204 Questions
What is the source of impurities in boilers?
Both make-up water and condensate returning from steam-utilizing processes
What happens to the impurities when water treatment chemicals are added to the boiler water?
They react with the chemicals and form new compounds that precipitate from solution
What can happen if impurities are left unaddressed in boilers?
Waterside scale and corrosion occur
What can happen when precipitates settle out in boilers?
They can bake onto heat transfer surfaces or obstruct boiler water circulation
What can happen when impurities increase in concentration in the boiler water?
The tendency for boilers to carry-over impurities with the steam increases
What can happen when scale-forming compounds are deposited in the superheater tubing?
Superheater overheating and failure occur
What is the term used to describe the accumulated precipitated and suspended matter at the base of a boiler shell?
Mud
What is the primary factor that affects the rate of precipitate formation in a boiler system?
Make-up water quality
Why is it necessary to use high-quality make-up water in boilers with high make-up requirements?
To prevent mud and scale formation
What is the purpose of Bottom Blowoff in a boiler system?
To remove accumulated sediment at the base of the boiler
What is the recommended frequency of Bottom Blowoff according to ASME VII?
At least once every 24 hours
What is the effect of flashing water when blowoff valves are opened?
Vibration and shaking in the blowoff line
What is the purpose of designing blowoff piping for shock service?
To withstand the shock and thermal expansion of the blowoff piping
What are the components of a Bottom Blowoff system?
Blowoff valves, blowoff piping, and blowoff vessels
What is the primary consideration when designing blowoff valves?
Material strength and resistance to erosion
What is the exception to the requirement for blowoff piping in boilers?
Hot water heating boilers
What is a result of carryover in steam boilers?
Deposits of silica on turbine blading
What is the purpose of blowdown and blowoff in steam boilers?
To prevent the accumulation of sediment and dissolved solids
What is the main difference between blowoff and blowdown systems in heating boilers and power boilers?
Heating boilers have less robust blowoff and blowdown systems
What is the term 'bottom blowoff' referring to?
The intermittent removal of sediment accumulated in drums, shells, and headers
What is the ideal scenario for boiler feedwater sources?
Every kilogram of steam produced is returned to the boiler in a 100% pure state
What is the primary source of boiler water impurity?
Make-up water
What is the purpose of external water treatment equipment?
To convert dissolved calcium and magnesium compounds to sodium compounds
What is the purpose of internal chemical treatment in steam boilers?
To precipitate scale-forming calcium and magnesium
What is the result of carryover in terms of turbine efficiency?
Reduced turbine efficiency
What is the purpose of the blowoff line in steam boilers?
To blow out sediment and impurities from the boiler under pressure
What is the minimum number of boiler blowoff valves required by ASME B31.1?
One
What type of valve is shown in Figure 2?
Y-Type Globe Valve
What is the purpose of the port in the lower part of the plunger in a seatless slow-opening valve?
To allow boiler water to flow through the valve
What is the advantage of a Y-type valve over a regular globe valve?
It has a lower pressure drop
What is the function of the spring in a quick-opening valve?
To force the disc against the seat
What can happen if a quick-opening valve is left leaking for a long time?
The valve seat and disc will wire draw
What type of valve is required by ASME B31.1 to be at least one in a power boiler?
Slow-Opening Valve
What is the characteristic of a slow-opening valve?
It requires at least five 360° turns of the operating mechanism to open or shut
What is the purpose of the markings on a quick-opening valve?
To indicate the valve is open or shut
What happens when the plunger hole in a seatless slow-opening valve aligns with the valve inlet?
The valve is open
What is the primary purpose of blowoff piping?
To allow for thermal expansion and contraction
What is the function of a blowoff vessel?
To depressurize and cool the blowoff water
What is the minimum pressure requirement for the installation of a blowoff vessel?
103 kPa
What is the purpose of the inlet line in a blowoff vessel?
To mix the incoming hot water with the cooler water in the tank
What is the maximum temperature allowed for the blowoff water at the outlet of the blowoff vessel?
65°C
What is the purpose of the anti-siphon hole in a blowoff vessel?
To prevent the vessel from draining completely
What is the result of inadequate blowoff?
Increased sediment accumulation and adhesion to heat transfer surfaces
What is the purpose of quenching water in some blowoff vessels?
To cool the blowoff water to a safe temperature
What is the ASME code that specifies the materials and design of power boiler blowdown piping?
