NFPA 54 National Fuel Gas Code Practice Test

The correct type of valve that can be used to admit standby supply gas while simultaneously shutting off the regular supply is the 3-way valve. A 3-way valve has three ports: one for the incoming gas supply, one for the outgoing gas line, and a third that can be utilized for an alternative gas source. This design allows for the effective switching between the regular gas supply and a standby supply without needing to disconnect or manually operate multiple valves. In practical applications, the 3-way valve enables seamless transitions between gas sources, ensuring that if the regular supply fails or requires maintenance, the standby gas can be brought online quickly. This is particularly crucial in systems where continuous gas supply is essential for operation. The other types of valves do not offer this same level of functionality. A 2-way valve only has two ports and is typically used to either allow or block flow, but it cannot facilitate the simultaneous use of two separate gas supplies. A manual valve requires physical operation to close off or open a gas line, which doesn't afford the automatic switching capability that a 3-way valve provides. A pressure regulator, while an essential component in a gas supply system, is used to control and reduce pressure in the gas line, not to manage multiple gas supplies