3B1 ABSA FINAL EXAM TEST 2026\2027.
Combustion air for the burners is preheated to ______ in the air heater section by combustion gases leaving the
economizer section.
350°C
Most downcomers run horizontally between the steam drum and the mud drum.
False
Steam bubbles form in the hottest tubes and rise to the steam drum where the steam is separated out of the
water and steam mixture. Circulation is maintained by water returning to the mud drum through the cooler tubes.
The hotter tubes (the risers) are the ones in the radiant area of the furnace and the hottest areas of the
generating bank of tubes.
True
What is the main advantage of the packaged boiler?
Low cost
Generally, two types of draft fans are used. A(n) _____ ____ fan supplies air to the air preheater. The preheated
air for combustion goes to the coal pulverizers and to the burners. A(n) ______ ____ fan exhausts the combustion
gases from the air heater to the stack.
Forced draft, induced draft
One square metre of heating surface equals 10 kilowatts. The heating surface of a boiler must be determined by
computing the area of the surface involved in square metres. Where a computation is to be made of a curved
surface, the surface with the greater radius is taken.
True
When the boiler provides the entire steam supply to an electric generating unit, the output of the boiler is
expressed in terms of power output of the generator (e.g. a 300 megawatt boiler).
True
What is the range for packaged watertube boiler capacities?
2300 kg to 65 000 kg per hour
What is the output of field-erected boilers?
150 000 kg/h or more
The A-, D-, and O- type boilers have furnaces cooled by _________ lining the furnace walls.
Watertubes
Where electric power is used as the heating source, the boiler rating is the maximum kilowatt rating of which
aspect?
Heating element
The difference in density between water and saturated steam becomes progressively less with increased
pressure and disappears altogether at the critical pressure of _______ .
22 090 kPa
The main feature of a controlled circulation boiler is a (circulating) pump, which is used to provide circulation.
True
The advantage of forced circulation in a boiler is a _________ flow in all tubes.
Positive
The steam separating equipment separates the _______ from the steam/water mixture.
,3B1 ABSA FINAL EXAM TEST 2026\2027.
Steam
Not all once-through boilers use forced circulation.
False
The arrangement of a once-through boiler has no drums. How many passes through the unit does it take to heat,
evaporate, and superheat the feedwater?
One passage
Steam generators operating above critical pressure are said to be ______-critical, and steam generators
operating below critical pressure are classed as ____-critical.
Super, sub
A steam generating unit consists of a number of elements, all of which contribute to the production of steam.
Which of the following is not an element of a typical steam generator?
Water conditioner
Natural circulation in a boiler depends on the ___________ in the density of a column of water and the density of a
column that contains a steam/water mixture.
Difference
Feedwater entering the boiler section first passes through the __________ section where it is heated by the
combustion gases leaving the boiler.
Economizer
The disadvantages of forced circulation in a boiler are the __________ of equipment such as pumps and piping
Increased costs
There are several factors that influence the natural circulation in a watertube boiler. Which of the following is NOT
one of those factors?
The diameter of the steam drum.
The downcomers are located in the ______ regions of the boiler, or external to the furnace altogether. The risers
are located in the ________ zones of the boiler, and are exposed to radiant heat of the furnace or to the very hot
flue gases near the furnace.
Cooler, hottest
The control methods used for reheater temperature are the same as those used for __________ temperature
control.
Superheater
Reheaters are located in the furnace in areas of relatively _____ gas temperatures.
High
When the boiler is shut down, the air preheater should be inspected for signs of _______.
Corrosion
When starting up a boiler, a steam flow is needed through the __________ tubes for cooling
Superheater
The boiler tubes of the ______ wall are placed side by side and touching each other to form a continuous water-
cooled envelope around the furnace.
Tangent tube
The water and water/steam mixture in the steam generation tubes is at _________ temperature.
Saturation
, 3B1 ABSA FINAL EXAM TEST 2026\2027.
