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

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 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