrical and they look like an airfoil wing.
Reaction blades
## Footnote
These blades use a pressure difference between the inlet and outlet of the blades to harness the steam energy.
28
This style of steam turbine blade is symettrical.
Impulse blades
## Footnote
These blades harness the velocity of the steam to impart energy into the blades.
29
This style of steam turbine blade uses a pressure difference between the inlet and outlet of the blades to harness the steam energy.
Reaction blades
## Footnote
This pressure differntial results in axial thrust being developed across the blade.
30
This style of steam turbine blade harnesses the velocity of the steam to impart energy into the blades (Newton's Third Law).
Impulse blades
## Footnote
Also called "bucket" blades.
31
This style of steam turbine blades is also known as a "bucket" blade.
Impulse blades
32
What is the enthalpy of steam?
The total energy content of the steam.
## Footnote
This includes the energy from heat, weight, pressure and velocity.
33
The total energy available from steam is due to its heat, weight, pressure and velocity. This is known as the:
Enthalpy of the steam
## Footnote
The total energy of the steam.
34
True or false: The blade shape on a steam turbine rotor determines the principle used to harness the energy of the steam and how efficiently it is accomplished.
True
35
What effect does an impulse nozzle have on steam in a turbine?
It changes the steam pressure to steam velocity in one step.
## Footnote
Nozzles increase the speed of the steam.
Pressure ↓ = Velocity ↑
36
This component of a steam turbine directs the incoming steam at the rotor blades while also changing the pressure of the steam to velocity in one step.
Impulse nozzles.
## Footnote
These are also known as straight nozzles.
37
In a steam turbine, how do impulse rotor blades harness the steams energy?
By changing the direction of the steam.
## Footnote
This change in direction results in a loss of steam velocity due to the energy imparted to the turbine rotor in the form of mechanical energy (Newton's Third Law).
38
What effect does the change of direction of the steam as it passes through an impulse rotor blade have on the velocity of the steam?
Velocity ↓
## Footnote
This change in direction results in a loss of steam velocity due to the energy imparted to the turbine rotor in the form of mechanical energy (Newton's Third Law).
39
What effect does the change of direction of the steam as it passes through an impulse rotor blade have on the pressure of the steam?
The steam pressure remains constant.
## Footnote
There is no change in steam pressure across the blade when the steam passes through it.
40
1. In a steam turbine, is there a pressure drop acorss impulse blading?
2. Why is this?
1. No.
2. There is no change in the space between the entry and exit throught the blading.
## Footnote
This also results in there being minimal axial thrust developed.
41
1. Is sealing required between rows of impulse blades in steam turbines?
2. Why is this?
1. No.
2. Because there is no pressure differential between the inlet and outlet of the blade.
## Footnote
This also means that there is minimum axial thrust produced by this style of blading.
42
With this type of steam turbine, the velocity of the steam is absorbed by two or more rows of moving bucket blades with rows of fixed or reversing flow guide blades, attached to the casing, between them.
Velocity compounding turbine.
| This design is very common in small impulse turbines.
## Footnote
There is no sealing required between the blades, as there is no pressure drop across both impulse blades and redirection blades.
43
What effect do fixed guide blades (re-directional blades) have on the:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?
1. Pressure = unchanged
2. Velocity = unchanged
3. Volume = unchanged
## Footnote
These blades only receive redirect the steam to the next row of rotor blades, and have no effect on the steam pressure, velocity, or volume.
44
True or false: In steam turbines, re-directional blades and fixed guide blades are the same thing.
True
## Footnote
These are found in impulse turbines or sections.
45
This style of steam turbine blade is not symettrical and their tips are not parallel to the shaft.
Reaction blades.
## Footnote
This style of blade produces a pressure drop across them, which results in axial thrust.
46
With this style of steam turbine blade, the space between the blades is smaller at the exit, resulting in the steam accelerating as it passes through the blading, resulting in a pressure drop that causes the steam to "push" the blade as it leaves.
Reaction blades.
## Footnote
This pressue drop across the blades pushes on the blades as it leaves → a reaction → this is essentially lift (air wing).
47
Why are steam turbines rarely purely reaction blade turbines?
The length of the turbine would be excessive.
