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Millwrong > Steam Turbines A > Flashcards

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.

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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.

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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.

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4
Q

What causes a sentinel valve to blow?

A

Excess steam pressure.

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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.

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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.

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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.

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8
Q

True or false: Steam leaks can be invisible.

A

True

Dry steam is invisible to the naked eye.

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9
Q

What two advanced tools are used for leak detection on steam turbines?

A
  1. infrared thermography
  2. ultrasonic acoustic equipment

Never use your hand or any body part to check for leaks.

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10
Q

What two basic tools can be used to detect steam leaks on a turbine?

A
  1. stick with a rag
  2. piece of cardboard

NeverNever use your hand or any body part to check for leaks.

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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.

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12
Q

Inspection and testing of the trip mechanism should be done only with the steam turbine _______.

A

unloaded (uncoupled)

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13
Q

What four piping systems must be blocked in before work can proceed on a steam turbine?

A
  1. steam supply
  2. jacking oil
  3. lubrication oil
  4. hydraulic oil

This is in addition to LOTO of all electrical, mechanical and potential energy.

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14
Q

True or false: Ensure that you check for radiation levels when working on a steam turbine at a nuclear reactor.

A

True

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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.

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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.

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17
Q

Define Newton’s Third Law.

A

For every action, there is an equal and opposite reaction.

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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.

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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.

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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.

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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.

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22
Q

What type of steam is desireable for powering turbines?

A

Dry steam

Steam that has no condensation present.

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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).

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24
Q

Steam turbines are divided into what two operational types?

A
  1. Impulse type.
  2. Reaction type.

These are based off of the shape of their blades.

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25
Q

Small steam turbines tend to use the ____ principle.

A

impulse

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26
Q

Large steam turbines tend to use the ____ principle.

A

reaction

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27
Q

This style of steam turbine blade is not symmetrical and they look like an airfoil wing.

A

Reaction blades

These blades use a pressure difference between the inlet and outlet of the blades to harness the steam energy.

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28
Q

This style of steam turbine blade is symettrical.

A

Impulse blades

These blades harness the velocity of the steam to impart energy into the blades.

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29
Q

This style of steam turbine blade uses a pressure difference between the inlet and outlet of the blades to harness the steam energy.

A

Reaction blades

This pressure differntial results in axial thrust being developed across the blade.

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30
Q

This style of steam turbine blade harnesses the velocity of the steam to impart energy into the blades (Newton’s Third Law).

A

Impulse blades

Also called “bucket” blades.

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31
Q

This style of steam turbine blades is also known as a “bucket” blade.

A

Impulse blades

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32
Q

What is the enthalpy of steam?

A

The total energy content of the steam.

This includes the energy from heat, weight, pressure and velocity.

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33
Q

The total energy available from steam is due to its heat, weight, pressure and velocity. This is known as the:

A

Enthalpy of the steam

The total energy of the steam.

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34
Q

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.

A

True

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35
Q

What effect does an impulse nozzle have on steam in a turbine?

A

It changes the steam pressure to steam velocity in one step.

Nozzles increase the speed of the steam.

Pressure ↓ = Velocity ↑

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36
Q

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.

A

Impulse nozzles.

These are also known as straight nozzles.

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37
Q

In a steam turbine, how do impulse rotor blades harness the steams energy?

A

By changing the direction of the steam.

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).

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38
Q

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?

A

Velocity ↓

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).

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39
Q

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?

A

The steam pressure remains constant.

There is no change in steam pressure across the blade when the steam passes through it.

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40
Q
  1. In a steam turbine, is there a pressure drop acorss impulse blading?
  2. Why is this?
A
  1. No.
  2. There is no change in the space between the entry and exit throught the blading.

This also results in there being minimal axial thrust developed.

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41
Q
  1. Is sealing required between rows of impulse blades in steam turbines?
  2. Why is this?
A
  1. No.
  2. Because there is no pressure differential between the inlet and outlet of the blade.

This also means that there is minimum axial thrust produced by this style of blading.

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42
Q

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.

A

Velocity compounding turbine.

