SAFE BOILER OPERATION
FUNDAMENTALS—SPECIAL
ENGINEER'S GUIDE FOR THE STATE
OF MINNESOTA QUESTIONS AND
ANSWERS
first law of thermodynamics - ans-Energy cannot be created or destroyed
second law of thermodynamics - ans-Heat flows from a higher temperature material to a
lower temperature material
How does the boiling point of water change with steam pressure? - ans-The boiling
point of water increases as steam pressure increases
latent heat - ans-Heat that causes a state change but doesn't change the temperature
sensible heat - ans-Heat that causes a temperature change without a state change
Conduction - ans-The direct transfer of heat from one substance to another substance
that it is touching.
Convection - ans-The transfer of heat by the movement of a fluid
Radiation - ans-Energy that is radiated or transmitted in the form of rays or waves or
particles. Produced upon contact with opaque objects
What are examples of conduction, convection, and radiation in a boiler? - ans-Heat
radiates from combustion flames to the metal surfaces of the boiler, the metal surfaces
conduct heat from the hot side to the cooler side where metal is covered by water or
steam. Heat moves within the steam/hot water via convection.
Firetube boiler - ans-A boiler with tubes of combustion gases passing through the water
space.
, Watertube boiler - ans-A boiler in which water passes through tubes surrounded by
gases of combustion. It provides greater horsepower, steam volume, and pressures.
Low pressure steam heating boiler - ans-Steam is supplied at pressures up to 15 psi
Low Pressure Hot Water Heating Boiler - ans-Supplies hot water at pressure up to 160
psi and a T less than 250°F
Hot Water Supply Boiler - ans-For space heating at pressures of not more than 160 psi
and T under 210°F
Power Hot Water Boiler - ans-Heats liquid to a p greater than 160 psi or a T greater
than 250°F
Power Steam Boiler - ans-Steam is generated at p > 15psi
Low Pressure Steam Boiler - ans-MAWP < 15 psi
High pressure steam boiler - ans-MAWP > 15 psi
Boiler Horsepower (BHP) definition - ans-Heat required to evaporate 34.5 lb/hr water
from and at a T of 212°F
BHP in Btu/hr - ans-33,472 Btu/hr
How does water circulation in a firetube boiler work? - ans-Water is heated by the
firetubes, which decreases its density, causing it to rise and circulating cooler, more
dense water down to be heated
Dryback boiler - ans-Type of firetube boiler. Has a dry turnaround chamber, easier
inspection and maintenance
Wetback boiler - ans-Type of firetube boiler. Water enclosed back end that redirects
gases, more efficient and require less maintenance
HRT - ans-Horizontal Return Tubular
HRT Boiler - ans-A firetube boiler with the tubes running horizontally, suspended over a
furnace
Industrial watertube boiler - ans-Consists of a steam drum and a mud drum
Commercial watertube boiler - ans-Produces steam/hot water for commercial/med size
applications, there are straight tube, bent tube, and membrane watertube types
FUNDAMENTALS—SPECIAL
ENGINEER'S GUIDE FOR THE STATE
OF MINNESOTA QUESTIONS AND
ANSWERS
first law of thermodynamics - ans-Energy cannot be created or destroyed
second law of thermodynamics - ans-Heat flows from a higher temperature material to a
lower temperature material
How does the boiling point of water change with steam pressure? - ans-The boiling
point of water increases as steam pressure increases
latent heat - ans-Heat that causes a state change but doesn't change the temperature
sensible heat - ans-Heat that causes a temperature change without a state change
Conduction - ans-The direct transfer of heat from one substance to another substance
that it is touching.
Convection - ans-The transfer of heat by the movement of a fluid
Radiation - ans-Energy that is radiated or transmitted in the form of rays or waves or
particles. Produced upon contact with opaque objects
What are examples of conduction, convection, and radiation in a boiler? - ans-Heat
radiates from combustion flames to the metal surfaces of the boiler, the metal surfaces
conduct heat from the hot side to the cooler side where metal is covered by water or
steam. Heat moves within the steam/hot water via convection.
Firetube boiler - ans-A boiler with tubes of combustion gases passing through the water
space.
, Watertube boiler - ans-A boiler in which water passes through tubes surrounded by
gases of combustion. It provides greater horsepower, steam volume, and pressures.
Low pressure steam heating boiler - ans-Steam is supplied at pressures up to 15 psi
Low Pressure Hot Water Heating Boiler - ans-Supplies hot water at pressure up to 160
psi and a T less than 250°F
Hot Water Supply Boiler - ans-For space heating at pressures of not more than 160 psi
and T under 210°F
Power Hot Water Boiler - ans-Heats liquid to a p greater than 160 psi or a T greater
than 250°F
Power Steam Boiler - ans-Steam is generated at p > 15psi
Low Pressure Steam Boiler - ans-MAWP < 15 psi
High pressure steam boiler - ans-MAWP > 15 psi
Boiler Horsepower (BHP) definition - ans-Heat required to evaporate 34.5 lb/hr water
from and at a T of 212°F
BHP in Btu/hr - ans-33,472 Btu/hr
How does water circulation in a firetube boiler work? - ans-Water is heated by the
firetubes, which decreases its density, causing it to rise and circulating cooler, more
dense water down to be heated
Dryback boiler - ans-Type of firetube boiler. Has a dry turnaround chamber, easier
inspection and maintenance
Wetback boiler - ans-Type of firetube boiler. Water enclosed back end that redirects
gases, more efficient and require less maintenance
HRT - ans-Horizontal Return Tubular
HRT Boiler - ans-A firetube boiler with the tubes running horizontally, suspended over a
furnace
Industrial watertube boiler - ans-Consists of a steam drum and a mud drum
Commercial watertube boiler - ans-Produces steam/hot water for commercial/med size
applications, there are straight tube, bent tube, and membrane watertube types
