Hazard ID and Human Error Flashcards
Why is it important to identify all hazards?
Because it is the hazards that tends to cause accidents. Or the interaction of two or more obvious things can lead to an unusual event.
What are the stages in controlling hazards?
- Identify - we need to predict everything that could happen
- Assess - We need to judge which events are significant.
- Control - Reduce/ eliminate unwanted consequences.
What are some hazards in the work environment?
Improper PPE, improper lifting technique, improper chair height.
Why do we care about controlling hazards?
To prevent injuries or deaths. We need to be able to identify all hazards in the process for this reason.
What are each of these colours associated with in the chemical hazard identification system?
- Blue
- Red
- White
- Yellow
- Blue = Health Hazard
- Red = Fire Hazards, Flash Points
- White = Specific Hazard e.g. acid, alkali, oxidiser
- Yellow = Instability
What is the flash point?
The temperature at which a particular organic compound gives off sufficient vapour to ignite the air.
What numbers are also associated with the colours as a measure of the danger they pose?
- 0 = would be a material that is non-hazardous
- 4 = would be a relatively dangerous material such as low flash point
What are the 2 philosophies behind hazard identification?
- Experience
2. Predictive
What two things are associated with experience in hazard identification?
- Codes of Practice = set down by public notes
- Checklists = tick boxes to show following safety rules
What are codes of practice?
Minimum standards of construction, maintenance, management. Procedures have to comply.
Give some examples of different standards.
- National Standards (BSI)
- Industry Standards (API, CIA)
- Company Standards and Codes
- Company procedures
What are codes of practice based on?
They rely on a body of established practice.
What are checklists?
You tick off things that need to be done. These are for every stage in a design process and operation.
What are checklists based on?
They rely on knowledge and lots of experience. Very experienced people can write a checklist.
What is the significance of the checklists?
Allows you to be able to contradict management above you.
What are the advantages of checklists?
- Allows you to be able to contradict management above you
- Simple to use - little experience required
- Can be “universal”
- Process specific checklists maintain corporate memory of pitfalls
What are the disadvantages of checklists?
- Reactive (It’s from experience that went wrong, not predicting)
- Experience needed to construct checklist
- Need commitment to maintain quality
- Need a complete set of hazards which takes time
What does the predictive philosophy entail?
HAZOP
What does HAZOP stand for?
Hazard and Operability Study
Where in the plant is HAZOP type studies carried out?
At various stages of design, there is usually a final HAZOP at the end when the design is finalised using the Engineering Line Diagram.
What is the aim of HAZOP?
To identify the effect on the process of all possible deviations from normal operation and to assess whether these pose a significant safety risk or operability problem.
HAZOP is a line-by-line study. What happens in each line?
Each variable in the line is assessed. We identify all hazards by checking all possible deviations. Generate every possible way the process can be different and check risk/probability
Give some examples of the team for a HAZOP study.
Chairman, Designers, Operating Management, Chemists, Control Engineers, Mechanical Engineers
Why is there such a wide variety in the HAZOP study team?
All the team need to be able to draw on a lot of experience from ideally a wide variety of processes.
How would we go about a HAZOP study?
The plant is divided into sections. Normal operation of the section is described by the designer, outlining operating conditions and the intention of control. Each line in the section is considered in turn. For each variable deviations from normal operations are generated using a set of guide words.
Give some examples of guide words and to which variables they apply.
- None: can only apply to flow
- More of: the variable is higher than intended (temperature, concentration)
- Less of: the variable is less than intended
- Part of: this refers to composition, a component is missing
- Reverse: flow is in opposite direction
- More than: an extra component is present. Always consider air and water and components present in adjacent sections/ lines.
With what words do we describe a deviation?
A guide word and a variable
For each deviation, what does the team judge?
- the deviation is credible: all causes are justified
- what safeguards they are to prevent/ameliorate the deviation
- what the consequences are and that they are sufficient to need action
- Agree on actions
- Record on feedings
What are some consequences of a deviation in a HAZOP?
It does not have to be an injury or a fatality. It can be an equipment failure or loss of product quality.
What about the solutions of the hazards identified in the HAZOP?
It is not the responsibility of the HAZOP team to provide detailed solutions.
What are the advantages of HAZOP?
- Can be used for novel processes
- It is comprehensive and should identify all possible problems
- Uses creative thinking and pooled experience of team
- It is very widely used and well regarded
What are the disadvantages of HAZOP?
- time consuming, tedious, expensive. Ties up senior staff for long periods.
- Relies on experience
- Can be devalued by plant modification. Have to check that implementing safety measures movies it back to safe region.