ASME B31.1
Why is it important to anchor blowoff piping to prevent transmission of motion back to the boiler?
To prevent damage to the boiler and its components
What is the primary reason for positioning bottom blowoff valves at the lowest parts of the boiler?
To prevent the accumulation of suspended matter at the bottom of the water space
Why is it essential to lock out and tag boilers open for maintenance or inspection during bottom blowoff?
To prevent blowoff water from entering the open drum of another boiler
What is the primary purpose of having an assistant watch the gauge glass during bottom blowoff?
To warn the operator if the boiler water level gets too low
What should be done with blowoff valves after a blowoff operation is complete?
Confirm they are shut and verify the sequence
What is the recommended practice for operating blowoff valves during bottom blowoff?
Open and close them slowly to prevent water hammer
Why is it important to visibly number or identify boilers in a multiple boiler plant?
To prevent blowing off the wrong boiler
What is the purpose of quenching water during bottom blowoff?
To prevent thermal shock
Why is it recommended to perform bottom blowoff when the boiler load is low or moderate?
To minimize disruption to boiler water circulation
What is the purpose of the valve closest to the boiler in a blowoff valve combination?
To protect the valve from erosive action
What should be done during a bottom blowoff operation to prevent water hammer?
Open the blowoff valves slowly and in the proper sequence
What is the purpose of a guard valve in a combination quick-opening and slow-opening valve arrangement?
To act as a shut-off valve adjacent to the boiler
What is the recommended sequence for opening and closing valves in a combination quick-opening and slow-opening valve arrangement?
Open the guard valve first and close it last, and open the blowoff valve last and close it first
What can happen if the correct operating sequence is not followed when using two seatless slow-opening valves?
The valve body may crack due to water compression
What is the purpose of a surface blowoff system in a boiler?
To remove impurities from the boiler water surface
What is the importance of using a graduated metering valve in a continuous surface blowoff system?
It allows for more precise control of the blowoff flow rate
Why is it important to follow the correct operating sequence when using two hard-seated slow-opening valves?
To ensure one valve is the guard valve and the other is the blowing valve
What is the purpose of the perforated pipe in a surface blowoff system?
To remove impurities from the boiler water surface
What can happen if the blowoff valve is pumped to blow off the boiler?
Water hammer will occur
Why is it important to ensure that the valve furthest from the boiler is opened first and closed last when using two seatless slow-opening valves?
To prevent water from becoming trapped between the valves
What is the purpose of the isolation valve in a surface blowoff system?
To isolate the boiler from the blowoff system
What is the primary consequence of impurities being left unaddressed in boilers?
Creation of waterside scale and corrosion
What is the purpose of adding water treatment chemicals to the boiler water?
To react with impurities and form precipitates that can settle out
What is the result of precipitates settling out in low water cutoff float cages and water columns?
Interference with cutoff and gauge glass operation
Why do impurities increase in concentration in the boiler water as the boiler operates?
Because of the concentration of impurities in the feedwater
What is the consequence of carryover in steam boilers?
Deposits of scale-forming compounds in the superheater tubing
What is the source of impurities in boilers?
Make-up water and condensate returning from steam-utilizing processes
What is the primary consequence of not performing blowdown and blowoff in steam boilers?
Scale formation and sediment accumulation
Why is make-up water a primary source of boiler water impurity?
It contains varying amounts of suspended matter, dissolved solids, and dissolved gases
What is the purpose of adding chemicals to boiler water?
To precipitate scale-forming calcium and magnesium
What can happen if impurities are not removed from the boiler water?
Scale formation and sediment accumulation will occur
What is the difference between surface blowoff and bottom blowoff?
Surface blowoff removes sediment, while bottom blowoff removes dissolved solids
Why is it important to ensure that the blowdown system is operated correctly?
To prevent the accumulation of sediment and dissolved solids
What is the result of not treating make-up water before adding it to the boiler?
Impurities will enter the boiler and cause problems
What is the purpose of external water treatment equipment?
To convert calcium and magnesium compounds to sodium compounds
What is the cause of carryover in steam boilers?
All of the above
What is the result of carryover in terms of turbine efficiency?
Decreased efficiency
What is the primary factor that affects the rate of precipitate formation in a boiler system with high steam production?
Quality of make-up water
Why is it necessary to design blowoff piping for shock service?
To prevent all of the above
What is the characteristic of a blowoff valve that is specially designed for severe service?