## Footnote
The pressure drop (and consequent reaction on the turbine blade) is small at each row of blades. In order to harness all of the steam energy, more blades would be required, which would result in a very long turbine.
48
How is the number of overall blades rows on a reaction bladed turbine reduced?
By having a velocity compounding impulse section at the inlet.
49
What two effects does having an impulse section at the inlet of a reaction turbine serve?
1. Reduces the turbine length (shorter).
2. Improves efficiency*.
## Footnote
*Because there is no pressure drop across the impulse blading at the inlet (very high pressures), sealing between the rows is not necessary which leads to less interal leakage between stages in the impulse section.
50
In a steam turbine, thrust is always in the direction ____ (towards/away) from the nozzles/steam inlet.
away
51
Where is the inboard bearing located on a steam turbine?
At the steam inlet.
| This is the opposite end from the coupling.
## Footnote
This is also the location for the thrust bearing.
52
Fill in the blank: Multiple stages of reaction blading in a steam turbine is called a ________ ________ turbine.
pressure compounding
53
In a steam turbine, what effect do stationary reaction blades have on:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?
1. Steam pressure ↓
2. Steam velocity ↑
3. Steam volume ↑
## Footnote
Stationary reaction blades act like nozzles, decreasing the pressure while increasing the velocity.
54
# Answer with etiher drops or rises.
Fill in the blank: In a reaction steam turbine, the steam pressure 1.________ across both the fixed and moving blades while the absolute velocity 2.________ in the fixed blades and 3.________ in the moving blades.
1. drops
2. rises
3. drops
55
In a reaction steam turbine, why is there a velocity drop in the moving blades?
They are imparting energy into the rotor wheel.
## Footnote
Newton's Third Law
56
What are two problems that the pressure drop across moving reaction turbine blades causes?
1. The steam wants to leak around the periphery of the blades rather than passing through them.
2. Creates an unbalanced axial thrust on the rotor.
## Footnote
Both lead to reaction turbines being more complicated, longer and more expensive to build and maintain.
57
In a steam turbine, what has the largest single effect on overall efficiency of the turbine?
The design of the turbine blades.
58
Which type of steam turbine requires the use of shaft seals and shroud seals between rotor stages?
Reaction turbines.
## Footnote
The pressure drop across the reaction blades causes a pressure diference between the inlet and outlet of the blade, which results in steam wanting to bypass the blades.
59
What are the most common ways that steam turbine blades are attached to the rotor?
With the dovetail or fir tree method.
60
In a steam turbine, what is a low-pressure rotor blade?
A blade design with a twisted profile.
## Footnote
The gives the blade a partial impulse profile near the base and a reaction profile near the tip.
61
This type of steam turbine rotor blade has a twist in it, which results in the blade having a partial impulse profile near the base and a reaction profile near the tip.
Low-pressure blades.
## Footnote
These blades have a twisted profile.
62
What are four purposes for attaching shrouding around the periphery of steam turbine rotor blades?
1. Maintains blade spacing.
2. Reduce leakage paths.
3. Strengthens the assembly.
4. Redcues vibration*.
## Footnote
The shroud changes the natural frequency of the blades.
63
How is shrouding attached to the periphery of steam turbine rotor blades?
Rivited in sections over a tenon.
## Footnote
A tenon is a rivet that holds the shroud to the blade.
64
In steam turbines, what is a tenon?
A rivet that holds the shroud to the rotor blade.
65
In a steam turbine, what is wire lacing?
A steel wire that is threaded through the blades at intermediate lengths from the base.
## Footnote
This acts to stiffen and dampen the blades which reduces their tendency to vibrate.
66
What effect does lacing have on rotor blades inside of steam turbines?
It stiffens and dampens the blades.
## Footnote
This reduces their tendency to vibrate.
67
True or false: You can find shrouds or wire lacing on steam turbine rotor assemblies, but never both.
False.
## Footnote
Wire lacing can be used on blades along with a shroud.
68
True or false: When steam turbine blades get very large, shrouding is not used, but for added strength and stiffness, wire lacing is used.
True
69
True or false: Shrouds on steam turbine rotors often have sealing around the periphery to prevent leakage.
True
## Footnote
This is seen more on reaction type blading, as impulse blading does not require sealing.
70
How is sealing accomplished on steam turbine rotors that do not have shrouds?