This design is very common in small impulse turbines.

There is no sealing required between the blades, as there is no pressure drop across both impulse blades and redirection blades.

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43
Q

What effect do fixed guide blades (re-directional blades) have on the:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?

A
  1. Pressure = unchanged
  2. Velocity = unchanged
  3. Volume = unchanged

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.

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44
Q

True or false: In steam turbines, re-directional blades and fixed guide blades are the same thing.

A

True

These are found in impulse turbines or sections.

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45
Q

This style of steam turbine blade is not symettrical and their tips are not parallel to the shaft.

A

Reaction blades.

This style of blade produces a pressure drop across them, which results in axial thrust.

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46
Q

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.

A

Reaction blades.

This pressue drop across the blades pushes on the blades as it leaves → a reaction → this is essentially lift (air wing).

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47
Q

Why are steam turbines rarely purely reaction blade turbines?

A

The length of the turbine would be excessive.

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.

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48
Q

How is the number of overall blades rows on a reaction bladed turbine reduced?

A

By having a velocity compounding impulse section at the inlet.

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49
Q

What two effects does having an impulse section at the inlet of a reaction turbine serve?

A
  1. Reduces the turbine length (shorter).
  2. Improves efficiency*.

*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.

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50
Q

In a steam turbine, thrust is always in the direction ____ (towards/away) from the nozzles/steam inlet.

A

away

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51
Q

Where is the inboard bearing located on a steam turbine?

A

At the steam inlet.

This is the opposite end from the coupling.

This is also the location for the thrust bearing.

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52
Q

Fill in the blank: Multiple stages of reaction blading in a steam turbine is called a ________ ________ turbine.

A

pressure compounding

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53
Q

In a steam turbine, what effect do stationary reaction blades have on:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?

A
  1. Steam pressure ↓
  2. Steam velocity ↑
  3. Steam volume ↑

Stationary reaction blades act like nozzles, decreasing the pressure while increasing the velocity.

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54
Q

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.

A
  1. drops
  2. rises
  3. drops
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55
Q

In a reaction steam turbine, why is there a velocity drop in the moving blades?

A

They are imparting energy into the rotor wheel.

Newton’s Third Law

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56
Q

What are two problems that the pressure drop across moving reaction turbine blades causes?

A
  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.

Both lead to reaction turbines being more complicated, longer and more expensive to build and maintain.

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57
Q

In a steam turbine, what has the largest single effect on overall efficiency of the turbine?

A

The design of the turbine blades.

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58
Q

Which type of steam turbine requires the use of shaft seals and shroud seals between rotor stages?

A

Reaction turbines.

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.

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59
Q

What are the most common ways that steam turbine blades are attached to the rotor?

A

With the dovetail or fir tree method.

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60
Q

In a steam turbine, what is a low-pressure rotor blade?

A

A blade design with a twisted profile.

The gives the blade a partial impulse profile near the base and a reaction profile near the tip.

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61
Q

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.

A

Low-pressure blades.

These blades have a twisted profile.

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62
Q

What are four purposes for attaching shrouding around the periphery of steam turbine rotor blades?

A
  1. Maintains blade spacing.
  2. Reduce leakage paths.
  3. Strengthens the assembly.
  4. Redcues vibration*.

The shroud changes the natural frequency of the blades.

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63
Q

How is shrouding attached to the periphery of steam turbine rotor blades?

A

Rivited in sections over a tenon.

A tenon is a rivet that holds the shroud to the blade.

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64
Q

In steam turbines, what is a tenon?

A

A rivet that holds the shroud to the rotor blade.

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65
Q

In a steam turbine, what is wire lacing?

A

A steel wire that is threaded through the blades at intermediate lengths from the base.

This acts to stiffen and dampen the blades which reduces their tendency to vibrate.

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66
Q

What effect does lacing have on rotor blades inside of steam turbines?

A

It stiffens and dampens the blades.

This reduces their tendency to vibrate.

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67
Q

True or false: You can find shrouds or wire lacing on steam turbine rotor assemblies, but never both.

