What is the service pressure requirement for shutoff valves?

The requirement that the service pressure of shutoff valves must be greater than the rated service pressure of the entire system is crucial for ensuring safety and reliability in CNG delivery systems. This standard is in place to provide a margin of safety, helping to prevent valve failure due to pressure surges or unexpected pressure changes within the system. Having a shutoff valve rated for pressure higher than that of the system allows it to operate effectively without compromising the integrity of the system under various operating conditions.

It's important to note that pressure fluctuations can occur during normal operations or in the event of sudden valve closures. Therefore, the shutoff valves must be designed to handle these potential increases in pressure, hence the requirement for a higher service pressure rating. This requirement helps mitigate risks of leaks or failure, thus ensuring the safe transportation and delivery of compressed natural gas.

The other options, which suggest matching, being less than, or having no specific requirement regarding service pressure, do not align with safety protocols necessary for handling high-pressure systems like those found in CNG delivery applications. Meeting or exceeding the rated pressure is fundamental for maintaining operational reliability and safety.