221 Questions
What is the purpose of maintaining a vacuum in the condenser?
To extract the maximum amount of work from the steam
How does condensing the steam at the lowest practical pressure benefit the turbine?
It increases the turbine's thermal efficiency
Why should the condensate temperature be close to the steam temperature for efficient operation?
To minimize the latent heat removed from the steam
What is the effect of using the exhaust steam for heating or process work on the overall plant efficiency?
Increases the plant's thermal efficiency significantly
Which condition leads to the most efficient utilization of cooling water in the condenser?
Narrower difference between cooling water exit temperature and steam inlet temperature
How does adding a condenser to the turbine affect its efficiency?
Increases the turbine's efficiency by 50%
What is the primary purpose of a condenser in a steam plant?
To improve overall thermal efficiency
What is a secondary purpose of a condenser in a steam plant?
To reduce thermal losses
What role does a condenser play in removing non-condensible gases from the steam/condensate system?
It acts as a deaerator
What is the largest heat exchanger in a steam plant?
The condenser
What is the largest single heat loss in the steam cycle?
The heat loss from the condenser
What is the role of the turbine in a steam plant?
To convert the energy in the steam into mechanical work
What is one of the key benefits of a condenser in a steam plant?
Enhancing the thermal efficiency of the plant by producing a vacuum at the turbine exhaust
What is the significance of the condenser in reducing thermal losses?
It condenses exhaust steam to produce condensate for returning to the boiler
How does the condenser contribute to the overall efficiency of a steam plant?
By expanding steam to a lower pressure at the turbine exhaust
Which statement accurately describes the role of a condenser in a steam plant?
It converts steam back to water for reuse in the boiler
What is the primary effect of the condenser operation on the exhaust steam in a steam plant?
Converting the steam back to water for recirculation
In a steam plant, what is an additional benefit of the condenser operation apart from increasing thermal efficiency?
Reducing the presence of air and non-condensible gases in downstream systems
What is the optimal difference between the steam inlet temperature and the cooling water exit temperature for the most efficient utilization of the cooling water?
A small difference in temperature
What happens to the efficiency of a turbine when the exhaust steam is used for heating or process work instead of being condensed?
The efficiency increases significantly
What role does the latent heat of the steam play in the condenser's performance in a steam plant?
It improves the condenser's efficiency
How does maintaining a vacuum in the condenser affect the performance of a steam turbine in a steam plant?
It improves the turbine efficiency
When adding a condenser to a turbine, how much does its efficiency typically improve?
By 50%
Which factor has the greatest impact on the overall efficiency of a steam plant that uses the exhaust steam for heating or process work?
The quality and design of the heat exchangers
What is the primary reason why direct contact condensers are not widely used in service?
They require chemical treatment of the cooling water
What is the function of the tailpipe or barometric leg in a barometric condenser?
To carry the condensate down to the hotwell by gravity
What is the purpose of the convergent nozzles in an ejector condenser?
To create areas of low pressure and vacuum
What is the requirement for the elevation of the condenser above the hotwell in a barometric condenser?
It should be sufficient to allow the water to flow out by gravity
What is the purpose of the vacuum pump or steam ejector system in a barometric condenser?
To remove air and other non-condensable gases from the condensing space
What is a characteristic of an ejector condenser?
It is suitable for moderate vacuum
What is the primary purpose of a jet condenser?
To cool the exhaust steam and convert it into liquid
In a surface condenser, what is the function of the small diameter tubes?
To cool the exhaust steam indirectly
What happens to the combined cooling water and condensed steam in a jet condenser?
They are drained to the hotwell
What is the role of the boiler feedwater pump in a jet condenser system?
To take suction from the hotwell and send feedwater to the boiler
What happens to the excess condensate in a jet condenser system?
It overflows or is pumped into the cooling pond
What is a key difference between contact and surface condensers?
The direct contact between the cooling water and exhaust steam
What is the primary reason why direct contact condensers are not widely used in service?
They allow non-condensable gases to accumulate in the steam/condensate system.
