2. Systems Hazards Analysis
•– includes the human component (a strength of Job
Safety Analysis) and the hardware component (a strength
of Failure Mode and Effect Analysis)
•Argument: is that failures or undesired events may be
eliminated by systematically tracking through the system,
looking for hazards that may result in a failure situation.
•In the language of SHA, the terms process, operation, and
task have specific meanings.
3. Process – means the combination of operations and tasks
that unite physical effort and physical and human
resources to accomplish a specific purpose.
Operation – is a major step in the overall process (e.g.,
drilling and countersinking stock on a drill press)
Task – is a particular action required to complete the
operation (e.g., placing a cutting tool in a holder before
sharpening the tool on the grinder).
4. One type of hazard analysis includes identifying and recording
information relating to:
1.Process (turning between centers on a machine lathe)
2.Major unit operation required to complete the process ( rough – turning
steel stock)
3.Tasks required to complete an operation (select cutting tool and place
in holder)
4.Variance from safe practices with the potential to cause hazards (
incorrect cutting tool used)
5.Hazard that has the potential to cause an injury ( worker in proximity to
lathe when incorrect cutting tool used)
5. 6. Triggering event causing hazards to result in incident, brought
about by human error or situational, or environmental factors
(starting the lathe)
7. Incident resulting from effect of triggering event on hazard (
stock comes off centers when lathe is running)
8. Effect indicating type of injury or damage resulting from the
incident ( eye injury)
9. Hazard consequence classification(called the severity index in
FMEA)
10. Hazard probability (same as in FMEA)
6. 11. Procedural requirements to eliminate or
reduce hazards in the workplace
12. Safety and personal protective equipment
requirements to reduce the possibility of injuries
and illnesses while performing operations and
task,
13. Instructions/recommendations to ensure
safety and health in the workplace.
7. INDUCTIVE METHODS OF ANALYSIS ANALYZE THE
COMPONENTS OF THE SYSTEM AND POSTULATE
THE EFFECTS OF THEIR FAILURE ON TOTAL
SYSTEM PERFORMANCE.
8. DEDUCTIVE METHODS
•Deductive methods of analysis move from
the end event to try to determine the
possible causes. They determine how a
given end event could have happened.
One widespread application of deductive
systems safety analysis is FAULT TREE
ANALYSIS.
9. FAULT TREE ANALYSIS – postulated the
possible failure of a system and then identifies
component states that contribute to the failure.
- FTA uses Boolean logic and algebra to
represent and quantify the interactions between
events. The primary Boolean operators are
AND and OR gates.
10. For an AND gate, the probability of the output event is the
intersection of the Boolean probabilities, or the product of
the probabilities of the input events,
11. For an OR gate, the probability of the output event is the
sum of the union of the Boolean probabilities, or the sum
of the probabilities of the input events minus all of the
products.
