4-Hazard Avoidance (2) [Compatibility Mode]
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Transcript of 4-Hazard Avoidance (2) [Compatibility Mode]
1
APPROACHES TO HAZARD APPROACHES TO HAZARD
AVOIDANCEAVOIDANCE
PM DR. WILFREDO HERRERA LIBUNAO
TermsTerms
• Hazard- A source or a situation with a
potential for harm to humans, property and
damage of environment or a combination of
these.
• Danger- Relative exposure to hazard.
• Risk- A combination of likelihood of
occurrence and severity of injury or damage.
• Safety- being relatively free from harm,
danger, damage, injury
Classification & Potential Sources of HazardsClassification & Potential Sources of Hazards
Classification Example of Hazards
• Mechanical - Sharp points & edges, overload.
• Electrical - Insulation damaged or cover broken
• Biological - Exposed, airborne/blood borne
• microorganism.
• Chemical - Expose to carcinogens chemical
• Ergonomics - Expose to unnatural postures
• Psychological- Stress or violent at workplace.
Accident TheoriesAccident Theories
• Domino Theory
• Energy Theory
• Single Factor Theories
• Multiple Factor Theories
Domino Theory (Heinrich)
1. Injury is caused by
2. Accidents which are caused by
3. Unsafe acts or conditions which are caused by
4. Undesirable traits (e.g., recklessness, nervousness, temper, lack of knowledge, unsafe practices) which are caused by
5. Social environment
Domino Theory Cont.Domino Theory Cont.
• Stop the sequence by removing or
controlling contributing factors
• Strong emphasis is placed on the middle
domino: unsafe acts or conditions
2
Energy Theory (Haddon)Energy Theory (Haddon)
• Accidents & Injuries involve the transfer of
energy, e.g., fires, vehicle accidents,
projectiles, etc.
• Transfer of energy from a “potential” to
“kinetic”
• Attack problems in parallel rather than
serial (as is presumed in Domino Theory)
Energy Theory Cont.Energy Theory Cont.
10 Strategies to Prevent or Reduce10 Strategies to Prevent or Reduce
1. Prevent the marshalling of energy
- don’t produce the energy
- substitute safe substances for dangerous ones
- don’t produce gun powder
2. Reduce the amount of energy marshaled
- keep vehicle speeds down
- reduce chemical concentrations
- don’t let kids climb above 3 feet
3. Prevent the release of energy
- elevator brakes; prevent flammables from igniting
4. Modify the rate at which energy is released
from its source or modify the spatial distribution of
the released energy
- reduce the slope on roadways
5. Separate in space or time the energy being
released from the structure that can be damaged or
the human who can be injured
- separate pedestrians from vehicles
6. Separate the energy being released from a structure or person that can suffer loss by interposing a barrier
- safety glasses, highway median barriers
7. Modify the surfaces of structures that come into contact with people or other structure
- rounded corners, larger surface areas for tool handles
8. Strengthen the structure or person susceptible to damage
-fire or earthquake resistant structures, training, vaccinations
9. Detect damage quickly and counter its
continuation or extension
- sprinklers that detect heat
- tire tread wear bands
10. During the period following damage and
return to normal conditions, take measures to
restore a stable condition
- rehab an injured worker
- repair a damaged vehicle
Single Factor TheoriesSingle Factor Theories
• Assumes that when one finds a cause, there
is nothing more to find out
• Weak theory, there can be so much more to
learn!
3
Multiple Factor TheoriesMultiple Factor Theories
• Accidents are caused by many factors working together
• The theory and the analysis is more complex, but more realistic than Single Factor Theory
• Consider the Four M’s:
– management, man, media,
machine
– And their interactions
Primary
CauseSecondary
Cause
Contributin
g
Causes
Concepts of Hazard AvoidanceConcepts of Hazard Avoidance
• Approaches
1. Enforcement
2. Psychological
3. Engineering
4. Analytical
• To be successful you must have top management support!
1. Enforcement Approach1. Enforcement Approach
• Your approach to hazard avoidance is entirely
predicated upon avoiding regulatory fines.
• Many companies establish their safety programs to
meet OSHA requirements thinking that is
adequate.