A

False.

Wire lacing can be used on blades along with a shroud.

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68
Q

True or false: When steam turbine blades get very large, shrouding is not used, but for added strength and stiffness, wire lacing is used.

A

True

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69
Q

True or false: Shrouds on steam turbine rotors often have sealing around the periphery to prevent leakage.

A

True

This is seen more on reaction type blading, as impulse blading does not require sealing.

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70
Q

How is sealing accomplished on steam turbine rotors that do not have shrouds?

A

By making the ends of the blades very thin and having minimal clearances between the blades and casing.

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71
Q

Why is it critical that steam turbine rotor blades be placed in their required positons on the rotor?

A

To maintain rotor balance.

The rotor and blade assembly is statically and dynamically balanced at the factory, with the blade positons labelled.

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72
Q

What is a steam turbines critical speed?

A

Speeds at which the rotor becomes unstable and begins to vibrate violently.

These speeds are determined by the rotor’s natural frequency.

73
Q

On steam turbine rotors, these speed ranges are when the natural frequency of the rotor blade corresponds with the rpm frequency.

A

Critical speed ranges

Steam turbines may have more than one → 1st critical, 2nd critical, etc.

74
Q

What must happen if a steam turbine needs to run above a critical speed?

A

Accelerate quickly through the critical speed range.

If the turbine lingers in critical speeds, the excessive vibrations could cause significant damage.

75
Q

True or false: Stationary reaction blades are the same as reaction nozzles.

A

True

76
Q

In larger steam turbines, nozzles are comprised of reaction-type shaped blades fixed in a stationary housing called a:

A

Diaphragms.

These are anchored to the turbine casing.

77
Q

In reaction turbines, what do reaction nozzles attach to and seal against?

A

Diaphragms.

These are located between each row of rotating blades in a reaction turbine.

78
Q

When steam passes through any reaction type nozzle, what happens to the:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?

A
  1. Steam pressure ↓
  2. Steam velocity ↑
  3. Steam volume ↑

Reaction type nozzle = stationary reaction blade

79
Q

In reaction turbines, why do the turbine blades get longer in each successive stage?

A

To accomodate the steam expansion.

The steam volume increases after it passes through each reaction type nozzle.

80
Q

What are two ways that manufacturers use to determine steam turbine staging?

A
  1. By the number of rotating rows of blades.
  2. By the number of pressure drops across the turbine.
81
Q

Which type of steam turbine is more efficient at high pressures?

A

Impulse turbines.

These turbines do not require sealing between stages.

82
Q

Which type of steam turbine is more efficient at low pressures?

A

Reaction turbines.

83
Q

What is one stage in an impulse turbine?

A

One rotating wheel.

Each rotating wheel in an impulse turbine is considered a single stage.

84
Q

What is one stage in a reaction turbine?

A

A ring of reaction nozzles and the associated rotor wheel.

One pressure drop.

85
Q

What are the three types of turbine sections found in large turbine arrangements with three or more cylinders?

A
  1. High-pressure section
  2. Inetermiediate-pressure section
  3. Low-pressure section
86
Q

When referring to steam turbines, what are cylinders, casings, or sections?

A

Turbine housings

87
Q

This type of steam turbine blade has about the same efficiency at all loads except for lower pressures.

A

Impulse blades

88
Q

What types of rotor blades would be seen in a velocity compounding turbine?

A

Sets of impulse (bucket) blades.

It would also have a straight or impulse nozzle.

89
Q

This type of steam turbine is considered inefficient at higher pressures due to leakage past the blade tips.

A

Reaction turbines

This leakage is caused by the pressure differential between the inlet and outlet of the blades.

90
Q

This type of steam turbine is good for varying loads, using high pressure steam, and for using all the energy in the steam.

A

Combination impulse/reaction turbine.

The impulse blades are always first, at the higher pressure end of the turbine.

91
Q

What effect does a combination impulse/reaction turbine have on the overall size of the steam turbine?

A

It makes it smaller.

92
Q

What is a tandem-compound turbine?