By making the ends of the blades very thin and having minimal clearances between the blades and casing.
71
Why is it critical that steam turbine rotor blades be placed in their required positons on the rotor?
To maintain rotor balance.
## Footnote
The rotor and blade assembly is statically and dynamically balanced at the factory, with the blade positons labelled.
72
What is a steam turbines critical speed?
Speeds at which the rotor becomes unstable and begins to vibrate violently.
## Footnote
These speeds are determined by the rotor's natural frequency.
73
On steam turbine rotors, these speed ranges are when the natural frequency of the rotor blade corresponds with the rpm frequency.
Critical speed ranges
## Footnote
Steam turbines may have more than one → 1st critical, 2nd critical, etc.
74
What must happen if a steam turbine needs to run above a critical speed?
Accelerate quickly through the critical speed range.
## Footnote
If the turbine lingers in critical speeds, the excessive vibrations could cause significant damage.
75
True or false: Stationary reaction blades are the same as reaction nozzles.
True
76
In larger steam turbines, nozzles are comprised of reaction-type shaped blades fixed in a stationary housing called a:
Diaphragms.
## Footnote
These are anchored to the turbine casing.
77
In reaction turbines, what do reaction nozzles attach to and seal against?
Diaphragms.
## Footnote
These are located between each row of rotating blades in a reaction turbine.
78
When steam passes through any reaction type nozzle, what happens to the:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?
1. Steam pressure ↓
2. Steam velocity ↑
3. Steam volume ↑
| Reaction type nozzle = stationary reaction blade
79
In reaction turbines, why do the turbine blades get longer in each successive stage?
To accomodate the steam expansion.
## Footnote
The steam volume increases after it passes through each reaction type nozzle.
80
What are two ways that manufacturers use to determine steam turbine staging?
1. By the number of rotating rows of blades.
2. By the number of pressure drops across the turbine.
81
Which type of steam turbine is more efficient at high pressures?
Impulse turbines.
| These turbines do not require sealing between stages.
82
Which type of steam turbine is more efficient at low pressures?
Reaction turbines.
83
What is one stage in an impulse turbine?
One rotating wheel.
| Each rotating wheel in an impulse turbine is considered a single stage.
84
What is one stage in a reaction turbine?
A ring of reaction nozzles and the associated rotor wheel.
| One pressure drop.
85
What are the three types of turbine sections found in large turbine arrangements with three or more cylinders?
1. High-pressure section
2. Inetermiediate-pressure section
3. Low-pressure section
86
When referring to steam turbines, what are cylinders, casings, or sections?
Turbine housings
87
This type of steam turbine blade has about the same efficiency at all loads except for lower pressures.
Impulse blades
88
What types of rotor blades would be seen in a velocity compounding turbine?
Sets of impulse (bucket) blades.
## Footnote
It would also have a straight or impulse nozzle.
89
This type of steam turbine is considered inefficient at higher pressures due to leakage past the blade tips.
Reaction turbines
## Footnote
This leakage is caused by the pressure differential between the inlet and outlet of the blades.
90
This type of steam turbine is good for varying loads, using high pressure steam, and for using all the energy in the steam.
Combination impulse/reaction turbine.
## Footnote
The impulse blades are always first, at the higher pressure end of the turbine.
91
What effect does a combination impulse/reaction turbine have on the overall size of the steam turbine?
It makes it smaller.
92
What is a tandem-compound turbine?
A large turbine consisting of several section (cylinders or casings) connect at their shafts.
93
What is the shaft arrangement for a tandem-compound turbine assembly?
Several sections connected at their shafts with rigid couplings.
## Footnote
These sections are co-linear, from end-to-end.
94
What is a steam extraction turbine?
A steam turbine where steam is extracted off at certain points to be used in other plant processes.
## Footnote
These can include feed-water heating, extraction to avoid wet steam in later stages, etc.
95
What determines the location of extraction steam valves on a turbine?
The pressure required.
## Footnote
The further the extraction point is from the SAV, the lower the pressure.
96
On a steam turbine, what is a SAV?
A steam admission valve.
## Footnote
These are located within the steam chest.
97
The further the extraction valve on a steam turbine is from the SAV, the ________ the steam pressure.
lower
98
What are the two types of steam extraction methods on extraction turbines?