In a jet condenser, what is the significance of the combined cooling water and condensed steam draining to the hotwell?
This enables the boiler feedwater pump to draw water for the boiler from the hotwell efficiently.
Why should the condensate temperature be close to the steam temperature for efficient operation in a steam plant?
To minimize thermal losses in the condenser.
What is a secondary purpose of a condenser in a steam plant, apart from increasing thermal efficiency?
To eliminate non-condensable gases from the steam/condensate system.
What is the effect of using the exhaust steam for heating or process work on the overall plant efficiency?
It decreases the plant efficiency by not allowing for the recovery of exhaust steam energy.
What is the role of the tailpipe or barometric leg in a barometric condenser?
It maintains the vacuum within the condenser by preventing air leakage.
How does the design of an ejector condenser enable the flow of exhaust steam into the condenser?
By increasing the pressure gradient across the turbine exhaust and condenser using convergent nozzles
Which factor primarily determines the required length of the tailpipe in a barometric condenser?
The required vacuum level in the condenser
What is a significant challenge in maintaining a low-level jet condenser's efficiency?
The need for a chemical treatment of cooling water to prevent contamination of the condensate
Why are direct contact condensers not widely used in service?
Because they require chemical treatment of cooling water to avoid contamination of the condensate
Which statement accurately describes the role of atmospheric conditions in the design of a barometric condenser?
Lower atmospheric pressure will create a larger pressure head to allow condensate flow out by gravity
What is the primary disadvantage of using an ejector condenser?
The ejector condenser is suitable for moderate vacuum only
What is the purpose of the external fins on the tubes in a condenser?
To increase the surface area available for heat transfer
In a downflow condenser, where does the steam enter and where does the condensate exit?
Steam enters at the top and condensate exits at the bottom center
What is the primary function of air extraction baffles in a downflow condenser?
To direct rising air and other gases under the baffles
What is the difference between a downflow and a central flow condenser in terms of steam flow?
Steam flows from top center to bottom in downflow and radially in for central flow
How does the condenser assist in maintaining the condensate temperature near the saturation temperature in a steam plant?
By allowing steam lanes to deliver steam to the hotwell
What influences the direction of steam flow in a central flow condenser?
The position of the air extraction point
Why is it important to prevent steam from entering the air removal equipment in a downflow condenser?
To ensure proper functioning of the equipment
What is the significance of the pass arrangement of cooling water in a downflow condenser?
To extract heat from the exhaust steam
Why is the cooling water introduced at the top of the water box in a downflow condenser?
To ensure uniform cooling of the tubes
What is the effect of creating a low-pressure area below the inverted “V” baffle in a central flow condenser?
To encourage steam flow toward the center
What is the primary difference between surface condensers and direct contact condensers?
Surface condensers do not contact the steam and cooling medium directly, while direct contact condensers do.
Which cooling system is most efficient when using a reusable supply of cooling water?
Water-cooled condenser with a cooling tower
In a surface condenser, what is the role of the tubes?
The tubes are used to contain the cooling medium, while the steam occupies the shell and surrounds the outside surface of the tubes.
How does the design of an air-cooled condenser differ from a water-cooled condenser?
An air-cooled condenser uses air as the cooling medium, while a water-cooled condenser uses water.
What is the purpose of the cooling tower in a water-cooled condenser system with a reusable supply of cooling water?
The cooling tower is used to cool the cooling water after it has absorbed heat in the condenser, using water spray and evaporation.
Which cooling system is the most environmentally friendly option for surface condensers?
Air-cooled condenser
What is the primary method of heat transfer in a surface condenser?
Heat transfer by conduction via a separating surface
In a water-cooled surface condenser utilizing a river water supply, where does the cooling water end up?
It is discharged back into the river at a point downstream of the water intake
What is the main purpose of the cooling tower in a water-cooled surface condenser system with a reusable cooling water supply?
To remove heat from the cooling water using water spray and evaporation
How is air used as a cooling medium in an air-cooled surface condenser?
