Compressed gas tanks

For mechanical explosions a reaction does not occur and the energy is obtained from the energy content of the contained substance. If this energy is released rapidly, an explosion may result. Examples of this type of explosion are the sudden failure of a tire full of compressed air and the sudden catastrophic rupture of a compressed gas tank. 

Figure 14.3 shows a typical capillary gas chromatograph with the major components labeled. This gas chromatograph set up includes compressed gas tanks for the carrier gas (mobile phase) and any necessary detector gases, an auto-injector that employs a micro-syringe for delivering the necessary small sample volumes and an inlet capable of the... 

Carbon fiber introduction into commercial markets happened in the mid-1960s and since then their application has increased substantially. Some of these applications include airplanes, spacecraft parts, compressed gas tanks, automotive parts, bridges, reinforced concrete, structural reinforcement, recreational sports equipment, and electrochemical systems [6,7]. 

Nitric oxide at about 50 ppm compressed with very pure nitrogen in gas (flinders is provided for this purpose, and the true concentration is established by comparison with that of a compressed-gas tank that can be obtained from the National Bureau of Standards, as a standard reference material. The nitric oxide meter is calibrated repeatedly at several concentrations of nitric oxide, and the mass flow meters are recalibrated often with absolute bubble meters. 

To control the rate of flow and releasing pressure, gases are released from compressed gas cylinders by regulators (see Sec. 5.2) at a user-defined pressure. A regulator can display the amount of gas remaining in a compressed gas tank (in cubic feet of gas), but not in a liquefied gas tank. 

Compressing a gas allows a lot of gas to exist in a small amount of area for transportation, storage, and use. It is physically easier to deal with a compressed, gas tank that is 9 in. in diameter and 51 in. tall than to store the approximately several hundred cubic feet of gas contained within. 

Table 5.1 Agencies involved in Standardization of Compressed Gas Tanks...

A series of letters and numbers are stamped on the shoulders of compressed gas tanks (see Fig. 5.2) to provide coded information for tank inspectors. These numbers tell under what codes the tank was made, the manufacturer, service pressure, serial number of the tank, and when it was last inspected and by whom. The manner in which the codes are laid out varies, and it may be difficult for an untrained person to interpret. However, to the compressed gas industry, they are important for preventing mistakes from the misuse of the containers. 

Sections of a compressed gas tank are designed to provide safety for potentially abusive conditions. The most common structural protection is the tank cap, which is placed over the valve, then screwed onto the threaded neck of the compressed gas tank (see Fig. 5.2). In addition, you can obtain separate foot-rings that help a cylinder stand up, along with protective girdles for around the valve area. 

There are various color codes that are used with compressed gas tanks, but only the color codes of the medical gas industry are consistent. Note however, that the identifying colors from the United States and Canada are not consistent with each other (see Table 5.4). 

Compressed gas tanks of large industries (or of particular gas distributors) are often color-coded by their own specifications for easy ownership identification and/or gas type recognition. You should never trust the color markings of compressed gas tanks for identification unless the tank is used in medicine. The medical industries of both the United States and Canada have established color codes for medicinal gas tanks, but unfortunately they do not agree with each other (see Table 5.4). Otherwise, always depend on formal markings or labels for gas identification. If there is any question as to the contents of any compressed gas tank, do not use it instead, return the tank to your gas distributor for identification and/or replacement. 

Always Secure Compressed Gas Tanks. A compressed gas tank should never be allowed to stand free. Instead, it should be supported by an approved tank support and the screws should be tightened by a wrench, not just by hand. If lying horizontal, the compressed gas tank should be prevented from rolling. 

Just about everyone has heard stories of compressed gas tanks being knocked over, thus snapping off the main valve, turning the compressed gas tank into a rocket. The Compressed Gas Association claims that this orifice is too small for the tank to become a projectile. However, if the tank contains a flammable gas, the question of whether the tank will turn into a rocket is of secondary importance. 

Keep Electric Lines Free from Compressed Gas Tanks. Compressed gas tanks are made of metal. Keeping electric lines away from compressed gas tanks helps to prevent spark development and potential shock to the user. 

If you should come upon someone who is frozen by electric shock to an electrified compressed gas tank, do not handle the person with your bare hands. First, if possible, quickly ascertain the source of the electricity and if it is safe and easy to stop the current, do so. Otherwise, be sure you are not standing on, or in, water, and use something that is nonconducting (e.g., a broom handle) to pull the victim from the electrified tank. Call for medical attention immediately. 

Keep Compressed Gas Tanks Away from High Heat. Compressed gas cylinders should not be subjected to atmospheric temperatures above 130°F. A compressed gas cylinder should never be subjected to a direct flame. If defrosting an iced or frozen tank, water above 130°F should not be used. If compressed gas tanks need to be left outside, they should be kept in a shaded environment. 

Compressed Gas Tanks Should be Properly Moved. Compressed gas tanks should never be dragged, slid, or allowed to bang against one another. One should use a proper hand-truck or other suitable device for transporting the specific type of compressed gas tank. Compressed gas tanks should never be lifted by their caps, by magnets, or by ropes, chains, or slings unless the manufacturer has provided attachments (such as lugs) on the tanks. 

Compressed Gas Tanks Should Be Properly Stored. When a variety of different gases are to be stored together, they should be separated by type. For example, combustible gases should never be stored directly next to sources of oxygen. They should also be separated as to whether they are full or empty. After a tank has... 

When you empty a tank, other people s confusion and frustration can be prevented if you detach the regulator and identify the tank as empty before you call your gas people requesting a fresh tank. Likewise, if you need to remove the regulator on a partially emptied compressed gas tank, replace the protective cap+ and label the tank to indicate it is not a full tank, noting the remaining partial pressure. 

A compressed gas tank, when filled, may contain up to 2500 lb/in.2 of pressure. These tremendous pressures cannot be throttled by the main tank valve to pressures that are usable in the laboratory. All the main tank valve can do is release or prevent the release of gas, not control the pressure with which a gas is released. A regulator is required to reduce the gas pressure in a controlled, stable, consistent, and reliable manner. 

If you have pressurized air in your lab, you can use a motorless hot air gun. These units are smaller than standard hot air guns and are typically about the size of small home hair dryers. Motoiiess hot air guns only require heating filaments because they do not have fans. To use one, a flexible tube is attached to an air supply and the hot air gun. If your lab does not have plumbed-in compressed air, or the location of your outlet is too far away from where you want to use the hot air gun, another option is to use a compressed gas tank of air. Do not use compressed oxygen or any flammable gas for the air supply. You could use an inert gas, such as nitrogen for your air supply, but it would be costly. 

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