A single element feedwater system compensates for variations in:
a. Level and pressure
b. Shrinkage and swell
c. Level only
d. Pressure only
e. flow only
With On – Off boiler feed water control, water is supplied _____________ to the boiler, either by fully opening or fully closing a valve in the feedwater line.
In ______ control, a change in drum level causes a proportional change in output from the transmitter to reposition the feedwater control valve to correct the drum level setpoint.
A rapid increase in boiler load causes an immediate increase in steam flow from the boiler, which creates a sudden _____ in the boiler steam drum pressure.
A sudden increase in load, a decrease in drum pressure, and an immediate increase in heat release, is called ______.
The two-element feedwater control system, is similar to the single element type, only with a ______ flow transmitter added.
A two-element control system may be called a _________ system as it anticipates what will happen to the drum level with a change in load and acts accordingly to avoid large level fluctuations.
a. reverse feed
Shrinkage may be the result of:
1. A reduction in boiler output
2. An increase in firing rate
3. A decrease in firing rate
4. An increase in steam drum pressure
a. 1, 3, 4
b. 1, 2, 3
c. 2, 3, 4
d. 1, 2, 4
Three-element feedwater control compensates for:
1. Level variation
2. Steam flow variation
3. Feedwater flow variation
4. Shrinkage and swell
a. 2, 3, 4
b. 1, 3, 4
c. 1, 2, 4
d. 1, 2, 3, 4
e. 1, 2, 3
The three-element feedwater control system overcomes the effects of swell and shrinkage and also responds to _________ flow.
An oxygen analyzer can also be provided to indicate the excess oxygen in the flue gas, assisting the operator to control the excess air and increasing boiler _______.
A pressure modulating control (pressuretrol):
a. Maintains a constant firing rate
b. Will vary fuel and air supply according to steam pressure
c. Cannot be adjusted
d. Can vary fuel and air supply separately
e. Starts and stops the burner at predetermined settings
Will vary fuel and air supply according to steam pressure
Direct combustion control measures and responds to:
a. Air flow and steam pressure
b. Air flow and fuel flow
c. Steam pressure only
d. Steam pressure and fuel flow
e. Steam pressure and steam flow
Steam pressure only
By measuring and comparing the steam and the ________, it is possible to obtain efficient combustion in a boiler by maintaining a proper steam to airflow ratio.
d. drum level
The furnace pressure controller will adjust the boiler ______ dampers to keep the pressure constant at all boiler loads.
e. Induced draft
In a fuel flow – airflow combustion control system, the fuel flow signal makes the final adjustment to the ________.
d. drum level
When increasing the firing rate manually it is best to:
a. Increase air flow before fuel flow
b. Increase fuel flow before air flow
c. Increase air and fuel together
d. It really doesn't matter
e. Decrease fuel flow before increasing air flow
Increase air flow before fuel flow
Before making adjustments or altering the fuel-air ratio of a combustion control system, we would:
a. Measure fuel flow
b. Analyze flue gas
c. Increase air flow
d. Decrease firing rate
e. Measure steam flow
Analyze flue gas
When master controller output goes directly to a fuel valve and a modulating relay we have:
a. Multi-element control
b. Air flow-fuel flow control
c. Fuel flow-air flow control
d. Steam flow-air flow control
e. Positioning Control
Fuel flow-air flow control
n a airflow-fuel flow combustion control, airflow signal becomes the set point of the ____ controller.
d. drum level
The attemperator is used to control the temperature of feedwater from the economizer
To maintain turbine __________ and avoid fluctuations in the turbine metal temperatures, it is necessary to hold the superheated steam temperature and the reheated steam temperature, at a constant value.
There are two types of attemperators used:
a. surface type
b. spray type
c. direct contact type
d. cross flow type
e. A, D
f. A, C
The direct contact attemperator, which is also referred to as the ______ type desuperheater, introduces feedwater into the superheated steam, through a spray nozzle.
The ______ ,used in the spray desuperheater, must be of the highest quality since any solids carried over will cause deposits in superheater tubes and on turbine blades.
The Gas Recirculation method is used to maintain the desired steam temperature at ________ loads.
Gas bypass method involves the separation of the convection section of the boiler into two, or more, _________ gas passes.
At high loads when the steam temperature tends to go above the desired value, the tilting burners are tilted ___________.
At low loads when the steam temperature drops, the tilting burners are tilted _________.
a. Function during operation
b. Function during start up and shut down
c. Function during start up
d. Function during shut down
e. Function during emergency situations
Function during start up and shut down
On a semi-automatic boiler the programming controls are activated by:
b. The operator
d. Water level
e. Temperature and pressure
Purging a furnace means:
a. Ensuring the furnace is pressurized with air
b. Ensuring air is flowing through the furnace
c. Ensuring fuel is entering the furnace
d. Causing air to flow for no more than five seconds
e. Ensuring the air flow to the furnace has stopped
Ensuring air is flowing through the furnace
Pilot gas valve and ignition transformer should be energized:
a. Before pre purge
b. During post purge
c. After pre purge
d. On program start
e. after the pilot burner is lit
After pre purge
Limit switches of a programmed circuit tend to be:
a. In parallel
b. Normally closed
c. In series
d. Activated by the programmer
e. supervise the pilot flame
When we manually close the start switch we:
a. Close the fan circuit
b. Energize the programmer
c. Close the timer circuit
d. Initiate the purge dampers
e. energize the spark igniter
Close the timer circuit
At the end of the pre-purge the timer:
a. Opens the fuel valve
b. Opens the pilot valve
c. Goes through an ignition trial
d. Energizes the ignition transformer
e. shuts off the igniter and the pilot
Energizes the ignition transformer
When steam pressure reaches cut-out value:
a. The timer stops
b. The master relay becomes energized
c. The coil of the burner valve is de-energized
d. The timer causes the fuel valve to close
e. the flame scanner becomes de-energized