A

A large turbine consisting of several section (cylinders or casings) connect at their shafts.

93
Q

What is the shaft arrangement for a tandem-compound turbine assembly?

A

Several sections connected at their shafts with rigid couplings.

These sections are co-linear, from end-to-end.

94
Q

What is a steam extraction turbine?

A

A steam turbine where steam is extracted off at certain points to be used in other plant processes.

These can include feed-water heating, extraction to avoid wet steam in later stages, etc.

95
Q

What determines the location of extraction steam valves on a turbine?

A

The pressure required.

The further the extraction point is from the SAV, the lower the pressure.

96
Q

On a steam turbine, what is a SAV?

A

A steam admission valve.

These are located within the steam chest.

97
Q

The further the extraction valve on a steam turbine is from the SAV, the ________ the steam pressure.

A

lower

98
Q

What are the two types of steam extraction methods on extraction turbines?

A
  1. Controlled extraction.
  2. Uncontrolled extraction.
99
Q

True or false: Steam extraction can be used to replace wet steam in later stages of a turbine with dry steam.

A

True.

The expansion and removal of energy from the steam leads to increased moisture as the steam crosses the staturation point.

100
Q

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?

A

The steam becomes wetter as energy is removed and the steam crosses the saturation point (condensing point).

This is one reason why wet steam may be extracted and replaced with dry steam.

101
Q

At what pressure range do boilers operate the most efficiently?

A

At high pressures.

102
Q

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.

A

Extraction turbines.

These style of turbines increase the efficiency of the facility.

103
Q

What effect do extraction valves have on the pressure inside the turbine?

A

None

Extraction valves do not affect the pressure inside the turbine, rather reduce the volume/flow of the steam inside the turbine.

104
Q

What effect do extraction valves have on the velocity inside the turbine?

A

Velocity ↓

The extraction valves remove volume/flow from the turbine (pressure remain unchanged).

105
Q

What valve is a steam extraction valve connected to?

A

The governor.

The more steam is extracted, the more steam is admitted.

106
Q

As it related to steam turbines, what is a condesner?

A

A heat exchanger that turns the steam back into hot water.

These are always located at the outlet of the turbine, usually below the turbine.

107
Q

On a condesning steam turbine, what effect does the condensing of steam into water have on the pressure inside of the condenser?

A

It creates a low pressure (vacuum) in the condenser.

108
Q

On a condensing steam turbine, what effect does the condenser have on the overall steam turbine efficiency?

A

It increases efficiency

This is due to less backpressure and recycled condensate.

109
Q

In what two ways is the efficiency of a condensing turbine increased by the condenser?

A
  1. Reduced backpressure.
  2. Recycled condensate.
110
Q

What type of turbines are considered back-pressure turbines?

A

Non-condesning turbines

Any turbine without a condesner is considered a back-pressure turbine.

111
Q

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.

A

True

112
Q

True or false: An almost perfect vacuum is achieved with a condenser on a condesning turbine.

A

True

Almost 29.92 inHg

113
Q

On a steam turbine, what is a rupture disk?

A

A single use safety device that opens in the case of cylinder overpressure (a pressure relief valve).

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
Q

What condition does a rupture disk prevent?

A

Overpressure

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
Q

Are rupture disks resettable?

A

No

Rupture disks are one time use, and must be replaced if burst.

116
Q

On a steam turbine assembly, the ________ is where the fuel is burned and the water is changed to high-pressure steam.

A

boiler

117
Q

Where is the high-pressure steam from the boiler piped into on a steam turbine?

A

Into the steam chest.

118
Q
  1. What is the most common type of casing found on steam turbines?
  2. Why is this?
A
  1. Horizontally split.
  2. This casing design allows for easy access to most of the inner components.
119
Q

What type of casing would be found on a steam turbines with very high pressures?

A

Double casings

These are common on very large turbines.

120
Q

On what type of turbines are sentinel valves found?

A

On small impulse turbines.

121
Q

What component of a steam turbine harnesses the energy of steam?

A

The rotor assembly

Specifically the rotor blades.

122
Q

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.

