Oxy-Acetylene Welding and Cutting / Electric, Forge and Thermit Welding together with related methods and materials used in metal working and the oxygen process for removal of carbon

by Harold P. Manly

After calculating the withdrawal of the whole number of torches according to the work they are to do for this period of five hours the proper generator capacity may be found on the basis of one cubic foot of gas per hour for each pound of carbide. Thus if the torches were to use sixty cubic feet of gas per hour, five hours would call for three hundred cubic feet and a three hundred pound generator should be installed. Generators are rated according to their carbide capacity in pounds.

Charging.--The carbide capacity of the generator should be great enough to furnish a continuous supply of gas for the maximum operating time, basing the quantity of gas generated on four and one-half cubic feet from each pound of lump carbide and on four cubic feet from each pound of quarter, intermediate sizes being in proportion.

Generators are built in such a way that it is impossible for the acetylene to escape from the gas holding compartment during the recharging process. This is accomplished (1) by connecting the water inlet pipe opening with a shut off valve in such a way that the inlet cannot be uncovered or opened without first closing the shut off valve with the same movement of the operator; (2) by incorporating an automatic or hydraulic one-way valve so that this valve closes and acts as a check when the gas attempts to flow from the holder back to the generating chamber, or by any other means that will positively accomplish this result.

In generators having no separate gas holding chamber but carrying the supply in the same compartment in which it is generated, the gas contained under pressure is allowed to escape through vent pipes into the outside air before recharging with carbide. As in the former case, the parts are so interlocked that it is impossible to introduce carbide or water without first allowing the escape of the gas in the generator.

It is required by the insurance rules that the entire change of carbide while in the generator be held in such a way that it may be entirely removed without difficulty in case the necessity should arise.

Generators should be cleaned and recharged at regular stated intervals. This work should be done during daylight hours only and likewise all repairs should be made at such a time that artificial light is not needed. Where it is absolutely necessary to use artificial light it should be provided only by incandescent electric lamps enclosed in gas tight globes.

In charging generating chambers the old ash and all residue must first be cleaned out and the operator should be sure that no drain or other pipe has become clogged. The generator should then be filled with the required amount of water. In charging carbide feed machines be careful not to place less than a gallon of water in the water compartment for each pound of carbide to be used and the water must be brought to, but not above, the proper level as indicated by the mark or the maker's instructions. The generating chamber must be filled with the proper amount of water before any attempt is made to place the carbide in its holder. This rule must always be followed. It is also necessary that all automatic water seals and valves, as well as any other water tanks, be filled with clean water at this time.

Never recharge with carbide without first cleaning the generating chamber and completely refilling with clean water. Never test the generator or piping for leaks with any flame, and never apply flame to any open pipe or at any point other than the torch, and only to the torch after it has a welding or cutting nozzle attached. Never use a lighted match, lamp, candle, lantern, cigar or any open flame near a generator. Failure to observe these precautions is liable to endanger life and property.

Operation and Care of Generators.--The following instructions apply especially to the Davis Bournonville pressure generator, illustrated in Figure 11. The motor feed mechanism is illustrated in Figure 12.

Before filling the machine, the cover should be removed and the hopper taken out and examined to see that the feeding disc revolves freely; that no chains have been displaced or broken, and that the carbide displacer itself hangs barely free of the feeding disc when it is revolved. After replacing the cover, replace the bolts and tighten them equally, a little at a time all around the circumference of the cover--not screwing tight in one place only. Do not screw the cover down any more than is necessary to make a tight fit.