Watertube Boilers Flashcards
In a longitudinal straight tube boiler the downcomer fed
a) “cool” water to the steam drum
b) “hot” water to a riser
c) “cool” water to a rear header
d) “cool” water to a front header
e) “hot” water to the water tubes
c) “cool” water to a rear header
A packaged watertube boiler having two mud drums is the
a) “O” type
b) “D” type
c) three drum bent-tube type
d) “A” type
e) Sterling type
d) “A” type
High pressure watertubes
a) are always smaller than firetubes
b) are elliptical in cross-section
c) are always straight
d) can be of various bent configurations
e) require pumps for circulation
d) can be of various bent configurations
Bent tube watertube boilers
a) cannot have the furnace water-lined
b) make more efficient use of the furnace
c) are externally fired
d) cannot be fitted with heat recovery components
e) have poor utilization of floor space
b) make more efficient use of the furnace
A cross drum straight tube boiler
a) could not have higher capacity than a longitudinal drum
unit
b) was usually only of single pass design
c) could have more inclined tubes than a longitudinal drum
unit
d) is a very popular design in today’s plants
e) was internally fired
c) could have more inclined tubes than a longitudinal drum
unit
Watertube boilers are better suited to higher pressures than firetube boilers, because they: 1. incorporate a bent tube design 2. are larger than firetube boilers 3. do not have flat surfaces subjected to pressure 4. usually have smaller diameter tubes 5. have smaller diameter drums a) 1, 2 b) 1, 3, 5 c) 2, 3, 5 d) 1, 2, 5 e) 1, 3, 4, 5
e) 1, 3, 4, 5
The use of bent tube boiler designs allows the furnace wall to be lined with tubes, thereby exposing more of the heating surface to a) convection heat b) conducted heat c) radiant heat d) residual heat e) latent heat
c) radiant heat
The bent tube boiler design allows the tubes to be attached radially on the outside of the a) furnace b) superheater c) economizer d) shell or drum e) air preheater
d) shell or drum
Since furnace pressure is often positive on a packaged
watertube boiler, in order to prevent flue gas leakage
a) an induced draft fan is incorporated
b) smoke stacks are made taller
c) an economizer is used
d) a steel casing forms a seal for the furnace
e) sootblowers cannot be used
d) a steel casing forms a seal for the furnace
Excessive vibrations caused by inadequate support of a watertube boiler can result in
a) insulation failure
b) water level control problems
c) tube failure
d) drum fracture
e) combustion control problems
a) insulation failure
A problem with a D-type watertube packaged boiler is
a) excessive vibration
b) ceiling height requirements
c) refractory maintenance for the external furnace
d) its need to be top supported
e) its poor water circulation
a) excessive vibration
A unit which would most likely utilize a cyclone furnace would be the a) Sterling watertube boiler b) steam generator c) packaged watertube boiler d) "D" type boiler e) three drum bent-tube boiler
b) steam generator
Large steam generating units may have their superheaters located: 1. beneath the furnace 2. in the convection zone 3. in the main waterwall header 4. in the radiant zone 5. in the downcomer pipe a) 2, 4 b) 4, 5 c) 1, 3 d) 1, 2, 5 e) 3, 4, 5
a) 2, 4
Large steam generators
a) are bottom supported
b) are fired by pulverized coal only
c) have sluggish water circulation
d) are usually of the water tube type
e) have beaded tubes
d) are usually of the water tube type
Large steam generating units are usually built so that high
pressure, high temperature, and dry steam can be generated in
order that
a) more fuel can be fired
b) large steam turbines can be used to drive electrical generators
c) higher furnace temperatures can be attained
d) less water treatment is necessary
e) stack temperatures can be maintained at a high level
to prevent condensation
b) large steam turbines can be used to drive electrical generators
A steam generator economizer is usually located
a) between the air preheater and ID fan
b) between the primary and secondary superheaters
c) after the reheater
d) in the furnace section
e) between the air preheater and primary superheater
e) between the air preheater and primary superheater
The most economical fuel to burn in a steam generator is
a) natural gas
b) crushed coal
c) heavy fuel oil
d) pulverized coal
e) crude oil
d) pulverized coal
Economizers
a) increase the boiler efficiency
b) are installed before the superheater
c) increase the steam temperature
d) increase the air temperature
e) increase the flue gas temperature
a) increase the boiler efficiency
Air heaters in a boiler
a) are installed between the superheater and the economizer.
b) reduce the temperature of the flue gases going to the stack.
c) help the boiler from freezing during the winter period.
d) increase the flue gas temperature.
e) maintain a steady higher temperature in the stack
b) reduce the temperature of the flue gases going to the stack.
Air heaters are implemented in steam generating units in order to: 1. recover heat from the hot flue gases 2. improve boiler thermal efficiency 3. produce dryer steam 4. heat the feedwater a) 1, 2 b) 2, 3 c) 1, 2, 4
a) 1, 2
Combustion air for the burners is preheated in the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ by hot flue gases. a) economizer b) air heater c) superheater d) windbox e) furnace
b) air heater
