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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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17
Q

What must be equipped in a prime mover to prevent catastrophic failure or damage?

A

An overspeed shutdown safety device.

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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.

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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.

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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.

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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.

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22
Q

What are the three components common to all automatic governor systems?

A

Detection.
Transmission.
Correction.

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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.

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24
Q

What are the most common types of throttle valve governors?

A

Automatic or vacuum governors and centrifugal governors.

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25
Q

In a vacuum governor, how is engine speed monitored and adjusted?

A

Engine vacuum causes a diaphragm to move, adjusting the throttle valve to regulate air-fuel mixture and maintain speed.

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26
Q

What does a governor’s control rack do in a diesel engine?

A

Adjusts the amount of fuel injected into the cylinders, increasing or decreasing speed as required.

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27
Q

Why is oil maintenance critical in hydraulic governor systems?

A

To prevent contamination, wear, and ensure smooth operation over extended periods.

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28
Q

What are the primary functions of a governor on steam turbines?

A

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.

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29
Q

What is the purpose of overspeed control systems in turbines?

A

Overspeed control systems protect the turbine from destruction in the event of overspeed situations.

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30
Q

What do governors automatically control in stationary engines?

A

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.

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31
Q

What are the three essential components common to all automatic governor control systems?

A

Detection, transmission, and correction.

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32
Q

How do isochronous governors differ from variable speed governors?

A

Isochronous governors maintain a uniform, constant speed without fluctuation, while variable speed governors allow adjustment of speed within a range.

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33
Q

What is the function of a pressure-regulating governor?

A

Pressure-regulating governors maintain constant pipeline pressure by throttling the pump as needed.

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34
Q

How does an electric load-sensing governor operate?

A

It detects changes in load and adjusts the fuel supply to maintain stable frequency and speed in electric power generation plants.

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35
Q

What parameters must be monitored for gas turbine governors?

A

Parameters include actuator position, turbine rpm, compressor inlet air temperature and pressure, and combustor discharge pressure.

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36
Q

How does a vacuum governor regulate engine speed?

A

A vacuum governor uses intake manifold vacuum to adjust throttle valve position, controlling the air-fuel mixture.

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37
Q

Why is an increase in fuel burned important for a gas turbine?

A

It produces more heat, enabling the turbine to carry a larger load.

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38
Q

What is the primary purpose of speed-limiting governors?

A

Speed-limiting governors prevent overspeeding but do not shut down the unit. Instead, they limit it to a maximum speed.

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39
Q

What controls a diesel engine’s governor system?

A

The governor system adjusts fuel delivery by controlling a linkage connected to a control rack that modifies the plunger’s position in the cylinders.

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40
Q

How does a pressure-regulating governor adjust pump speed?

A

It senses pressure through bellows or a diaphragm, which moves the control rod to adjust the pump’s throttle.

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41
Q

What is the purpose of a governor in rotating equipment?

A

A governor maintains the integrity and safety of the rotating equipment by sensing and controlling its speed during operation.

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42
Q

Why is an overspeed shutdown safety device essential for prime movers?

A

It protects against runaway conditions that can damage the prime mover or driven machine and potentially cause catastrophic failure.

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43
Q

What adjustments are typically made when placing a new governor into service?

A

The speed setting screw is manually decreased to ensure the speed is lower than required during the initial startup.

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44
Q

What should be done to the air intake on engines during an overspeed situation?

A

The air intake manifold should be shut off to prevent damage.

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45
Q

List three routine preventative maintenance steps for governors.

A

Lubricate all linkages and pivot points, replace worn parts, and check clearances using manufacturer specifications.

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46
Q

What is the primary cause of hunting in governors?

A

Hunting occurs when the governor reacts too quickly to speed changes, resulting in repeated over-correction.

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47
Q

Define speed droop in governors.

A

Speed droop is the percentage decrease in speed required by the governor to provide an increase in throttle during load changes.

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48
Q

What are the primary components of a flyweight governor?

A

Flyweights, speeder spring, rotating ballhead, and control rod.

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49
Q

What is the role of centrifugal force in a flyweight governor?

A

Centrifugal force moves the flyweights outward, adjusting the control rod to maintain engine speed.

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50
Q

Why is complete reduction of friction in a flyweight governor undesirable?

A

It could result in oscillation of the speed adjustment, requiring further corrections.

