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WorksheetsHigh Pressure Boilers Chapter 9
Total questions: 25
Worksheet time: 13mins
The primary function of a combustion control system is to regulate the ___ in a boiler.
fuel supply
air supply
draft
all of the above
ON/OFF control is used to start and stop a burner ___.
and modulate the flame to match steam load
without modulating the flame to match steam load
based on measured fuel flow
based on measured draft
A siphon is used to protect an operating pressure control from ___.
live steam
water
air
gas
An operating pressure control must be connected to the ___.
main steam line
main feedwater line
highest part of the steam side of the boiler
water side of the boiler below the NOWL
The two settings found on the boiler operating pressure control are used to ___.
set the operating steam pressure range of the boiler
eliminate low water
maintain high and low fire
warn the operator of flame failure
The combustion blower continues to run after fuel is shut off to the burner during ___.
postpurging
prepurging
synchronization
ignition
The programmer in an ON/OFF control system is used to ___.
control the burner firing cycle
control the boiler operating range
secure the burner in the event of low water
regulate the steam flow
To eliminate the danger of a furnace explosion during startup, the programmer must allow ___.
main flame ignition
proving of the main flame
a prepurge period
a varying steam load
The purpose of the flame sensor in a flame scanner is to prove ___.
only the pilot
only the main flame
both the pilot and the main flame
the proper boiler water level
The flame sensor is sensitive to ___.
heat
temperature
pressure
infrared, visible, or ultraviolet light
In the event of flame failure, the programmer ___.
automatically goes through a new firing cycle
shuts the burner down
vents the fire tubes
starts the induced draft fans
A modulating control system is sensitive to changes in the ___.
boiler water level
firing rate
steam flow
steam pressure
A(n) ___ is a controller that distributes steam production requirements across several boilers to maintain the steam pressure at the setpoint.
plant master
operating pressure control
ON/OFF control
programmer
A preignition check includes ___.
verifying that the fuel pressure proving switch is closed
lighting the pilot
proving the pilot
proving the main flame
After a programmer proves the main flame, it ___.
verifies fuel pressure
verifies airflow through the furnace
releases to automatic control
postpurges the furnace
If steam is being used faster than it is being generated, the ___.
steam pressure increases
steam pressure decreases
combustion control closes the fuel valve
combustion control closes the inlet damper
A high-limit pressure control ___.
has a modulating controller
uses a high/low/OFF controller
uses differential pressure settings
has a manual reset
The flow of fuel through valves and air through dampers is usually ___.
nonlinear
linear
non adjustable
set at maximum
Single-point positioning uses the ___ as the controller input and has only one output.
fuel flow
airflow
steam pressure
steam temperature
A low firing rate needs ___ than a high firing rate.
more excess air
less excess air
more single-point positioning
less single-point positioning
Parallel positioning uses steam pressure as the controller input and ___.
has ON/OFF fuel flow
bypasses the postpurge
uses one output signal
uses two output signals
A modulating control system adjusts the firing rate proportional to the ___.
steam load
amount of excess air available
flue gas analysis
water level
Nonlinear flow means that the percent a valve or damper is open does not necessarily correspond to ___.
percent of flow
controller output
steam pressure
water level
___ control increases safety by adding a linking system that prevents the airflow from going too low for the amount of fuel flow during load changes.
Cross-limited
Modulating
Single-point positioning
ON/OFF with modulating
___ is used to adjust the air-fuel ratio based on the results of a flue gas analysis.
Metering control
Burner management
Purging
Oxygen trim