It is made of materials that are strong at high pressures and temperatures
What is the minimum design pressure of the blowoff piping system components that exceeds the MAWP of the boiler?
It is specified in ASME B31.1
What is the purpose of the anti-siphon hole in a blowoff vessel?
To prevent the formation of a vacuum in the vessel
What is the result of inadequate blowoff in a boiler system?
The formation of mud and scale in the boiler
What is the primary purpose of the frequency and duration of blowoff in a boiler system?
To remove accumulated sediment at the base of the boiler
What is the effect of flashing water when blowoff valves are opened?
A sudden temperature rise and the formation of steam
What is the purpose of the rules for blowoff valves and blowoff piping in ASME B31.1 and ASME IV?
To ensure the safe operation of the boiler
What is the characteristic of a boiler system that requires high-quality make-up water?
It has a high make-up water requirement
What is the primary consideration for selecting the construction material of blowoff valves in power boilers?
Boiler pressure and temperature
What is the purpose of the stem angle in a Y-type globe valve?
To reduce the pressure drop across the valve
What is the primary characteristic of a slow-opening valve?
It requires multiple 360° turns of the operating mechanism to change from fully closed to fully open
What is the function of the port in the lower part of the plunger in a seatless slow-opening valve?
To facilitate the flow of boiler water through the valve
Why is it important to ensure that the valve does not leak for a long time in a quick-opening valve?
To prevent the valve seat and disc from wire drawing
What is the purpose of the markings on the body of a quick-opening valve?
To enable the operator to determine the valve's position
What is the advantage of using a Y-type valve over a regular globe valve?
It reduces the pressure drop across the valve and enables sediment and water to freely discharge
What is the purpose of the spring in a quick-opening valve?
To provide a tight seal between the valve disc and seat
What is the primary advantage of using a hard-seated valve over a seatless valve?
It is more durable and resistant to wear and tear
What is the purpose of the welded bonnet in a Y-type valve?
To enhance the valve's structural integrity and prevent leakage
What is the primary reason why waterwall header blowoff is never performed when large steam generating units are in operation?
To prevent loss of water circulation and exposure to overheating
What is the purpose of quenching water in some blowoff vessels?
To prevent thermal shock
Why is it important to ensure that any boilers open for maintenance or inspection are properly locked out and tagged during bottom blowoff?
To prevent blowoff water from entering the open drum of another boiler
What is the recommended practice when operating blowoff valves during bottom blowoff?
Open the valves slowly and in the proper sequence
What is the purpose of the valve closest to the boiler in a blowoff valve combination?
To protect the valve from the erosive action of the boiler water
What is the primary consideration when designing blowoff valves?
Preventing erosion of the valve
What can happen if the blowoff valves are not operated slowly and in the proper sequence during bottom blowoff?
Water hammer may occur
Why is it important to verify that quenching water is on before beginning the blowoff procedure?
To prevent thermal shock
What is the purpose of having an assistant watch the gauge glass during bottom blowoff?
To warn the operator if the boiler water level gets too low
What is the primary purpose of performing bottom blowoff?
To remove suspended matter and sediment from the boiler
What is the main purpose of the blowoff vessel in a boiler system?
To depressurize the blowoff water and cool it to a suitable temperature for the sewer system
According to the CSA B51 Code, what is the maximum temperature allowed for the blowoff water at the outlet of the blowoff vessel?
65°C
What is the primary purpose of the anchor in the blowoff piping system?
To prevent the transmission of motion from the piping to the boiler
What is the result of inadequate blowoff in a boiler system?
Sediment accumulation and adherence to heat transfer surfaces and other boiler parts
What is the primary function of the anti-siphon hole in a blowoff vessel?
To prevent the vessel from draining completely
What is the primary reason for using a slow-opening valve in a blowoff system?
To prevent water hammer
What is the purpose of the inlet line in a blowoff vessel?
To mix the incoming hot water with the cooler water in the vessel
What is the requirement for the installation of a blowoff vessel according to the CSA B51 Code?
For all boilers operating above 103 kPa gauge
What is the purpose of the valve closest to the boiler in a combination quick-opening and slow-opening valve arrangement?
To act as a guard valve
Why is it important to follow the correct operating sequence when using two seatless slow-opening valves?
To prevent valve damage
What is the purpose of the inspection and cleaning access in a blowoff vessel?
To facilitate the inspection and cleaning of the vessel
What is the purpose of a surface blowoff system in a boiler?
To remove impurities from the boiler water surface
What is the effect of excessive blowoff in a boiler system?
