Effect on learning

Learning depends on the operational situation. The situation affects the value of a learning cycle and therefore determines the selected action.

Learning is possible only when the relevant state is apparent to the operator.

Case studies

State visibility is a key factor in many celebrated accidents. Latent states were involved in:

• The steering lever of the Torrey Canyon
• Two valves at the TMI accident

Design

State visibility is achieved by visibility add-ons, namely, resilience add-ons incorporated in the functional unit.

Examples

• Inherent visibility, such as of a Power On/Off switch, when no special hardware are needed to achieve the visibility. The active state is identified based on the voltage of the circuit.
• Sensory-based visibility, such as of a boiler temperature, when extra hardware, such as a thermometer, is needed to identify the active state.

Visibility and complexity

  The system design should consider only two types of components: those which are essential, and those which are redundant.

• The essential components should be visible. The operators need to know about instances of faults, and they should be equipped with means to accomplish this requirement.
• The redundant components should be eliminated, to reduce complexity, in order to improve the extended reliability

Related topic

Updated on 14 Jul 2016.