3 HAZARD CONTROL

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3 HAZARD CONTROL
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The hazard of sharks 1/6
Sharks are a dormant hazard
Figures in the slides 26 retrieved from
http//www.safework.sa.gov.au/
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The hazard of sharks 2/6
Potential or armed hazard
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The hazard of sharks 3/6
Eliminating hazard
Replace sharks with toys
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The hazard of sharks 5/6
Introducing administrative tools
May be you will have time to escape
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The hazard of sharks 4/6
Engineering out the problem
Encage yourself!
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The hazard of sharks 6/6
Provision of personal protective equipment
An armoured holiday
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Hazard control in the risk analysis
Where we are?
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Methods to control hazards
Two groups of options
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Accident prevention
Accident prevention
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1. Eliminating hazards 1/4
General

• The following general features of hazard control
  should be observed
• Designs to eliminate hazards are most preferred
  over any other method.
• Where safeguards by design are not feasible,
  protective safety devices should be employed.
• Where neither design nor safety devices are
  practical, automatic warning devices should be
  incorporated.
• Where none of the above is feasible, escape
  procedures and personnel training should be used.

• Accident prevention

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1. Eliminating hazards 2/4
Intrinsic safety

• The most effective method of avoiding accidents
  is with designs that are intrinsically safe.
  Intrinsic safety can be achieved by either two
  methods
• Eliminating the hazard entirely.
• Limiting the hazard to a level below which it
  can do no harm.

• Accident prevention

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1. Eliminating hazards 3/4
Complete elimination good housekeeping
Tripping over misplaced objects, slipping on wet
or oily surfaces, and spontaneous ignition of
trash or oily rags can be eliminated simply by
keeping facilities clean and orderly.

• Accident prevention

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1. Eliminating hazards 4/4
Complete elimination examples

• Using non-combustible instead of combustible
  materials. This method has been observed with
  paints, fabrics, hydraulic fluids, solvents, and
  electrical insulation.
• Using pneumatic or hydraulic, instead of
  electric, systems where there is a possibility of
  fire or excessive heating. Fluid control systems
  are often applied for this reason.
• Rounding edges and corners on equipment so
  personnel will not injure themselves.
• Eliminating leaks using continuous lines with as
  few connections as possible.

• Accident prevention

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2. Limiting hazard level 1/2
Hazard level limitation
In certain instances the type of hazard can not
itself be eliminated. However, the level of the
hazard might be limited so no injury or damage
will result.

• Accident prevention

Electricity under some circumstance can be
fatal. It may be possible to eliminate any
adverse effects by using low-voltage, low
temperature power, such as 12-volt power or
battery power.
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2. Limiting hazard level 2/2
Hazard level limitation examples

• Providing overflow arrangements that will prevent
  liquid levels from getting too high.
• Using solid state electrical devices where
  flammable or explosive gases may be present, so
  any power requirements will be far less than
  required for ignition of a flammable mixture.
• Ensuring that the concentration of a flammable or
  toxic gas is far less than a dangerous limit. If
  the limit is exceeded, a blower could be started
  automatically or inert gas introduced.
• Adding diluters to air where flammable dusts are
  present to minimize the possibility of an
  explosion.
• Incorporating automatic relief provisions to keep
  pressure within a safe limit.
• Using grounds on capacitor or capacitive circuits
  to reduce charge accumulations to acceptable
  levels after power is shut off. This will lessen
  the tendency for an electric shock.

• Accident prevention

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3. Isolating hazards 1/4
General
Isolation here separation employed as an
accident prevention measure.
Fire requires the presence of a fuel, oxidiser,
and ignition source. Isolating any one of these
from the other two will eliminate any possibility
of fire. Some grades of bituminous coal are
often stored underwater, isolating the coal from
the oxygen and ignition source needed for fires
to start spontaneously.

• Accident prevention

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3. Isolating hazards 2/4
Isolation examples

• Isolating workers inside protective garments or
  equipment to prevent environmental injuries.
• Use of thermal insulation to prevent persons from
  contacting hot surfaces which can burn them.
• Use of isolators to keep noise inside closed
  spaces.
• Use of explosion-proof or encapsulated
  electrical equipment in flammable atmospheres.
• Keeping corrosive gases and liquids from
  incompatible metals or other materials that might
  be affected adversely.

• Accident prevention

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3. Isolating hazards 3/4
Lockins lockouts
Lockout prevents an event form occurring or
prevents a person, object, force, or other factor
from entering an undesired zone. Lockin
keeps a person, object force, process, or other
factor form leaving a restricted zone.

• Accident prevention

Lockout example a switch closing electrical
circuit secured with a lock that only specific
persons can open. Lockin example the same
switch with lock preventing opening of the
circuit.
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3. Isolating hazards 4/4
Interlocks

• Interlocks initiate/prevent action or motion
  other send signals to other devices which
  initiate/prevent the action or motion
• Parameter sensing presence, absence, excess, or
  inadequacy of pressure, temperature, flow or
  other parameter permits or stops action.
• Timers and time delays operation of the
  equipment can take place only after a specific
  length of time has passed.
• Photoelectric devices interruption or presence
  of light on a photoelectrical cell generates a
  signal which can stop or initiate action.

• Accident prevention

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4. Fail-safe designs
Equipment failures yield a high percentage of
accidents

• Since failures will occur, fail-safe arrangements
  are often made to prevent injury to personnel,
  major catastrophes, damage to equipment, or
  degraded operations
• Fail-passive arrangements circuit breakers and
  fuses for protection of electrical devices which
  deenergise system in case of overload.
• Fail-active arrangements a battery operated
  smoke detector maintains energised state of the
  system but activates eliminating the possibility
  of accident (sprinklers, say).
• Fail-operational arrangement allows system
  functions to continue safely until corrective
  action is possible.