Discharge of treated water, internal treatment chemicals, and heat from the boiler
What is the purpose of the ASME B31.1 Power Piping Code in relation to blowoff piping?
To specify the materials and design of power boiler blowdown piping
What can happen if the correct operating sequence is not followed when using two hard-seated slow-opening valves?
The valve may be damaged
Why is it important to ensure that the valve furthest from the boiler is opened first and closed last when using two seatless slow-opening valves?
To prevent valve damage
What is the characteristic of a slow-opening valve in a blowoff system?
It opens slowly to reduce the possibility of water hammer
What is the purpose of an isolation valve in a surface blowoff system?
To isolate the surface blowoff system from the boiler
What can happen if the blowoff valve is pumped to blow off the boiler?
Water hammer may occur
What is the purpose of a guard valve in a combination quick-opening and slow-opening valve arrangement?
To ensure a leak-tight shut-off adjacent to the boiler
What is the primary reason for controlling the concentration of dissolved solids in boiler water?
To prevent carryover and impede heat transfer
What are the examples of dissolved solids in boiler water?
Various sodium compounds, such as carbonates, bicarbonates, chlorides, and phosphates
What is the effect of high concentrations of dissolved solids in boiler water?
It can lead to carryover and impede heat transfer
How do dissolved solids enter the boiler water?
They enter the boiler with the make-up water, or return with the condensate
What is the purpose of continuous blowdown in boiler operation?
To control the concentration of dissolved solids in boiler water
What can happen if the concentration of dissolved solids is not controlled in boiler water?
It can lead to foaming and priming
What is the primary purpose of continuous blowdown in a boiler?
To control the concentration of dissolved solids in the boiler water
What is the main factor that determines the quality of feedwater required for a boiler?
Boiler operating pressure
What is the purpose of filtering and softening returns with condensate polishing equipment?
To remove suspended matter from the returns
What is the term used to describe the measurement of dissolved solids concentration in boiler water?
Specific conductance
What is the primary function of the internal continuous blowdown collection pipe in the steam drum?
To collect boiler water with the highest dissolved solids concentration
What is the purpose of measuring the solids concentration of the boiler water during continuous blowdown?
To adjust the metering valve to maintain the prescribed solids concentration
What is the purpose of the CBD valve in a blowdown system?
To control the flow of blowdown water to the blowoff vessel
What is the result of not controlling the concentration of dissolved solids in the boiler water?
Scale formation and potential boiler damage
What is the recommended practice for determining the blowdown rate?
Conducting regular water tests at the beginning of every shift
Why is it important to adjust the CBD valve carefully?
To prevent excessive blowdown and waste of treated water
What is the purpose of ASME B31.1 code in relation to blowdown systems?
To specify the materials and design of power boiler blowdown piping
What is the recommended material for blowdown piping in boilers operating at pressures higher than 690 kPa?
Steel, at least Schedule 80
What is the primary purpose of installing a heat recovery system in a blowdown system?
To conserve heat energy and reduce energy losses
What is the effect of high-pressure boilers on the need for feedwater quality?
Increased need for high-quality feedwater
What is the purpose of ultra-pure make-up water in high-pressure boilers?
To reduce the need for internal boiler water treatment chemicals
What is the effect of excessive continuous blowdown on a boiler system?
It wastes treated water, chemicals, and heat
What is the purpose of the vernier scale on a CBD valve?
To indicate the valve position and facilitate fine flow control
What factor determines the design pressure of the blowdown piping system?
The boiler's MAWP
What is the primary reason for installing a single shut-off valve in the CBD line?
To isolate the boiler from the blowdown system
What is the purpose of adjusting the flow of blowdown water in a boiler system?
To regulate the TDS concentration in the boiler water
What is the primary benefit of using an automated continuous blowdown system?
Reducing the total amount of blowdown and fuel costs
What is the purpose of the heat exchanger in a blowdown heat recovery system?
To recover heat from the blowdown water and preheat the make-up water
Why is it important to regularly inspect the blowoff system?
To prevent thermal shock and wear and tear on components
What is the recommended material for blowoff piping operating above 690 kPa?
Schedule 80 steel
What is the purpose of the 45° elbow in blowoff piping?
To reduce the risk of erosion and corrosion
What should be done if a valve is found damaged during inspection?
Replace it with the exact same valve
What is the benefit of increasing the temperature of the feedwater by 5°C?