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51
Q

What is the main purpose of the governor rod in steam turbines?

A

To adjust the steam valve based on the speed of the turbine.

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52
Q

What happens when a steam turbine experiences overspeed?

A

The governor shuts the steam valve, reducing the flow and slowing the turbine.

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53
Q

What is the main function of isochronous control governors?

A

To maintain a uniform and constant speed without fluctuation.

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54
Q

Where are electric load-sensing governors typically used?

A

In power plants, where maintaining a stable frequency is critical.

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55
Q

How does a variable speed governor differ from an isochronous governor?

A

It allows adjustment to maintain any selected speed, not just constant speed.

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56
Q

What causes pressure-regulating governors to adjust the pump speed?

A

Changes in fluid pressure.

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57
Q

How do gas turbine governors adjust the turbine load?

A

By increasing or decreasing the amount of fuel burned.

58
Q

What are some key parameters monitored in gas turbines?

A

Turbine RPM, actuator position, compressor inlet air temperature and pressure, and combustor discharge pressure.

59
Q

What is the purpose of flyweights in a mechanical governor?

A

To sense speed changes and adjust the governor mechanism accordingly.

60
Q

What causes hunting in governors, and how can it be resolved?

A

Hunting is caused by overreaction to speed changes. It can be resolved by adjusting the speed droop settings.

61
Q

What is ‘hunting’ in governor systems?

A

Hunting refers to when a governor reacts too quickly to speed changes, causing continuous overcorrection, leading to instability.

62
Q

What is speed droop, and why is it important in governors?

A

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
Q

At what point is the flyweight’s centrifugal force balanced in a mechanical governor?

A

The flyweight’s centrifugal force is balanced when it equals the compression force of the governor spring, stabilizing the control rod.

64
Q

What are some limitations of pure mechanical governors?

A

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
Q

What is the function of the speeder spring in a flyweight governor?

A

The speeder spring opposes the centrifugal force of the flyweights, maintaining balance and controlling speed.

66
Q

Why is it undesirable to completely eliminate friction in a flyweight governor system?

A

Eliminating all friction causes the governor to oscillate like a pendulum after speed setting changes, reducing stability.

67
Q

How does a mechanical-hydraulic governor differ from a mechanical governor?

A

A mechanical-hydraulic governor includes a hydraulic system to provide additional force to move larger valves and linkages.

68
Q

What issue arises with simple mechanical-hydraulic governors, and how is it addressed?

A

Simple mechanical-hydraulic governors often experience hunting due to instability. Adding a speed droop mechanism helps stabilize the system.

69
Q

What is the role of speed droop in preventing hunting?

A

Speed droop requires a reduction in speed before the governor increases throttle, helping to avoid continuous oscillations.

70
Q

How does a speed droop governor stabilize operations?

A

It uses mechanical linkages to adjust both the speeder spring compression and throttle settings simultaneously, ensuring stable speed adjustments.

71
Q

What are the two independent systems used for controlling steam turbine speed?

A
  1. Operating speed control (governor) for regular adjustments. 2. Overspeed control to protect the turbine from destruction during overspeed conditions.
72
Q

What is the primary role of a governor in steam turbines?

A

The governor adjusts the steam valve to maintain or change turbine speed as required.

73
Q

What happens when the flyweights in a steam turbine governor detect overspeed?

A

The flyweights move outward, closing the steam valve and reducing speed.

74
Q

What determines the power output of a gas turbine?

A

The amount of fuel burned determines the power output, as more fuel generates more heat to carry a greater load.

75
Q

Why is it essential for a gas turbine governor to control fuel flow carefully?

A

Rapid changes in fuel flow can cause airflow mismatches, leading to incomplete combustion or excessive fuel delivery.

76
Q

What are pressure-regulating governors primarily used for?

A

They ensure constant pipeline pressure in pumping applications.

77
Q

How is pressure adjusted in a pressure-regulating governor?

A

By varying the needle valve or orifice size to control pressure changes.

78
Q

What is the key feature of an isochronous governor?

A

It maintains a constant and uniform speed without fluctuation.

79
Q

What mechanism allows variable speed governors to adjust speed?

A

Centrifugal flyweights adjust speed by opposing the compression spring force.

80
Q

How do speed-limiting governors differ from other governors?

A

They prevent overspeeding by limiting speed to a maximum without shutting down the system.

81
Q

What is the purpose of an isochronous governor in power generation applications?