Air is forced through a series of finned tubes
What is the primary reason for the use of external fins on the tubes in a surface condenser?
To increase the heat transfer surface area
What is the main reason for maintaining a low vacuum in a surface condenser?
To improve steam turbine efficiency
What is the primary purpose of the steam lanes in a downflow condenser?
To allow steam to flow down to the hotwell to heat and deaerate the condensate
What is the main difference between a downflow and a central flow condenser?
The direction of the steam flow
What is the purpose of the air extraction baffles in a downflow condenser?
To prevent steam from entering the air removal equipment
What is the effect of maintaining a controlled water level in the hotwell of a downflow condenser?
It enables the condensate temperature to be maintained near the saturation temperature
What is the purpose of the external fins on the tubes in an air-cooled condenser?
To increase the surface area for heat transfer
How does the design of a central flow condenser encourage the radial flow of steam?
By locating the air extraction points at the center of the shell
What is the primary advantage of using a surface condenser over a direct contact condenser?
Separation of the steam and cooling water
What is the purpose of the horizontal fans in an air-cooled condenser?
To supply cooling air upwards through the tube bundles
In a downflow condenser, what is the purpose of the steam headers supplying exhaust steam at the apex of each section?
To distribute the exhaust steam evenly to each tube bundle
What is the primary purpose of the support plates in a surface condenser?
To support the condenser shell and tubes
How are the condenser feet supported in larger designs?
Supported on springs
What is the purpose of an expansion joint in a surface condenser?
To allow longitudinal movement between the exhaust flange and the machine foundations
What is the shape of the cross-section of the condenser shell?
Cylindrical, oval, or rectangular
Where does the cooling water enter and exit the water box in a downflow condenser?
Enters at the bottom and exits at the top
What is the material used to manufacture the condenser shell and exhaust neck?
Welded steel
What is the purpose of the expansion joint in the shell of a condenser?
To eliminate stresses on the tubes
What material is commonly used to make tube plates, also known as tubesheets, in condensers?
Admiralty brass or Muntz metal
Why are collar bolts used to fasten the tube plate to the shell?
To allow the water box to be opened without disturbing the shell-to-tube plate joint
What is the advantage of using packed tube ends?
They allow the tube to move axially in the packing
What is the primary material used to make water boxes in large condensers?
Steel
What is the purpose of the stay bolts or stay rods in the water boxes?
To support the tube sheet against the condenser vacuum
What is the advantage of using small diameter tubes in a condenser?
They give the best heat transfer since the required wall thickness is less
Why are welded, steel plates with stainless steel cladding used as an alternative to tube plates made of brass or Muntz metal?
They are less expensive
How are tubes typically installed in a condenser?
By expanding, or with combinations of expanding, ferrules, metallic and fiber packings
What is the primary function of the support plates in a surface condenser?
To support the shell and tubes
How are tubes typically installed in a surface condenser?
Vertically and supported by the support plates
What is the purpose of the expansion joint in a surface condenser?
To allow thermal expansion of the shell
In a downflow surface condenser, how does the cooling water enter and exit the water box?
Enters at the bottom and exits at the top
What is the purpose of the hotwell in a surface condenser?
To collect and store condensed steam
What is the shape of the cross-section of the condenser shell in a surface condenser?
Either cylindrical, oval, or rectangular
What is the main purpose of the stay bolts or stay rods in the water boxes of a condenser?
To support the tube sheet against the condenser vacuum
Why can't condenser tubes be made of iron?
Iron corrodes easily in seawater
What is the primary role of the collar bolts?
To allow the water box to be opened without disturbing the shell and tube plate joint
Why are Admiralty brass and Muntz metal the typical materials used for condenser tube plates?
They are resistant to corrosion
Which of the following is NOT a common method of tube end fastening?
Riveting
What is the main reason why larger diameter tubes are not used in condensers?
They give poor heat transfer
Why are cast iron water boxes used in classic water-cooled condensers?
Because they are durable
Why are Admiralty brass and aluminum brass preferred over cupro-nickel as materials for condenser tubes?
