The operational states

This accident involves the latent faults:

• Stuck resin in the filter of one of the six condensate polishers
• Valve stuck open enabled water to enter the instrument air line
• PORV was stuck open, enabling pressure reduction.

Each fault is associated with a two- state state machine, comprising the states (On, Off).

Each of the operational modes assumes a certain active state of a relevant state machine.

• The states of the filters are (blocked, free). In normal production, the proper state is "free".
• The states of the valve preventing water entry to the instrument air line are (open, closed). In normal production the proper state is "closed".
• The states of the PORV are (open, closed). When the pressure is in the safety boundaries, the proper state should be "closed".

  To enable identification of scenario- situation mismatch, the states should be defined explicitly, and the Situation analyzer should generate alarms in cases of mismatch.

  Guidelines for state management

Updated on 18 Apr 2016.