A

To maintain constant speed regardless of load changes.

82
Q

What role does the receiving piston play in an isochronous governor system?

A

It is held in equilibrium by the centering spring and moves oil back to the sump to maintain stable speed without hunting.

83
Q

What is the purpose of the amplifier chamber in a hydraulic governor system?

A

To strengthen the weak pressure signal from the pump, allowing it to be measured effectively.

84
Q

How does the amplifier valve function in a hydraulic governor system?

A

It opens when pressure overcomes the force of the accelerator control spring, increasing fuel delivery.

85
Q

What is the role of the servo piston in the hydraulic governor?

A

To adjust the control rod position, moving it towards a no-fuel or maximum fuel position depending on system pressure.

86
Q

How does a hydraulic governor differ from a mechanical-hydraulic governor?

A

It relies on hydraulic force from a pump to control the servo valve, adjusting throttle settings directly.

87
Q

What is the speed-sensitive element in a pure hydraulic governor?

A

A change in pressure of the fluid discharged from a shaft-mounted pump.

88
Q

What happens when the needle valve is adjusted in a hydraulic governor?

A

Opening the valve increases speed, while closing it reduces speed by adjusting pump pressure.

89
Q

What is the major difference in a mechanical-hydraulic governor compared to a flyweight-only system?

A

It includes a separate hydraulic system to provide extra power for operating large valves and linkages.

90
Q

Why is it necessary to include hydraulic power in large turbines?

A

To move extensive linkages and large valves that cannot be operated solely by flyweights.

91
Q

What is speed droop in a governor system?

A

The change in speed required to produce a change in throttle, used to control hunting and provide stability.

92
Q

How is speed droop added to a simple governor system?

A

By adding a mechanical linkage between the servo and the governor speed setting.

93
Q

What happens when the speed setting decreases in a speed droop governor?

A

The throttle position adjusts, and the system stabilizes at a lower fuel setting.

94
Q

What component keeps the stop valve open in normal operation?

A

The main oil pump supplies pressure to the stop valve control cylinder to keep it open.

95
Q

How is system pressure maintained in a hydraulic governor?

A

A pressure-regulating valve ensures constant pressure and allows for leak-off lubrication to bearings.

96
Q

What is the primary goal of an isochronous governor?

A

To maintain a constant speed, regardless of load variations, especially in power generation applications.

97
Q

How does the isochronous system maintain equilibrium in the governor?

A

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
Q

What feature helps the isochronous governor prevent hunting?

A

An adjustable leak in the form of a needle valve to provide transient speed control.

99
Q

What does a hydraulic governor use as a speed-sensitive element?

A

The change in pressure of a fluid discharged from a shaft-mounted pump.

100
Q

What happens when the orifice in a hydraulic governor is opened?

A

It causes a drop in pressure, opening the governor to increase speed.

101
Q

What is the role of the amplifier chamber in a hydraulic governor?

A

It strengthens the weak pressure signal from the gear pump, making it measurable and effective in controlling the servo piston.

102
Q

What is the function of an electrohydraulic governor?

A

To allow precise speed and load control with faster response times using electrical signals.

103
Q

What are the advantages of an electrohydraulic governor?

A

Quick response to transient speed changes, automatic load division, adaptability to complex control, and independence from engine drive.

104
Q

How does an electrical solenoid operate in a governor system?

A

It uses magnetic attraction to pull the iron core into the coil, compressing a spring to control fuel delivery.

105
Q

What are the three components of an electronic governing system?

A

Sensors to detect speed/load, a system controller (computer) to process signals, and an actuator to move the fuel control mechanism.

106
Q

How does the electronic governor ensure efficient operation?

A

By separating detection, transmission, and correction tasks into distinct system components.

107
Q

What role does the DC tachometer play in an electronic solenoid-operated governor?

A

It provides the current flow to the solenoid for precise control of fuel delivery.

108
Q

What is the effect of increasing spring compression in the accelerator control of an electrohydraulic governor?

A

It allows more fluid to pass, opening the amplifier valve further to increase speed.

109
Q

What is the primary use of an electronic governing system?

A

To provide precise speed and load control in power plants and remote installations requiring synchronized operation.

110
Q

What is the primary purpose of an overspeed trip mechanism?

A

The purpose is to prevent a turbine or engine from exceeding its safe operational speed, which could cause catastrophic failure or damage.