They are less expensive
What is the main disadvantage of using welded, steel plates with stainless steel cladding as an alternative to tube plates made of brass or Muntz metal?
They are expensive
What is the effect of installing ferrules at tube ends in condensers?
They improve heat transfer
What is the purpose of the baffle plates in the condensers described?
To direct the steam to the coolers for recovery as condensate
In the operation described, where does the cooling water typically enter the ejector cooler?
At the bottom and flows upwards through the cooler tubes
What can air leaks in the condenser system cause?
Increase in the condensate temperature
How may air leaks be located in the condenser system?
By shutting down the turbine and condenser and filling with water
In Figure 26, why are U-bends present in the drain lines from the first and the second stages of the ejector?
To prevent air from being sucked into the hotwell
What is the purpose of the orifice in the ejector nozzle?
To draw non-condensable gases into the ejector
Why does the cooling water in the ejector cooler absorb heat from the ejector steam?
To create a feedwater heater effect
What is the effect of a choked ejector nozzle in the condenser system?
Reduction in condenser efficiency
What is the significance of the nozzle and venturi in the operation of the ejector in Figure 25?
To draw non-condensable gases into the ejector
How is the operation of the two-stage ejector in Figure 24 different from the single-stage ejector in Figure 22?
Two-stage ejector has higher steam pressure entering
What is the purpose of the nozzle in an air ejector?
To create a high velocity jet
How does the venturi tube in an air ejector aid in air extraction?
By increasing the velocity and creating a lower pressure
What is the main reason for non-condensable gases accumulating in the steam space of a condenser?
Air leakage through glands, joints, and flanges
What is a common device used to continuously remove air from a condenser?
A steam-jet ejector
What is the function of baffle plates in a downflow condenser?
To trap air for extraction
What is the effect of non-condensable gases accumulating in the steam space of a condenser?
Reducing the vacuum and reducing heat transfer
What is the primary consequence of air accumulation in the steam space of a condenser?
Reduced vacuum and decreased heat transfer
How does a venturi tube aid in air extraction in an air ejector?
By creating a lower pressure at the entrance to the ejector
What is the purpose of baffle plates in a downflow condenser?
To trap air
What is the primary mechanism of air removal in an air ejector?
Entrainment with high-velocity steam
Why is it necessary to continuously remove air from the steam space of a condenser?
To maintain vacuum and efficient heat transfer
What is the effect of high-pressure steam expansion through a nozzle in an air ejector?
Conversion of pressure energy into kinetic energy
What is the main purpose of the baffle plates in the condensers described in the figures?
To guide the air/steam mixture to special coolers at the air extraction points
What is the benefit of using feedwater or condensate as the cooling water for the ejector cooler?
It makes efficient use of the ejector steam
What is the purpose of the U-bends in the drain lines of the three-stage ejector?
To act as air seals
Why is it important to prevent air from being sucked into the hotwell of the main condenser?
To prevent a decrease in plant efficiency
What is the purpose of the steam strainer in the ejector?
To prevent the orifice in the ejector nozzle from becoming choked with foreign matter
What happens to the steam and gases in the first stage of the two-stage steam-jet air ejector?
The steam and gases are directed over the cooler tubes several times by the baffles
What is the purpose of the cooling water in the ejector cooler?
To absorb heat from the ejector steam
Why is it important to regulate the steam pressure to the ejectors?
To ensure efficient operation of the ejectors
What is the effect of air leaks in the condenser system?
It decreases plant efficiency
What is the primary purpose of the atmospheric relief valve in a condenser?
To vent steam to atmosphere if the pressure rises above atmospheric
What would happen if the cooling water flow stopped while the condenser was in service?
The condenser shell would fail due to high pressure
Why is a water seal usually fitted to the atmospheric relief valve?
To prevent air from leaking into the condenser
What is the purpose of the test lever on the atmospheric relief valve?
To test the valve when the machine is off load
What would happen if the atmospheric relief valve fails to operate?
The condenser shell would fail due to high pressure
What is a potential danger to be guarded against in a condenser?
