06-Fault Tree Analysis#

Fault tree analysis (FTA) is a top-down, deductive failure analysis in which an undesired state of a system is analyzed using boolean logic to combine a series of lower-level events. This analysis method is used to understand how systems can fail, to identify the best ways to reduce risk, and to estimate event rates of a safety accident or a particular system level (functional) failure.

Helpful Reading#

Example of Fault Tree Analysis (FTA)#

Procedure#

A batch reactor is used to complete a reaction needed for the benefit of others. The reactor process has the following processing steps:

  1. The reactor is filled with the raw material, a somewhat toxic material.

  2. The reactor is heated to the desired temperature (100 F).

  3. The reactor is pressurized to the desired pressure (20 psig).

  4. Reactant B is slowly added to the reactor. An exothermic reaction occurs and the jacket must begin to cool the reactor to maintain the desired temperature.

  5. The reaction proceeds at a given reaction rate at that temperature and pressure until all of the reactant B has been added.

  6. The reactor is cooled to room temperature and the product is removed.

Some Hazards#

  • Product C has a low boiling point and is toxic. If the reactor is not cooled properly, the product will vaporize and escape from the reactor.

  • If stirring is not maintained, the reaction will not proceed at the desired rate and the reactor will overheat.

  • Reactor is used for multiple products

Image of the batch reactor credit to: https://www.essentialchemicalindustry.org/processes/chemical-reactors.html

Combination of FTA and FMEA:#

An accident investigation prior to the accident

Example start on an FTA: (lower left is ‘Blades fall off’)

Example breakout of the FTA referencing the 1 node under ‘PRV Fails’

Example start of the FMEA/ Hazards Analysis