1. Controlled extraction.
2. Uncontrolled extraction.
99
True or false: Steam extraction can be used to replace wet steam in later stages of a turbine with dry steam.
True.
## Footnote
The expansion and removal of energy from the steam leads to increased moisture as the steam crosses the staturation point.
100
What effect does the expansion and removal of energy from the steam as it passes through the turbine have on the moisture content of the steam itself?
The steam becomes wetter as energy is removed and the steam crosses the saturation point (condensing point).
## Footnote
This is one reason why wet steam may be extracted and replaced with dry steam.
101
At what pressure range do boilers operate the most efficiently?
At high pressures.
102
With this type of steam turbine setup, the turbine is used like a regulator to step down the steam pressure to allow it to be used elsewhere in the facility.
Extraction turbines.
## Footnote
These style of turbines increase the efficiency of the facility.
103
What effect do extraction valves have on the pressure inside the turbine?
None
## Footnote
Extraction valves do not affect the pressure inside the turbine, rather reduce the volume/flow of the steam inside the turbine.
104
What effect do extraction valves have on the velocity inside the turbine?
Velocity ↓
## Footnote
The extraction valves remove volume/flow from the turbine (pressure remain unchanged).
105
What valve is a steam extraction valve connected to?
The governor.
## Footnote
The more steam is extracted, the more steam is admitted.
106
As it related to steam turbines, what is a condesner?
A heat exchanger that turns the steam back into hot water.
## Footnote
These are always located at the outlet of the turbine, usually below the turbine.
107
On a condesning steam turbine, what effect does the condensing of steam into water have on the pressure inside of the condenser?
It creates a low pressure (vacuum) in the condenser.
108
On a condensing steam turbine, what effect does the condenser have on the overall steam turbine efficiency?
It increases efficiency
## Footnote
This is due to less backpressure and recycled condensate.
109
In what two ways is the efficiency of a condensing turbine increased by the condenser?
1. Reduced backpressure.
2. Recycled condensate.
110
What type of turbines are considered back-pressure turbines?
Non-condesning turbines
## Footnote
Any turbine without a condesner is considered a back-pressure turbine.
111
True or false: The condesning action in a condesing steam turbine results in a very large pressure difference between the steam inlet and the condesner.
True
112
True or false: An almost perfect vacuum is achieved with a condenser on a condesning turbine.
True
## Footnote
Almost 29.92 inHg
113
On a steam turbine, what is a rupture disk?
A single use safety device that opens in the case of cylinder overpressure (a pressure relief valve).
## Footnote
A rupture disk is a pressure relief device that serves as a safety mechanism in a steam turbine system, designed to rupture at a predetermined pressure to prevent overpressure damage.
114
What condition does a rupture disk prevent?
Overpressure
## Footnote
A rupture disk is a single use pressure relief device that serves as a safety mechanism in a steam turbine system, designed to rupture at a predetermined pressure to prevent overpressure damage.
115
Are rupture disks resettable?
No
## Footnote
Rupture disks are one time use, and must be replaced if burst.
116
On a steam turbine assembly, the ________ is where the fuel is burned and the water is changed to high-pressure steam.
boiler
117
Where is the high-pressure steam from the boiler piped into on a steam turbine?
Into the steam chest.
118
1. What is the most common type of casing found on steam turbines?
2. Why is this?
1. Horizontally split.
2. This casing design allows for easy access to most of the inner components.
119
What type of casing would be found on a steam turbines with very high pressures?
Double casings
## Footnote
These are common on very large turbines.
120
On what type of turbines are sentinel valves found?
On small impulse turbines.
121
What component of a steam turbine harnesses the energy of steam?
The rotor assembly
## Footnote
Specifically the rotor blades.
122
In steam turbines, ________ are stationary blades or orifices that direct the steam towards the blades and change high pressure from the boiler into high velocity.
nozzles
123
This steam turbine component is a stationary separator between the discs of the rotor, and is fixed to the case and sealed around the shaft.
Diaphragms
124
In a steam turbine, this component admits steam to the nozzles.
Steam admission valve
| Also known as the steam valve.
## Footnote
This is controlled by the governor.
125
This component of a steam turbine shuts off all steam to the turbine in the event of an overspeed situation.
The stop valve
## Footnote
This valve is located in the steam chest, ahead of the SAV.
