Welding is a way of joining two metals together. This is done by fusing them together. This requires a high temperature locally. Sometimes additional welding material is added.
We distinguish two ways of welding: electric and oxy-fuel.
In electric welding, an electric arc is used, which makes the material locally very hot. In fact, electric welding is nothing but a controlled short circuit.
In oxy-fuel welding, the heat comes from a glass flame, which is amplified by additional oxygen. The flammable gases are:
- Acetylene;
- Propane;
- Mixed gases.
The risks that occur in both electric and oxy-fuel welding are:
- Fire and explosion hazards;
- Exposure to noxious fumes;
- Harmful noise (noise);
- Harmful radiation;
- Excessive heat.
Fire- and explosion hazard
There may be a risk of fire and explosion due to the unnoticed discharge of gases and/or oxygen. This leakage can occur due to hose leaks, burners that are not closed properly or defective valves. In that case, the so-called hose rupture protection must be applied. This automatically stops the gas and/or oxygen supply in the event of a major leak.
There is a risk of explosion in particular when oxy-fuel welding is carried out on closed or almost closed vessels. When the vessel heats up, the gases present in the vessel may ignite.
Exposure to harmful fumes
Oxy-fuel welding (and cutting) can produce harmful gases and mists. These pose a health hazard. Think, for example, of welding in confined spaces or when there is little ventilation. Danger can arise from:
- Combustion products;
- The gases that may be generated from the surrounding air at a high temperature of the welding flame;
- The substances released from the processed material.
The burning of acetylene or propane by the burner will not only involve the oxygen from the oxygen cylinder, but also from the surrounding air. If the combustion is not complete, the highly toxic carbon monooxide (CO) will be created. In an area that is not well ventilated, the oxygen content of the air is also reduced by the oxygen consumption of the welding flame. So always make sure there is sufficient ventilation! Also, due to the high temperature of the welding flame (approximately 3000 oC), nitrogen oxides are formed from the nitrogen and oxygen of the air. These are called 'nitrous fumes'. These fumes are highly toxic even in low concentrations and can cause disease (pulmonary edema).
Harmful noise
Depending on the process, the type of voltage and the environment of the welder, harmful noise may occur. Harmful noise is defined as a sound pressure level exceeding 80 dB(A).
If the noise level of the welding process itself is sufficiently low, there is always exposure to noise caused by the removal of slag or the grinding of the welds.
Harmful radiation
During electric welding, bright, visible light rays as well as ultraviolet and infrared rays are emitted. The visible radiation causes glare, resulting in eye fatigue. The ultraviolet (UV) radiation can inflame the cornea (the well-known welding eyes), while also causing skin burn. The infrared radiation (IR) causes damage to the eye when it has a prolonged effect due to drying of the tear fluid. Clouding of the lens of the eye can also occur.
Excessive heat
Due to heat radiation from an object on which work is being carried out, it is possible that an employee becomes a victim of the so-called campfire effect. This means that it gets a lot of heat radiation at the front and nothing at the back. This can lead to health problems, especially if it occurs frequently.
Some safety precautions in relation to Fire and explosion hazards are:
- Strictly follow the measures indicated by the work permit;
- Flammable substances and goods must be removed or adequately shielded (parting, gas-free, covering);
- A suitable fire extinguisher (extinguishing powder or CO2) must always be available for welding;
- If necessary, keep a fire watch;
- Make sure that there are no materials (wood, paper, plastic, etc.) under the welding area that could catch fire.
Some safety precautions related to exposure to welding fumes include:
- Depending on the coating of the welding electrode used, measures must be taken to remove the welding fumes and other harmful gases and vapours.
- Proper ventilation or extraction must be applied.
- If proper ventilation or extraction is not possible, a fresh air cap or a special filter mask should be used.
- First, remove the protective layer from the welding surface.
- Check the protective layer for the presence of Chromium VI, or assume that it contains Chromium VI and take appropriate measures to prevent Chromium VI exposure.
- Oil, grease and other must also be removed
A safety measure to be taken in relation to exposure to high noise levels is:
- Always use hearing protection.
- Use a good welding hood or welding helmet with a welding window, tailored to the welding process to be performed.
- Use well-fitting, suitable work clothing.
- Do not weld with uncovered body parts, no matter how hot it is. This is due to ultraviolet radiation.
- For the welding helper, it is recommended to wear at least welding goggles.
A safety measure to be taken in relation to excessive heat:
- Wear protective clothing in accordance with the length of time you have to weld.
- Wear heat-resistant gloves.
- Make sure there are plenty of breaks or variety with other activities.
- Drink regularly and sufficiently to prevent dehydration
Talk to each other about the following:
- Do we recognize the risks mentioned above?
- Do we always take the measures as described?
- Do we have the necessary PPE?
- Always ensure adequate ventilation and preferably use local extraction, especially in small spaces.
- If sufficient air exchange is not feasible, each welder must use a fresh air cap or a half-mask with a fresh air hose, the air of which has been filtered through a special installation and supplied at the correct pressure.
- The nitrous (nitrogen-containing) gases released during hot firing, welding or cutting can cause symptoms of pulmonary edema.
- Leaking taps (especially oxygen) pose a serious fire hazard.
- Greasy clothes that come into contact with oxygen burn like a torch. Against this danger and the spread of a lot of oxygen in the event of a hose breakage, outflow limiters are used.
- Also pay attention to the correct installation of the pressure reducing valve. To do this, use a gasket ring made of acetone-resistant rubber near the gas cylinder and make sure that all connections are free of grease.
- The valve must be suitable for the gas pressure stamped on the bottle. A flame extinguisher must be installed directly behind the pressure reducing valve of the gas cylinders. In spite of these provisions, make sure that no oil or grease (including a greasy rag) comes into contact with the oxygen bottle.
- The key that allows the valve on the bottle to be turned off (in case of fire or in the event of longer work stoppages) must be located on the shut-off spindle of the bottle in use.
- Never use a burner to "tap something".
- Gas and oxygen cylinders must be tied in a vertical position (+ 1 meter apart), or on a welding cart against each other, but always with a sheet steel bulkhead between the heads of the bottles.
- If this is not possible, use them lying down, but at an angle of at least 30o and with the pressure reducing valves up, so that the liquid from the bottle cannot affect the hose and not too much acetone is extracted from the acetylene bottle.
- Always use hoses of good quality and equipped with approved hose clamps.
- Special regulations always apply to welding in areas at risk of fire or in areas where aggressive chemicals are used.
- The welder must have a written work permit before work can begin. Always check that the safety measures indicated on the permit have indeed been taken. After all, it's all about your safety.
- Drums, tanks and pipes must be protected against the risk of explosion before welding or cutting can take place.
- Pay attention to the additional risk of fire caused by the foam material that is widely used today. This is not only used for insulation, but also as packaging material.
- Make sure a portable fire extinguisher is nearby.
- Use a good pair of welding goggles!
Scan de volgende code met de app om deze toolbox te bekijken.