Figure 1–6Details a cross section of oxygen valve
Why should the welder position the cylinders between himself and the regulators when opening the cylinder valves?
If a regulator fails internally, releasing high-pressure gas from a cylinder into the regulator’s low-pressure side, the regulator housing and gauges may explode. Fatalities have resulted from such malfunctions.
If an acetylene cylinder has been incorrectly transported on its side, why should the welder avoid immediate use?
The acetylene gas and the acetone in which it is dissolved may become mixed in the area just below the valve, resulting in both gaseous acetylene and liquid acetone at the top of the cylinder. This is where acetylene exits the cylinder and goes through the valve to enter the regulator. Both acetylene gas and liquid acetone will be drawn into the regulator possibly ruining the rubber components of the regulator and torch and creating a safety hazard. The weld metallurgy may also be contaminated.
What should the welder do knowing that a newly delivered acetylene cylinder has been incorrectly transported on its side?
Upright the cylinder and wait at least one-half hour before connecting and using the cylinder to allow the liquid phase of the acetone to separate from the acetylene gas in the upper portion of the cylinder. That way no acetone will be drawn into the regulator possibly damaging its seals. Also, acetone in the weld flame will contaminate the weld pool and spoil the weld.
How can one readily distinguish between the oxygen fitting swivel nut and one for acetylene?
Acetylene, like most other fuel gas handling equipment, has a notch or groove cut in the middle of the edges of the hexagonal faces of the swivel nut. This is a flag for a left-handed thread. See Figure 1–7.
Figure 1–7Compares connector nuts used on oxygen and acetylene equipment
Are all oxygen cylinders painted green?
Frequently, oxygen cylinders are painted green or have a green band, but the only sure way to determine the contents of a compressed gas cylinder is to read the adhesive label on it. This label is required by law and should not be removed. Do not go by its color as there is no color code. Unlike civilian industry, the US armed forces do color code their cylinders.
What pressures should full oxygen cylinder and full acetylene cylinder gauges show at 70°F (21°C)?
The acetylene should show 225 psi (15.5 bar) and the oxygen 2250 psi (155 bar). Note that these pressures will fluctuate with ambient temperature.
What do the letters and numbers stamped on the neck of high-pressure cylinders indicate?
The stampings indicate which US Department of Transportation specifications the cylinder meets, what type steel was used, who fabricated it, and when.
•Steel stamp markings such as “DOT-3A-2400” indicate the cylinder was made to US Government Department of Transportation (DOT) specifications, the “3A” denotes chrome manganese steel (or “AA” for molybdenum steel), and the “2400” the maximum filling pressure in psi.
•The oldest date indicates the month and year of manufacture. Subsequent dates, usually at five year intervals, indicate when mandatory hydrostatic pressure testing was performed and by whom. See Figures 1–8 and 1–9.
Figure 1–8High-pressure cylinder markings
Figure 1–9Acetylene cylinder markings
What are common oxygen cylinder sizes?
Figure 1–10 shows high-pressure cylinder sizes. Many gases in addition to oxygen, like nitrogen, carbon dioxide, and argon come in high-pressure cylinders.
Figure 1–10Oxygen cylinder sizes
What factors govern the choice of oxygen and acetylene cylinder size?
Smaller cylinders are suitable for refrigeration repairman who must climb ladders with OAW equipment, but they are impractical for most work. For example, a 55 ft3 (1557 liter) oxygen cylinder would last under two hours cutting
What are the common acetylene cylinder sizes?
See Figure 1–11.
Figure 1–11Acetylene cylinder sizes
Why are pressure gauges on acetylene cylinders poor indicators of remaining gas quantity?
Gas pressure remains nearly constant at a given temperature as acetylene gas is withdrawn from solution in acetone until very little gas remains. The best way to determine a cylinder’s remaining contents is to compare its current weight with its empty weight. Note that the weight of the empty cylinder is stamped on its top. There are 14.6 ft3 of acetylene for every pound of cylinder weight over its empty weight, or one liter of acetylene for every 1.1 grams of cylinder weight over the empty weight. Drawing acetylene from cylinders at pressures below 25 psi (1.7 bar) can cause acetone to be withdrawn from the cylinder.
Under what ownership arrangement may compressed gas cylinders be offered to users by welding equipment suppliers?
•Outright sale of the cylinder with the right to exchange it for a filled one of equal size by paying for refill is most economical in the long run. Usually one gas supplier will accept the cylinders you obtained from another at no additional charge. There will be a problem swapping cylinders if an embossed owner’s name appears on the neck ring.
•Cylinders may be rented by the month or year. Excellent when you don’t have a long-term need for them, just an immediate one.
•Some distributors lease cylinders for a year or more; some for 99 years.
•There