Governor Flashcards
1
Q
What is the primary function of a governor in rotating equipment?
A
To maintain the integrity and safety of rotating equipment by sensing and controlling the machine’s speed during operation.
2
Q
Why must an overspeed shutdown safety device be installed on a governor system?
A
To protect against runaway conditions that could cause damage to the prime mover and driven machine or result in catastrophic failure.
3
Q
What adjustment is recommended for a new governor during installation?
A
Manually decrease the governor speed setting screw so that the initial start-up speed is lower than required.
4
Q
What is commonly done on engines to prevent damage during an overspeed situation?
A
The air inlet to the intake manifold is shut off to stop the engine.
5
Q
What are the key maintenance tasks for a governor system?
A
Lubricate all linkages and pivot points, replace worn parts, check and adjust clearances, inspect the throttle valve, and clean the trip valve.
6
Q
What is an indication that dirt or sludge is present in the housing of a governor?
A
The presence of dirt or sludge indicates that the governor needs to be dismantled, cleaned, and inspected.
7
Q
When should a governor system be overhauled?
A
Whenever there is contamination in the hydraulic system or during a major overhaul of the engine or turbine.
8
Q
What are some signs that indicate the need for an oil change in a governor system?
A
Changes in oil appearance, burnt smell, traces of moisture, changes in viscosity, or excessively worn parts.
9
Q
What precautions should be taken during the overhaul of a governor system?
A
Replace all seals and gaskets, check linkages for stiffness, clean lines and passages, and flush the system with the correct hydraulic oil.
10
Q
Why is oil maintenance critical in a hydraulic governor system?
A
To prevent contamination and damage to sensitive components, ensure smooth operation, and avoid catastrophic system failure.
11
Q
What are the routine maintenance tasks for a mechanical governor?
A
Ensure knife edges and pivot points are in good condition, sliding parts are not binding, and anti-friction bearings are free of wear.
12
Q
What is a critical danger associated with governor system malfunctions?
A
It can result in catastrophic system failure or loss of life to operating and maintenance personnel.
13
Q
What is the primary function of a governor in a prime mover?
A
To automatically control the speed of the prime mover under varying load conditions.
14
Q
List three key actions performed by a governor on a prime mover.
A
Maintain the selected speed.
Limit slow and fast speeds.
Shut down the prime mover if it overspeeds.
15
Q
What are the two independent systems used for controlling the speed of steam turbines?
A
The operating speed control or governor to actuate the steam valves.
The overspeed control system to protect the turbine from destruction in case of an overspeed situation.
16
Q
Why is it necessary to manually decrease the governor speed setting screw when placing a new governor into service?
A
To ensure the speed is lower than required at initial start-up.
17
Q
What must be equipped in a prime mover to prevent catastrophic failure or damage?
A
An overspeed shutdown safety device.
18
Q
What happens during overspeed in engines, and how is it commonly mitigated?
A
The air inlet to the intake manifold is shut off to prevent further acceleration.
19
Q
What routine preventative maintenance tasks are essential for governors?
A
Lubricate all linkages and pivot points.
Replace worn parts.
Check governor clearances and adjustments using manufacturer specifications.
Inspect and clean the trip valve and governor throttle valve.
20
Q
What are the primary causes of governor system malfunctions?
A
Incorrect speed setting.
Improper steam pressure (steam turbines) or fuel delivery (stationary engines or gas turbines).
Manual overrides or control valves blocking fuel or steam delivery.
21
Q
What steps are required during a major overhaul of a governor system?
A
Replace all seals and gaskets.
Check and ensure mechanical tolerances match original specifications.
Flush parts with the correct hydraulic oil.
22
Q
What are the three components common to all automatic governor systems?
A
Detection.
Transmission.
Correction.
23
Q
Explain how a mechanical-hydraulic governor works.
A
It uses hydraulic pressure to actuate a spool valve that controls the steam valve to adjust speed.
24
Q
What are the most common types of throttle valve governors?
A
Automatic or vacuum governors and centrifugal governors.
25
In a vacuum governor, how is engine speed monitored and adjusted?
Engine vacuum causes a diaphragm to move, adjusting the throttle valve to regulate air-fuel mixture and maintain speed.