126
Most larger steam turbines use bearings that have self-aligning spherical seats. What are two reasons for this?
1. Allow the bearings to tilt according to the sag in the turbine shaft.
2. Maintain shaft (journal) contact during thermal growth.
127
What two valves are contained within the steam chest of a steam turbine?
1. The stop valve.
2. The SAV (governor valve).
## Footnote
The stop valve is always upstream of the SAV.
128
On a steam turbine, which valve within the steam chest is connected to the steam inlet?
The stop valve
## Footnote
The stop valve is always upstream of the SAV.
129
What type of bearing is used to control thrust on a purely impulse bladed steam turbine?
A deep groove ball bearing.
## Footnote
Impulse blades generate minimal thrust.
130
What type of bearing is used to control thrust on a steam turbine with reaction blading?
A set of tilting-pad bearings.
## Footnote
The thrust collar can be either an integral part of the shaft or attached to the shaft.
131
Why are tilting-pad thrust bearings selected for axial thrust control in steam turbines?
They are able to maintain full contact on the thrust collar when the shaft tilts due to sag.
132
Where is the thrust bearing usually located on the steam turbine?
At the steam inlet end
## Footnote
This is often the end that is opposite the coupling
133
True or false: The high temperatures, high load bearing surfaces, and high speeds are why plain journal bearings and tilting-pad thrust bearings are selected for steam turbines.
True
134
Which type of babbit would be selected for high temperature applications: lead based babbit or tin based babbit.
Tin based babbitt
135
What type of shaft seals would be found on smaller, slow speed steam turbines?
Carbon seals
## Footnote
These seals cannot handle the surface speeds found on larger machines.
136
What type of shaft seals would be found on larger, high speed steam turbines?
Labyrinth seals
## Footnote
This has to do with the surface speeds found on some of the larger machines.
137
On steam turbines using carbon shaft seals, what kind of clearance should be expected between the OD of the shaft and the ID of the seal?
0.001"
138
True or false: In steam turbines, when carbon ring seal to shaft clearances are too large, the seal can be adjusted by filling the end gaps.
False
## Footnote
These ends are precision machined, and cannot be adjusted in the field.
139
When installing carbon ring seals into a steam turbine, how should the match marks (dots) be installed in relation to pressure?
The match marks must face towards pressure.
## Footnote
When installed, these seals must be free to move axially for proper sealing.
140
In a steam turbine, what component holds a carbon seal together?
Garter springs
141
True or false: In steam turbines, carbon ring seals must be installed so that they can rotate as well as move axially.
False
## Footnote
While they do need to move axially, carbon ring seals must be installed with an anti-rotation tab to prevent rotation.
142
This type of steam turbine seal operates on the principle of pressure dropping each time the steam accelerates past the knife-edge restriction.
Labyrinth seals
## Footnote
Axial shaft position is critical to the survival of these seals.
143
What type of seal is used when the thermal growth of a steam turbine exceeds the capability of labyrinth seals?
Annunlus seals
## Footnote
Axial movement (from thermal growth) is not a factor with this type of seal.
144
This type of steam turbine seal consists of a set of knife edges fitting close to a journal-like shaft section.
Annulus seals
145
In a high speed steam turbine, on which type of seal is axial shaft position critical to the survival of the seal: annulus seals or labyrinth seals?
Labyrinth seals
## Footnote
Axial movement is not a factor with annulus seals.
146
Which type of seal would be used if the thermal growth of a larger steam turbine is excessive?
Annulus seals
147
This type of turbine seal is a series of labyrinth seals with steam pockets between them where steam is introduced or bled off.
Steam seals
## Footnote
These seals use steam pressure to keep contaminants out.
148
On a steam turbine, what type of seal would be used for sealing very high pressures or when sealing a vacuum on the condesner end of a large turbine?
Steam seals
149
True or false: In steam turbines, air or other contaminants are considered non-condensables.
True
## Footnote
A non-condesnable is anything that isn't water → this includes nitrogren, oil, etc.
150
On what type of steam turbine would blade seals be found?
Reaction turbines
## Footnote
Blade seals are used on the periphery and shaft to prevent steam leakage.
151
True or false: Steam turbine blade seals are a variation of a labyrinth seal.
