112 Questions
What is a key characteristic of a firetube boiler?
The water and steam surround the products of combustion.
What was a major issue with early firetube boilers?
Much heat was passed to brickwork rather than boiler water.
What was an improvement made to early firetube boilers?
Directing combustion gases through firetubes submerged in boiler water.
What is an advantage of firetube boilers over watertube boilers of comparable rating?
They contain more water, storing more heat energy.
Why can firetube boilers tolerate lower quality feedwater?
Because they have no small water passages to block.
What has led to the modern firetube boiler being safer than its early counterparts?
The development of design codes and advancements in welding methods.
What is a major disadvantage of firetube boilers?
They are limited in operating pressure to about 2.4 MPa.
What is the primary reason locomotive boilers were taken out of service and placed in stationary service?
They were no longer needed for steam traction engines.
What is the purpose of staybolts in locomotive boilers?
To support the waterlegs.
What is a characteristic of HRT boilers?
The combustion gases make two passes on their way to the chimney.
What is the main reason HRT boilers are no longer constructed?
They are inefficient due to extensive field-erected brickwork.
What is the steaming capacity range of HRT boilers?
500 to 7000 kg/h
What is the main advantage of firetube boilers over watertube boilers?
They are less expensive to purchase.
What is the type of boiler shown in Figure 1?
Locomotive boiler.
What is the primary application of firebox boilers?
Low-pressure heating service.
Why are locomotive boilers expensive to construct?
They require a lot of staying, which increases construction costs.
What is the primary advantage of moving the furnace to within the shell of a boiler?
Increasing the heat transfer to the boiler water
What is the name of the boiler design that is suitable for both high-pressure and low-pressure service?
Scotch boiler
What term does ASME use to refer to all types of boilers, regardless of their design?
Firetube boilers
What is the purpose of the reversing chamber in a multi-pass boiler?
To redirect the flow of flue gas
What is the disadvantage of adding extra passes to a boiler?
Increasing the cost of the boiler
What is the reason for the development of multi-pass boilers?
To lengthen the flue gas path without increasing the boiler length
What is the term for the pathway through which the products of combustion flow in one direction?
Pass
Why is the Scotch boiler often called a Scotch Marine boiler?
Because it was originally designed for use on ships
What is the purpose of the corrugated furnace in a Scotch boiler?
To contain the water below the furnace
What is the term for the type of Scotch boiler that has a water-cooled surface at the rear of the boiler?
Wet-back boiler
What is a major drawback of modern firetube boilers with multiple passes?
They require more powerful draft fans.
What is the primary heat transfer mechanism in the furnace tube of a two-pass firetube boiler?
Radiation
What is the main advantage of a single-pass firetube boiler?
It has more radiant heat transfer surface.
What is the purpose of the reversing chamber in a two-pass firetube boiler?
To change the direction of the flue gas flow.
What is the main reason why multiple-pass boilers have more tubes than single-pass boilers?
To increase the heat transfer surface area.
What is the main difference between a dry-back and a wet-back three-pass firetube boiler?
The pressure vessel design.
Why do multiple-pass boilers require fewer tubes in each pass?
To reduce the total cross-sectional area of each pass.
What is the main advantage of a vertical tubeless boiler?
It is a simple, packaged design.
What is the purpose of the flame retainer rings in a vertical tubeless boiler?
To swirl the hot combustion gases.
What is the main difference between a firetube boiler and a vertical tubeless boiler?
The presence of firetubes.
What is the advantage of using corrugated furnaces?
Increasing heat transfer surface area
What is the primary purpose of the flame retainer rings in a firetube boiler?
To slow the progress of the combustion gases and maximize contact time between the water and the hot gases
What is the purpose of staybolts in firetube boilers?
To support the flat surfaces of the boiler
What is the function of the fins welded to the outside of the boiler shell?
To increase the convective heat transfer to the water inside the shell
What is the difference between through stays and staybolts?
Staybolts are used where through stays would block manhole access
What is the maximum allowable working pressure that special designs of firetube boilers can be manufactured to?
3450 kPa
What is the primary mechanism of water circulation in firetube boilers in steam service?
Natural convection
What is the purpose of the small hole drilled into the end of through stays and staybolts?
To serve as a telltale for corrosion or cracking
Where is the lowest permissible water level typically taken in locomotive and firebox boilers?
25 mm above the crown sheet
What is the advantage of using reinforced furnace tubes?
They can be made thinner for the same working pressure
What is the purpose of corrugations and reinforcing rings on furnace tubes?
To strengthen the furnace
How are tubes in a firetube boiler typically joined to the tubesheets?
By expanding, welding, or both
What is the typical rating range for vertical tubeless boilers?
40 to 600 kW
What is the purpose of the doors in a firetube boiler?
To contain the combustion gases, direct the products of combustion, and provide access for inspection and maintenance
What is the effect of corrugations on furnace turbulence?
They increase furnace turbulence
What is the function of the reversing chamber in a firetube boiler?
To direct flue gas around the outside of the boiler shell
What is the purpose of the inner door and baffle in a firetube boiler with multiple passes?
To redirect the flue gas
What is the consequence of uneven water circulation in firetube boilers?
Sludge accumulation directly below the furnace tube
What is the purpose of the tubesheets in a firetube boiler?
To accept firetubes and the furnace tube
Why are tubes in a firetube boiler installed differently in each pass?
Due to differences in temperature
What was the primary reason for the development of submerged furnace tubes in early firetube boilers?
To reduce heat loss to the brickwork
What is the primary benefit of the large water volume in firetube boilers?
Quick response to load changes without pressure loss
Why did design codes become necessary for firetube boilers?
