NIULPE STUDY EXAM QUESTIONS WITH
CORRECT ANSWERS
Low-Pressure Steam Boiler | |
A boiler that operates at a maximum allowable working pressure
| | | | | | | | | |
(MAWP) of not more than 15 psi. Primarily used for heating buildings
| | | | | | | | | | | |
such as schools, apartments, warehouses, and factories, and for heating
| | | | | | | | |
domestic water.
| |
High-Pressure Steam Boiler | |
A boiler that operates at a maximum allowable working pressure
| | | | | | | | | |
(MAWP) of more than 15 psi. Also known as power boilers. Used in
| | | | | | | | | | | | |
generating electricity and in industrial and commercial locations
| | | | | | |
Firetube Steam Boiler
| |
A boiler in which hot gases of combustion pass through tubes that are
| | | | | | | | | | | | |
surrounded by water. May be either high pressure or low pressure.
| | | | | | | | | | |
Firetube boilers are used where moderate pressures are needed and
| | | | | | | | | |
large quantities of steam are not required. Common types include:
| | | | | | | | | |
,Horizontal return tubular boiler, scotch marine boiler, and vertical
| | | | | | | | |
firetube boiler. |
Advantages of FIretube Boilers | | |
Design for pressure up to a maximum of 350 psi and approximately
| | | | | | | | | | | |
2000 BHP. Advantages: Can be factory assembled, initial cost is less than
| | | | | | | | | | |
a watertube boiler, requires little or no setting, contains larger volume
| | | | | | | | | | | |
of water for a given size compared to a watertube boiler, requires less
| | | | | | | | | | | | |
headroom.
Steam Pressure and Temperature Relationship
| | | |
20-259, 30-274, 40-287, 50-298, 60-307, 70-316, 80-324, 90-331, 100-
| | | | | | | |
338, 150-366, 200-388, 250-406, 300-422 (PSI-DEGREES)
| | | | |
Heating Surface |
A part of a boiler with water on one side and heat and gases of
| | | | | | | | | | | | | | |
combustion on the other. By increasing the heating surface, more heat
| | | | | | | | | | |
is transferred from the gases of combustion.
| | | | | |
, Thermal Efficiency |
When larger quantities of steam are generated, the thermal efficiency
| | | | | | | | | |
of a boiler increases. Thermal efficiency is the ratio of the heat absorbed
| | | | | | | | | | | |
by a boiler (output) to the heat available in the fuel (input) including
| | | | | | | | | | | | | |
radiation and convection losses. Modern firetube boilers with improved
| | | | | | | | |
design and teat transfer rates have achieved thermal efficiency rates as
| | | | | | | | | | |
high as 90% to 95% | | | |
Furnaces
A furnace is a location where the combustion process takes place. A
| | | | | | | | | | | |
furnace is also known as a firebox or combustion chamber. Placing an
| | | | | | | | | | | |
internal furnace within the boiler shell greatly increases the heating
| | | | | | | | | |
surface. This also increases heat absorption through radiant heat
| | | | | | | | |
transfer.
Dry-Back Boiler |
A firetube boiler with a refractory-lined rear door that directs the gases
| | | | | | | | | | | |
of combustion from the furnace to the first pass of tubes or from one
| | | | | | | | | | | | | |
section of tubes to another. | | | |
Wet-Back Boiler |
CORRECT ANSWERS
Low-Pressure Steam Boiler | |
A boiler that operates at a maximum allowable working pressure
| | | | | | | | | |
(MAWP) of not more than 15 psi. Primarily used for heating buildings
| | | | | | | | | | | |
such as schools, apartments, warehouses, and factories, and for heating
| | | | | | | | |
domestic water.
| |
High-Pressure Steam Boiler | |
A boiler that operates at a maximum allowable working pressure
| | | | | | | | | |
(MAWP) of more than 15 psi. Also known as power boilers. Used in
| | | | | | | | | | | | |
generating electricity and in industrial and commercial locations
| | | | | | |
Firetube Steam Boiler
| |
A boiler in which hot gases of combustion pass through tubes that are
| | | | | | | | | | | | |
surrounded by water. May be either high pressure or low pressure.
| | | | | | | | | | |
Firetube boilers are used where moderate pressures are needed and
| | | | | | | | | |
large quantities of steam are not required. Common types include:
| | | | | | | | | |
,Horizontal return tubular boiler, scotch marine boiler, and vertical
| | | | | | | | |
firetube boiler. |
Advantages of FIretube Boilers | | |
Design for pressure up to a maximum of 350 psi and approximately
| | | | | | | | | | | |
2000 BHP. Advantages: Can be factory assembled, initial cost is less than
| | | | | | | | | | |
a watertube boiler, requires little or no setting, contains larger volume
| | | | | | | | | | | |
of water for a given size compared to a watertube boiler, requires less
| | | | | | | | | | | | |
headroom.
Steam Pressure and Temperature Relationship
| | | |
20-259, 30-274, 40-287, 50-298, 60-307, 70-316, 80-324, 90-331, 100-
| | | | | | | |
338, 150-366, 200-388, 250-406, 300-422 (PSI-DEGREES)
| | | | |
Heating Surface |
A part of a boiler with water on one side and heat and gases of
| | | | | | | | | | | | | | |
combustion on the other. By increasing the heating surface, more heat
| | | | | | | | | | |
is transferred from the gases of combustion.
| | | | | |
, Thermal Efficiency |
When larger quantities of steam are generated, the thermal efficiency
| | | | | | | | | |
of a boiler increases. Thermal efficiency is the ratio of the heat absorbed
| | | | | | | | | | | |
by a boiler (output) to the heat available in the fuel (input) including
| | | | | | | | | | | | | |
radiation and convection losses. Modern firetube boilers with improved
| | | | | | | | |
design and teat transfer rates have achieved thermal efficiency rates as
| | | | | | | | | | |
high as 90% to 95% | | | |
Furnaces
A furnace is a location where the combustion process takes place. A
| | | | | | | | | | | |
furnace is also known as a firebox or combustion chamber. Placing an
| | | | | | | | | | | |
internal furnace within the boiler shell greatly increases the heating
| | | | | | | | | |
surface. This also increases heat absorption through radiant heat
| | | | | | | | |
transfer.
Dry-Back Boiler |
A firetube boiler with a refractory-lined rear door that directs the gases
| | | | | | | | | | | |
of combustion from the furnace to the first pass of tubes or from one
| | | | | | | | | | | | | |
section of tubes to another. | | | |
Wet-Back Boiler |
