Straight answers to the questions people ask most when choosing and using regulators, hoses, torches and other gas equipment.
How do I choose the right gas regulator?
A regulator must be made for the specific gas it is used on, such as oxygen, acetylene, propane, argon or a shielding gas mix. The cylinder connection, the pressure ratings and the outlet all differ, so never use a regulator on a gas it was not designed for.
Then decide what you need it to do. Gas welding and cutting regulators have pressure gauges, while shielding gas regulators for MIG and TIG normally have a flowmeter showing litres per minute. Check that the cylinder thread matches your cylinders and that the maximum pressure and flow suit the job. Follow the maker's instructions when fitting.
What does a flowmeter do, and do I need one for MIG and TIG?
A flowmeter shows how much shielding gas is flowing to the torch, usually in litres per minute. That matters because too little gas leaves the weld unprotected, causing porosity, while too much wastes gas and can pull air into the weld through turbulence.
Some regulators have a flow tube or gauge scaled in flow, while others use a pressure gauge only, which is less exact because the real flow also depends on the hose and torch. Most MIG and TIG welders prefer a regulator with a flow reading so they can set the flow correctly for the job.
What is a flashback arrestor and do I need one?
A flashback arrestor is a safety device fitted in a fuel gas or oxygen line that stops a flame from travelling back through the hose into the regulator and cylinder. Most types also include a non-return valve and a cut-off that shuts off the gas if it overheats or a flashback occurs.
It is a basic safety item for oxy-fuel equipment, and they are normally fitted to the regulator outlets and at the torch inlets. They must be rated for the gas they protect, and must be checked, tested and replaced as the manufacturer and your risk assessment require. Never remove or bypass one.
How do I choose gas hoses, and what do the colours mean?
Hoses must be made for the gas and the working pressure, and be the right bore for the torch and the flow you need. In the UK the hoses are colour-coded, with blue used for oxygen, red for acetylene and other fuel gases and orange for propane and LPG, but check the markings on the hose rather than relying on colour alone.
Fuel gas connections use a left-hand thread, often shown by a groove cut in the nut, while oxygen uses a right-hand thread. This stops them being crossed by mistake. Replace hoses that are cracked, burnt, worn or damaged, and never repair them with tape.
How do I check my gas equipment for leaks?
Use a leak detection fluid made for the purpose, or a mild soapy solution, brushed or sprayed on every joint with the gas turned on. Bubbles show a leak. Do not use oil or grease, and never look for leaks with a flame.
Check the cylinder connection, regulator, hoses, arrestors and torch fittings whenever you set up. If you find a leak, shut off the cylinder, release the pressure safely and fix it before you go on. Do not over-tighten fittings to cure a leak, because a damaged seat or hose needs replacing. Work in a well-ventilated area.
How do I use and store gas cylinders safely?
Cylinders must be kept upright and secured against falling, whether they are in use, in transit or in store. A purpose-made cylinder trolley with a chain or strap is the safest way to move and use them. Never roll a cylinder along the ground or lift it by the valve.
Keep cylinders away from heat, flame and sparks, and store oxygen and fuel gases apart. Keep valves, regulators and fittings free from oil and grease, particularly on oxygen. Close the cylinder valve when you finish, and follow the gas supplier's guidance and your own risk assessment.