What is the most significant factor affecting the efficiency of a steam turbine?
- Steam temperature
- Steam pressure
- Moisture content in the steam
- Turbine speed
Correct Answer: Moisture content in the steam
Correct Answer Explanation: The presence of moisture in the steam can significantly reduce turbine efficiency. This is because the condensation process within the turbine can lead to erosion, decreased energy extraction, and even potential damage to the turbine blades.
Which type of turbine is known for using multiple stages of expanding nozzles and stationary buckets to extract energy from steam?
- Westinghouse-Parsons
- Curtis
- De Laval
- Rateau
Correct Answer: Curtis
Correct Answer Explanation: The Curtis turbine utilizes a multi-stage design with expanding nozzles and stationary buckets to efficiently extract energy from the steam. This design allows for more efficient energy extraction compared to single-stage designs.
What is the primary purpose of labyrinth packing in a steam turbine?
- To lubricate the bearings
- To control the steam flow
- To prevent steam leakage
- To regulate the turbine speed
Correct Answer: To prevent steam leakage
Correct Answer Explanation: Labyrinth packing is used to create a seal around the turbine shaft, minimizing the leakage of steam from the high-pressure areas to the low-pressure areas. This helps maintain efficiency and prevent unnecessary steam consumption.
Why is maintaining a high vacuum in the condenser crucial for turbine operation?
- It reduces the risk of steam leaks.
- It increases the temperature of the steam.
- It enhances the efficiency of the turbine.
- It improves the lubricating properties of the oil.
Correct Answer: It enhances the efficiency of the turbine.
Correct Answer Explanation: A high vacuum in the condenser allows the steam to expand more completely, extracting more energy and resulting in increased turbine efficiency.
What type of oil is recommended for lubricating steam turbines?
- Vegetable oil
- Animal oil
- Mineral oil
- Synthetic oil
Correct Answer: Mineral oil
Correct Answer Explanation: Pure mineral oil, free from contaminants like animal or vegetable oils and acids, is essential for lubricating steam turbines. Impurities in the oil can damage turbine components and lead to performance issues.
What is the function of the turbine governor?
- To control the steam flow to the turbine
- To lubricate the turbine bearings
- To prevent steam leaks
- To measure the turbine speed
Correct Answer: To control the steam flow to the turbine
Correct Answer Explanation: The turbine governor regulates the speed of the turbine by adjusting the steam flow to the turbine. This mechanism ensures consistent turbine operation at the desired speed and prevents overspeeding.
What is the purpose of the safety-stop governor in a steam turbine?
- To monitor the oil pressure
- To control the steam flow
- To prevent the turbine from overspeeding
- To measure the vacuum in the condenser
Correct Answer: To prevent the turbine from overspeeding
Correct Answer Explanation: The safety-stop governor is a critical safety device that shuts off steam flow to the turbine if it exceeds its safe operating speed. This prevents catastrophic failure from overspeeding and potential damage to the turbine and its surrounding infrastructure.
How does superheating steam impact the efficiency of a steam turbine?
- It reduces the moisture content in the steam.
- It increases the pressure of the steam.
- It reduces the speed of the turbine.
- It improves the lubrication of the turbine.
Correct Answer: It reduces the moisture content in the steam.
Correct Answer Explanation: Superheating steam raises its temperature above its boiling point at a given pressure, reducing the moisture content. This drier steam leads to improved turbine performance and reduced fuel consumption.
What type of condenser is particularly well-suited for use with steam turbines?
- Jet condenser
- Surface condenser
- Barometric condenser
- Ejector condenser
Correct Answer: Surface condenser
Correct Answer Explanation: Surface condensers are well-suited for steam turbines because they allow for the recovery of high-quality condensate, which can be used as boiler feedwater. This reduces water consumption and improves the overall efficiency of the power plant.
Which of these auxiliaries is NOT essential for proper steam turbine operation?
