What is a requirement for appliances operating at pressures equal to or greater than the test pressure during isolation?

Appliances operating at pressures equal to or greater than the test pressure during isolation must have their shutoff valves closed. This is crucial because closing the shutoff valves prevents the flow of gas into or out of the appliance. By isolating the appliance in this way, it helps mitigate the risk of gas leaks or pressure build-up, ensuring that the system can be safely tested or maintained without the possibility of hazardous exposure or accidents.

This practice is an important safety measure in handling gas appliances and systems, particularly when they are subjected to testing or maintenance at high pressure. It protects both the equipment being worked on and the safety of personnel working in proximity to these appliances.