111
Q

How does the overspeed trip mechanism operate independently of the normal governor system?

A

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
Q

At what percentage above maximum speed should the overspeed trip be set?

A

The overspeed trip should be set to operate at about 10% to 15% above the maximum speed under normal operating conditions.

113
Q

What happens to the basic mechanical overspeed trip pin during overspeed conditions?

A

The spring compression is overcome, and the pin is thrown out by centrifugal force, activating the trip mechanism.

114
Q

Describe the movement of the soft iron core in a solenoid-operated pilot valve.

A

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
Q

How do magnetic pickups contribute to governor operation in a turbine?

A

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
Q

What advantage do multiple magnetic pickups provide in turbine operation?

A

They allow the system to continue running if one pickup fails and can be serviced or calibrated while the machine remains operational.

117
Q

What is the role of the system controller in an electrohydraulic governor?

A

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
Q

What forces control the movement of the pilot valve in a solenoid-operated system?

A

The movement is controlled by the magnetic force generated by the solenoid and the spring force opposing it.

119
Q

Why is regular testing of the overspeed trip mechanism necessary?

A

To ensure the mechanism is functioning correctly and will protect the system during an overspeed event.

120
Q

What does the ‘dead band area’ refer to in mechanical governors?

A

It refers to the range of movement where there is no control action due to insufficient force or sensitivity in the linkage.

121
Q

How is fuel control adjusted in a solenoid-operated pilot valve system?

A

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
Q

What is the role of the amplifier chamber in a hydraulic governor system?

A

It strengthens the pressure signal from the pump to control the amplifier piston and regulate fuel delivery.

123
Q

How does the pressure relief valve contribute to the hydraulic governor system?

A

It maintains consistent system pressure by relieving excess pressure, ensuring stable operation.

124
Q

Why is speed droop important in mechanical-hydraulic governors?

A

Speed droop provides stability by allowing a reduction in speed before the governor increases throttle, preventing hunting.

125
Q

What is the purpose of an overspeed trip mechanism?

A

To prevent a turbine or engine from entering a runaway condition by stopping the turbine in the event of an overspeed situation.

126
Q

Why should the overspeed governor be independent of the regular governor system?

A

To ensure protection even if the regular governor fails due to linkage, fuel control, or other malfunctions.

127
Q

What is the recommended overspeed trip setting relative to normal operating speed?

A

It should be set to operate at 10-15% above the maximum speed under normal conditions.

128
Q

What must be done after the overspeed trip has been activated?

A

It must be manually reset.

129
Q

Why should overspeed trips be tested regularly, and how often should they be tested?

A

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
Q

What is the primary advantage of hydraulic overspeed trips in large systems?

A

They are well-suited for moving large valves due to their ease of control and capability to generate unlimited force.

131
Q

What happens in a hydraulic overspeed trip during normal operation?

A

The trip pin holds the spool valve open, allowing oil to pressurize the trip valve piston and keep it in the open position.

132
Q

What occurs in the overspeed condition of a hydraulic overspeed trip?

A

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
Q

List the advantages of an electronic overspeed trip.

A

High accuracy and repeatability, fast response time, ability to test and replace without shutdown, resistance to temperature and humidity, and no mechanical wear.

134
Q

What type of signal is processed by an electronic overspeed trip system, and how many sensors are typically used?

A

Magnetic pickup sensors process speed signals, typically using a three-sensor system for redundancy and accuracy.

135
Q

What corrective action should be taken if the trip mechanism is improperly adjusted?

A

Adjust the spring compression on the trip pin.

136
Q

How should you address a defective trip mechanism?

A

Replace worn or damaged parts.

137
Q

What should be done if excessive vibration causes a false trip?

A

Determine and correct the cause of the vibration.

138
Q

What corrective action is recommended when the valve stem binds and sticks due to tight packing after maintenance?

A

Exercise caution when tightening the packing.

139
Q

What is the solution if the linkage is binding because of tight pivot points or bent linkage?

A

Replace worn or damaged linkage parts and adjust.

140
Q

What action should be taken if the clearance between the trip pin and linkage is too large?

A

Adjust to the manufacturer’s recommended setting.

141
Q

How can you prevent trip valve sticking caused by scale buildup or foreign material?

A

Manually trip the valve on a weekly basis to prevent scale buildup or, if this is not sufficient, disassemble and clean the valve.