By Safety Management Group
You’ll find a variety of pressurized containers all over construction sites and industrial settings. In fact, tanks for compressed gases are so common that it’s very easy to take them for granted and forget that they can be extremely dangerous in several ways.
One obvious hazard that comes to mind is the potential for pressurized containers that are full of flammable gases to explode. Besides the danger for fire, pressurized tanks and other containers can become projectiles in an explosion, causing damage and injury far from the actual site of ignition. Cylinders can fly with enough force to break through a concrete block wall. Another key hazard involves leaks in tanks, valves, and seals that allow the poisonous, noxious, corrosive, or flammable gases within the tanks to escape.
Because workers do often take pressurized containers for granted, they may handle them roughly or place them in areas and positions that are inherently unsafe. They may also miss signs of danger, such as cracks, broken regulators and valves, and other damage to the tanks and any piping associated with them.
Another issue related to flammability involves the flash points of flammable gases. If a gas that’s stored in a pressurized container has a flash point that’s below the ambient air temperature of the room or area in which it’s being used, any release of the gas could create an immediate fire or explosion hazard.
If the volume of gas released in an area is large enough to displace the oxygen that’s normally present, workers in the area face a danger of asphyxiation. That can happen even with “inert” gases such as nitrogen and helium. In addition, some gases may also react to other gases in the air.
KNOW WHAT’S INSIDE
OSHA considers any storage tank or vessel that is expected to operate at pressures about 15 PSIG to be a pressure vessel. By law, compressed gas cylinders must include clear identification of the contents. Never make assumptions about the contents based upon the size, color, or other features of the container, or based upon the cap. If a worker is given an unmarked container, or it the labeling has someone fallen off or been obscured, the worker should not use the container, and it should be marked and returned to its source.
Cylinders containing flammable gases must be stored away from potential ignition sources, such as open flames or equipment that generates sparks. (And never store acetylene gas cylinders on their sides.) Oxygen cylinders must be kept a safe distance from cylinders containing flammable gases, or separated by a firewall. Areas where tanks are stored should feature clear signage warning of dangers.
Piping for gases should also be clearly labeled as to the type of gas and the destination of the pipe. The labels should be color-coded, so that potential hazards such as flammability are immediately identifiable.
HANDLE THEM CAREFULLY
Because a fall can damage a pressurized container, release the contents, and injure someone in the immediate area, it’s important to secure containers to keep them from tipping over. If a non-tipping base or cage isn’t available, containers can be secured with straps or safety chains.
Make sure that you can always access the valve on cylinders, whether you’re currently using or storing them. If you’re not using a cylinder, shut the valve off. Make sure that you only adjust valves with the proper tools, and install regulators according to instructions.
Open valves slowly to ensure that that they are working properly, and make sure you point the valve opening away from workers when opening any cylinders containing a gas that’s toxic or a potential irritant.
If a worker notices that a tank appears to be leaking, action must be taken immediately. If the tank can be relocated safely, it should be moved to a safer area. The workers should also notify the supervisor or safety manager immediately. While it may be tempting to try to make a minor repair, that can create a greater hazard.
Although cylinders may be heavy and well-constructed, they are still subject to damage when being moved. Make sure that covers are tightly attached, and move only one cylinder at a time using the correct type of cart and proper securing. Never drag cylinders across the floor or roll them on their sides or edges.
REGULATORS, CONNECTIONS AND PIPING
Because it can be dangerous for incomputable gases to mix, the compressed gas industry has created different types of value connections for each type of gas. In addition to variations in sizes, threading differs from one type to the next. To ensure safe operation of the pressurized containers and ensure that incompatible gases don’t mix, always use the specific connections for the particular gas you are using.
The same holds true for regulators and piping. For example, it’s not safe to run acetylene gas through copper piping, or to use cast iron in the presence of chlorine gas. Make sure that the correct materials are being used. After all connections have been made, open the valve slightly and check the connections with a soap solution to ensure that there aren’t any leaks. If piping will be used for a considerable length of time, or if the area in which the piping is run undergoes substantial temperature or humidity changes, check the connections periodically to ensure that expansion and contraction have not led to leaks.
In workplaces that require a very high volume of gases, bulk pressurized cylinders with multiple valves may be employed. When working with these, ensure that all of the valves are properly marked.
Finally, whenever workers connect and disconnect gas lines, regulators, and other components, they need to wear the correct personal protective equipment, such as a face shield.
WRAPPING UP THE JOB
Once the task has been completed, close the valve on the cylinder. Depending on the gas being used and the nature of the work, any gas remaining in the lines may need to be bled off. If the cylinder is empty, replace the valve cap, mark the cylinder empty, and move it to the place at which the gas vendor will pick it up for refilling. Never store empty cylinders in the same location as full ones, as that may create confusion.
If a cylinder may have become contaminated (even if you are not certain), label it to indicate the possible contamination so the supplier can check it