Chapter 9 Flashcards
A flame rod flame scanner can be used to detect the presence of a pilot flame or a main burner flame
True False
true
A thermocouple flame detector:
a. Generates voltage
b. Reacts to the conductivity of the flame
c. Reacts to the light of the flame
d. All of the above
a
To test the flame failure device on a boiler, it is necessary to:
a. simulate a flame failure condition
b. fire the boiler to operating pressure prior to the test
c. maintain a minimum pressure of 75% of the safety valve setting during test
d. switch the boiler blower to continuous operation
a
Flame rods should be checked at regular intervals for:
a. build up of deposits
b. continuity at the hot junction
c. build-up on the scanner lens
d. deformation of the bimetallic strip
a
A photoelectric cell
a. Relies on flame ionization to detect the presence of flame
b. Is a flame scanner
c. Generates voltage when it is heated by the flame
d. Is commonly known as a “cad” cell
b
In an infrared scanner type flame detector, the presence of flame causes a/n ____________ within the cell
a. Temperature rise resulting in a linear expansion that closes the burner switch
b. Drop in electrical resistance resulting in a fluctuating voltage across the cell
c. Bimetallic strip to close the burner switch
d. Increase in electrical resistance resulting in the opening of the circuit in the cell
b
The thermocouple must ___________ in order to generate voltage
a. sense heat at the reference junction
b. sense current at the reference junction
c. sense UV light at the hot junction
d. sense heat at the hot junction
d
A properly installed flame rod flame scanner
a. is attached directly to the oil burner
b. extends into the flame
c. opens the safety circuit when a safe flame is sensed
d. generates voltage when it is heated
b
A flame rod flame detector forms an electrical circuit using:
a. The flame rod, the thermocouple, and the burner
b. The flame rod, the flame, and the burner
c. The spark igniters, the flame rod, and the flame
d. The flame rod, the spark igniters and the pilot valve
b
The flame rod:
a. Senses direct spark
b. is a flame rectification type sensor
c. Rectifies a lead sulphide cell
d. is a heat rectification type sensor
b
What is the maximum time allowed for a gas valve to close following a flame failure on a gas burner that is monitored by an electronic flame scanner
a) 10 seconds
b) 5 seconds
c) 2 seconds
d) 4 seconds
d
A cad cell reacts to:
a) visible light rays in a flame
b) UV light rays in a flame
c) heat in the flame
d) IR rays in a flame
a
The flame rod:
a) Senses direct spark
b) is a flame rectification type sensor
c) Rectifies a lead sulphide cell
d) is a heat rectification type sensor
b
A thermocouple flame detector:
a) Generates voltage
b) Reacts to the conductivity of the flame
c) Reacts to the light of the flame
d) All of the above
a
The ____________ is the first boiler component energized once the controller identifies that conditions are safe to start the boiler and the last de-energized on shutdown
a) flame detector relay
b) low water cut off
c) combustion air blower
d) air proving switch
c
A photoelectric cell
a) Relies on flame ionization to detect the presence of flame
b) is commonly known as a “cad” cell
c) Generates voltage when it is heated by the flame
d) Is a flame scanner
d
A flame rod flame detector forms an electrical circuit using:
a) the flame rod, the spark igniters and the pilot valve
b) The flame rod, the thermocouple, and the burner
c) The flame rod, the flame, and the burner
d) The spark igniters, the flame rod, and the flame
c
When the hot junction of a thermocouple is exposed to heat its temperature is higher than that of the cold junction and a small _____ is generated.
A.Voltage
B.Conductance
C.Resistance
D.Wattage
E.Amperage
a
In an oil fired boiler the fuel enters the furnace in a _____ state mixes with combustion air and is ignited.
A.Liquid
B.Solid
C.Vapourized
D.Mixed
E.Gaseous
c
The rectifying photocell, shown in Fig. 10, is also known as a _____ cell.
A.UV
B.IR
C.Photoelectric
D.Rectifying
E.Cad
e
The time taken for the automatic pilot valve to close in the event of a loss of flame detection is about _____ seconds
A.10
B.4
C.15
D.2
E.20
a
Unburned fuel collecting in the furnace can mix with the combustion air and may ignite, causing a
A.Boiler drum failure
B.Fire tube failure
C.Serious explosion
D. Water tube explosion
E.Spike in steam production
c
In a gas fired boiler the fuel enters the furnace in a _____ state mixes with combustion air and is ignited.
A.Solid
B.Gaseous
C.Mixed
D.Vapourized
E.Liquid
b
A flame rod uses the principle that a flame is capable of:
A.Holding the solenoid open
B.Holding the solenoid closed
C.Heating the rod
D.Supplying fuel to the burner
E.Conducting electricity
e
The most commonly used flame detection devices are:
1. Ultraviolet detectors
2. Thermocouples
3. Flame rods
4. Infrared detectors
5. Photoelectric cells
A.1, 2, 3
B.1, 2, 4
C.2, 3, 4
D.2, 3, 5
E.3, 4, 5
d
If for any reason, the burner should go out during normal operation, or the fuel should fail to ignite during startup:
A.The air to the burner must be shut off immediately
B.The fuel to the burner must be shut off immediately
C.Increase the combustion air flow
D.Increase the fuel flow
E.No action is required
b
The voltage supply generated by the thermocouple is usually not more than:
A.50 millivolts
B.0 millivolts
C.30 millivolts
D.15 millivolts
E.100 millivolts
c
What is the voltage level generated by a thermocouple
a.30 millivolts
b. 15 millivolts
c. 60 millivolts
d. 100 millivolts
a
what is the maximum allowable water temperature in a hot water boiler
a. 200 c
b. 75 c
c. 150 c
d, 120 c
d
what is the maximum time allowed for a gas valve to close following a flame failure on a gas burner with an elctronic flame scanner
a. 5 sec
b. 2 sec
c. 4 sec
d. 10 sec
c
the time taken for the automatic pilot valve to close in the event of a loss of flame detection is about
a. 5 sec
b. 10 sec
c. 15 sec
d. 22 sec
b