The temperatures of the flue gas leaving the preheater must be kept above the _______ to avoid condensation.
Dewpoint
The _________ increases the temperature of the steam from the HP turbine back up to superheat temperature.
Reheater
In order to direct the flow of combustion gas over the tubes in a watertube boiler, it is necessary to use _______.
Baffles
B1C04Q02 The __________ economizer, which is the more common type, features rows of horizontal tubes,
located outside the furnace proper.
Separate
Furnace baffles can be placed so as to cause the gases to flow at right angles to the tube length, in which case
they are called ________ baffles.
Cross
Furnace baffles may be placed so as to cause the gases to flow parallel to the tubes, in which case they are called
_________ baffles.
Longitudinal
The separately fired superheater is located in a _______ apart from the main steam generator and is independent
of the steam generator operating conditions.
Furnace
B1C04Q01 In some cases, __________ or desuperheaters are located between superheater stages, which allows
steam temperatures to be maintained relatively constant over a wide load range.
Attemperators
Metal fin bars are welded to adjacent tubes, forming a continuous surface and a pressure-tight wall. This is
referred to as a welded fin tube wall or a ________ wall.
Membrane
B1C04Q03 In regards to air heater corrosion, sulfur dioxide in the presence of water vapour forms __________.
Sulfurous acid
The water ________at the economizer exit is always below that of the steam drum to prevent steaming in the
economizer.
Temperature
Wet tubes on start-up of the boiler are a _______ occurrence, caused by condensation on the tube walls.
Normal
There is no steam flow through the ______ tubes before the steam turbine has a steam flow through it. Be careful
not to increase boiler firing too rapidly and overheat the reheat tubes during start-up.
Reheater
Furnace baffles are usually constructed of ___________ material and may be made up of individual bricks or tiles.
Refractory
The reheater receives steam that has already expanded through a portion of the turbine, and as a result of this
expansion, has dropped in pressure and in _________.
Temperature
In the reheater, the steam has its temperature raised to about the same temperature as was initially provided by
the _________.
Combustion air for the burners is preheated to ______ in the air heater section by combustion gases leaving the
economizer section.
350°C
Most downcomers run horizontally between the steam drum and the mud drum.
False
Steam bubbles form in the hottest tubes and rise to the steam drum where the steam is separated out of the
water and steam mixture. Circulation is maintained by water returning to the mud drum through the cooler tubes.
The hotter tubes (the risers) are the ones in the radiant area of the furnace and the hottest areas of the
generating bank of tubes.
True
What is the main advantage of the packaged boiler?
Low cost
Generally, two types of draft fans are used. A(n) _____ ____ fan supplies air to the air preheater. The preheated
air for combustion goes to the coal pulverizers and to the burners. A(n) ______ ____ fan exhausts the combustion
gases from the air heater to the stack.
Forced draft, induced draft
One square metre of heating surface equals 10 kilowatts. The heating surface of a boiler must be determined by
computing the area of the surface involved in square metres. Where a computation is to be made of a curved
surface, the surface with the greater radius is taken.
True
When the boiler provides the entire steam supply to an electric generating unit, the output of the boiler is
expressed in terms of power output of the generator (e.g. a 300 megawatt boiler).
True
What is the range for packaged watertube boiler capacities?
2300 kg to 65 000 kg per hour
What is the output of field-erected boilers?
150 000 kg/h or more
The A-, D-, and O- type boilers have furnaces cooled by _________ lining the furnace walls.
Watertubes
Where electric power is used as the heating source, the boiler rating is the maximum kilowatt rating of which
aspect?
Heating element
The difference in density between water and saturated steam becomes progressively less with increased
pressure and disappears altogether at the critical pressure of _______ .
22 090 kPa
The main feature of a controlled circulation boiler is a (circulating) pump, which is used to provide circulation.
True
The advantage of forced circulation in a boiler is a _________ flow in all tubes.
Positive
The steam separating equipment separates the _______ from the steam/water mixture.
