IS 11006 and EN ISO 5175-1: flashback arrestor standards

What a flashback actually is

A flashback is the flame travelling backwards — from the torch tip, up the hose, toward the regulator and the cylinder.

It happens when the flame front moves upstream faster than the gas is flowing out. The usual triggers are mundane: a blocked or damaged nozzle, incorrect pressures, a torch tip touching the work, gas withdrawn faster than a cylinder can safely deliver. The consequence is not mundane. A flashback that reaches a cylinder of dissolved acetylene can start a decomposition inside it, and acetylene decomposes explosively without needing any oxygen at all.

A flashback arrestor is the device that stops the flame before it gets there.

The standards

IS 11006:2011 — the Indian Standard for flashback and flame arrestors on acetylene lines and cutting equipment. This is the code quoted on Indian tenders and purchase specifications.

IS 16485:2020 — flame arresters, performance. A performance standard sitting alongside the device standard.

EN ISO 5175-1 — the international standard for safety devices for fuel gases and oxygen, with a type-test regime widely referenced in export specifications. If you are supplying into an export contract, check which standard the specification names, because the two are not interchangeable on paper even where the device would satisfy both.

IS 5903:2014 covers safety devices for gas cylinders more broadly, and is a separate matter from the line-mounted arrestor.

Not the same as a non-return valve

This is the substitution that gets made on cost grounds, and it is worth being direct about.

A non-return valve stops gas flowing the wrong way. A flashback arrestor stops a flame. A flame front travels far faster than the reverse gas flow a check valve is built to catch, so a non-return valve on its own will not stop a flashback.

Many arrestors incorporate a non-return valve as one element among several — typically alongside a sintered flame-arresting element, a thermal cut-off that closes on heat, and sometimes a pressure-sensitive cut-off. That combination is what makes it an arrestor. A check valve by itself is not one, whatever the supplier’s catalogue calls it.

Where they go: two per line

The rule is one at the regulator outlet, one at the torch inlet — on both the fuel gas and the oxygen line.

Fitting a single device is the most common shortfall we see, and it reads as compliance on a checklist while leaving a real gap:

• Regulator only protects the cylinder, and leaves the whole length of hose unprotected. Hose fires are not a small event.
• Torch only protects the hose, and leaves the cylinder exposed to anything that gets past it.

Both lines need protection. An oxygen line carrying a flame back toward a cylinder is not the lesser case — oxygen makes everything burn, including the metal of the fitting itself.

They are consumables

A flashback arrestor is a safety device that is used up, not a permanent fitting.

Replace after any flashback event. The device has done its job. It has been subjected to exactly the flame and heat it was designed to absorb once, and it must not be trusted to do it again.

Replace after any thermal cut-out operation, for the same reason.

Replace at the manufacturer’s stated interval, and check flow and leak-tightness within that period. An arrestor that has silently clogged restricts gas flow, which causes the unstable flame conditions that cause flashbacks — a failed arrestor can be the thing that creates the event it was fitted to stop.

An arrestor does not have a safety data sheet

We are asked for an “MSDS for flashback arrestors” often enough that it belongs on this page.

There isn’t one, and that is not an oversight. A safety data sheet describes a chemical substance or mixture. Equipment is an article and falls outside the scope of GHS safety data sheets. Asking a manufacturer for an SDS on a brass fitting will produce either a polite refusal or — worse — a fabricated document.

What a purchasing file actually needs for equipment is the technical datasheet and the declaration of conformity. Our safety data sheets cover the gases; the flashback arrestors page covers the equipment side.

What KIGL makes

We manufacture flashback arrestors, which puts us in an awkward position writing this page: everything above is advice to buy more of a product we sell. So it is worth saying that the advice does not depend on buying them from us. Fit two per line, on both lines, from whoever you like, and replace them when they have done their work.

Specifications for our own range are on the flashback arrestors page. Note that we make no certification claim on this page or that one — a claim of type-test certification is only worth making with the certificate in hand, and until it is confirmed, no such claim is made.

For the gases these devices protect, see dissolved acetylene and industrial oxygen, and the acetylene standards page for the wider regulatory picture.

These pages are not the official text. BIS holds copyright to the Indian Standards and sells the authoritative version, which is the only document that counts for compliance. Nothing here overrides the Gas Cylinders Rules, your PESO licence, your insurer’s requirements, or your own written procedures.

KIGL’s own arrestors

KIGL manufactures flashback arrestors at the Kolkata works, and the range holds type-test certification to IS 11006 and to EN ISO 5175-1.

That distinction is worth understanding, because it is where most of this market is vague. Conforming to a standard is a statement a manufacturer makes about its own design. A type test is an independent body taking production samples and testing them to destruction against the standard — flame arrest, gas non-return, thermal cut-off, flow and pressure drop — and issuing a certificate against that result. Ask any supplier which of the two they hold. The answer separates the trade quickly.

A copy of the certification is sent on request with a quotation or against a tender.