Problem 11-4. The concept of "fail safe" 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.
Solution for Problem 11-4
Problem 11-5. Conduct a safety review for the design of the system described in Example
11-2. This reactor is used to polymerize ethylene oxide to form polyols.
Solution for Problem 11-5