• This is a bare minimum approach. While it may
seem cost effective, it likely is not in the big
picture.
2. Psychological Approach2. Psychological Approach
• Your approach to hazard avoidance is based on a psychological (or behavior-based) approach.
• The behavioral approach has been popular and widely used.– DuPont STOPTM (Safety Training Observation Program)• http://www2.dupont.com/Safety_Products/en_US/products/programs_training/index.html
• To be successful, this approach needs to be ever vigilant, and must be infused with some engineering and analytical components
3. Engineering Approach3. Engineering Approach
• The engineering approach to hazard avoidance utilizes controls measures starting with engineering (then administrative, then PPE)
• Consideration of (see next slides)– Safety Factor Concept
– Fail-Safe Concept
– Design Principles – Design for Safety
• Be careful to avoid a false-sense of security from engineering and technology
Safety Factor ConceptSafety Factor Concept
• Since there is a chance element in safety, we can improve our chances by implementing a “safety factor”
– Scaffolding – 4:1• Designed to withstand 4 times the intended load
– Overhead crane hoists – 5:1
– Scaffold ropes – 6:1
• Why not use 10:1 as a standard?? $$$$$
• Beware when using field tables or computer programs. Are the safety factors applied or not??
4
FailFail--Safe ConceptSafe Concept1. General fail-safe principle• The resulting status of a system, in event of failure of one of
its components, shall be in a safe mode.
2. Fail-safe principle of redundancy• A critically important function of a system, subsystem, or
components can be preserved by alternative parallel or standby units.
3. Principle of worst case
• The design of a system should consider the worst situation to which it may be subjected in use.
• Murphy’s Law: If anything can go wrong, it will.
Engineering Design PrinciplesEngineering Design Principles
• Eliminate
• Substitute
• Guard
• Barriers
• Warn with alarms
(auditory, visual)
• Labels
• Filters
• Exhaust ventilation
• Human Interface
4. Analytical Approach4. Analytical Approach
• The analytical approach to hazard avoidance
utilizes various qualitative and quantitative tools
– Accident Analysis
– System Safety Techniques (see next slide)
– Loss Incident Causation Models
• Proximal and Distal Causes (McClay)
– Toxicology
– Epidemiology
– Cost-Benefit Analysis
System Safety TechniquesSystem Safety Techniques
• Preliminary Hazard Analysis
• Hazard Tracking Log
• Subsystem Hazard Analysis
• System Hazard Analysis
• Operating Hazard Analysis
• Change Analysis
• Accident Analysis
• Time-Loss Analysis
• Event and Causal Factor Charts
• Process Safety Management
• Fault Tree Analysis (FTA)
• Energy Trace & Barrier Analysis (ETBA)
• Failure Mode & Effects Analysis (FMEA)
• Project Evaluation Tree (PET)
• Management Oversight & Risk Tree (MORT)
• Software Hazard Analysis
• Common Cause Failure Analysis
• Sneak Circuit Analysis
How Safe is Safe Enough?How Safe is Safe Enough?
• Can absolute safety be achieved?
• Remember the concept of “risk”.
• What is “acceptably safe”?
• Remember the Risk Assessment Matrix:
Severity versus Frequency
Hazard IdentificationHazard Identification
• To keep workplace safe and healthy.
-employers should make sure there are no hazards to which employees could be exposed.
• Employers should look for hazards in advance
as part of their risk management plan to prevent potential hazards.
