IS 308 and IS 7312: the standards for dissolved acetylene in India

Why acetylene is a special case

Every other industrial gas we fill shares a cylinder standard. Oxygen, nitrogen, argon, hydrogen, carbon dioxide and nitrous oxide all go into cylinders built to IS 7285. Acetylene does not, and the reason is worth understanding before reading any of the standards.

Acetylene decomposes explosively under pressure without needing oxygen at all. It is not a fuel that becomes dangerous when it meets air; it is a molecule that comes apart on its own if compressed. That single property makes an ordinary compressed-gas cylinder impossible.

So the gas is dissolved in acetone, which is absorbed into a porous mass filling the whole cylinder. What you are handling is not a tank of gas — it is a solid block, soaked in solvent, holding acetylene in solution. Every acetylene-specific standard in the list below exists because of that.

The five standards that matter

IS 308 — the gas. The specification for dissolved acetylene: purity and the impurity limits, principally phosphine and hydrogen sulphide, which are the contaminants that come through from calcium carbide. This is the standard quoted on tenders and the one KIGL fills to at ≥98 %.

IS 7312:2018 — the cylinder. Welded or seamless steel dissolved-acetylene cylinders, 0.5 to 130 litres water capacity. Covers the shell, the porous mass and the solvent charge. It is not interchangeable with IS 7285 in either direction.

IS 16271:2014 — inspection at filling. Acetylene is explicitly excluded from IS 16050, the general standard for inspection at time of filling, and gets its own. The checks differ because the things that can be wrong differ: the state of the porous mass and the acetone level have no equivalent on any other cylinder.

IS 8433:2017 — periodic inspection. Inspection and maintenance of DA cylinders in service. Acetylene runs a shorter requalification cycle than other gases — two years against five in group practice — because the porous mass settles and cracks, and acetone is lost through normal use. Neither shows up on the kind of hydrostatic test that requalifies an oxygen cylinder.

IS 11006:2011 — flashback protection. The Indian Standard for flame arrestors on acetylene lines and cutting equipment. A flashback travels back up the hose towards the cylinder; the arrestor is what stops it. We manufacture these, and we would still tell you to fit them.

Alongside these sit IS 5903:2014 for cylinder safety devices, IS 15975:2020 for filling conditions, and above all of them the Gas Cylinders Rules, 2016, administered by PESO, which is where the legal obligation actually lives. The Indian Standards tell you how; the Rules tell you that you must.

What this means in practice

Never accept an acetylene cylinder without checking the test date. The two-year cycle is short enough that overdue cylinders circulate, and a customer holding one is holding a compliance problem as well as a safety problem.

Never lay one down. Horizontal storage lets liquid acetone reach the valve, and it is then drawn off with the gas — starving the porous mass, contaminating the flame and damaging downstream equipment. A cylinder that has been horizontal must stand upright for at least an hour before use.

Never draw too fast. Exceeding the safe withdrawal rate pulls acetone out with the gas. Where a high continuous rate is needed the answer is a cascade, not a bigger single cylinder.

Never use copper. Acetylene forms explosive copper acetylides. This rules out copper and high-copper alloys anywhere in contact with the gas — a detail that catches people fitting general-purpose fittings.

Fit arrestors at both ends. Regulator and torch. One is not a system.

Who writes these standards

The BIS committee responsible for gas cylinders is MED-16, and the KIGL group has contributed to the committee work behind the Indian standards for acetylene cylinders and generators. That is the reason these pages exist: the questions arrive weekly from purchase teams and safety officers, the answers are spread across a dozen separate documents that cost money to obtain, and we are in an unusually good position to explain them.

What follows from that is a limit as much as a claim. These pages are not the official text. BIS holds copyright and sells the authoritative version, and where compliance is at stake that is the only document that counts. Nothing here overrides the Gas Cylinders Rules, your PESO licence, or your own written procedures.

Related reading

For the gas itself and how we supply it, see dissolved acetylene. For the analytical grade, ultra-high-purity acetylene. For the plant that generates it, the acetylene gas plant page and our operation and maintenance guide. For hazard data, the acetylene safety data sheet.