4-Hazard Avoidance (2) [Compatibility Mode]

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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

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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!

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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??

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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


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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 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.


A typical format:

Component Function Failure

Mode

Failure

Rate

Failure

Effect

Criticality Detection

Method

Preventative

Measures


• 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.

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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.



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.


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


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


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).

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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

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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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4-Hazard Avoidance (2) [Compatibility Mode]

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