- Circulating pumps
- Condensers
- Boiler feed pumps
- Steam traps
Correct Answer: Steam traps
Correct Answer Explanation: While steam traps are important for removing condensate from steam lines, they are not essential for the immediate operation of a steam turbine. The other options, circulating pumps, condensers, and boiler feed pumps, are crucial for ensuring the proper functioning and efficiency of the steam turbine.
What is the typical speed range of a 1500-kilowatt Curtis turbine between no load and full load?
- 1%
- 2%
- 4%
- 6%
Correct Answer: 2%
Correct Answer Explanation: A 1500-kilowatt Curtis turbine typically has a speed range of around 2% between no load and full load. This variation is due to the governor’s regulation of steam flow to maintain a consistent speed.
What is the purpose of the baffler in a Curtis turbine?
- To reduce steam leakage
- To control the steam flow
- To maintain a constant oil film in the step-bearing
- To regulate the turbine speed
Correct Answer: To maintain a constant oil film in the step-bearing
Correct Answer Explanation: The baffler in a Curtis turbine helps to maintain a constant oil film in the step-bearing, which is a critical component for supporting the turbine rotor. This constant oil film improves lubrication and reduces wear on the bearing.
What is the typical oil pressure used by the Allis-Chalmers steam turbine governor to operate the steam valves?
- 10 pounds per square inch
- 20 pounds per square inch
- 30 pounds per square inch
- 40 pounds per square inch
Correct Answer: 20 pounds per square inch
Correct Answer Explanation: The Allis-Chalmers steam turbine governor uses an oil pressure of about 20 pounds per square inch to operate the steam valves. This system provides for quick and reliable valve operation, ensuring smooth control of steam flow to the turbine.
What is the typical radial blade clearance in a Westinghouse-Parsons turbine?
- 0.005 to 0.025 inches
- 0.015 to 0.075 inches
- 0.025 to 0.125 inches
- 0.050 to 0.250 inches
Correct Answer: 0.025 to 0.125 inches
Correct Answer Explanation: The radial blade clearance in a Westinghouse-Parsons turbine is typically between 0.025 and 0.125 inches. This clearance is critical for preventing blade rubbing and ensuring smooth operation, allowing for proper steam flow and energy extraction.
What is the typical axial clearance in a Westinghouse-Parsons turbine?
- 1/16 to 1/4 inch
- 1/8 to 1/2 inch
- 1/4 to 1 inch
- 1/2 to 2 inches
Correct Answer: 1/8 to 1/2 inch
Correct Answer Explanation: The axial clearance in a Westinghouse-Parsons turbine varies from 1/8 to 1/2 inch. This clearance allows for slight axial movement of the rotor during operation, preventing excessive wear and tear on the bearings and other components.
What is the maximum recommended oil pressure in the bearings of a Westinghouse-Parsons turbine?
- A few feet
- A few inches
- A few pounds per square inch
- A few hundred pounds per square inch
Correct Answer: A few feet
Correct Answer Explanation: The oil pressure in the bearings of a Westinghouse-Parsons turbine should not exceed a few feet. This ensures proper lubrication without excessive pressure on the bearings, minimizing wear and tear on the bearings and other components.
What is the primary reason why the water used to seal the turbine glands should be free from scale-forming impurities?
- To prevent corrosion
- To improve lubrication
- To enhance the vacuum in the condenser
- To prevent deposits that hinder gland operation
Correct Answer: To prevent deposits that hinder gland operation
Correct Answer Explanation: Impurities in the water used for sealing the turbine glands can lead to deposits that hinder proper gland operation. This can result in steam leakage, reduced turbine efficiency, and even damage to the glands.
What is the maximum recommended temperature of the oil flowing to and from the bearings in an Allis-Chalmers turbine?
- 100 degrees Fahrenheit
- 120 degrees Fahrenheit
- 135 degrees Fahrenheit
- 150 degrees Fahrenheit
Correct Answer: 135 degrees Fahrenheit
Correct Answer Explanation: The temperature of the oil flowing to and from the bearings in an Allis-Chalmers turbine should not exceed 135 degrees Fahrenheit. This temperature range ensures optimal lubrication without excessive oil deterioration, minimizing wear and tear on the bearings.
