Ask for "DA" at any gas counter in Andhra Pradesh and you'll get a maroon cylinder of acetylene. But what does DA actually mean, and why does acetylene need such careful handling? Here's a plain-language explanation for welders, fabricators and site supervisors.
DA = dissolved acetylene
Acetylene (C₂H₂) is a fuel gas. It has a problem: compressed on its own above roughly 15 psi (about 1 bar), it can become unstable and decompose violently, even without air. So it can't be squeezed into a cylinder the way oxygen or nitrogen can.
The solution is clever. A DA cylinder is packed with a porous filler, a sponge-like mass, soaked in a solvent, usually acetone. Acetylene dissolves in the acetone the way CO₂ dissolves in a soda bottle. Spread through thousands of tiny pores, the gas stays stable, and the cylinder can hold a useful amount. That's why it's called dissolved acetylene.
Why DA cylinders must stay upright
Because there's liquid acetone inside, a DA cylinder must always be used and stored upright. If it's used lying down, acetone can come out with the gas. This damages regulators and hoses, gives a poor, spitting flame, and reduces the cylinder's safe capacity. If a cylinder has been transported lying down, stand it upright and let it settle before use. Many welders wait at least an hour.
The oxy-acetylene flame
Burnt with oxygen, acetylene gives one of the hottest fuel-gas flames, above 3,000 °C, and concentrates its heat in a small inner cone. By adjusting the oxygen and acetylene valves on the torch, you get three flame types:
- Neutral flame: roughly equal oxygen and acetylene, with a sharp inner cone. Used for most welding and cutting of steel.
- Carburising (reducing) flame: extra acetylene, with a feathery zone around the inner cone. Used for some hard-facing and special work.
- Oxidising flame: extra oxygen, with a short, pointed, noisy inner cone. Used for some brass and bronze work.
DA vs LPG for gas cutting
Many workshops ask whether they can use LPG instead of DA for cutting. The short answer: sometimes.
| DA (acetylene) | LPG | |
|---|---|---|
| Flame temperature | Hottest, very concentrated | Lower, spread out |
| Preheat time | Fast | Slower |
| Gas welding of steel | Yes, the standard choice | Not suitable |
| Cutting thick steel in volume | Good | Often more economical |
| Oxygen consumption | Lower | Higher |
| Torch and nozzles | Acetylene type | Needs LPG-type nozzles |
If you do welding, brazing, heating or precise cutting, DA is the right gas. Some heavy cutting operations switch to LPG to save cost, but they need the correct equipment and use more oxygen. Never use an acetylene nozzle with LPG or the other way round.
Two rules every DA user should know
The 15 psi rule
Never set an acetylene regulator above 15 psi (about 1 bar) working pressure. Most cutting and welding work needs much less.
The 1/7 rule
Don't draw acetylene from a cylinder faster than about one-seventh of its contents per hour. Drawing too fast pulls acetone out with the gas. If your big cutting nozzle needs more, connect two or more cylinders through a proper manifold, or ask us for advice.
Handling DA cylinders safely
- Keep cylinders upright and chained, in a shaded, ventilated place, away from oxygen cylinders when stored.
- Fit flashback arrestors on both the oxygen and acetylene lines.
- Check for leaks with soapy water, never with a flame.
- Light the torch with a spark lighter, not a matchbox or cigarette lighter.
- If a DA cylinder gets hot or is involved in a fire, don't try to move it. Clear the area and call the fire service on 101.
- Close the cylinder valve when work stops.
Common questions
Is DA gas the same as acetylene?
Yes. DA is acetylene supplied dissolved in acetone inside the cylinder. "DA gas", "DA cylinder" and "acetylene gas" all mean the same thing at the counter.
What colour is a DA cylinder?
In India, DA cylinders are painted maroon. Always read the stencilled gas name too.
Where can I get DA gas in Kurnool?
Parameswara Traders on Bellary Road supplies DA gas with refilling, exchange, cylinders on deposit and delivery, along with oxygen and regulators. Call 094400 79857.
See DA gas cylinders in Kurnool and oxygen gas for supply details.