By Safety Management Group
It was only a small propane tank, similar to those used on construction sites and in industrial locations. The propane was supposed to be supplying a small heater, but much of it was actually escaping through a leaky valve. The gas ignited, and the resulting explosion killed 74 spectators attending a holiday ice skating show, and injured another 400. The 1963 incident at the Indiana State Fair Coliseum was one of the worst disasters in the state’s history.
Disasters like that may be rare, but they provide a stark reminder of the potential danger lurking within the compressed gas cylinders you’ll find at many job sites. Yet those cylinders are so common that many workers take them for granted.
Three aspects of cylinders pose problems. First, their weight means that can cause damage or injury if they fall over or are allowed to roll. Second, their contents may be explosive, flammable, corrosive, or may pose any number of hazards to nearby workers. Finally, the fact that they are pressurized means that they can become projectiles if a valve breaks off– and a regulator that becomes detached can also fly through the worksite at dangerously high speed.
The best way to protect workers from the hazards associated with compressed gas cylinders is to follow the five basic safety practices outlined here.
1. Store cylinders properly. The safe way to store cylinders depends on the type of cylinder, its contents, and the nature of the site. For example, OSHA rules provide different guidance for storage on construction sites and industrial settings.
Keep cylinders out of the sun, away from sources of flame or sparks, and out of areas in which temperatures may exceed 125oF. Separate them by the types of hazards their contents pose. For example, don’t store any types of oxidizers within 20 feet of flammable gases, unless the cylinders are separated by a firewall.
While most types of cylinders can be stored safely on their sides, acetylene cylinders are unique and must be kept vertical. Acetylene is inherently unstable, so it is usually dissolved into acetone and stored in a cylinder that has been filled with a porous material such as diatomaceous earth or crushed firebrick (which helps to keep it stable). If the cylinder is left on its side, the liquid acetone could leak through the valve, creating a fire hazard and reducing the quality of the gas. In addition, you should never use copper fittings or tubing with acetylene tanks.
2. Keep cylinders secured. A cylinder that falls over can easily crush a foot, damage machinery, or cause a variety of other problems. A cylinder rolling through a jobsite can be terrifying. That’s why it’s important to properly secure cylinders, whether that’s with straps, guards, or chains. Never remove the cap from a cylinder until it has been secured.
On some jobsites, “dog bones” may be used to secure cylinders to one another when other means of securing them are unavailable. While this approach can work, be careful that the number of cylinders that are being secured this way doesn’t exceed the capacity of the “dog bone” or other devices being used, and ensure that the cylinders cannot fall over.
3. Inspect cylinders before moving or using. The workers who use the cylinders are the first line of defense against problems. Paying close attention to the condition of the cylinders and valves minimizes the chances that an accident will occur.
Start by checking the cylinder for any obvious damage. If a cylinder doesn’t have a legible description of the contents, do not use it. Some workers simply verify that the cylinder is the correct color, but the use of color varies by manufacturer, so that’s not a safe method.
Make sure the cylinder is equipped with the correct regulator, and inspect the regulator and cylinder valves to verify that they haven’t been compromised with solvent, dirt, or lubricants such as grease or oil.
When you need to move a cylinder, always use a cart or basket, because dragging or rolling them can create damage. In addition, be sure that the protective cap is in place before you move the cylinder, and never move a cylinder that still has a regulator attached.
4. Open them carefully. Take your time when opening valves, because opening then too quickly can cause high-pressure gas to damage the regulator and valve seats. Start by relieving the regulator’s spring force by easing off the pressure adjustment screw before you open the valve, and make sure the outlet is pointing away from you. Be sure to use the correct tools. Using a pair of pliers can damage the valve and create a dangerous situation. Leaving the valve key or other tool in place will make it easier to close the valve quickly in the event of an emergency.
If the valve appears to be damaged, do not open it. In addition, don’t use lubrication to try to loosen stuck valves or components. Notify your gas supplier so they can inspect it and perform any necessary repairs.
When using cylinders with flammable gases such as acetylene, do not open the valve more than three-quarters of a turn to minimize the risk of an explosion, and to ensure that you can close the valve quickly if needed. Also, if you’re working with gases that may be toxic or cause irritation, do not open the valve unless you’re under a fume hood or protected by a similar ventilation device.
5. Follow procedures for empty cylinders. Always leave some residual pressure in the cylinder, rather than emptying it all the way. Be sure to close the valve completely, so that moisture or other contaminants cannot get into the tank. Replace the protective cap, label the cylinder as empty, and store it away from filled cylinders
