e7.5 - Failure tracing methodologies Flashcards
HAZOP
Used for complex processes such as chemical plant operation
Uses a multi-disciplinary approach
Usually carried out at design stage
Intention to identify deviations from normal operation
Deviations prompted with the use of guide words
Process is broken into smaller elements
Consequences of deviations are identified
Study leader co-ordinates group through process
Documented and recorded
Key words
Guide words - deviations from intention e.g. more, less, as well as
Property words - design conditions (parameters) e.g. flow, pressure, vibration, temperature
Each property word is considered at each point in the process
The guide words are applied and the consequences and causes discussed
Guide words
NO or NOT
MORE
LESS
AS WELL AS
PART OF
REVERSE
OTHER THAN
NO or NOT
Complete negation of the design intent
MORE
Quantitative increase
LESS
Quantitative decrease
AS WELL AS
The design intention is achieved but with additional activity e.g. impurity, corrosion
PART OF
Only part of the design intention is achieved
REVERSE
Logical opposite of the design intent
OTHER THAN
Something quite different from the intention happens e.g. complete substitution of material
Procedure
Study leader applies first guide word
Team brainstorm process intention using property words, e.g. what happens if there is NO FLOW to this pump….
Team determine how this might occur, and consider the potential consequences
Team determine any design modifications/solutions
Study leader applies second guide word
Fault Tree Analysis (FTA)
Seeks to identify all possible causes of failure
Multi-causation approach
Top down (starts with a fault or failure - top event)
Logic based assessment process
Shows relationship between cause and effect
Logic gates AND and OR
Standard symbols used in diagrams
Probabilities can be used to make it a quantitative tool