• Accident prevention

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5. Failure minimization
Reducing critical failures causing accidents

• Safety factors and margins over-design of the
  system.
• Failure rate reduction increase expected
  lifetimes.
• Parameter monitoring keep under surveillance
  specific parameters, say, temperature, noise, gas
  concentration.

• Accident prevention

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6. Warning means and devices 1/3
Avoiding accidents by attracting attention
Visual sense

• Accident prevention

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6. Warning means and devices 2/3
Avoiding accidents by attracting attention
Auditory sense

• Accident prevention

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6. Warning means and devices 3/3
Avoiding accidents by attracting attention
Smell

• Accident prevention

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7. Safe procedures
when all else fails, read the instructions
The need to follow prescribed procedures. Safe
procedures should include any warnings about
hazards established by the analysis of the
system. Unfortunately, since many people to not
read operating procedures until they have run
into difficulty (when all else fails, read the
instructions), and ignore warnings, this method
has low priority in rating means of preventing
accidents.

• Accident prevention

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8. Backout recovery
A near-miss

• A failure, error, or other adverse condition may
  eventually develop into a mishap. At this time, a
  contingency or emergency may then exist.
• By suitable action an accident can be avoided
  from this abnormal situation, which may be an
  extremely dangerous one.
• Failure to act correctly or adequately can permit
  the situation to deteriorate into a mishap.
• This interim period extends from the time the
  abnormality appears until normality is recovered
  or accident develops.
• If recovery takes place, the incident can be
  considered a near-miss.

• Accident prevention

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Minimising and controlling damage
Damage minimisaiton
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1. Isolation and barriers 1/2
Weak link component designed to fail at low
level of stress

• Distance by sitting possible points of accidents
  far from persons, equipment, or vulnerable
  structures.
• Deflectors can be used to lessen damage by
  deflecting or absorbing energy. The reminder
  should then constitute less than the amount that
  would be damaging (heat reflectors from fires,
  noise shields, or sloped barricades between
  explosive storage buildings)
• Containment to prevent the spread of fire such as
  sprinkler systems.
• Barriers of metal, concrete blocks, or other
  impenetrable or nonconductive material.

Damage minimisaiton
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1. Isolation and barriers 2/2
The tanks protective barrier in gas station
Damage minimisaiton
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2. Personal protective equipment 1/3
Categories

• For scheduled hazardous operation spray painting
  would require protective clothing during
  scheduled operations.
• For investigative and corrective purposes it may
  be necessary to determine if the environment is
  dangerous because of a leak, contamination, or
  other condition.
• Against accidents this may be constitute the
  severest requirements because the first few
  minutes after an accident takes place may be the
  most critical.

Damage minimisaiton
Reaction time to suppress or control any injury
or damage is extremely important. Because of
this, protective equipment must be simple and
easy to don and operate, especially because it is
often required at a time of stress.
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2. Personal protective equipment 2/3
The hazard of entering a tank scheduled/investiga
tive operation
Damage minimisaiton
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2. Personal protective equipment 3/3
Protection in case of accident accidental
release of toxic material
Damage minimisaiton
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3. Weak links 1/2
Weak link component designed to fail at low
level of stress
The most common example is electrical fuse

• Boilers with mechanical fuses that melt when
  water levels drop excessively so steam can escape
  so there is no rupture.
• Sprinklers that open to release water for fire
  extinguishing.
• Drop-off panels that will fail along designed
  fault lines to provide openings to energy of an
  explosion.

Damage minimisaiton
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3. Weak links 2/2
Ronan Point Explosion fatal structural collapse,
UK 1968
           
Damage minimisaiton
Floor 18, Apartment 90
Only a few weeks after the occupants had moved
in, a gas explosion demolished a load bearing
wall, causing the collapse of one entire corner
of the building. Four people were killed in the
collapse, and seventeen were injured.
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4. Escape and survival equipment 1/2
Abandoning or scarifying structures, vehicles, or
equipmentto avoid injury and to personnel
Damage minimisaiton
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4. Escape and survival equipment 2/2
Telescopic Poles in Aluminium/Carbon Fibre
Damage minimisaiton
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5. Rescue procedures and equipment
Persons involved in an accident and not able to
escape
A rescuer can be everyone

• Fellow workers familiar with the plant, hazards,
  equipment, and who may have been advised of what
  to do in any emergency.
• Untrained persons unfamiliar with equipment
  (passers-by, say).
• Persons knowledgeable and capable of handling the
  need.

Damage minimisaiton
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6. Minor loss acceptance
The decision to accept losses of potential
accidents can be made on the based on the results
of a quantitative risk assessment.
Damage minimisaiton
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To end of part three
Examination questions

• What are the methods of accident prevention? List
  at least one example of application of each
  method.
• How can the magnitudes of hazards be limited?
  Describe how a design can be intrinsically safe.
• How can isolation be used to keep personnel from
  accidents?
• What is meant by keeping equipment fail-safe? How
  can it be done?
• How are monitors used to prevent accidents? Give
  three applications. List the characteristics a
  good monitor should have.
• What is the buddy system and how is it used? What
  are the two types of the buddy system?
• Tell how the human senses can be used as
  monitoring and warning devices ad give some
  examples of each.
• What are back-out and recovery as they apply to
  accident prevention?
• List the methods by which injury and damage can
  be minimised in the event of an accident.
• What is the weak link? Describe some common
  types.
• Describe the relations between escape, survival,
  and rescue. Tell how equipment designs and
  procedures can be developed for them.