A

nozzles

123
Q

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.

A

Diaphragms

124
Q

In a steam turbine, this component admits steam to the nozzles.

A

Steam admission valve

Also known as the steam valve.

This is controlled by the governor.

125
Q

This component of a steam turbine shuts off all steam to the turbine in the event of an overspeed situation.

A

The stop valve

This valve is located in the steam chest, ahead of the SAV.

126
Q

Most larger steam turbines use bearings that have self-aligning spherical seats. What are two reasons for this?

A
  1. Allow the bearings to tilt according to the sag in the turbine shaft.
  2. Maintain shaft (journal) contact during thermal growth.
127
Q

What two valves are contained within the steam chest of a steam turbine?

A
  1. The stop valve.
  2. The SAV (governor valve).

The stop valve is always upstream of the SAV.

128
Q

On a steam turbine, which valve within the steam chest is connected to the steam inlet?

A

The stop valve

The stop valve is always upstream of the SAV.

129
Q

What type of bearing is used to control thrust on a purely impulse bladed steam turbine?

A

A deep groove ball bearing.

Impulse blades generate minimal thrust.

130
Q

What type of bearing is used to control thrust on a steam turbine with reaction blading?

A

A set of tilting-pad bearings.

The thrust collar can be either an integral part of the shaft or attached to the shaft.

131
Q

Why are tilting-pad thrust bearings selected for axial thrust control in steam turbines?

A

They are able to maintain full contact on the thrust collar when the shaft tilts due to sag.

132
Q

Where is the thrust bearing usually located on the steam turbine?

A

At the steam inlet end

This is often the end that is opposite the coupling

133
Q

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.

A

True

134
Q

Which type of babbit would be selected for high temperature applications: lead based babbit or tin based babbit.

A

Tin based babbitt

135
Q

What type of shaft seals would be found on smaller, slow speed steam turbines?

A

Carbon seals

These seals cannot handle the surface speeds found on larger machines.

136
Q

What type of shaft seals would be found on larger, high speed steam turbines?

A

Labyrinth seals

This has to do with the surface speeds found on some of the larger machines.

137
Q

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?

A

0.001”

138
Q

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.

A

False

These ends are precision machined, and cannot be adjusted in the field.

139
Q

When installing carbon ring seals into a steam turbine, how should the match marks (dots) be installed in relation to pressure?

A

The match marks must face towards pressure.

When installed, these seals must be free to move axially for proper sealing.

140
Q

In a steam turbine, what component holds a carbon seal together?

A

Garter springs

141
Q

True or false: In steam turbines, carbon ring seals must be installed so that they can rotate as well as move axially.

A

False

While they do need to move axially, carbon ring seals must be installed with an anti-rotation tab to prevent rotation.

142
Q

This type of steam turbine seal operates on the principle of pressure dropping each time the steam accelerates past the knife-edge restriction.

A

Labyrinth seals

Axial shaft position is critical to the survival of these seals.

143
Q

What type of seal is used when the thermal growth of a steam turbine exceeds the capability of labyrinth seals?

A

Annunlus seals

Axial movement (from thermal growth) is not a factor with this type of seal.

144
Q

This type of steam turbine seal consists of a set of knife edges fitting close to a journal-like shaft section.

A

Annulus seals

145
Q

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?

A

Labyrinth seals

Axial movement is not a factor with annulus seals.

146
Q

Which type of seal would be used if the thermal growth of a larger steam turbine is excessive?

A

Annulus seals

147
Q

This type of turbine seal is a series of labyrinth seals with steam pockets between them where steam is introduced or bled off.

A

Steam seals

These seals use steam pressure to keep contaminants out.

148
Q

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?

A

Steam seals

149
Q

True or false: In steam turbines, air or other contaminants are considered non-condensables.

A

True

A non-condesnable is anything that isn’t water → this includes nitrogren, oil, etc.

150
Q

On what type of steam turbine would blade seals be found?

A

Reaction turbines

Blade seals are used on the periphery and shaft to prevent steam leakage.

151
Q

True or false: Steam turbine blade seals are a variation of a labyrinth seal.