26
What does a governor’s control rack do in a diesel engine?
Adjusts the amount of fuel injected into the cylinders, increasing or decreasing speed as required.
27
Why is oil maintenance critical in hydraulic governor systems?
To prevent contamination, wear, and ensure smooth operation over extended periods.
28
What are the primary functions of a governor on steam turbines?
The governor regulates operating speed by controlling steam valves to speed up or slow down the turbine and prevents overspeeding to protect against mechanical damage.
29
What is the purpose of overspeed control systems in turbines?
Overspeed control systems protect the turbine from destruction in the event of overspeed situations.
30
What do governors automatically control in stationary engines?
Governors automatically control the speed of a prime mover under varying load conditions by maintaining selected speed, limiting fast speeds, and shutting down the prime mover if it overspeeds.
31
What are the three essential components common to all automatic governor control systems?
Detection, transmission, and correction.
32
How do isochronous governors differ from variable speed governors?
Isochronous governors maintain a uniform, constant speed without fluctuation, while variable speed governors allow adjustment of speed within a range.
33
What is the function of a pressure-regulating governor?
Pressure-regulating governors maintain constant pipeline pressure by throttling the pump as needed.
34
How does an electric load-sensing governor operate?
It detects changes in load and adjusts the fuel supply to maintain stable frequency and speed in electric power generation plants.
35
What parameters must be monitored for gas turbine governors?
Parameters include actuator position, turbine rpm, compressor inlet air temperature and pressure, and combustor discharge pressure.
36
How does a vacuum governor regulate engine speed?
A vacuum governor uses intake manifold vacuum to adjust throttle valve position, controlling the air-fuel mixture.
37
Why is an increase in fuel burned important for a gas turbine?
It produces more heat, enabling the turbine to carry a larger load.
38
What is the primary purpose of speed-limiting governors?
Speed-limiting governors prevent overspeeding but do not shut down the unit. Instead, they limit it to a maximum speed.
39
What controls a diesel engine’s governor system?
The governor system adjusts fuel delivery by controlling a linkage connected to a control rack that modifies the plunger’s position in the cylinders.
40
How does a pressure-regulating governor adjust pump speed?
It senses pressure through bellows or a diaphragm, which moves the control rod to adjust the pump’s throttle.
41
What is the purpose of a governor in rotating equipment?
A governor maintains the integrity and safety of the rotating equipment by sensing and controlling its speed during operation.
42
Why is an overspeed shutdown safety device essential for prime movers?
It protects against runaway conditions that can damage the prime mover or driven machine and potentially cause catastrophic failure.
43
What adjustments are typically made when placing a new governor into service?
The speed setting screw is manually decreased to ensure the speed is lower than required during the initial startup.
44
What should be done to the air intake on engines during an overspeed situation?
The air intake manifold should be shut off to prevent damage.
45
List three routine preventative maintenance steps for governors.
Lubricate all linkages and pivot points, replace worn parts, and check clearances using manufacturer specifications.
46
What is the primary cause of hunting in governors?
Hunting occurs when the governor reacts too quickly to speed changes, resulting in repeated over-correction.
47
Define speed droop in governors.
Speed droop is the percentage decrease in speed required by the governor to provide an increase in throttle during load changes.
48
What are the primary components of a flyweight governor?
Flyweights, speeder spring, rotating ballhead, and control rod.
49
What is the role of centrifugal force in a flyweight governor?
Centrifugal force moves the flyweights outward, adjusting the control rod to maintain engine speed.
50
Why is complete reduction of friction in a flyweight governor undesirable?
It could result in oscillation of the speed adjustment, requiring further corrections.
51
What is the main purpose of the governor rod in steam turbines?
To adjust the steam valve based on the speed of the turbine.
52
What happens when a steam turbine experiences overspeed?
The governor shuts the steam valve, reducing the flow and slowing the turbine.
53
What is the main function of isochronous control governors?
To maintain a uniform and constant speed without fluctuation.
54
Where are electric load-sensing governors typically used?
In power plants, where maintaining a stable frequency is critical.
55
How does a variable speed governor differ from an isochronous governor?
It allows adjustment to maintain any selected speed, not just constant speed.
56
What causes pressure-regulating governors to adjust the pump speed?
