Cylinders acetylene

Acetylene cylinders are fitted with safety devices to release the acetylene ia the event of fire. Cylinders manufactured ia the United States are equipped with safety devices which contain a fusible metal that melts at 100°C. In large cylinders the safety devices are ia the form of a replaceable, threaded steel plug with a core of fusible metal. Small cylinders (0.28 and 1.12 m 10 and 40 fT, respectively) may have the fusible metal ia passages ia the cylinder valve. 

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. 

A proprietary sintered metal arrester was made by the Linde Division of Union Carbide Corporation (now Praxair) for rise in processes handling acetylene, but is no longer made by Praxair (Dickerman 1999). A sintered metal flashback flame arrester for rise on an acetylene cylinder is made by Western Enterprises of Westlake, OH. Figure 5-4c shows a sintered metal flame-arresting element. 

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. 

Fig. 12. Apparatus for the preparation of 1,2-dicarbaclovodo-decarborane 12) (B10C2H12). (A) acetylene cylinder (B) nitrogen...

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. 

If cylinders are to be brought into the laboratory, they should only be transported on purpose-built trolleys, to which they can be securely chained during transport. Acetylene cylinders must be kept more or less vertical, for reasons discussed in Chapter 2, section 5. The total number of cylinders in the laboratory at any one time must be kept to the minimum possible, especially for fuels and oxidants, and in routine use all cylinders must be securely chained or strapped to a bench or wall. They should be positioned for easy access and so that they will not block a rapid exit. It is perfectly feasible to run two flame spectrometers from a single acetylene cylinder, via a T junction, although individual flash-back arrestors should be fitted in the lines to both instruments. If an acetylene cylinder is used inside the laboratory, it is especially important to check for gas leaks whenever the cylinder head is changed. Don t rely on the smell of escaping gas, which will only detect fairly major leaks. Use of a paint brush and a soap solution is more reliable, as bubbles will be clearly seen if gas is escaping. 

A strongly reducing fuel-rich nitrous oxide—acetylene flame is superior to other flames for sensitivity and freedom from interferences. Optimisation of burner height is important as absorption signal is fairly dependent on observation height. In aqueous systems interference from calcium has been controlled by the addition of aluminium or Na2S04. Reduced sensitivity has been reported in the presence of acetone vapour from depleted acetylene cylinders. 

The acetylene cylinder must be chained securely to the wall or laboratory bench. Work on a vacuum system requires a preliminary review of procedures and careful execution in order to avoid damage to the apparatus and possible injury from broken glass in addition, the liquid nitrogen used for cold traps must be handled properly (see Appendix C). Safety glasses must be worn. Acetylene is flammable no flames can be permitted in the synthesis area. Take great care not to allow oxygen condensation to occur in the presence of acetylene (potentially explosive). Carry out as many operations as possible in a fume hood. Dispose properly of excess CaC2. 

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. 

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