Gas Piping Systems Flashcards
6 cards from real 306A practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Gas Piping Systems flashcards as text
What is a 'gas train' on a commercial gas appliance?
Answer: The assembly of safety devices (valves, regulators, and controls) on the gas supply line immediately before the burner
A gas train is the complete assembly of gas safety and control devices mounted in sequence on the gas supply line upstream of the burner. It typically includes a manual shut-off valve, drip leg, pressure regulator, safety shut-off valve(s), and a pilot ignition system.
What is the purpose of a 'proof of closure' switch on a gas safety valve?
Answer: To verify that the safety shut-off valve has fully closed before allowing the ignition sequence to begin
A proof of closure switch confirms that the gas safety shut-off valve is fully closed before the controller allows a new ignition cycle to begin. This prevents unburned gas from accumulating if the valve failed to close completely during the previous shutdown.
What is the hazard of operating a gas appliance with a cracked heat exchanger?
Answer: Products of combustion, including carbon monoxide, can enter the living space through the crack
A cracked heat exchanger allows combustion gases, including deadly carbon monoxide, to mix with the heated air being distributed through the home. This is an immediate life-safety hazard requiring the appliance to be shut down.
What is the minimum distance a gas meter must be from any source of ignition or electrical panel?
Answer: 3 m (10 feet)
Gas meters must be installed at least 3 m (10 feet) from any source of ignition, electrical service entrance, or electrical panel. This clearance helps prevent ignition of gas if a small leak develops at the meter or connections.
What type of gas valve is used as the main manual shut-off for a building's gas supply?
Answer: Ball valve or plug valve with a quarter-turn operation
A ball valve or plug valve with a quarter-turn handle is used for main gas shut-offs because it provides a clear visual indication of open (handle parallel to pipe) or closed (handle perpendicular) and can be operated quickly in an emergency.
What does 'gas-tight' mean in the context of gas piping installation?
Answer: All joints and connections are sealed to prevent any gas leakage, as verified by a pressure test
Gas-tight means that all pipe joints, connections, and valves are completely sealed against gas leakage. This is verified by pressure testing the system at the required test pressure for the specified duration with zero pressure drop.