HOT WORK

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HOT WORK

• Helen Verstraelen

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HOT WORK?

• Cutting and welding operations for construction /
  demolition activities that involve the use of
  (portable) gas or arc welding equipment. Gases
  frequently used
• Acetylene
• Oxygen

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HOT WORK
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ACETYLENE
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ACETYLENE C2H2

• Fire and explosion data
• Flash point -18C
• Auto ign. Temp. 305C
• LEL 2,5 UEL 100
• Extinguish with CO2 or dry chemical
• Health hazard data
• Asphyxiant, irritant and anesthetic
• no TLV, about 100mg/l may be tolerated for 0,5 to
  1 hour
• No chronic harmful effects evidence
• Thermal burns possible

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ACETYLENE

• Stored in cylinder
• Completely filled with porous filler material
• diatomaceous earth
• charcoal
• asbestos (strengthener)
• cement (binder)
• Acetone used to solve the acetylene

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ACETYLENE

• Always keep cylinder in upright position
• Prevent loss of acetone and so reduce the
  cylinders ability to hold dissolved acetylene
• Handle with care
• Dropping can cause leakage
• Filler can break and cause voids where acetylene
  can accumulate and decompose
• Cylinders designed for temp up to 52C

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ACETYLENE

• Keep flammable gas cylinders from oxidizing gas
  cylinders
• Soap test regulator, torch, hose and cylinder
  connection before placing acetylene equipment in
  service
• Move leaking cylinders to open area
• In most cases, it is best to allow a burning
  acetylene cylinder to burn itself out
• Keep valves closed when not in use

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OXYGEN

• Fire and explosion data
• NA
• Oxygen is nonflammable, but supports and
  vigorously accelerates combustion of flammables.
  Some materials non combustible in air, will burn
  in the presence of oxygen
• Materials that burn in air, will burn violently
  in atmosphere richer than approx 25 Oxygen

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OXYGEN

• Health hazard data
• NA
• Non toxic under normal conditions, necessary to
  support life
• Liquid oxygen or cold gas will freeze tissues and
  can cause severe cold burns
• Oxygen at higher concentrations can produce cough
  and chest pain
• 100 within 8 to 24 h
• 60 within several days
• Much quicker under high pressure, also other
  nervous system malfunctions

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WELDING HEALTH PROBLEMS

• Gases and fumes
• Inhaling toxic gases from base material, filler
  material, coatings, paints, shielding gases,
  chemical reactions, contaminants in the air.
  Effects are different for each gas. Short and
  long term reactions from fever to cancer
• Heat
• Can cause burns, eye injuries, heat stress or
  heat stroke

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WELDING HEALTH PROBLEMS

• Radiation
• UV radiation Burns can occur without prior
  warning. Arc-eye. UV reacts with O and N to
  form ozone and nitrogen oxides. These are toxic
  and can cause lung diseases
• IR radiation May heat the skin and the tissues
  below the surface.
• Visible light Can cause adaptation and shading
  of the eye, to protect the retina.
• Noise
• Musculoskeletal injuries

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UNSAFE PRACTICES

• No competent fire watch
• Combustible materials, vapors not moved
• Hot work near heavy concentration of dust or
  combustible vapors
• Proper type of fire extinguisher not at the scene
• Oxygen and gas cylinder not in upright position
• Oxygen and gas hoses with mechanical damage
• No shutoff valves
• Hoses not removed after work

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REDUCING RISKS

• Identify hazards (type welding, materials used,
  environment)
• Use safety data sheets
• Eliminate or substitute hazardous materials
• Make sure workspace is proper ventilated
• Use Shielding
• Follow safe working practices

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REDUCING RISKS

• Monitor the air
• Welding only for proper trained personnel
• Complete the hot work permit and stick to its
  requirements
• Wear personal protective equipment
• Helmet, goggles, clothing
• Always used along with, but never instead of
  engineering controls and safe working practices.

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PPE
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HOT WORK PERMIT

• The hot work permit system is intended to educate
  the parties involved in construction of the
  hazards and to implement control measurements to
  help mitigate them.

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HOT WORK PERMIT
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HOT WORK PERMIT
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HOT WORK PERMIT
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HOT WORK
The first question you should always ask
yourself CAN THE JOB BE AVOIDED? IS THERE A
SAFER WAY?
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EXAMPLE HOT WORK ON CARGO CONTAINMENT SYSTEMS OF
GAS CARRIERS

• In repair yards cargo- and ballast tanks, pipes,
  void spaces are safe in terms of concentrations
  of O2, flammable and toxic gases
• most tanks have some external thermal insulation
• mineral wool
• perlite
• balsa wood
• polystyrene
• polyurethane

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INSULATION

• mineral wool
• manufactured by melting volcanic rock and
  limestone and spinning the molten material into
  wool.
• thermal insulation
• passive fire protection
• chemical inert
• non combustible
• open cell structure thus capable of absorbing
  hydrocarbon liquids or vapours

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INSULATION

• perlite
• finely powered volcanic rock
• inert
• can absorb liquid
• used on refrigerated LPG tankers in 60, 70 and
  80, treated with silicone to stick

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INSULATION

• balsa wood
• open grain structure very good insulation
• used in early membrane systems
• in case of fire rapid spread because open
  structure
• can absorb several times its own weight of water
  and therefore also petroleaum liquids or vapours

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INSULATION

• polystyrene and polyurethane
• highly inflammable
• covered with protective aluminium foil
• when ignited, release large quantities of toxic,
  black smoke

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HOT WORK IN SHIPYARDS

• Gas carriers under construction
• Welding before insulation is fitted
• Insulation stored in safe place
• Beware for solvents in glues
• No self adhesive plastic protection. This will
  encourage spread of fire

insulation material without and with plastic
protection
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HOT WORK IN SHIPYARDS

• Gas carriers in service
• Fully pressurised ships
• Generally not larger than 2000m³
• These ships do not need extra insulation
• Easy to detect safe working conditions
• No hot work casualties recorded for these type of
  ships

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HOT WORK IN SHIPYARDS

• Gas carriers in service
• Semi pressurised vessels
• Generally u to 20 000m³ capacity
• Insulated with polyurethane foam, glued to the
  tank surface and covered with a galvanised steel
  or aluminium foil
• Extra attention required when hot work is carried
  out
• gas entered in insulation
• solvents in glue
• Fully refrigerated vessels
• Most common
• same insulation and precautions as above