Standards · IS 308:1988 · IS 7312 · IS 8433
IS 308: the Indian Standard for dissolved acetylene and what it requires
IS 308 specifies dissolved acetylene as a product: minimum purity of 98 %, and limits on phosphine and hydrogen sulphide carried over from the calcium carbide. The cylinder, its porous mass, the colour, the retest interval and the safety code each come from 4 further standards.
- Standard
- IS 308:1988
- Minimum purity
- ≥98 % C₂H₂
- Impurities limited
- Phosphine and hydrogen sulphide
- Cylinder standard
- IS 7312
- Retest interval
- 2 years
What IS 308 covers
IS 308:1988, Dissolved Acetylene, is the Indian Standard that specifies acetylene as a product. It sets the minimum acetylene content — 98 % — and limits the impurities that arrive with it.
It does not specify the cylinder, the porous mass, the solvent, the colour or the retest interval. Each of those has its own standard. That is the normal pattern across every Indian gas standard: one document for the product, several more for what it arrives in.
| Standard | What it governs |
|---|---|
| IS 308 | The gas — purity and impurity limits |
| IS 7312 | The cylinder, its porous mass and acetone charge |
| IS 8433 | Two-yearly periodic inspection |
| IS 4379 | Maroon, the identifying colour |
| IS 14814 | Code of safety — handling, storage, use |
The impurities it limits
The two that matter are phosphine (PH₃) and hydrogen sulphide (H₂S).
Both come from the calcium carbide itself, not from the process — so they are always present to some degree in generated acetylene and must be removed by purification. They attack downstream equipment and they affect flame chemistry.
More usefully for a buyer: their level is the clearest single measure of whether the purification train on the generating plant is being maintained. A plant with tired purifiers keeps producing gas that looks normal and quietly carries more of both into cylinders. The damage lands on the customer’s equipment, which is why it goes unnoticed for so long.
IS 308 against IS 14814
These get confused, and the distinction is simple:
- IS 308 says what the gas must be.
- IS 14814 says what you must do with it — storage, handling, piping, purging, use.
Most buyers need both. Note that IS 14814:2023 supersedes the 2000 edition, which is still cited in a good deal of circulating material.
Why the retest interval is two years
Every other compressed gas cylinder in the range is hydrostatically requalified every five years under IS 8451. Dissolved acetylene is inspected every two, under IS 8433.
The reason is that an acetylene cylinder is not simply a steel shell. It contains a porous mass charged with acetone, and the inspection has to assess the mass and the solvent as well as the metal — see why acetylene is dissolved in acetone.
A supplier who treats acetylene cylinders on a five-year cycle has misunderstood which standard applies to them.
What KIGL does with it
Dissolved acetylene is filled at the Guwahati works to IS 308, into cylinders built and requalified to IS 7312 and IS 8433, identified maroon under IS 4379.
KIGL also builds the plants that generate it, to IS 8471 — which means the purification train that determines whether the gas meets IS 308 is equipment we design as well as operate. The full conformance register is on the standards hub.
IS 308 — frequently asked questions
What does IS 308 actually specify?
The gas as a product: a minimum acetylene content of 98 %, and limits on the impurities that carry over from calcium carbide — principally phosphine and hydrogen sulphide. It does not specify the cylinder, the porous mass, the solvent, the colour or the retest interval; each of those has its own standard, which is the normal pattern across every Indian gas standard.
Why are phosphine and hydrogen sulphide the impurities that matter?
Because they come from the calcium carbide itself rather than from the process, so they are always present to some degree and must be removed by purification. They attack downstream equipment and affect flame chemistry, and their level is the clearest measure of whether the purification train on the generating plant is being properly maintained.
Is 98 % the purity KIGL supplies?
It is the minimum the standard requires and what KIGL's industrial fill is held to. Higher purity is available against a specific enquiry, and separate high purity and ultra-high-purity grades exist for work that industrial acetylene cannot serve. The grade ladder is set out on the acetylene grades guide.
What is the difference between IS 308 and IS 14814?
IS 308 specifies the product. IS 14814 is the Code of Safety — how acetylene is handled, stored, piped and used. One tells you what the gas must be; the other tells you what you must do with it. Buyers usually need both, and the 2023 edition of IS 14814 supersedes the 2000 one.
Why is the retest interval two years rather than five?
Because a dissolved acetylene cylinder is not just a steel shell. It contains a porous mass charged with acetone, and both have to be assessed as well as the metal. IS 8433 governs that inspection. Compressed gases are inspected every five years under IS 8451; acetylene is the exception across the whole range.
Does KIGL manufacture to IS 308?
Yes. Dissolved acetylene is filled at the Guwahati works to IS 308, into cylinders built and requalified to IS 7312 and IS 8433, identified maroon under IS 4379. The conformance register on the standards hub sets out what KIGL works to for each activity and at which works.
Enquiries
Request a quotation
State the gas or equipment, the quantity or capacity, and your location. KIGL will confirm the grade, the cylinder or plant size, and whether the location can be served from Noonmati, or through our agent network.