A rise in condensate level
What is the primary role of the vacuum relay in a turbine governor system?
To operate between 10 and 40 kPa absolute pressure and unload the turbine accordingly
What is the purpose of the high water-level alarm in a condenser system?
To supplement the gauge glass and indicate when the condensate level is too high
What is the most common method used to detect leaks in the condenser tubes?
Electrical purity method (conductivity)
How are condensate polishers used in maintaining the purity of the condensate?
By cleaning up the condensate when the leak is larger than the polishers can handle
What is the primary reason for using double-flow type condensers in large systems?
To operate at half load or less
What is the significance of using fluorescein dye in detecting leaks in the condenser tubes?
It helps in locating very small leaks
What is the main purpose of the silver nitrate test in detecting leaks in the condenser tubes?
To create a milky-white silver chloride precipitate
What is the role of the condenser system in reducing thermal losses in a steam plant?
By maintaining the low vacuum condition in the condenser
What is a potential consequence of not maintaining a low vacuum condition in a surface condenser?
The turbine output will decrease due to the activation of the vacuum unloader relay
What is the purpose of the external fins on the tubes in a condenser?
To increase the heat transfer efficiency between the steam and the cooling water
What hazard does the atmospheric relief valve protect against in a condenser?
Rise in pressure above atmospheric
Why must the atmospheric relief valve vent the full flow of exhaust steam to atmosphere?
To prevent damage to the condenser shell
What prevents atmospheric air from leaking into the condenser through the atmospheric relief valve line?
Water seal
What is the function of the test lever on the atmospheric relief valve?
Test valve operation
What causes the atmospheric relief valve to open in a condenser?
Difference in pressure
Why is the atmospheric relief valve designed to prevent positive pressure in the condenser shell?
To prevent shell failure
What is the purpose of the vacuum relay set to operate between 10 and 40 kPa absolute pressure?
To regulate the turbine speed
Why is the high water-level alarm essential for a condenser?
To trigger the vacuum unloader relay
How does the conductivity meter detect cooling water leaks in the condensate?
By detecting impurities affecting electrical conductivity
What would happen if a leak in a condenser tube is not quickly detected and corrected?
The steam output of the turbine would decrease
Why are single-flow type condensers required to be taken out of service for repairs?
To drain and open for repair work
How does adding fluorescein dye aid in detecting leaks in condenser tubes?
By glowing fluorescent under ultraviolet light
What is the function of the collar bolts in a condenser?
To support the weight of the condenser
Why are large condensers usually designed as double flow?
To facilitate half-load tube repairs
What is the significance of maintaining a vacuum in the condenser?
To improve the condensate temperature
How do impurities, like salt water, leaking into the condenser affect the operation of the steam turbine?
Decrease turbine output
What is the primary function of an extraction or condensate pump?
Maintaining a constant level in the hot well while pumping condensate
What is a key characteristic of the vertical, well type extraction pump?
It experiences less cavitation than horizontal pumps
Why is a very low NPSH (net positive suction head) necessary for extraction pumps?
To reduce cavitation when pumping near boiling water
What is the purpose of the air-release line connected to the vertical multistage extraction pump?
To release air from the well to prevent cavitation
Why are extraction pumps subjected to severe conditions in operation?
Because they have to deal with maintaining levels and handling varying capacities
What makes the vertical, well type extraction pump more suitable for preventing cavitation?
It has an airtight well with an air-release line to the condenser
What is the primary method of cooling water after it leaves the condenser when the water source is limited?
Using a cooling tower
What is the main purpose of the cooling tower in a water-cooled surface condenser system with a reusable cooling water supply?
To cool the water that has passed through the condenser
What type of pump is most commonly used for cooling in a steam power plant?
Vertical mixed flow pump
What is the main disadvantage of using welded, steel plates with stainless steel cladding as an alternative to tube plates made of brass or Muntz metal?
They are not as resistant to corrosion
What is the purpose of the U-bends in the drain lines of the three-stage ejector?