A 1% increase in efficiency
What is the purpose of the solenoid valve in an automated continuous blowdown system?
To shut off the blowdown flow when the boiler is off
What is the consequence of not repairing or replacing damaged blowoff system components?
Increased risk of explosion and damage to the system
What should be inspected during regular blowoff system inspection?
The boiler blowoff vessel, blowoff valves, and blowoff piping
What is the primary reason why dissolved solids in boiler water can lead to superheater failure?
The dissolved solids concentrate in the boiler water, carrying over with the wet steam and potentially depositing in the superheater banks, impeding heat transfer.
What is the primary source of impurities in boiler water?
All of the above are potential sources of impurities in boiler water.
What is the effect of high concentrations of dissolved solids in boiler water?
They can lead to carryover, foaming, and priming, reducing the overall efficiency of the boiler.
What is the purpose of controlling the concentration of dissolved solids in boiler water?
To prevent carryover, foaming, and priming, and to reduce the risk of superheater failure.
What is the primary function of chelants in boiler water treatment?
To react with impurities and form precipitates that can be removed from the boiler.
What is the result of inadequate control of dissolved solids in boiler water?
Increased risk of superheater failure, carryover, foaming, and priming, and reduced overall efficiency of the boiler.
What is the primary purpose of ultra-pure make-up water in high-pressure boilers?
To reduce the need for internal boiler water treatment chemicals
What is the primary characteristic of a boiler system that requires high-quality make-up water?
High-pressure boilers
What is the consequence of not performing continuous blowdown in steam boilers?
Scale formation
What is the primary factor that determines the blowdown rate in a boiler system?
Rate of steam production
What is the purpose of continuous blowdown in boiler operation?
To reduce the concentration of dissolved solids in the boiler water
What is the primary source of impurities in boilers?
Make-up water
What is the relationship between the electrical conductivity of water and its dissolved impurities?
The conductivity of water increases with increasing impurities
What is the primary purpose of measuring the solids concentration of the boiler water?
To determine the blowdown rate
What is the term used to describe the total dissolved solids (TDS) concentration in boiler water?
Specific conductance
What is the primary reason for using continuous blowdown in high-pressure boilers?
To reduce the need for internal boiler water treatment chemicals
What is the primary benefit of implementing an automated continuous blowdown system?
Reducing total blowdown and eliminating TDS swings
What is the primary purpose of inspecting blowoff system components?
To identify potential safety hazards and preventive maintenance
What is the recommended material for blowoff piping in boilers operating above 690 kPa?
Schedule 80 steel
What is the consequence of not performing regular blowoff system inspections and maintenance?
Thermal shock and component failure
What is the benefit of using a heat recovery system in a blowdown system?
Improving boiler efficiency by preheating feedwater
What is the purpose of the solenoid valve in an automated continuous blowdown system?
To shut off the blowdown flow when the boiler is off
What is the recommended procedure for repairing or replacing blowoff system components?
Following guidelines and using certified materials and welders
What is the primary consideration when selecting blowoff valve materials?
Material strength and corrosion resistance
What is the consequence of using inadequate or corroded blowoff piping components?
Component failure and explosion risk
What is the purpose of the heat exchanger in a blowdown heat recovery system?
To heat the make-up water
At what location is the internal continuous blowdown collection pipe installed in the steam drum or boiler shell?
About 15 cm below the normal operating water level
What is the primary purpose of controlling the TDS concentration in boiler water through continuous blowdown?
To prevent excessive carryover
What is the requirement for blowdown piping material in boilers operating at pressures higher than 690 kPa?
It must be steel, and at least Schedule 80
What is the purpose of the vernier scale on a CBD valve?
To indicate the valve's opening position
Why is it necessary to carefully monitor and control manual continuous blowdown?
To prevent excessive blowdown waste
What is the typical percentage of the overall boiler steam flow rate for the CBD flow?
1% or more
What is the purpose of the CBD valve in a blowdown system?
To control the flow of blowdown water
What is the consequence of not opening the CBD valve sufficiently?
The TDS concentration will be too high
Why is it important to consider the rate of steam production and type of impurities in the make-up water when designing a blowdown system?
To determine the required blowdown rate
What is the advantage of using a V-notch plug valve in a blowdown system?
It provides more desirable flow characteristics
Learn about the importance of water treatment in boilers, the sources of impurities, and how they can affect boiler performance. Discover how water treatment chemicals can help mitigate these issues and maintain boiler efficiency.
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