J1 Assignments Flashcards
List the eight components of a gas valve-train (manifold) assembly.
- automatic ______ shut off valve
- B cock (____)
- pilot _____
- thermo_____
- A cock (___ burner)
- appliance _______
- automatic gas _____
- ____ gas burner(s)
- automatic safety shut off valve
- B cock (pilot)
- pilot burner
- thermocouple
- A cock (main burner)
- appliance regulator
- automatic gas valve
- main gas burners
Name two common types of manual gas shut-off valves that are used to control gas flow.
- lubricated
2. spring loaded
What do both of these valves have in common? ( spring loaded and lubricated shut off valves)
both open and close with a quarter of a turn
Draw an automatic gas safety shut-off valve in the closed position. Label and identify its parts.
Figure 5A from Student Guide.
Describe the operation of an automatic gas safety shut-off valve.
Its function is to provide gas shut down if pilot is extinguished. Most frequently used is electromagnet
Describe the operation of a solenoid gas valve.
When the electromagnet is energized, the valve stem (armature), with the valve disk attached is drawn off its seat, allowing gas to flow.
Describe the operation of a diaphragm gas valve.
- On a call for heat the electromagnet is energized.
- The electromagnet then pulls the armature into a position which blocks off the pressure port, allowing gas pressure above the diaphragm to bleed off through the vent port to a standing pilot flame
- The gas pressure below the diaphragm lifts the diaphragm and valve disk from the valve seat. This action allows gas to flow through the valve.
Describe the operation of a servo gas valve.
- On a call for heat, the bleed-valve operator is energized and opens.
- Gas under the main diaphragm now moves through the bleed valve and on through the servo regulator to the outlet of the main valve.
- The gas pressure on the top of the diaphragm now overcomes the effects of the spring and the gas pressure under the diaphragm and the main valve starts to open. (Note that the gas can be bled out faster through the servo regulator opening than it can enter through the small restrictor orifice).
Servo-operated and redundant gas valves are both types of _________ gas valves
combination
In a servo-operated valve, the force that opens the main valve is caused by:
a) a solenoid
b) gas pressure from a regulator
c) the inlet gas pressure of the valve
d) a spring
all of the above
In a redundant gas valve, the force that opens the main valve is caused by:
a) a solenoid
b) gas pressure from a regulator
c) the inlet gas pressure of the valve
d) a spring
c) the inlet gas pressure of the valve
If the main valve in a redundant gas valve failed open with debris when the call for heat is satisfied, the main flame would:
a) go out
b) keep burning until the flame safeguard lost the pilot flame
c) keep burning indefinitely
a) go out
A redundant gas valve could be used with a/an:
a) continuous pilot
b) intermittent pilot
c) interrupted pilot
d) continuous, intermittent or interrupted pilot
?
T or F
Rod-and-tube type gas control valves are primarily used on service water heaters.
true
T or F
The invar rod expands more than the copper tube.
false
