In addition to being rinsed, wiped dry, and properly stored, gas cylinders require additional maintenance, including: avoiding damage to the outside of the cylinder and its valve; preventing moisture from entering the cylinder; and regularly inspecting and testing the cylinder.
1 Correct Use of Gas Cylinders
Correct use of gas cylinders can avoid scratches or concave and convex holes on the surface of the gas cylinder, and can avoid damage to the gas cylinder valve. The damage to the outer surface of the gas cylinder will damage the original structural strength of the gas cylinder, and it cannot safely withstand the air pressure, especially the aluminum gas cylinder, and it is necessary to avoid the external damage of the gas cylinder. Before that, a stress test must be done.
Although modern gas cylinder valves are not prone to fall from the cylinder due to a collision, a slight collision can deform the brass cylinder valve, which can damage the expensive cylinder valve and make it impossible to use and repair , In order to avoid unnecessary collisions, divers must use the cylinders correctly to avoid the cylinders falling directly to the ground and causing collisions. When transporting gas cylinders, the gas cylinders must be correctly erected on the shelf or placed flat and fixed so that the gas cylinders will not shake from side to side.
2 Avoid Water Vapor Entering the Gas Cylinder
In a high-pressure gas cylinder, the concentration of oxygen is very high. At this time, the water vapor in the gas cylinder will become a catalyst for oxidation, which will cause damage to the contents of the gas cylinder, especially the water vapor containing salt will cause more damage to the gas cylinder. serious.
In environments with high oxygen levels, the rate of oxidation is faster than in the atmosphere; in the atmosphere, oxidation may take several weeks, whereas it may only take days or hours in a cylinder However, in a dry environment, even if the oxygen content is higher, oxidation is not easy to occur. Generally speaking, aluminum gas cylinders are not easily affected by water vapor and cause oxidation, but a layer of aluminum oxide will be formed on the inside of aluminum gas cylinders. When the aluminum oxide falls off, it may block the gas cylinder with air exhaust. valve or regulator, so it is important to keep the inside of the cylinder dry.
Ways to keep the inside of a gas cylinder dry
First of all, it must be confirmed that the compressor in which the gas cylinder is charged is equipped with a water removal system. In addition, it should be avoided that the air in the gas cylinder is completely used up, because when the air in the gas cylinder is completely used up, the water vapor will escape from the gas valve or regulator. Return to the cylinder.
Most gas cylinders are filled in a container with water, in which case water droplets will condense on the gas tube and the mouth of the cylinder, and if not handled carefully, moisture can easily enter its cylinder. Likewise, divers must avoid dripping water from the cylinder valve and regulator into the cylinder after diving.
The gas cylinder cannot be stored for a long time under the pressure of more than 100 pounds of internal pressure (or more than about 12 bar), because in this case, the concentration of oxygen will gradually decrease, and if it is used in the future, it will cause damage to the human body. s damage. It is best to store the gas cylinder in an upright manner. If there is water vapor, the water vapor will condense on the bottom of the gas cylinder.
3 Regular Inspection and Testing
In North America, gas cylinders must be visually inspected every year and pressure tested every 5 years, and each country has different regulations for these intervals.
Visual inspection is usually carried out by professionally trained personnel in retail stores. The inspection steps first remove the cylinder base and cylinder valve, and then inspect the outside of the cylinder for bruises or corrosion, and the inside of the cylinder. It is necessary to use a special lamp, which is inserted into the gas cylinder to illuminate, and then checked with the naked eye. Using a reflector can help inspectors to carefully inspect the inner part of the cylinder mouth.
Finally, check whether the cylinder valve operates smoothly and lubricate the threaded part of the cylinder valve. The cylinder valve must also be thoroughly inspected on a regular basis. After inspection, if the cylinder is not damaged or corroded, reassemble, inflate, and label the cylinder, and the inspector must handle it correctly; for aluminum with a little alumina inside the cylinder Gas cylinders can be rinsed with distilled water and dried with hot air. For steel gas cylinders with slight oxidation inside the gas cylinder, no treatment is required, because processing will reduce the strength of the steel gas cylinder. When the inside of the gas cylinder is seriously oxidized, it is necessary to remove the oxidized part by sandblasting or rolling grinding. The rolling grinding method is to put abrasive abrasive substances into the gas cylinder, and then roll the gas cylinder on the drum to remove the gas. Oxide removal, while sandblasting uses a gas containing abrasive substances that is sprayed directly into the cylinder to remove oxides.
Because both sandblasting and tumbling can thin the cylinder walls, both sandblasted or tumbling cylinders must be pressure tested before use. The pressure test is the so-called water pressure test. First, the cylinder is filled with water, and then the cylinder is placed in a high-pressure chamber filled with water. At this time, the pressure in the cylinder is increased to five times the maximum working pressure of the cylinder. Three out of three, the gas cylinder will expand slightly. Due to the expansion of the gas cylinder, the water in the high pressure chamber will be discharged. The discharged water is collected in the test tube and measured. If the amount of discharged water exceeds the allowable range , the cylinder can no longer be used.
The gas cylinder must be visually inspected once a year, and a pressure test must be done every 5 years. Divers should check the gas cylinder if there is abnormal noise inside the gas cylinder or if the filter of the regulator is red or green. If the cylinder is in the following conditions, a pressure test must be done:
1. When sandblasted or subjected to collision, which may affect the strength of the gas cylinder.
2. When the gas cylinder is inflated beyond its maximum working pressure.
3. When the cylinder is exposed to an environment exceeding 65°C.
4. When the cylinder has not been used for more than 2 years.
