Question
Specify the proper fail-safe action for the valves in the following services. Please explain your reasons.
A valve manipulates the flow of natural gas (combustible) to a furnace. Another valve manipulates the flow of combustion air to the same furnace.
Additional information-
The problem belongs to Mechanical Engineering and it is about a valve manipulating the flow of natural gas to a furnace. Another valve manipulates the flow of air to the furnace. The fail safe valve is to be given.