Which type of valve is required at the point of connection when a gas system has supplementary standby gas downstream of the meter?

When a gas system has supplementary standby gas downstream of the meter, a three-way valve is required at the point of connection. This type of valve is essential because it allows for the control and distribution of gas from multiple sources. The three-way valve can direct the flow of gas from either the primary supply or the standby supply, ensuring that one system can seamlessly take over if the other fails. This redundancy is crucial for maintaining a consistent and reliable gas supply, particularly in applications where downtimes must be minimized.

The design of the three-way valve provides the necessary functionality to switch between the two gas supplies efficiently, making it essential in systems where continuous operation is critical. Other valve types, such as two-way valves, do not provide this functionality since they can only control flow in one direction or between two points, thus lacking the redundancy needed for systems requiring standby capabilities. Therefore, the three-way valve is specifically chosen to manage the flow and ensure that the supplementary gas can be utilized effectively.