Operator Safety is always a key element of machine design 

Safety redundant sensors and pneumatics

Reactor lids cannot open when caustic solution in the tank

Caustic feed valves cannot open if the reactor lid is open

Rinse water feed valves cannot open if reactor lid is open

Exhaust fans run when caustic solution in the reactor

Fault or inconsistent sensor readings drain reactor

Reactor lid open/close are momentary push button 

Reactor lid full open tilt 10 degrees past vertical

Process pumps have freshwater flush for servicing

Reactor lid open restraint during servicing

Complete alarm systems with fault identification