Chapter 9 Boiler Combustion Controls

Question 1

1.With the photoelectric flame scanner upon loss of flame it should take no longer than _____ seconds for the gas valve to close.

A.20 
B. 2 
C. 1 
D. 4 
E. 10

Answer 1

D. 4 Seconds

Question 2

2. The most commonly used flame detection devices are:
3. Ultraviolet detectors
4. Thermocouples
5. Flame rods
6. Infrared detectors
7. Photoelectric cells

A. 1, 2, 3 
B. 2, 3, 4 
C. 3, 4, 5 
D. 1, 2, 4 
E. 2, 3, 5

Answer 2

E. 2, 3, 5

thermocouples,flame rods,photoelectric

Question 3

3.The infrared scanner is mounted on the end of a sighting tube in such a way that its temperature will not exceed:

A. 100°C (212°F) 
B. 75°C (167°F) 
C. 150°C (302°F) 
D. 120°C (248°F) 
E. 50°C (98°F)

Answer 3

E. 50°C (98°F)

Question 4

4.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. Amperage 
B. Voltage 
C. Wattage 
D. Resistance 
E. Conductance

Answer 4

B. Voltage

Question 5

5. A thermocouple consists of "two dissimilar wires welded together" at one end to form a: 
A. Hot junction 
B. Cold junction
C. Electric circuit
D. Reference junction 
E. Metering junction

Answer 5

A. Hot junction

Question 6

6. A photoelectric cell reacts to the _____ emitted by the flame.
7. Ultraviolet rays
8. Thermocouples
9. Flame rods
10. Infrared rays

A. 1, 2 
B. 2, 3 
C. 1, 4 
D. 2, 4 
E. 1, 3

Answer 6

C. 1, 4

Note: Ultraviolet and Infrared Reys

Question 7

7.If the “pilot flame fails”, no power is generated by the thermocouple preventing the _____ from supplying fuel to the burner on boiler startup.

A. Pilot fuel control valve 
B. Air supply valve 
C. Operating control 
D. Main fuel control valve 
E. Main relay valve

Answer 7

D. Main fuel control valve

Question 8

8. Each “automatically fired hot water boiler” shall have a high limit temperature control that will shut off the fuel supply to the boiler to prevent the water from exceeding the maximum “allowable temperature” of:

A. 200°C (392°F) 
B. 75°C (167°F) 
C. 120°C (248°F) 
D. 100°C (212°F) 
E. 150°C (302°F)

Answer 8

C. 120°C (248°F)

Question 9

9. The infrared scanner contains a \_\_\_\_\_ cell which reacts to infrared rays. 
A. Lead sulphate 
B. Sodium sulphide 
C. Lithium bromide 
D. Lead sulphide 
E. Sodium chloride

Answer 9

D. Lead “sulphide”

Question 10

10.This scanner is “mounted as close to the flame” as physically possible without subjecting it to an “temperature over”:

A. 100°C (212°F) 
B. 75°C (167°F) 
C. 150°C (302°F) 
D. 120°C (248°F) 
E. 50°C (98°F)

Answer 10

A. 100°C (212°F)

Question 11

11. The rectifying photocell, shown in Fig. 10, is also known as a \_\_\_\_\_ cell. A. IR 
B. Cad
C. Rectifying 
D. Photoelectric 
E. UV

Answer 11

B. Cad

Question 12

12.In an oil fired boiler the fuel enters the furnace in a _____ state mixes with combustion air and is ignited.

A. Gaseous
B. Vapourized
C. Liquid D. Solid
E. Mixed

Answer 12

B. Vapourized

Question 13

13. The voltage supply generated by the thermocouple is usually not more than:

A. 50 millivolts 
B. 15 millivolts 
C. 0 millivolts 
D. 100 millivolts 
E. 30 millivolts

Answer 13

E. 30 millivolts

Question 14

14.”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. Water tube explosion 
D. Serious explosion 
E. Spike in steam production

Answer 14

D. Serious explosion