True
## Footnote
These seals work to limit pressure leakage due to a of a bunch of successive pressure drops.
152
This component of a steam turbine converts kinetic energy from the steam into mechanical energy.
The rotor blades
153
What is the moment weight of a steam turbine rotor blade?
The weight of the blade multiplied by the radial distance to the centre of gravity.
154
Steam turbine manufactureres record the moment weights of each rotor blade. What two things does this do?
1. Minimizes the amount of balancing required*.
2. A blade can be replaced with the need for rebalancing.
## Footnote
*Blades of equal moment weight can be installed opposing each other, resulting in a more balanced rotor from the factory.
155
What type of coupling is usually found on a steam turbine?
Rigid couplings
156
On steam turbines, when installing a rigid coupling, why is it important to handle the coupling bolts with care and to install them into their proper locations?
Fit and balance of the coupling.
157
True or false: Most steam turbine failures occur because of some type of lubrication issue.
True
158
True or false: When the steam leaves the nozzle of the steam turbine, it changes from potential energy into kinetic energy.
True
## Footnote
Bernouilli's Principle → kinetic (velocity) ↑ and potential (pressure) ↓
159
True or false: The blades of an impulse-style turbine are shaped like airplane wings.
False
## Footnote
Reaction-style blades are shaped like an airplane wing.
160
True or false: The energy that is harnessed by reaction blades of a steam turbine depends on only the change of direction of the steam as it strikes the blades.
False
## Footnote
Reaction blades harness the kinetic energy of the the steam through this interaction as well as through the pressure drop (reaction or lift) of the rotor blades.
161
True or false: In reaction-type turbines, there is a pressure drop across both the stationary blades (nozzles) and the moving blades.
True
## Footnote
This pressure drop converts the steam energy from pressure to velocity (Bernoulli’s Principle)
162
True or false: When a turbine is staged, it means that the steam passes through more than one set of blades.
True
163
True or false: The nozzle ring attaches to the steam chest side of the turbine casing.
True
164
True or false: Carbon rings are used to keep the oil in the bearing housings.
False
## Footnote
Carbon rings are used to prevent steam from leaking out of the turbine.
165
True or false: The largest blades of a steam turbine are at the high-pressure end of the machine.
False
## Footnote
The largest blades are at the low-pressure end, due to the expansion of steam as it looses some of its energy.
166
Which valve is modulated to maintain the desired speed of the turbine?
The SAV
## Footnote
The steam admission valve.
167
Which section of a tandem-compound steam turbine has the largest size?
The low-pressure section.
168
Which section of a tandem-compound steam turbine has the smallest size?
The high-pressure section.
169
In a steam turbine, what effect do rotary reaction blades have on:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?
1. Steam pressure ↓
2. Steam velocity ↓
3. Steam volume ↑
## Footnote
The drop in velocity is due to the kinetic energy being imparted into the rotor blade. The drop in pressure is due to the design of the blade, and the volume increase is caused by the pressure dropping, which increases volume.
170
What happens to the steam pressure and velocity as the steam flows through the reaction blades on the rotor of a steam turbine?
Pressure ↓
Velocity ↓
## Footnote
Volume increases, due to the drop in pressure.
171
Why is the diameter of the steam turbine rotor shaft an important factor for the type of seal used on the turbine?
The larger the diameter, the faster the surface speed.
## Footnote
This determines what type of seal can be used.
172
What effect does lacing have on a turbine blade?
Reduces vibration
## Footnote
They act to stiffen and dampen the blades which reduces their tendency to vibrate.
173
Fill in the blank: Multiple stages of impulse blading in a steam turbine is called a ________ ________ turbine.
velocity compounding
174
What design of turbine would have a pressure and velocity diagram as shown?
Velocity compounding
## Footnote
The single pressure change indicates that there are only impulse nozzle in the turbine.
175
What design of turbine would have a pressure and velocity diagram as shown?
Combination impulse/reaction turbine.
176
What design of turbine blade would have a velocity increase on a pressure and velocity diagram?
A reaction blade
177
What effect does wire lacing have on the vibration of steam turbine rotor blades?
Wire lacing reduces vibration
## Footnote
Wire lacing acts to stiffen and dampen the blades which reduces their tendency to vibrate.
178
In steam turbines, ________ increase the speed of steam.
Nozzles