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Actions & RecommendationsActions & Recommendations
• All related statements should be made
• With no cost restrains
• Should be reviewed every 4 months
• Need management support
Risk AssessmentRisk Assessment
• Is the process of evaluating the risk to
safety & health from hazards at work
Types
- Qualitative
- Semi-quantitative
- Quantitative
How To Assess RiskHow To Assess Risk
1) Look for the Hazards
2) Decide who might be harmed & how
3) Evaluate the risk and check what is
done to prevent it from happening
4) Record finding
5) Review assessment and revise it if
necessary
• Qualitative risk assessment involves making a formal
judgement on the consequence and probability using:
Risk = Severity x Likelihood
Qualitative Risk Qualitative Risk AssessmentAssessment
Example:
The likely effect of a hazard may for example be rated:
1. Major
Death or major injury or illness causing long term disability
2. Serious
Injuries or illness causing short-term disability
3. Slight
All other injuries or illnesses
Qualitative Risk Assessment…cont’dQualitative Risk Assessment…cont’d
The likelihood of harm may be rated
1. High
Where it is certain that harm will occur
2. Medium
Where harm will often occur
3. Low
Where harm will seldom occur
Qualitative Risk Assessment…cont’dQualitative Risk Assessment…cont’d
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Risk
=
Severity of Harm
x
Likelihood of occurrence
• This simple computation gives a risk value of between 1 and 9 enabling a rough and ready comparison of risks.
• In this case the lower the number, the greater the risk, and so prioritises the hazards so that control action can be targeted at higher risks.
Qualitative Risk Assessment…cont’dQualitative Risk Assessment…cont’d
Qualitative Risk TableQualitative Risk Table
Severity
Likelihood
High
(1)
Medium
(2)
Low
(3)
Major (1) 1 2 3
Serious (2) 2 4 6
Slight (3) 3 6 9
SemiSemi--Quantitative Risk AssessmentQuantitative Risk Assessment
• Severity Categories
1. First Aid
2. Less than 4 days M/C
3. More than 4 days M/C
4. Fatality & Permanent Disability
SemiSemi--Quantitative Risk AssessmentQuantitative Risk Assessment
• Likelihood Occurrence
1. Yearly
2. Monthly
3. Weekly
4. Daily
SemiSemi--Quantitative Quantitative Risk TableRisk Table
LIKELIHOOD
S
E
V
E
R
I
T
y
Yearly Monthly Weekly Daily
1 2 3 4
First Aid 1 1 2 3 4
< 4 Days MC 2 2 4 6 8
> 4 Days MC 3 3 6 9 12
Fatality &
Permanent
Disability
4 4 8 12 16
Quantitative Quantitative Risk AssessmentRisk Assessment
• In cases where hazards are numerous and
complex
e.g.; Chemical process plant, chemical
laboratories
Should have Job Safety Analysis (JSA)
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Advanced Risk Assessment
Techniques
Quantitative Risk Assessment
• QRA is most commonly used in the process industries to
quantify the risks of ‘major hazards’.
• QRA used in the offshore oil and gas industries, the
transport of hazardous materials, the protection of the
environment, mass transportation (rail) and the nuclear
industry.
Quantitative Risk Assessment (1)
• Individual Risk is defined as ‘the frequency at which an individual may be expected to sustain a given level of
harm from the realisation of specific hazards’.
• Societal Risk
Usually expressed as risk contours:
CHLORINE
INSTALLATION
10-6/year
risk contour
0.3*10-6/year
risk contour
Site for
proposed
developmen
t
VILLAGE
10-5/year
risk contour
1 km
Failure Modes and Effect Analysis
The system is divided into sub systems that can be
handled effectively.
It involves:
• Identification of the component and parent system.
• Failure mode and cause of failure.
• Effect of the failure on the subsystem or system.
• Method of detection and diagnostic aids available.
Failure Modes and Effect Analysis
A typical format:
Component Function Failure
Mode
Failure
Rate
Failure
Effect
Criticality Detection
Method
Preventative
Measures
Failure Modes and Effect Analysis
• For each component’s functions, every conceivable modeof failure is identified and recorded.
• It is also common to rate the failure rate for each failuremode identified.
• The potential consequences for each failure must beidentified along with its effects on other equipment,components within the rest of the system.
• It is then necessary to record preventative measures thatare in place or may be introduced to correct the failure,reduce its failure rate or provide some adequate form ofdetection.
8
Hazard & Operability Studies
• HAZOP is a team approach, involving a team of people
representing all different functions in a plant.
• They identify all the deviations by ‘brain-storming’ to a set
of guide words which are applied to all parts of the system.
The process is as follows:
� The system is divided into suitable parts or sub-systems, which are then analysed one at a time.
� For each sub-system each parameter (flow, temperature, pressure, volume, viscosity etc.) that has an influence on it, is noted.
