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Harris 19-6 Acetylene

Harris 19-6 Acetylene FAQs

Answers to common questions about the mixers, neck tubes, cutting attachments and nozzles used on a hand-held oxy-acetylene torch.

What parts make up an oxy-acetylene hand torch, and does each part have to suit acetylene?icon-minus-redicon-plus-red

A hand torch is built from a handle or shank with the gas valves, a mixer where the oxygen and fuel gas meet, a neck or flame tube, and a nozzle or tip at the end. Cutting attachments and heating nozzles fit onto the same shank.

Mixers, nozzles and attachments are usually made for a particular fuel gas, because the internal passages are sized for that gas. Check the marking and the maker's manual before fitting anything, and do not assume a part sold for another fuel will work on acetylene.

How do I choose the right welding or brazing nozzle size?icon-minus-redicon-plus-red

Nozzles are chosen by the bore size that suits the thickness of the metal. Small nozzles suit sheet and light work, and larger ones suit thicker material. Each nozzle size has its own recommended acetylene and oxygen pressures and flow rates, which the maker gives in a chart.

Start from the maker's nozzle chart for your torch and the thickness you are joining. A nozzle that is too small struggles to melt or heat the joint, while one that is too large can overheat thin work. If you are unsure, our team can help you choose.

How does a cutting attachment work, and what size nozzle do I need?icon-minus-redicon-plus-red

A cutting attachment has two oxygen supplies to the nozzle. One oxygen stream is mixed with acetylene to make the preheat flames, and a separate stream, controlled by a lever, is the cutting oxygen that burns through the heated steel.

The cutting nozzle is chosen by the thickness of the material, as the diameter of the cutting oxygen hole is matched to the job. Too little cutting oxygen gives poor slag removal, and too much gives a rough finish. Keep the nozzle at the distance the maker recommends from the plate, as too close or too far disturbs the cut.

What is the correct way to purge, light and shut down an oxy-acetylene torch?icon-minus-redicon-plus-red

Before lighting, purge the hoses one at a time by opening the gas supply to each hose for a few seconds, then close the torch valve. This flushes out any flammable mixture. Work in a well-ventilated area, light the gas with a spark ignitor, and use the correct pressures and nozzle size for the job.

When you have finished, turn off all valves at the cylinders and torch, then vent the excess gas from the hoses. Do not use the equipment unless you have been trained, and follow the maker's instructions and your risk assessment.

What is the difference between a flashback arrestor and a non-return valve?icon-minus-redicon-plus-red

A flashback arrestor is designed to stop a flame, using an element such as fine mesh or metal foam that cools it out. Some also have a cut-off valve that operates on pressure or temperature. A non-return valve only controls the direction of flow, so oxygen cannot pass into the fuel line or the reverse. It has no flame-stopping ability.

HSE guidance is to fit flashback arrestors, or an equivalent device, at the regulators on both the oxygen and acetylene cylinders, and non-return valves on the torch. Fitting them is not a substitute for safe working practice.

How should I look after nozzles and what happens if they are damaged or blocked?icon-minus-redicon-plus-red

Inspect nozzles regularly and make sure they are not blocked by dirt or spatter. Poorly maintained nozzles cause turbulent gas flow, which increases the risk of flashback. Replace any nozzle that is damaged.

Do not hold the nozzle too close to the workpiece, as it can overheat and cause a flashback or backfire. Clean tips with the correct cleaning tools and take care not to enlarge or scratch the bore. If the nozzle seat or mixer is damaged and the connection leaks, replace the part or have it repaired rather than overtightening it.