valve train components Flashcards
In order, what are the components found in a gas valve train?
automatic safety shut off, b-cock, a-cock , appliance reg, automatic gas valve, thermocouple, pilot burner, main burner
Where should an appliance shut off valve be located?
before the appliance and the dirt pcoket
what are the differences between a plug valve and a ball valve?
ball valve is a stainless steel ball, plug is a tapered drilled plug. plug valves can be lubricated while in service, ball valves can not.
what is a automatic safety shut off valve, and what is its function?
controlled by a solenoid and powered by a thermocouple. confirms that there is a pilot flame present
what is the relationship between a pilot flame and a thermocouple?
a pilot flame is used to light the main burner, a thermocouple is placed beside the pilot flame to ensure that the pilot flame exists and open the gas valve for firing.
if the pilot flame is extinguished, the solenoid is de-energized and the gas valve closes to stop the flow of gas. what is this called?
100% safe
what is considered 80% safe or a wild pilot?
only the main burned is isolated if the pilot is extinguished, still allowing gas to go to the pilot.
this valve is used to isolate and regulate flow to the pilot burner. what is it?
B-cock (pilot valve)
what does the A-cock isolate
isolates gas to downstream appliances while still allowing gas to the pilot
what are different types of direct operating controls in appliances?
thermostats, aqua stats, pressuretrols
what does ffrt stand for?
flame failure response time
gases that are lighter than air have a ffrt of what?
90 seconds
gases that are heavier than air have a ffrt of what?
20 seconds
appliaces over 400 btuh have a ffrt of what?
4 seconds
