Storing acetylene cylinders in India: what the Gas Cylinders Rules 2016 and IS 14814 actually require

Storing dissolved acetylene cylinders in India is governed by two documents that most workshops have never read: the Gas Cylinders Rules 2016, administered by the Petroleum and Explosives Safety Organisation (PESO), and IS 14814:2023, the Indian code of safety for acetylene. The rules are short and mostly physical. Keep the cylinders upright, keep them away from oxygen, keep them cool and ventilated, keep ignition sources out, and know whether your quantity needs a licence. This page sets out each requirement with its clause, and notes where international practice adds a number the Indian text leaves open.

The line is 25 cylinders. Rule 44(b)(iv) of the Gas Cylinders Rules 2016 says no licence is needed to possess acetylene in cylinders in the dissolved state when the total quantity does not exceed twenty-five at a time. The exemption is for own use. A fabrication shop running two or three cutting stations from a stock of a dozen cylinders needs nothing from PESO beyond the cylinders themselves being compliant and in test.

Above 25 cylinders, or for any storage for sale or trading, a Form F storage licence is required. Because acetylene is a flammable gas, the application goes to the Chief Controller of Explosives at Nagpur, not to a circle office. Rule 48(1) adds that a Form F applicant for flammable gas storage for sale or trading must first obtain a no-objection certificate from the District Authority. The licence plan must show the surrounding area within 100 m of the facility (Rule 47(1)(a)(iii)). The fee for a dissolved acetylene store of up to 200 cylinders is Rs 2,000, with Rs 2,000 for every additional 200 or part thereof, and a Form F licence runs until 30 September of the year to which it is granted, for a maximum of ten years (Rule 51(2)). The cost of compliance is not the fee; it is the shed, the clearances and the time.

A dealer or a large user holding a Form F licence must also observe the licence conditions printed with the form, which carry most of the numbers on this page. The Gas Cylinders Rules guide covers the filling side; this page stays with storage.

Three of these deserve explanation, because the reason behind the rule is what makes people follow it.

A dissolved acetylene cylinder is a steel shell filled with a porous mass soaked in acetone, and the acetylene is in solution in the acetone. Acetone is a liquid and obeys gravity. Lay the cylinder down and acetone collects against the valve; stand it up and open the valve at once, and the first gas out carries liquid acetone with it. That damages the regulator diaphragm, contaminates the hose and gives a sooty, unstable flame. The Indian code's half-hour settling period is the time for the solvent to drain back into the mass. The longer explanation, including what acetone carry-over does to a weld, is on the page on why acetylene cylinders must stand upright. The C.P.I. 1968 safety code, remarkably, had no upright-storage rule at all; it is one of the genuine improvements in the modern Indian text.

An acetylene leak in a shed is a flammable mixture waiting for a spark. The same leak next to a leaking oxygen cylinder is a mixture with no spark required to be serious: an enriched atmosphere lowers the energy needed to ignite anything in the shed, including clothing. The C.P.I. 1968 code records that workmen's clothes and cleaning rags ignite at an oxygen content of only 25 to 30 %. That is why both the Indian licence conditions and IS 14814 separate the two gases, and why CGA G-1 in the United States specifies 20 ft (6.1 m) or a 5 ft non-combustible partition with a one-hour fire rating. EIGA Doc 123 uses the same device, allowing the spacing between cylinder storage areas to fall to nil only where a one-hour fire partition is interposed, and keeps ignition sources 3 m from any storage area.

IS 14814:2023 gives acetylene a specific gravity of 0.906 relative to air at 15 °C. That is lighter than air, but only just. A plume from a leak drifts rather than rises, cools against a wall and can pool as readily as it can climb. The C.P.I. 1968 practice for acetylene plant buildings, and a sound rule for cylinder stores, is non-closing ventilation openings at both floor level and in the ceiling, with mechanical ventilation where natural flow is not enough. A store of non-combustible construction, open-sided or louvred on at least two faces, under a light roof that shades the cylinders from the sun, satisfies every one of the rules in the table above at once. A cellar, a basement, a closed container or a brick room with a single door satisfies none of them.

Acetylene is gas group IIC, the most onerous group, and IS 14814:2023 clause 7.3.4 requires every meter, switch, fuse, socket, fixed lamp and hand lamp in acetylene filling and storage premises to be of flameproof construction to IS/IEC 60079-1. Rule 22 of the Gas Cylinders Rules requires the same for any premises storing flammable gas, effectively earthed. The practical answer for a small store is the one the C.P.I. code recommended in 1968: keep the electrical equipment outside the gas-tight envelope altogether, and light the store by daylight and by fittings mounted outside its walls.

The required notice under IS 14814 clause 7.4 reads SMOKING STRICTLY PROHIBITED, NO NAKED FLAME, AVOID LEAKAGES. The 1968 code offered a human-factors note that still reads well: some manufacturers change the colour of the danger notice from time to time so that people keep seeing it, while others hold to a standard red or yellow. Either way, the rule only works if a supervisor enforces it.

Every cylinder in the store also speaks for itself. The cylinder label described in IS 14814:2023 cl 7.4 warns that the cylinder must not be filled with any other gas, that no oil goes on the valve, and that the next test date is on the metal ring between valve and neck; if that date is past, the cylinder is not accepted for filling. Rule 42 adds the date of last filling, the weight of gas filled, the full cylinder weight and the filler's name. A storekeeper who reads the ring and the label on receipt has done most of the inspection the rules expect of them. What to look for on arrival is set out in buying acetylene: what to check.

The Indian rules state the principle: no high temperature, no direct sun. CGA G-1 supplies the figures the trade uses internationally, 51.7 °C maximum in storage and 48.9 °C in use. Acetylene's critical temperature is 35.15 °C (IS 14814:2023), which an Indian summer afternoon exceeds; as the cylinder warms, the loaded solvent expands and the settled pressure climbs with every degree. The settled pressure is set at 15 °C, and the Gas Cylinders Rules cap it at 16 kgf/cm² at that temperature (Rule 37(vi)); a cylinder in the sun is simply not at the temperature its filling was designed for. The CSB investigation of the 2005 St Louis cylinder-yard fire (CSB Safety Bulletin, June 2006) found that returned, part-full cylinders on asphalt heated faster than full ones; the cylinders that vented first held propylene, but the mechanism applies to any yard, which is a reason to shade the empties bay as carefully as the full stock. The physics is on the critical temperature page.