� Guidewords are applied to each parameter in each subsystem. The intention is to prompt creative discussion of deviations and possible consequences
� For each significant deviation, possible causes are
identified.
Hazard & Operability Studies
Hazard & Operability Studies
Example
• Consider the simple process diagram below. It represents a
plant where substances A and B react with each other to
form a new substance C. If there is more B than A there
may be an explosion.
AB
V1V2
V3
V4
V5
A < B = Explosion C
Example from Harms Ringdahl L (1995), Safety Analysis: Principals and Practice in Occupational Safety, Elsevier Applied Science.
The HAZOP sheet for the section of the plant from A to C will be as
follows:
Guide Word Deviation Possible Causes Consequences Proposed
Measures
NO, NOT No A Tank containing A is empty.
V1 or V2 closed.
Pump does not work.
Pipe broken
Not enough A =
Explosion
Indicator for low
level.
Monitoring of flow
MORE Too much A Pump too high capacity
Opening of V1 or V2 is too
large.
C contaminated by
A. Tank overfilled.
Indicator for high
level.
Monitoring of flow
LESS Not enough
A
V1,V2 or pipe are partially
blocked. Pump gives low flow or
runs for too short a time.
Not enough A =
Explosion
See above
AS WELL AS Other
substance
V3 open – air sucked in Not enough A =
Explosion
Flow monitoring
based on weight
REVERSE Liquid
pumped
backwards
Wrong connector to motor Not enough A =
Explosion
A is contaminated
Flow monitoring
OTHER
THAN
A boils in
pump
Temperature too high Not enough A =
Explosion
Temperature (and
flow) monitoring.
Example from Harms Ringdahl L (1995), Safety Analysis: Principals and Practice in Occupational Safety, Elsevier Applied Science.
Fault Tree Analysis
• A fault tree is a diagram that displays the logical
interrelationship between the basic causes of the hazard.
• Fault tree analysis can be simple or complex depending on
the system in question. Complex analysis involves the use
of Boolean algebra to represent various failure states.
Fault Tree Analysis
• The first stage is to select the hazard or top event that is to
be analysed.
• The tree is structured so that the hazard appears at the top.
It is then necessary to work downwards, firstly by
identifying causes that directly contribute to this hazard.
• When all the causes and sub-causes have been identified,
the next stage is to construct the fault tree.
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Fault Tree Analysis
Symbol Designation Function
EVENT / CAUSE Causes or events that can be developed
further
BASIC
EVENT/CAUSE
Basic or Root Causes or events that cannot
be developed further
UNDEVELOPED
EVENT/CAUSE
Causes are not developed due to lack of
information or significance.
AND gate Output event occurs only if all input events
occur
OR gate Output event occurs if any one of the input
events occurs
Fault Tree Analysis
Example
• Consider the simple circuit diagram shown below:
+
-
LAMP
SWITCHFUSE
BATTERY
POWERUNIT
Example from Harms Ringdahl L (1995), Safety Analysis: Principals and Practice in Occupational Safety, Elsevier Applied Science.
Fault Tree Analysis
• The corresponding fault tree for the above circuit, with the top event
(or hazard) being the lamp not working is as follows:
Lamp does notlight
No currentthrough the lamp
No power supplyto the lamp
Broken circuitNo power feed
FaultyLamp
No Power
from battery
No Powerfrom unit
Broken
Circuit
Defectiveswitch
Defectivefuse
Example from Harms Ringdahl L (1995), Safety Analysis: Principals and Practice in Occupational Safety, Elsevier Applied Science.
Fault Tree Analysis• Make a fault tree analysis, with the top event (or hazard) being the
welding machine not working properly:
Welding machine not working properly
Practical Risk Assessment
Classify work activities
Identify hazards
Determine risk
Decide if risk is tolerable
Prepare risk control action plan
(if necessary)
Review adequacy of action plan
Classify Work Activities
Possible ways of classifying work activities
include:
• Geographical areas within/outside the organisation's
premises.
• Stages in the production process, or in the provision of a
service.
• Planned and reactive work.