Changes in fluid pressure.
57
How do gas turbine governors adjust the turbine load?
By increasing or decreasing the amount of fuel burned.
58
What are some key parameters monitored in gas turbines?
Turbine RPM, actuator position, compressor inlet air temperature and pressure, and combustor discharge pressure.
59
What is the purpose of flyweights in a mechanical governor?
To sense speed changes and adjust the governor mechanism accordingly.
60
What causes hunting in governors, and how can it be resolved?
Hunting is caused by overreaction to speed changes. It can be resolved by adjusting the speed droop settings.
61
What is 'hunting' in governor systems?
Hunting refers to when a governor reacts too quickly to speed changes, causing continuous overcorrection, leading to instability.
62
What is speed droop, and why is it important in governors?
Speed droop is a controlled decrease in speed required to trigger an increase in throttle. It stabilizes the system by preventing overcorrection or hunting.
63
At what point is the flyweight’s centrifugal force balanced in a mechanical governor?
The flyweight’s centrifugal force is balanced when it equals the compression force of the governor spring, stabilizing the control rod.
64
What are some limitations of pure mechanical governors?
Limitations include sensitivity issues, requiring large speed changes for valve positioning, difficulty with precise frequency control, and the presence of a 'dead band' where control rod movement does not occur.
65
What is the function of the speeder spring in a flyweight governor?
The speeder spring opposes the centrifugal force of the flyweights, maintaining balance and controlling speed.
66
Why is it undesirable to completely eliminate friction in a flyweight governor system?
Eliminating all friction causes the governor to oscillate like a pendulum after speed setting changes, reducing stability.
67
How does a mechanical-hydraulic governor differ from a mechanical governor?
A mechanical-hydraulic governor includes a hydraulic system to provide additional force to move larger valves and linkages.
68
What issue arises with simple mechanical-hydraulic governors, and how is it addressed?
Simple mechanical-hydraulic governors often experience hunting due to instability. Adding a speed droop mechanism helps stabilize the system.
69
What is the role of speed droop in preventing hunting?
Speed droop requires a reduction in speed before the governor increases throttle, helping to avoid continuous oscillations.
70
How does a speed droop governor stabilize operations?
It uses mechanical linkages to adjust both the speeder spring compression and throttle settings simultaneously, ensuring stable speed adjustments.
71
What are the two independent systems used for controlling steam turbine speed?
1. Operating speed control (governor) for regular adjustments. 2. Overspeed control to protect the turbine from destruction during overspeed conditions.
72
What is the primary role of a governor in steam turbines?
The governor adjusts the steam valve to maintain or change turbine speed as required.
73
What happens when the flyweights in a steam turbine governor detect overspeed?
The flyweights move outward, closing the steam valve and reducing speed.
74
What determines the power output of a gas turbine?
The amount of fuel burned determines the power output, as more fuel generates more heat to carry a greater load.
75
Why is it essential for a gas turbine governor to control fuel flow carefully?
Rapid changes in fuel flow can cause airflow mismatches, leading to incomplete combustion or excessive fuel delivery.
76
What are pressure-regulating governors primarily used for?
They ensure constant pipeline pressure in pumping applications.
77
How is pressure adjusted in a pressure-regulating governor?
By varying the needle valve or orifice size to control pressure changes.
78
What is the key feature of an isochronous governor?
It maintains a constant and uniform speed without fluctuation.
79
What mechanism allows variable speed governors to adjust speed?
Centrifugal flyweights adjust speed by opposing the compression spring force.
80
How do speed-limiting governors differ from other governors?
They prevent overspeeding by limiting speed to a maximum without shutting down the system.
81
What is the purpose of an isochronous governor in power generation applications?
To maintain constant speed regardless of load changes.
82
What role does the receiving piston play in an isochronous governor system?
It is held in equilibrium by the centering spring and moves oil back to the sump to maintain stable speed without hunting.
83
What is the purpose of the amplifier chamber in a hydraulic governor system?
To strengthen the weak pressure signal from the pump, allowing it to be measured effectively.
84
How does the amplifier valve function in a hydraulic governor system?
It opens when pressure overcomes the force of the accelerator control spring, increasing fuel delivery.
