Incident investigation workshop

OBSERVATION

• OBSERVATION
• Evidence (facts) gathered at the time or moment of failure
• Establish at the end of step 3 "Determine the Facts"
• In the WHY Tree, start with an Observation that is "physical or tangible", not something pertaining to a - person's actions or a system such as training, procedures, etc.
• HYPOTHESIS
• A possible cause for the event above it. A hypothesis becomes an intermediate cause or key factor once verified.
• Stating the hypotheses in broad, general terms helps insure some causes aren't overlooked or left out of consideration.
• Take small steps of logic; avoid the tendency to jump too far towards a key factor when moving down from one intermediate cause to the next group of hypotheses.
• WHY Tree leader should write down hypotheses suggested by the team without judging their merit.

BUILDING THE “WHY” TREE

• BUILDING THE “WHY” TREE
• The following pages show the steps to build a WHY Tree using a real plant example.
• Step 1. Define the Significant Event to Investigate

• CAUSE AND EFFECT IN WHY TREES
• Step 2. List the observations (facts: what was seen and heard)
• Step 3. Choose an observation to pursue first, based on its impact on the failure event or its frequency of occurrence.

BUILDING THE “WHY” TREE

• BUILDING THE “WHY” TREE
• Step 4. Hypothesize causes of the observation. Ask Why or How Can the observation
• have happened, using the question that makes the most sense.

• A fuse opened

• Overlands need reset

• Either

• Or

• Hypothesis as to Casue