In any accident or incident investigation it is essential that a formalized process is followed to absolutely determine and mitigate the Root Cause(s) of the incident. This is necessary to assure that the liabilities of operating the process or activity can be minimized to meet the acceptable risk criteria of the company. These acceptable risk criteria assure that the risk of harm to the employees, the public, the environment, and the capital investment meets the standards of the company and appropriate codes of regulatory agencies.
CHARTER OF THE INVESTIGATION TEAM
When an accident occurs it is imperative that techno-economic-chemical-design-technology-improvement charter an investigative team. This team must be comprised of the personnel with the needed skills to discover the accident root causes and develop potential fixes in any appropriate area. The charter should, if possible, be a written document coming from the responsible business manager for the area where the accident occurred.
Additional guidelines are presented, including the contents of the charter, considerations in team composition, and individual responsibilities.
RAPID RESPONSE – INTERVIEWS AND RECORDING
It is human nature for the facts of any incident/accident to become distorted as time passes. The quicker the team is formed and the Charter implemented the greater is the probability that the true root causes will be uncovered. The reasons for the distortion of the facts are many. It is not unusual for employees to formulate a rationale of the incident that absolves them from any responsibility. The facts of what happened may be somewhat unclear and the witnesses may piece together their own opinions about what happened and what the causes might be. Since all witnesses may have different backgrounds, different educational knowledge, or have observed events from a different vantage point, the facts can become distorted.
Additional considerations are presented for conducting interviews and examining the affected areas.
INCIDENT CAUSE(S) POSTULATES
With the interview accounts available, the team should develop scenarios of how the incident occurred. Use of logic diagrams to validate scenarios forms the basis of conclusively determining the cause and effect relationships that contain the root cause of the incident. The logic diagram will yield the event sequences and evidence clues that can be observed by system sampling or tests needed to prove that the true root causes in the proper sequence have been discovered. The sampling will by necessity corroborate the witness interviews. No theoretical scenario should be overlooked or discounted at this point in the investigation until facts invalidate the scenario theory.
Details are presented on the mechanics of scenario logic development, sampling requirements, and sampling protocol.
DEVELOP FULL DESCRIPTION OF THE ACCIDENT
With the logic diagram and the sampling reports and inspection reports the team proves or disproves the theory postulates thus determining the true scenario of the incident.
IDENTIFY PRELIMINARY LIST OF ROOT CAUSES
With the true scenario and root causes identified the team proceeds to work on recommendations to eliminate or control the root causes.
QUANTIFY THE ROOT CAUSES
After developing the root causes, a fault tree can be prepared from the finalized logic diagrams of the incident scenario. This logic treatment will list the root causes as primary events. Options for control or elimination of the root causes can then be evaluated by assigning failure rates and probabilities to the primary events. Solution of the fault tree quantifying the incident can determine the type of corrective measures that will produce acceptable control or prevention of a repeat incident.
Categories of primary events and potential fixes for the root causes are outlined.
REPORTING AND COMPLETION ACTIVITIES
Prescribed activities are presented for documenting the investigation and completing the work of the team.