Acetylene cylinder pressure

The tare weight (sometimes called stencil weight because it is cut into the cylinder metal) is the total weight of the cylinder and contents, but does not include a removable valve protection cap, if such is used. The saturation gas part of the tare weight is a calculated number which allows for the 11.4 g of acetylene required to saturate each 453.6 g of contained acetone at atmospheric pressure. The correct tare weight is an absolute necessity to the safe charging of acetylene cylinders. 

Figure 9.1 Acetylene (in acetone) full cylinder pressure versus temperature...

Figure 8.1 illustrates the rise in cylinder pressure with temperature. Normally, acetylene cylinders are fitted with a fusible metal plug which melts at about 100°C. 

This procedure is a good excercise in planning insufficient planning may give rise to undesired delay during the various operations, which may be a major cause of decreased yields. To give only one example one should control the pressure of the acetylene cylinder in advance. At least 100 liters of this gas are needed, and if the manometer on a 10 or 20-1 cylinder indicates a pressure of only a few atmospheres, one is likely to be confronted with the extremely unpleasant fact that the acetone in the cylinder wants to keep the acetylene for itself (If you are lucky, there is another acetylene cylinder in the lab )... 

Atomic absorption spectrometer with air-acetylene burner head. Pressurized acetylene cylinder. Air compressor. 

Turn on the main valve on the acetylene cylinder and ensure that the cylinder and outlet pressures and flow rate are correct. If the cylinder pressure is below the recommended value do not attempt to ignite the flame, as this will result in acetone being ignited in the flame. (Acetylene when stored under pressure is dissolved in acetone.)... 

One problem with the use of acetylene is its stability. Although it is stable at normal pressures and temperatures, if it is subjected to pressures as low as 15pounds per square inch gauge (psig) it can explode. To minimize the stability problem, acetylene transport is minimized. Acetylene contained in pressurized cylinders for welding and cutting is dissolved in acetone. A typical acetylene cylinder contains a porous filler made from a combination of materials such as wood chips, diatomaceous earth, charcoal, asbestos, and Portland cement. Synthetic fillers are also available. Acetone is placed in the cylinder and fills the voids in the porous material. Acetylene can then be pressurized in the cylinders up to approximately 250 pounds per square inch (psi) In a pressurized cylinder, 1 titer of filler can hold a couple of hundred titers of acetylene, which stabilizes it. Acetylene cylinders should not be stored on their sides because this could cause the acetone to distribute unequally and create acetylene pockets. 

Acetylene may spontaneously explode if its pressure exceeds 15psig. Commercial acetylene cylinders are filled with a porous material soaked in acetone which maintains a safe acetylene pressure by dissolving the gas. Acetylene should never be passed through a vacuum pump, which will compress the gas. 

Acetylene [74-86-2]y C2H2, is an extremely reactive hydrocarbon, principally used as a chemical intermediate (see Hydrocarbons, acetylene). Because of its thermodynamic instability, it cannot easily or economically be transported for long distances. To avoid large free volumes or high pressures, acetylene cylinders contain a porous solid packing and an organic solvent. Acetylene pipelines are severely restricted in size and must be used at relatively low pressures. Hence, for large-scale operations, the acetylene consumer must be near the place of acetylene manufacture. 

Never run acetylene cylinder after the pressure has dropped to 50 p.s.i, at lower pressures the gas will be contaminated with acetone. 

Cylinders used to store acetylene are made up of steel, containing a porous material and acetone. Acetone dissolves 25 volumes of acetylene at 1 atm and 300 volumes at 12 atm. Porous materials such as asbestos are used as a filler inside the cyhnder. Acetone is absorbed into it then the gas is filled (Meyer 1989). The cylinder pressure should not exceed 250 psi at 21 °C (70°F). The distribution or transportation through hose, pipe, or supply line should be at a pressure below 15 psi. Cylinders are stored upright. 

CGA G-1, 5.2.1 4.2.3.2 When acetylene cylinders are moved, they should not be subjected to abnormal mechanical shocks that might damage the cylinders, the valves, or the fusible pressure relief devices. Care shall be exercised to ensure that acetylene cylinders are not dropped or permitted to strike each other violently. 

CGA G-1, 5.2.5 4.2.3.S Unless acetylene cylinders are to be moved while secured in an upright position to a suitable hand truck, pressure regulators should be removed and valve protection caps, if provided for in the cylinder design, should be attached. 

Acetylene cylinders must be stored and used iu a vertical, valve-eud-up positiou only. Under no conditions should acetyleue be geuerated, piped (except iu approved cylinder manifolds), or utilized at a pressure in excess of 15 psi (103 kPa gauge pressure) or 30 psi (206 kPa absolute). The use of liquid acetylene is prohibited. The in-plant transfer, handling, and storage of acetylene in cylinders must be in accordance with the Compressed Gas Association in pamphlet C-1.3-1959. 

Prior to April 16, 1981, pressure relief devices required approval by the Bureau of Explosives of the Association of American Railroads. Subsequent to April 16, 1981, the U.S. Department of Transportation promulgated new regulations amending 49 CFR 173.34 to eliminate the need for pressure relief device approval by the Bureau of Explosives. It is now the responsibility of the individual manufacturer or shipper to conduct flow and/or fire tests on new pressure relief device combinations to show compliance with CGA S-1.1, Pressure Relief Device Standards-Part 1-Cylinders for Compressed Gases [4] CGA C-12, Qualification Procedure for Acetylene Cylinder Design [5] and CGA C-14, Procedures for Fire Testing of DOT Cylinder Safety Relief Device Systems [6], as applicable, and to retain test records of this compliance. 

F. The number and location of pressure relief devices for cylinders of any particular size shall be proved adequate as a result of the fire test. Any change in style of cylinder, a filler, or quantity of devices can only be approved if found adequate upon reapplication of the fire test. The fire test shall be conducted in accordance with CGA C-12, Qualification Procedure for Acetylene Cylinder Design [5]. 

This discussion may not cover all conditions, sizes, types of defects, or methods of inspection. More complete and specific coverage of the subject is found in CGA C-6, Standards for Visual Inspection of Steel Compressed Gas Cylinders, and 49 CFR 173.34 and 173.301 [10, 1]. For cylinders made from materials other than steel, see CGA C-6.1, Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders , CGA C-6.2, Guidelines for Visual Inspection and Requalification of Fiber Reinforced High Pressure Cylinders , CGA C-6.3, Guidelines for Visual Inspection and Requalification of Low Pressure Aluminum Compressed Gas Cylinders , CGA C-8, Standardfor Requalification of DOT-3HT, CTC-3H, and TC-3HTM Seamless Steel Cylinders , and CGA C-13, Guidelines for Periodic Visual Inspection and Requalification of Acetylene Cylinders [W, 12, 13, 14, 15]. 

Inspection of the cylinder bottom of low pressure and acetylene cylinders is important since this area is especially vulnerable to corrosion. 

Never tamper with pressure relief devices in valves or cylinders. Keep sparks and flames away from acetylene cylinders and under no circumstances allow a torch flame to come in contact with the fusible metal pressure relief devices, which melt at approximately 212°F (100°C). Should the valve outlet of an acetylene cylinder become clogged by ice, thaw with warm, but not boiling water. 

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