Which requirement is set forth regarding manual gas shutoff valves for regulators in series?

The requirement for manual gas shutoff valves for regulators in series specifies that a manual valve is needed at only the first regulator. This is primarily a safety measure that allows for the quick and efficient shutdown of gas flow before it reaches any subsequent regulators in the series. By having a valve at the first regulator, system operators can easily isolate the entire series of regulators from the gas supply for maintenance or emergency situations without the need to address each individual regulator.

This requirement is essential in maintaining safety and operational efficiency within gas systems. It ensures that in case of a leak or malfunction at any point in the series, intervention can occur swiftly at the source. Implementing a manual shutoff at both regulators is unnecessary because it could complicate maintenance and operational procedures while potentially introducing more points of failure.

Additionally, no manual valve requirement at any regulator would compromise safety standards, as it would not allow for proper isolation of the system. Optionally requiring a manual valve at both regulators adds unnecessary complexity without enhancing safety protocols. Hence, the stipulation for a manual valve at only the first regulator effectively balances safety, accessibility, and system integrity.