A

True

These seals work to limit pressure leakage due to a of a bunch of successive pressure drops.

152
Q

This component of a steam turbine converts kinetic energy from the steam into mechanical energy.

A

The rotor blades

153
Q

What is the moment weight of a steam turbine rotor blade?

A

The weight of the blade multiplied by the radial distance to the centre of gravity.

154
Q

Steam turbine manufactureres record the moment weights of each rotor blade. What two things does this do?

A
  1. Minimizes the amount of balancing required*.
  2. A blade can be replaced with the need for rebalancing.

*Blades of equal moment weight can be installed opposing each other, resulting in a more balanced rotor from the factory.

155
Q

What type of coupling is usually found on a steam turbine?

A

Rigid couplings

156
Q

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?

A

Fit and balance of the coupling.

157
Q

True or false: Most steam turbine failures occur because of some type of lubrication issue.

A

True

158
Q

True or false: When the steam leaves the nozzle of the steam turbine, it changes from potential energy into kinetic energy.

A

True

Bernouilli’s Principle → kinetic (velocity) ↑ and potential (pressure) ↓

159
Q

True or false: The blades of an impulse-style turbine are shaped like airplane wings.

A

False

Reaction-style blades are shaped like an airplane wing.

160
Q

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.

A

False

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
Q

True or false: In reaction-type turbines, there is a pressure drop across both the stationary blades (nozzles) and the moving blades.

A

True

This pressure drop converts the steam energy from pressure to velocity (Bernoulli’s Principle)

162
Q

True or false: When a turbine is staged, it means that the steam passes through more than one set of blades.

A

True

163
Q

True or false: The nozzle ring attaches to the steam chest side of the turbine casing.

A

True

164
Q

True or false: Carbon rings are used to keep the oil in the bearing housings.

A

False

Carbon rings are used to prevent steam from leaking out of the turbine.

165
Q

True or false: The largest blades of a steam turbine are at the high-pressure end of the machine.

A

False

The largest blades are at the low-pressure end, due to the expansion of steam as it looses some of its energy.

166
Q

Which valve is modulated to maintain the desired speed of the turbine?

A

The SAV

The steam admission valve.

167
Q

Which section of a tandem-compound steam turbine has the largest size?

A

The low-pressure section.

168
Q

Which section of a tandem-compound steam turbine has the smallest size?

A

The high-pressure section.

169
Q

In a steam turbine, what effect do rotary reaction blades have on:
1. Steam pressure?
2. Steam velocity?
3. Steam volume?

A
  1. Steam pressure ↓
  2. Steam velocity ↓
  3. Steam volume ↑

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
Q

What happens to the steam pressure and velocity as the steam flows through the reaction blades on the rotor of a steam turbine?

A

Pressure ↓
Velocity ↓

Volume increases, due to the drop in pressure.

171
Q

Why is the diameter of the steam turbine rotor shaft an important factor for the type of seal used on the turbine?

A

The larger the diameter, the faster the surface speed.

This determines what type of seal can be used.

172
Q

What effect does lacing have on a turbine blade?

A

Reduces vibration

They act to stiffen and dampen the blades which reduces their tendency to vibrate.

173
Q

Fill in the blank: Multiple stages of impulse blading in a steam turbine is called a ________ ________ turbine.

A

velocity compounding

174
Q

What design of turbine would have a pressure and velocity diagram as shown?

A

Velocity compounding

The single pressure change indicates that there are only impulse nozzle in the turbine.

175
Q

What design of turbine would have a pressure and velocity diagram as shown?

A

Combination impulse/reaction turbine.

176
Q

What design of turbine blade would have a velocity increase on a pressure and velocity diagram?

A

A reaction blade

177
Q

What effect does wire lacing have on the vibration of steam turbine rotor blades?

A

Wire lacing reduces vibration

Wire lacing acts to stiffen and dampen the blades which reduces their tendency to vibrate.

178
Q

In steam turbines, ________ increase the speed of steam.

A

Nozzles

Millwrong (27 decks)

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