,3B1 ABSA FINAL EXAM TEST 2026\2027.
Steam
Not all once-through boilers use forced circulation.
False
The arrangement of a once-through boiler has no drums. How many passes through the unit does it take to heat,
evaporate, and superheat the feedwater?
One passage
Steam generators operating above critical pressure are said to be ______-critical, and steam generators
operating below critical pressure are classed as ____-critical.
Super, sub
A steam generating unit consists of a number of elements, all of which contribute to the production of steam.
Which of the following is not an element of a typical steam generator?
Water conditioner
Natural circulation in a boiler depends on the ___________ in the density of a column of water and the density of a
column that contains a steam/water mixture.
Difference
Feedwater entering the boiler section first passes through the __________ section where it is heated by the
combustion gases leaving the boiler.
Economizer
The disadvantages of forced circulation in a boiler are the __________ of equipment such as pumps and piping
Increased costs
There are several factors that influence the natural circulation in a watertube boiler. Which of the following is NOT
one of those factors?
The diameter of the steam drum.
The downcomers are located in the ______ regions of the boiler, or external to the furnace altogether. The risers
are located in the ________ zones of the boiler, and are exposed to radiant heat of the furnace or to the very hot
flue gases near the furnace.
Cooler, hottest
The control methods used for reheater temperature are the same as those used for __________ temperature
control.
Superheater
Reheaters are located in the furnace in areas of relatively _____ gas temperatures.
High
When the boiler is shut down, the air preheater should be inspected for signs of _______.
Corrosion
When starting up a boiler, a steam flow is needed through the __________ tubes for cooling
Superheater
The boiler tubes of the ______ wall are placed side by side and touching each other to form a continuous water-
cooled envelope around the furnace.
Tangent tube
The water and water/steam mixture in the steam generation tubes is at _________ temperature.
Saturation
, 3B1 ABSA FINAL EXAM TEST 2026\2027.
The temperatures of the flue gas leaving the preheater must be kept above the _______ to avoid condensation.
Dewpoint
The _________ increases the temperature of the steam from the HP turbine back up to superheat temperature.
Reheater
In order to direct the flow of combustion gas over the tubes in a watertube boiler, it is necessary to use _______.
Baffles
B1C04Q02 The __________ economizer, which is the more common type, features rows of horizontal tubes,
located outside the furnace proper.
Separate
Furnace baffles can be placed so as to cause the gases to flow at right angles to the tube length, in which case
they are called ________ baffles.
Cross
Furnace baffles may be placed so as to cause the gases to flow parallel to the tubes, in which case they are called
_________ baffles.
Longitudinal
The separately fired superheater is located in a _______ apart from the main steam generator and is independent
of the steam generator operating conditions.
Furnace
B1C04Q01 In some cases, __________ or desuperheaters are located between superheater stages, which allows
steam temperatures to be maintained relatively constant over a wide load range.
Attemperators
Metal fin bars are welded to adjacent tubes, forming a continuous surface and a pressure-tight wall. This is
referred to as a welded fin tube wall or a ________ wall.
Membrane
B1C04Q03 In regards to air heater corrosion, sulfur dioxide in the presence of water vapour forms __________.
Sulfurous acid
The water ________at the economizer exit is always below that of the steam drum to prevent steaming in the
economizer.
Temperature
Wet tubes on start-up of the boiler are a _______ occurrence, caused by condensation on the tube walls.
Normal
There is no steam flow through the ______ tubes before the steam turbine has a steam flow through it. Be careful
not to increase boiler firing too rapidly and overheat the reheat tubes during start-up.
Reheater
Furnace baffles are usually constructed of ___________ material and may be made up of individual bricks or tiles.
Refractory
The reheater receives steam that has already expanded through a portion of the turbine, and as a result of this
expansion, has dropped in pressure and in _________.
Temperature
In the reheater, the steam has its temperature raised to about the same temperature as was initially provided by
the _________.