85
What is the role of the servo piston in the hydraulic governor?
To adjust the control rod position, moving it towards a no-fuel or maximum fuel position depending on system pressure.
86
How does a hydraulic governor differ from a mechanical-hydraulic governor?
It relies on hydraulic force from a pump to control the servo valve, adjusting throttle settings directly.
87
What is the speed-sensitive element in a pure hydraulic governor?
A change in pressure of the fluid discharged from a shaft-mounted pump.
88
What happens when the needle valve is adjusted in a hydraulic governor?
Opening the valve increases speed, while closing it reduces speed by adjusting pump pressure.
89
What is the major difference in a mechanical-hydraulic governor compared to a flyweight-only system?
It includes a separate hydraulic system to provide extra power for operating large valves and linkages.
90
Why is it necessary to include hydraulic power in large turbines?
To move extensive linkages and large valves that cannot be operated solely by flyweights.
91
What is speed droop in a governor system?
The change in speed required to produce a change in throttle, used to control hunting and provide stability.
92
How is speed droop added to a simple governor system?
By adding a mechanical linkage between the servo and the governor speed setting.
93
What happens when the speed setting decreases in a speed droop governor?
The throttle position adjusts, and the system stabilizes at a lower fuel setting.
94
What component keeps the stop valve open in normal operation?
The main oil pump supplies pressure to the stop valve control cylinder to keep it open.
95
How is system pressure maintained in a hydraulic governor?
A pressure-regulating valve ensures constant pressure and allows for leak-off lubrication to bearings.
96
What is the primary goal of an isochronous governor?
To maintain a constant speed, regardless of load variations, especially in power generation applications.
97
How does the isochronous system maintain equilibrium in the governor?
By using a floating lever assembly connected to the control rod, pilot valve, and receiving piston to keep the flyweights at the same speed.
98
What feature helps the isochronous governor prevent hunting?
An adjustable leak in the form of a needle valve to provide transient speed control.
99
What does a hydraulic governor use as a speed-sensitive element?
The change in pressure of a fluid discharged from a shaft-mounted pump.
100
What happens when the orifice in a hydraulic governor is opened?
It causes a drop in pressure, opening the governor to increase speed.
101
What is the role of the amplifier chamber in a hydraulic governor?
It strengthens the weak pressure signal from the gear pump, making it measurable and effective in controlling the servo piston.
102
What is the function of an electrohydraulic governor?
To allow precise speed and load control with faster response times using electrical signals.
103
What are the advantages of an electrohydraulic governor?
Quick response to transient speed changes, automatic load division, adaptability to complex control, and independence from engine drive.
104
How does an electrical solenoid operate in a governor system?
It uses magnetic attraction to pull the iron core into the coil, compressing a spring to control fuel delivery.
105
What are the three components of an electronic governing system?
Sensors to detect speed/load, a system controller (computer) to process signals, and an actuator to move the fuel control mechanism.
106
How does the electronic governor ensure efficient operation?
By separating detection, transmission, and correction tasks into distinct system components.
107
What role does the DC tachometer play in an electronic solenoid-operated governor?
It provides the current flow to the solenoid for precise control of fuel delivery.
108
What is the effect of increasing spring compression in the accelerator control of an electrohydraulic governor?
It allows more fluid to pass, opening the amplifier valve further to increase speed.
109
What is the primary use of an electronic governing system?
To provide precise speed and load control in power plants and remote installations requiring synchronized operation.
110
What is the primary purpose of an overspeed trip mechanism?
The purpose is to prevent a turbine or engine from exceeding its safe operational speed, which could cause catastrophic failure or damage.
111
How does the overspeed trip mechanism operate independently of the normal governor system?
It is designed to work independently by triggering the main steam supply valve to close or cutting fuel supply in case of overspeed, ensuring protection even if the governor fails.
112
At what percentage above maximum speed should the overspeed trip be set?
The overspeed trip should be set to operate at about 10% to 15% above the maximum speed under normal operating conditions.
113
What happens to the basic mechanical overspeed trip pin during overspeed conditions?
The spring compression is overcome, and the pin is thrown out by centrifugal force, activating the trip mechanism.
114
Describe the movement of the soft iron core in a solenoid-operated pilot valve.