What are the Mond Dow indices?
Used at conceptual and later stages of design to give relative hazard ratings for different plant sections or design alternatives. It uses a very structured calculation method to produce a single number representing the hazard life of a process. We come up with one final number.
What do all accidents have?
A human error element
What are the two types of human error?
- Active
- Passive
What is an active human error?
Someone did something wrong
What is a passive human error?
Someone had done something wrong either in the construction, design, management, safety culture.
What is the relationship between the human error element and the accident rate?
If we reduce the human error element then we reduce the accident rate.
What is at the top of an accident triangle?
A time-lost accident
What is a time-lost accident?
A worker is seriously injured, lose time and nobody is doing work. It can lead to hospital or death.
What are the progression of accidents on the accident triangle?
- Time lost accident
- Minor injury
- Permanent damage of property
- Near miss
- Unsafe behaviour
On the accident triangle, what are the probabilities of:(a) time lost accident
(b) minor injury
(c) permanent damage of property
(d) near miss
(e) unsafe behaviour
(a) 1
(b) 10
(c) 30
(d) 600
(e) ?000
How do we reduce the top of the accident triangle?
By reducing the size of the bottom of the triangle we can then reduce the size of the rest of the triangle.
What is a ‘near miss’ accident?
You almost get injured but you don’t. By reporting then you can reduce the risk of something happening.
What is routine behaviour?
What people are meant to do according to the manual and what they actually did.
What are different human error rates?
- Complicated, non-routine
- Non-routine, other simultaneous tasks
- Routine, requires care
- Routine, simple
- Simplest possible action
What is the relationship between the time you have available to react and the probability of error?
As the time available to react increases then the probability of error decreases. A second is not enough time to think about something. You will need to process and execute action. Even with an infinite amount of time, you will still get something wrong.
What are the different types of human errors?
- Slips
- Mistakes
- Violation
- Lack of ability
- Management error
What are slips?
Intention correct, action wrong. You know what you are meant to do.
What are mistakes?
Intention wrong, action in accordance with intention e.g. misinterpreting questions
What are violations?
Deliberate non-compliance. You know what you are meant to do and decide to do differently.
What are the different types of lack of ability?
Mental or physical
What are management errors?
Conflicting schemes that safety is important but so is production. This could also be confusing interactions, poor training, disregarding safety.
Why can somebody make a slip?
They are skill based and associated with routine tasks due to absent mindness and distraction.
What is insufficient to prevent slips?
Telling people to “pay attention” is not sufficient because they are not thinking at all.
What is sufficient to prevent slips?
You can’t change the person but you can change the consequence. You can design the task to be more slip proof and minimise the consequence. Slips will happen and these should be allowed for.
How do we minimise mistakes and failures?
- Increase understanding through training
- No contradictory messages
- Be explicit so no misinterpretation
- Monitoring
- Quality instructions
What is the shape of the relationship between error rate and load/ stress?
Minimum parabolic curve
What are the two different forms of mental ability?
- Underloading
- Overloading
What is underloading?
There is no simulation, in a meditative state. There is monotony. The error rate is high.
What is overloading?
There is a high stress and high error rate.
What is the optimum stress then associated with?
There would be an optimum arousal level. There is little bit of stimulation and little bit of stress to perform well.
In what events is it required that there is minimal arousal?
Non-routine events
Give some examples of non-routine events.
- Unexpected responses
- Illogical layout: e.g. knobs high up
- Mindset: You think you know what’s happening but something else is happening.
What are the three performance levels?
- Knowledge Based
- Rule Based
- Skills Based
What are knowledge based performance levels?
Solving problems from first principles. Errors due to incomplete information/ knowledge. You haven’t done the problem before but you know how to solve it.
What are rule based performance levels?
Solving problems using rules from previous training or experience. Errors due to misclassification of problem - wrong rule. You know the rules and you are applying them but you are applying the wrong rule.
What are skill based performance levels?
Carrying out routine tasks without conscious problem solving. Errors due to external variation. You know what you do so well, you just do it. Skill based errors are usually due to distractions, trying to deviate from routine etc.
If the situation is routine, expected and the control mode is automatic, what is the performance level?
Skill based
If the situation is familiar or trained for problems and the control mode is conscious and automatic, what is the performance level?
Rule based
If the situation is novel, difficult or dangerous and the control mode is mainly conscious, what is the performance level?
Knowledge based
What are the steps of minimising human error?
- Sound ergonomics including accessible physical layout and suitable response times
- Controls give expected response
- Design alarms to aid diagnosis of problems
- Avoid monotony
- Avoid conflicting information/instructions
- Train well