• Defined tasks (e.g. driving).
10
Identify Hazards
Broad categories of hazard
To help with the process of identifying hazards it
is useful to categorise hazards in different ways,
for example by topic, e.g.:
• Mechanical.
• Electrical.
• Radiation.
• Substances.
• Fire and explosion.
Hazards prompt-list
During work activities could the following hazards exist?
• Slips/falls on the level.
• Falls of persons form heights.
• Falls of tools, materials, etc., from heights.
• Inadequate headroom.
• Hazards associated with manual lifting/handling of tools, materials, etc..
• Hazards from plant and machinery associated with assembly, commissioning, operation, maintenance, modification, repair and dismantling.
Hazards prompt-list
• Vehicle hazards, covering both site transport, and travel by road.
• Fire and explosion.
• Violence to staff.
• Substances that may be inhaled.
• Substances or agents that may damage the eye.
• Substances that may cause harm by coming into contact with, or being absorbed through, the skin.
• Substances that may cause harm by being ingested (i.e., entering the body via the mouth).
• Harmful energies (e.g., electricity, radiation, noise, vibration).
Hazards prompt-list
• Work-related upper limb disorders resulting from
frequently repeated tasks.
• Inadequate thermal environment, e.g. too hot.
• Lighting levels.
• Slippery, uneven ground/surfaces.
• Inadequate guard rails or hand rails on stairs.
• Contractors' activities.
Determine risk
The risk from the hazard should be determined by
estimating the potential severity of harm and the
likelihood that harm will occur.
Severity of harm
Information obtained about work activities is a
vital input to risk assessment. When seeking to
establish potential severity of harm, the following
should also be considered:
• Part(s) of the body likely to be affected;
• Nature of the harm, ranging from slightly to extremely
harmful:
– 1) Slightly harmful, e.g.:
• Superficial injuries; minor cuts and bruises; eye irritation from
dust.
• Nuisance and irritation (e.g. headaches); ill-health leading to
temporary discomfort.
BS8800:1996
11
Severity of harm
– 2) Harmful, e.g.
• Lacerations; burns; concussion; serious sprains; minor
fractures.
• Deafness; dermatitis; asthma; work related upper limb
disorders; ill-health leading to permanent minor disability.
– 3) Extremely harmful, e.g.
• Amputations; major fractures; poisonings; multiple injuries;
fatal injuries.
• Occupational cancer; other severely life shortening diseases;
acute fatal diseases.
BS8800:1996
Likelihood of harm
When seeking to establish likelihood of harm the
adequacy of control measures already implemented
and complied with needs to be considered.
Issues considered:•Number of personnel exposed.
•Frequency and duration of exposure to the hazard.
•Failure of services e.g. electricity and water.
•Failure of plant and machinery components and safety devices.
•Exposure to the elements.
Likelihood of harm
• Protection afforded by personal protective equipment and
usage rate of personal protective equipment;
• Unsafe acts (unintended errors or intentional violations of
procedures) by persons, for example, who:
– 1) May not know what the hazards are.
– 2) May not have the knowledge, physical capacity, or skills to do
the work.
– 3) Underestimate risks to which they are exposed.
– 4) Underestimate the practicality and utility of safe working
methods.
Decide if risk is tolerable
One simple method for estimating risk levels and for
deciding whether risks are tolerable. Risks are classified
according to their estimated likelihood and potential
severity of harm.
Slightly harmful Harmful Extremely harmful
Highly unlikely TRIVIAL RISK TOLERABLE RISK MODERATE RISK
Unlikely TOLERABLE RISK MODERATE RISK SUBSTANTIAL
RISK
Likely MODERATE RISK SUBSTANTIAL
RISK
INTOLERABLE
RISK
Actions & Recommendations
• EL- Eliminate
• SL- Substitute
• IS- Isolation
• EC- Engineering Control
• AC - Administration Control
• PPE- Personal Protection Equipment
Actions & RecommendationsEg;
EL - stop work, cover hazard…
SL - use other route, other material..
IS - put up temporary barrier,…
EC - construct permanent wall,..
AC - put up notice, job rotation,…
PPE - gloves, respirator,……
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