To prevent the backflow of water
What is the main reason why larger diameter tubes are not used in condensers?
They are less efficient
What is a major disadvantage of horizontal extraction pumps compared to vertical multistage extraction pumps?
They are more prone to cavitation
What is the purpose of the air-release line connected to the vertical multistage extraction pump?
To release air to the condenser
Why must extraction pumps operate at near zero absolute suction pressure?
Because they pump nearly boiling water
What is the primary design consideration for extraction pumps?
To maintain a constant level in the hot well
What is a benefit of opposed impellers in extraction pumps?
They work in parallel
Why do extraction pumps have two or three stages?
To increase efficiency
What is the primary reason for using external fins on the tubes in a surface condenser?
To increase the heat transfer area without increasing the size of the condenser
What type of pump is most commonly used for cooling in a steam power plant?
Centrifugal pump
What is the significance of using fluorescein dye in detecting leaks in the condenser tubes?
It makes the leaking water visible under ultraviolet light
What makes the vertical, well type extraction pump more suitable for preventing cavitation?
Its low operating speed
What is a common device used to continuously remove air from a condenser?
Air ejector
What is the effect of a choked ejector nozzle in the condenser system?
Decreased air extraction
In the feedwater heater system described, where does the deaerated water go after leaving the deaerator?
To the high-pressure heaters
What is the purpose of the condensate booster pump in the feedwater heater system shown in Figure 34?
To supply the first high-pressure heater
What does the 3rd stage of feedwater heating represent in the system described?
Deaerating heater
What is the significance of having two levels of high-pressure heaters in the feedwater heating system?
To minimize water temperature fluctuations
What drives the operation of the high-pressure and low-pressure heaters in the feedwater heating system?
Bleed steam from the turbine
Why do the tubes in the feedwater heater system need to be able to expand differently from the shell?
To accommodate temperature variations
What material are the tubes of a high-pressure feedwater heater made of?
Carbon steel
What is the primary purpose of the expansion bellows or floating head in low-pressure feedwater heaters?
To allow for unequal expansion and contraction
What is the difference between low-pressure and high-pressure feedwater heaters?
The waterside of low-pressure heaters is exposed to the discharge pressure of the extraction pump, while the high-pressure heaters have the water side exposed to boiler feedpump pressure
Which design feature allows the tubes and shell of a high-pressure heater to expand at different rates without causing stress?
U-tubes
Which of the following is a common construction material for the shell of a low-pressure feedwater heater?
Mild steel
In a low-pressure feedwater heater, how are the tubes typically secured to the tube sheet?
Expanded
What is the primary benefit of using feedwater heaters in a steam plant?
To reduce the quantity of steam exhausted to the condenser
What is the primary material used to make the tubes in high-pressure heaters?
Carbon steel
What is the purpose of the expansion bellows or floating head in a low-pressure heater?
To allow for unequal expansion and contraction between the shell and the tubes
What is the primary difference between low-pressure and high-pressure heaters?
The pressure on the water side
What is the purpose of the tubes in a feedwater heater?
To heat the boiler feedwater
What is a characteristic of the shell in a low-pressure heater?
Made of mild steel
What is the primary function of the floating head in a horizontal, two-pass heat exchanger?
To allow for thermal expansion of the tubes
What is the purpose of the condensate booster pump in the feedwater heater system?
To increase the pressure of the condensate
Why are there two levels of high-pressure heaters in the feedwater heating system?
To optimize the temperature of the feedwater
What is the purpose of the deaerator in the feedwater heating system?
To remove dissolved oxygen from the condensate
What is the direction of steam flow in the feedwater heating system?
From the condenser to the boiler
What is the primary reason for the temperature of the feedwater increasing from 38°C to 255°C in the feedwater heating system?
To optimize the heat transfer in the boiler
Learn about the primary and secondary purposes of a condenser in a steam plant, including how it improves thermal efficiency and reduces thermal losses by condensing steam. Understand the role of producing and maintaining a vacuum at the turbine exhaust for better energy recovery.
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