HOT WORK
Up to 25 percent of
fatalities in shipyards
result from fires and
explosions caused by
hot work.
(Bureau of Labor Statistics USA)
Helen Verstraelen
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
HOT
WORK
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 fire
insulation
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