Many metal fabrication shops and welders perform repair or modification work on old equipment, both in a shop setting and in the field. Performing repair work on hollow structures can pose a significant hazard other than a large internal pressure buildup from heating which we discussed in the last welding safety article.
As an easy introduction, consider the need to perform cutting or welding on a tank that used to contain a flammable solvent. Empty of liquid means it is safe, right? Not necessarily. It is the vapors that burn, not the liquid. An “empty” hollow structure such as a tank could be the worst case scenario, full of flammable vapors. Given the right ratio of vapor to oxygen, that hollow structure is like a bomb, ready to explode as soon as enough energy is transferred from the hotwork process.
Serious issues affecting your health – and why TIG welding is the answer.
Hazards during welding can be quite obvious like the electric arc, molten metal, radiant heat, and the incredibly bright light from the arc. Other hazards such as metals in the weld fume plume or gases produced during the welding process are not always as obvious. Fortunately, TIG welding is one of the best processes for minimizing hazards to those often unidentified hazards.
We’re all familiar with what happens to ice when we warm it up, it melts. If we continue to warm the water until it boils it starts to quickly evaporate. Similar to water turning to steam, some of the molten metal during the welding process evaporates into the air. This metal then quickly solidifies into a very small particulate, or fume, as it cools. This is what we see rising from most weld processes.
When we’re performing Hardfacing tasks, a specific metal of concern to our health is chromium.
Eye injuries are one of the most common types of injuries to welders and they are also easy to prevent. Flying debris, intense light, and irritation from chemicals or fumes are all hazards to a welder’s eyes. It is important to remember that these hazards are also present for all who are near the welding operation, not just the welder.
The extremely bright light from arc welding can cause flash burn, similar to sunburn to the eyes. Use of a weld hood with the proper lens shade is essential. For new welders who are not sure which lens shade to use there are good resources available. Take a look at ANSI Z49.1 standard, Safety in Welding, Cutting, and Allied Processes which contains recommendations on which shade to use based on specific characteristics of the welding or cutting process.
We’ve heard about the health effects of hexavalent chromium from welding on stainless steel. Many of us have even felt the effects of overexposure to zinc oxide fumes from welding galvanized steel, commonly called metal fume fever. But what is the best way to prevent these health effects? Respiratory protection is often the first thought. However, engineering controls, such as adequate ventilation, can prevent the need to wear yet another piece of protective gear while welding.
Let’s take a step back and look at common types of ventilation used in the workplace. Dilution ventilation is the use of clean air to decrease the concentration of a contaminant of concern. This is commonly achieved by using a ventilation system to supply fresh air into a space. Dilution ventilation can work well for operations where the contaminant of concern has a relatively low toxicity level and is released over a large area. The use of large roof fans in a warehouse to dilute carbon monoxide released from a forklift is a good example.
Pittsburgh, PA. October 8, 2012 - Most of us are familiar with the concept that if a gas is heated it expands. This is described by Charles Law. If you inflate a balloon at room temperature and then place it in a freezer it decreases in volume. The balloon then returns to its original volume if warmed to room temperature again.
But, what happens when the gas is heated inside a rigid container such as a hollow metal structure which can’t expand? As the temperature in the hollow space increases the pressure increases. This is one of the reasons we have to be careful when doing hotwork, such as welding, on hollow structures.
