Welding and cutting metal
Note - For more information on cranes and lifting equipment see also 'Wagon Loads and Materials Handling - Materials Handling' which has sections on cranes, lifting aids and 'unit loads'. Railway operated fork lift trucks and straddle carriers are covered in 'Railway Company Goods Facilities - Container handling' For more information on trucks and lorries see also 'Appendix One - Roads and road traffic - Road Vehicles - Commercial Vehicles' for railway operated road vehicles see 'Railway Company Goods Facilities - Railway Owned Road Vehicles'. Barrels, sacks, cases, crates and other packaging that represent much of the 'clutter' in an industrial scene are discussed in 'Appendix One - Packaging Materials & Containers'.
Welding and cutting metal
Welding joins two pieces of metal together by heating them until they soften then pressing them together. The technique dates back to about 4000 BC the weld being formed by forcing the red hot metal edges together after heating in a furnace. Blacksmiths form welds in this way when making (for example) a ring of wrought iron. This remained the only way of welding metal until the mid nineteenth century when an American engineer called Elisha Thomas developed electrical resistance welding in which an electrical current is passed through the joint between to pieces of metal. Where the joint is rough the electrical resistance is high and the joint heats to the point where the metal melts and fuses together. Resistance welding was used to make welded steel pipes as early as the late 1880's.
The electric arc was originally developed in 1807 by Sir Humphrey Davy (1778-1829) but it was 1885 before someone devised an electric arc welding kit and 1890 before a Russian developed the consumable electrode which made it practicable. In 1904 the coated electrode (as used today) was invented but it was the 1920's before arc welding became common. Arc welding produces a very bright blue-white light, a lot of hard ultra violet light and even x-rays, if you look at it with the naked eye it will blind you very quickly indeed. Welders wear clothing with long sleeves and gloves to protect their skin and use a metal face mask with a darkened window set into it when working. They have to move the mask out of the way to see when the arc is not struck and early welders held the mask in one hand, by the early 20th century a lot of masks were fitted with a head band and had a hinged dark glass filter that could be flipped up when the worker needed to see. By the early 21st century electronic masks had been developed in which the window is a liquid crystal lined to a sensor, as soon as the arc is struck the window darkens, clever but I am not sure I would rely on it.
The illustration below shows a man welding on one end of a railway carriage, note the face mask (to protect his eyes), heavy gloves and leather apron (to protect him from any drops of molten metal).
Fig ___ Man arc welding (1930s)
Oxy-acetylene welding dates from the early 20th century, developed from gas cutting which dates from 1900 when the torch was invented by one Edmund Fouche. Oxy-acetylene gas torches can be used to weld two materials together or to cut through metal (hence the common term 'gas axe' for a set used in cutting).
The two cylinders are different sizes as you use different proportions of fuel and oxygen for different jobs and they are at different pressures. The two hoses are coupled together, on early sets the fuel line was red and the oxygen line black (the hoses were sheathed in rubber and nearly an inch thick) on more modern sets the fuel line is red and the oxygen line green, they have left and right hand threads to prevent them being connected the wrong way round. Welding and cutting require two different heads on the torch, cutting torches have a trigger to blast pure oxygen into the cut (this reacts with the hot metal forming an oxide slag which falls away). In a workshop the cylinders will be chained to a wall, for mobile use the two tanks are usually strapped to a simple two-wheeled trolley with the hose looped over the handle when not in use. The sketch below shows a typical 'gas axe' kit (it is a gas cutting set as it has the extra lever on the handle of the torch) and gas cylinders with the safety caps in place
Fig ___ Portable Oxy-acetylene kit and capped cylinders
The British Standard Colours for cylinders were established in the early 20th century, the oldest reference I have relates to the 1932 standard but I am not sure if that was the first. These colours were approved and retained in the 1973 British Standard, prior to the introduction of a Europe wide standard (although I am not sure when that came in). Oxygen cylinders were plain black (medical oxygen had the top dome painted with white and black quarters), acetylene were plain maroon, hydrogen, coal gas and propane were all plain signal red. In the 1973 version of the code there was an emphasis on labeling the bottles with the name and formula of the contents.
Oxygen and the fuel gasses used in this equipment are all highly dangerous, in the 1950s a fitter on a merchant ship had been working with a gas cutting set in a ship's engine room, he had been changing the bottles and had managed to release a lot of oxygen which had permeated his clothing. He then took the lift up to the main deck and on the way lit a cigarette, I gather there was not a lot of him left.
Acetylene is probably the most common fuel used, however it is tricky stuff to work with as at higher temperatures and pressures it becomes unstable and can explode. Inside the acetylene cylinder there is some form of absorbent material and the cylinder is half filled with acetone. The acetylene dissolves in the acetone, making it more stable. It is still dangerous however, I know of one case in the 1950s where a cylinder trolley fell over sideways, catching the head of the acetylene cylinder on a steel bench and breaking it off, the cylinder set off like a torpedo and punched through a thick brick factory wall before it came to rest. Oxygen is even more dangerous as it is under a higher pressure in the cylinder. When tanks secured to a trolley are being moved the protective cap should always be screwed in place to prevent the valve being knocked off in this way (although in practice this is seldom done).
Hydrogen can also be used as a fuel, although it does not burn as hot as acetylene it is cheaper and it can be pressurised safely so it is used for under water work (because of the pressure underwater acetylene becomes dangerously unstable at a depth of about 30 feet or 10m). Other fuels such as propane, gasoline and even propylene can also be used with oxygen for cutting and welding, however acetylene remains the most common option.
Another option is 'thermite welding' in which a case is built round the joint and filled with a material called 'thermite' mainly powdered aluminium with some powdered iron and magnesium. When ignited this mixture burns hot enough to melt steel. One application for thermite welding is joining sections of railway line together.
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