To ensure consistent design calculations and construction methods
What is the primary advantage of firetube boilers over watertube boilers of comparable rating?
More water volume and tolerance for lower quality feedwater
What led to the improvement in safety of modern firetube boilers compared to their early counterparts?
Improved control systems and welding methods
What was a major issue with early firetube boilers?
High heat loss to the brickwork
What is the primary reason for the limited operating pressure of firetube boilers?
Thicker shells would increase construction costs
What is the main advantage of locomotive boilers in steam locomotives and steam traction engines?
They are portable and can be easily moved
What is the primary advantage of a single-pass firetube boiler over multi-pass designs?
Increased radiant heat transfer surface
Why are horizontal return tubular (HRT) boilers no longer constructed?
All of the above
Why do multiple-pass firetube boilers require more powerful draft fans?
Because the boiler becomes more restrictive to flue gas flow
What is the purpose of the waterlegs in a locomotive boiler?
To support the crown sheet and wrapper sheet
What is the primary difference between a dry-back and a wet-back three-pass firetube boiler?
The pressure vessel design
What is the main difference between a locomotive boiler and a firebox boiler?
The design of the furnace
Why do four-pass firetube boilers have fewer tubes in each pass?
To reduce the total cross-sectional area of each pass
What is the advantage of using an all-welded construction in modern locomotive boilers?
It is stronger and more durable
Why are firetube boilers slow to heat up and bring to operating pressure and temperature?
The large water volume takes longer to heat
What is the advantage of a vertical tubeless boiler over other firetube designs?
It occupies very little floor space
What is the purpose of the flame retainer rings in a firetube boiler?
To facilitate hot combustion gases swirling
What is the purpose of the radial stays in a locomotive boiler?
To support the upper sections of the end plates
Why are HRT boilers often retrofitted for gas or oil firing?
To extend their lifespan
Why are single-pass firetube boilers more economical to maintain?
Due to the absence of internal baffles and refractory
What is the primary mechanism of heat transfer in the furnace tube of a two-pass firetube boiler?
Radiation
What is the primary application of firetube boilers?
Low-pressure heating service
What is the consequence of reducing the number of tubes in each pass of a four-pass firetube boiler?
Decreased total cross-sectional area of each pass
What is the primary application of vertical tubeless boilers?
Dry-cleaning, laundry, and small industrial applications
What is the primary reason for moving the furnace within the shell of a boiler?
To eliminate heat losses through the brick setting
What is the main advantage of a multi-pass boiler over a single-pass boiler?
Increased efficiency due to longer combustion gas paths
What is the primary purpose of the reversing chamber in a multi-pass boiler?
To redirect the flow of flue gas
What is the term used to describe the pathway through which the products of combustion flow in one direction?
Pass
What is the main disadvantage of adding extra passes to a boiler?
Increased complexity and cost due to additional reversing chambers
What is the primary advantage of a Scotch boiler over a firebox boiler?
Reduced heat losses due to the elimination of brick settings
What is the main reason why modern firetube boilers are more efficient than their early counterparts?
Internal firing and multi-pass designs
What is the primary reason why multi-pass boilers require more complex door designs?
To accommodate the additional reversing chambers
What is the primary advantage of a wet-back boiler over a dry-back boiler?
Increased heating surface due to water-cooled surfaces
What is the primary reason why firetube boilers are more suitable for low-pressure and high-pressure service?
Due to their internal firing and multi-pass designs
What is the primary purpose of the fins welded to the outside of the boiler shell?
To increase the convection heat transfer to the water inside the shell
What is the consequence of poor water circulation in firetube boilers?
Sludge accumulation and overheating of the furnace tube
What is the typical lowest permissible water level for locomotive and firebox boilers?
25 mm above the crown sheet
What is the purpose of the tubesheets in a firetube boiler?
To attach the firetubes and furnace tube to the boiler
What is the primary mechanism of water circulation in firetube boilers in hot water service?
Forced circulation
What is the maximum allowable working pressure that special designs of firetube boilers can be manufactured to?
3450 kPa
What is the purpose of the reversing chamber in a multi-pass firetube boiler?
To direct flue gas around the outside of the boiler shell
What is the typical rating range for vertical tubeless boilers?
40-600 kW
What is the primary advantage of using corrugated furnaces?
Improved structural strength and resistance to deformation
What is the term for the type of boiler that is suitable for both high-pressure and low-pressure service?
Firetube boiler
What is the primary benefit of using corrugated furnaces in boilers?
Improved heat transfer through increased surface area
Why are tubes in a firetube boiler installed differently in each pass?
To accommodate varying temperatures across passes
What is the purpose of the small hole drilled into the end of through stays and staybolts?
To act as a telltale for damage
What is the primary function of the tubesheets in a firetube boiler?
To support the furnace tube
What is the advantage of using ring-reinforced furnaces?
Thinner furnaces for the same working pressure
Why are firetubes not reinforced like furnace tubes?
Because they are not subject to external pressure
What is the purpose of the doors in a firetube boiler?
To direct the products of combustion through the flue gas passes
What is the primary benefit of using diagonal stays in firetube boilers?
They allow for manhole access to the waterside
Why are staybolts often attached by welding?
To provide a stronger joint between the tubesheet and the tube
What is the primary purpose of the inner door and baffle in a firetube boiler with multiple passes?
To redirect the flue gas
Explore the evolution of firetube boilers, from their early inefficiencies to significant design improvements. Learn how the direction of combustion gases and furnace tubes contributed to increased efficiency. Test your knowledge on this fundamental concept in boiler manufacturing!
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