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HOT WORK
Helen Verstraelen
Up to 25 percent of fatalities in shipyards result from fires and explosions caused by
hot work.(Bureau of Labor Statistics USA)
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
ACETYLENE
ACETYLENE C2H2
Fire and explosion data: Flash point: -18°C Auto ign. Temp.: 305°C 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
ACETYLENE
Stored in cylinder Completely filled with porous filler
material diatomaceous earth charcoal asbestos (strengthener) cement (binder)
Acetone used to solve the acetylene
ACETYLENE
Always keep cylinder in upright position Prevent loss of acetone and so reduce
the cylinder’s 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 52°C
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
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
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
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
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
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
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
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.
PPE
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.
HOT WORK PERMIT
HOT WORK PERMIT
HOT WORK PERMIT
HOT WORK
The first question you should always ask yourself:
CAN THE JOB BE AVOIDED? IS THERE A SAFER WAY?
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
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
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
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
INSULATION
• polystyrene and polyurethane:• highly inflammable• covered with protective aluminium foil• when ignited, release large quantities of
toxic, black smoke
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 fireinsulation material without and with plastic protection
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
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