NGI-Welding & Cutting-Part 02

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ELECTRODES CONTENTS

Carbon (C)Magnesium (Mg)Silesia (Si)Chrome (Cr)Nobelium (Nb)Titanium (Ti)Cadmium (Ca)Lead (Pb)Iron (Fe)

Zinc (Z)Nickel (Ni)Niobium (No)

Phosphor (P)

Molybdenum (Mo)

Aluminum (Al)

Sulpher (S)

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WELDING POWDERS

• Magnesium Silicate• Magnesium Oxide• Calcium Silicate• Calcium Oxide• Zirconium Silicate

• Calcium Fluoride• Aluminum Oxide• Silicon Oxide• Zirconium Oxide

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FUME HAZARDS

• Toxic gases and fumes produced in welding operations, create serious hazards.

• Fumes can be produced mainly from welding of greasy materials.

• All such materials should be degreased and dried before welding.

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METHODS OF WELDING & FUMES

WELDING PROCESSHAZARDOUS COMPONENTS

Metal arc – mild steelFe, Fluoride

Metal arcCr, Ni

Tungsten Inert Gas (TIG)Weld gases

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The inhalation of fumes from the welding or cutting of ZINC galvanized metal may result in “ Metal Fume Fever “ which is characterized by:

A raised temperature, aching muscles , shivering and sweating.

The symptoms develop in a few hours after exposure to the fumes and persist for approximately 24 hours.

The welding of brass, bronze and manganese steel generates large quantities of Carbon Monoxide and Carbon Dioxide gases.

The arc welding of iron and steel produces large quantities of fumes consisting of very fine particles of Iron Oxide.

METAL FUME FEVER

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EXPOSURE LIMIT

In general, an upper exposure limit for welding fumes is 5 mg/m3.

However for certain elements e.g. Cadmium, which may be present in welding fumes, lower limits are set.

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WORKING IN CONFINED SPACES

• Working in confined spaces is more dangerous due to accumulation of fumes and toxic gases generated by operations being done inside e.g. welding, flame cutting, lead lining, rubber lining, brush and spray painting, molding GRP (fiber glass), use of adhesives, solvents and etc.

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ARTIFICIAL VENTILATION

- For the purpose of welding fume extraction, a ventilation system could be considered as adequate if providing a minimum of

- Use of electrically powered ventilation for confined spaces is forbidden due to presence of flammable gases.

100 air changes per hour

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- Welder in a confined space must be accompanied by a person who stays outside and can give assistance.

- Mechanical ventilation should be installed to send out all fumes.

- Do not under any circumstances compressed oxygen for ventilation. Explosion can occur.

WELDING IN CONFINED SPACES

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Before any work can be allowed to commence in anenclosed space, the following conditions must be met:

. L.E.L. - less than 1%

• Oxygen - more than 20%

• H2S - less than 1 ppm.

• Carbon Monoxide - less than 1 ppm

WELDING/CUTTING IN CONFINED SPACES

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PRE-OPERATION CHECKS

Check that all tanks, vessels and equipments on which welding, cutting, brazing or soldering work is to be carried out, are free from gases and vapors and sludge.

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- Fire blankets are to be used to prevent falling sparks on to neibouring areas and equipments like draining pits.

- The work must be suitably screened to prevent sparks and hot metal from flying outside the immediate work area.

PRE-OPERATION CHECKS

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WELDING SHELTER

1. must Be non-combustible2. must Allow through

ventilation3. must Have interior surface

which minimize the reflection of dangerous radiations.

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SAFE WORK PRACTICES

• Follow safe Housekeeping principles

• All wooden scraps, Oily rags, flammables should be remove prior to start the work.

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SAFE WORK PRACTICES

• Remove any butane lighters, matches, or other combustibles from pockets prior to performing work.

• Do not perform

welding with oily clothing.

SHOULD BE REMOVED