The "fail safe" concept is used to specify the position (fail closed or fail open) of all process valves in the event of a utility failure. The specified fail open or fail closed puts the process in a safe mode of operation. Specify the proper fail-safe position for the following situations:

a. A process valve regulates the flow of steam that heats a solvent in a heat exchanger.

b. A valve controls the flow of a reactant (exothermic reaction) to a reactor.

c. A valve controls the flow of a reactant (endothermic reaction) to a reactor.

d. A valve controls the flow of natural gas to a furnace.

e. A remote valve is connected to a storage tank drain line.

f. A remote valve is connected to a fill line to a storage tank.

g. A valve controls the combustion air to a furnace.

h. A valve releases excessive pressures in a steam header.