What is a unique feature of a jet condenser that allows it to maintain a fairly high vacuum even with the air pump shut down?
- The pumping action of the falling water
- The high pressure of the steam
- The presence of a vacuum pump
- The use of a cooling tower
Correct Answer: The pumping action of the falling water
Correct Answer Explanation: A jet condenser utilizes a spray of water to condense the steam, and the falling water creates a pumping action that helps to maintain a fairly high vacuum even when the air pump is shut down.
What is the typical pressure setting for the turbine relief valve?
- 20 pounds by gage
- 30 pounds by gage
- 40 pounds by gage
- 50 pounds by gage
Correct Answer: 40 pounds by gage
Correct Answer Explanation: The turbine relief valve should be set to open at a relatively low pressure, around 40 pounds by gage. This prevents excessive pressure from building up in the turbine in case of a vacuum failure, safeguarding the turbine and its surrounding infrastructure.
What is the essential function of cooling towers in a condenser system?
- To remove heat from the circulating water
- To regulate the steam pressure
- To prevent steam leaks
- To improve the lubrication of the turbine
Correct Answer: To remove heat from the circulating water
Correct Answer Explanation: Cooling towers provide a large surface area for cooling the circulating water in a condenser system. This cooling is essential for maintaining the vacuum in the condenser and enhancing the efficiency of the turbine.
What can happen if the air leaks in the condenser are not properly sealed?
- Reduced vacuum and efficiency
- Increased steam pressure
- Improved lubrication
- Reduced steam consumption
Correct Answer: Reduced vacuum and efficiency
Correct Answer Explanation: Air leaks in the condenser can significantly reduce the vacuum and efficiency of the turbine. This is because the air reduces the ability of the condenser to efficiently condense the steam, impacting the turbine’s performance.
What is the recommended approach for bringing a steam turbine up to speed?
- Slowly and gradually to minimize vibration
- Rapidly and abruptly to maximize efficiency
- At a consistent speed to ensure stability
- At a rate determined by the turbine’s operating conditions
Correct Answer: Slowly and gradually to minimize vibration
Correct Answer Explanation: Turbines should be run up to speed slowly to minimize vibration and potential damage to the machine and its foundation. Rapid acceleration can cause instability and potentially lead to catastrophic failure.
Why is careful adjustment of the gland steam or water flow crucial?
- To improve the vacuum in the condenser
- To enhance the lubrication of the turbine
- To ensure proper sealing of the turbine shaft
- To control the steam flow to the turbine
Correct Answer: To ensure proper sealing of the turbine shaft
Correct Answer Explanation: The gland steam or water flow must be carefully adjusted to ensure proper sealing of the turbine shaft. Excessive gland flow can lead to increased steam consumption, reducing efficiency and increasing costs.
What factors can affect the efficiency of a steam turbine?
- Steam pressure
- Vacuum in the condenser
- Superheat
- All of the above
Correct Answer: All of the above
Correct Answer Explanation: The steam turbine’s efficiency can be affected by variations in steam pressure, vacuum, and superheat. Careful monitoring and adjustments are required to maintain optimal performance and maximize efficiency.
What can cause boiler priming, which can affect the steam consumption of a turbine?
- Excessive water in the boiler
- Insufficient steam pressure
- Poor lubrication
- High vacuum in the condenser
Correct Answer: Excessive water in the boiler
Correct Answer Explanation: Boiler priming occurs when excessive water is carried over with the steam, introducing water into the steam line. This can cause performance issues, reduce efficiency, and increase fuel consumption.
What is essential for successful steam power plant operation?
- Thorough understanding of turbine operation
- Careful attention to all components
- Interaction between the turbine and its auxiliaries
- All of the above
Correct Answer: All of the above
Correct Answer Explanation: A thorough understanding of turbine operation, careful attention to all components, and a deep understanding of the interaction between the turbine and its auxiliaries are all essential for successful and efficient steam power plant operation.