The soft iron core moves based on current flow. An increase in current pulls the core into the coil, while a decrease allows the spring to push it out, controlling the pilot valve’s operation.
115
How do magnetic pickups contribute to governor operation in a turbine?
Three magnetic pickups sense speed and send signals to the controller. If one fails, the system continues to operate using the remaining two signals.
116
What advantage do multiple magnetic pickups provide in turbine operation?
They allow the system to continue running if one pickup fails and can be serviced or calibrated while the machine remains operational.
117
What is the role of the system controller in an electrohydraulic governor?
It processes signals from sensors, compares the detected speed with the desired speed, and sends output signals to the actuator to adjust fuel delivery.
118
What forces control the movement of the pilot valve in a solenoid-operated system?
The movement is controlled by the magnetic force generated by the solenoid and the spring force opposing it.
119
Why is regular testing of the overspeed trip mechanism necessary?
To ensure the mechanism is functioning correctly and will protect the system during an overspeed event.
120
What does the 'dead band area' refer to in mechanical governors?
It refers to the range of movement where there is no control action due to insufficient force or sensitivity in the linkage.
121
How is fuel control adjusted in a solenoid-operated pilot valve system?
By altering the position of the iron core, which changes the oil flow through the pilot valve and affects the servo valve’s position.
122
What is the role of the amplifier chamber in a hydraulic governor system?
It strengthens the pressure signal from the pump to control the amplifier piston and regulate fuel delivery.
123
How does the pressure relief valve contribute to the hydraulic governor system?
It maintains consistent system pressure by relieving excess pressure, ensuring stable operation.
124
Why is speed droop important in mechanical-hydraulic governors?
Speed droop provides stability by allowing a reduction in speed before the governor increases throttle, preventing hunting.
125
What is the purpose of an overspeed trip mechanism?
To prevent a turbine or engine from entering a runaway condition by stopping the turbine in the event of an overspeed situation.
126
Why should the overspeed governor be independent of the regular governor system?
To ensure protection even if the regular governor fails due to linkage, fuel control, or other malfunctions.
127
What is the recommended overspeed trip setting relative to normal operating speed?
It should be set to operate at 10-15% above the maximum speed under normal conditions.
128
What must be done after the overspeed trip has been activated?
It must be manually reset.
129
Why should overspeed trips be tested regularly, and how often should they be tested?
To ensure a high degree of reliability. Manufacturers recommend testing at least quarterly, with two tests within a small tolerance of the required setting.
130
What is the primary advantage of hydraulic overspeed trips in large systems?
They are well-suited for moving large valves due to their ease of control and capability to generate unlimited force.
131
What happens in a hydraulic overspeed trip during normal operation?
The trip pin holds the spool valve open, allowing oil to pressurize the trip valve piston and keep it in the open position.
132
What occurs in the overspeed condition of a hydraulic overspeed trip?
The trip pin moves out, causing the spool valve to block oil supply and allowing the trip valve spring to close the trip valve, stopping fuel flow.
133
List the advantages of an electronic overspeed trip.
High accuracy and repeatability, fast response time, ability to test and replace without shutdown, resistance to temperature and humidity, and no mechanical wear.
134
What type of signal is processed by an electronic overspeed trip system, and how many sensors are typically used?
Magnetic pickup sensors process speed signals, typically using a three-sensor system for redundancy and accuracy.
135
What corrective action should be taken if the trip mechanism is improperly adjusted?
Adjust the spring compression on the trip pin.
136
How should you address a defective trip mechanism?
Replace worn or damaged parts.
137
What should be done if excessive vibration causes a false trip?
Determine and correct the cause of the vibration.
138
What corrective action is recommended when the valve stem binds and sticks due to tight packing after maintenance?
Exercise caution when tightening the packing.
139
What is the solution if the linkage is binding because of tight pivot points or bent linkage?
Replace worn or damaged linkage parts and adjust.
140
What action should be taken if the clearance between the trip pin and linkage is too large?
Adjust to the manufacturer’s recommended setting.
141
How can you prevent trip valve sticking caused by scale buildup or foreign material?
Manually trip the valve on a weekly basis to prevent scale buildup or, if this is not sufficient, disassemble and clean the valve.
