(37) Infra-red (heat) and ultra-violet (light) rays present to a small extent in the neutral flame are injurious to the naked eye. Colored glasses or goggles are used to shield the eyes when working with this flame. Too dark a glass should not be used, as it will cause a strain upon the eyes more injurious than the flame. Exposed metal frames should be avoided too, as they hold the heat and burn the operator.
(Courtesy of the Chicago Eye Shield Co.)
Fig. 26.—A Spectacle Made for Welders, having a Frame of Fiber and Arranged so that Lenses may be Replaced.
(Courtesy of the Chicago Eye Shield Co.)
Fig. 27.—Showing Cover Glass which Protects the Colored Lens and the Replaceable Features of a Modern Goggle.
(38) To shut off the apparatus for several hours or so, it is best to relieve all pressure from the lines, such as hose and so forth, and to do this close both tank valves; open the torch valves; release the tension on the regulator, by screwing the “cross-bar” to the left, and finally, close the torch valves. It is quite necessary that these torch valves closed, for quite frequently, if a small tip is in the torch and an excess of oxygen pressure comes through the line, when both torch valves are open, much of the oxygen may back up the acetylene line and cause a serious flashback when lighting up. This can be avoided by keeping both torch valves closed when not in use.
(39) If a valve on an empty acetylene cylinder is left open the acetylene gas will escape, and mixing with the air, which is a supporter of combustion, a very inflammable mixture will be formed. If any fire is present, such as might be smouldering in a forge, possibly not used for several hours or so, or a match lighted, or a flame started in any way, an explosion is likely to occur. When an acetylene cylinder is exhausted, as far as possible, in a moderately high atmospheric temperature, then shut off for a while and the temperature drops, air will be drawn into the vacuum thus formed when the valve is again opened. In this manner an explosive mixture forms in an empty acetylene cylinder and is certainly to be avoided. Care should be taken, especially in winter, to guard against such occurrences, as in some outlying shops a decided change in temperature takes place between closing time and starting up time the following morning. Acetylene tanks should always be securely closed when empty, not only for the above reasons but insomuch that each contains acetone, which is likely to escape if the tank is thrown around. Acetone is very costly and used extensively in the manufacture of smokeless powder, so that at times it is hard to replenish.
(40) Oxygen has an affinity for oils and greases, and should not be allowed to come in contact with them, especially in confined places, as a spontaneous combustion may result. Oils and greases should never be used around oxy-acetylene welding apparatus and on nearly every apparatus on the market the words “Use no oil,” will be found. Despite this precaution, however, many times ignorant operators will be found squirting oil into the holes around the regulator cap, and through the gauges, in order, as they say, to allow them to work easier. This use of oil should be discouraged, and the sooner the better.