Oxygen is not a fuel, but it makes everything around it burn hotter and faster. In a pressurized oxygen line, things that would never catch fire in air, like a smear of grease, a sliver of tubing, or even the metal itself, can ignite. I've seen good techs treat an O2 line like any other gas line. That's the mistake this post is meant to help you avoid.
Know how oxygen fires start
Most oxygen system fires trace back to a few well-known ignition sources:
- Contamination. Oil, grease, cutting fluid, fingerprints and lint are fuel. In oxygen they ignite at much lower energy than you'd expect.
- Particle impact. Chips and burrs carried by fast-moving gas can strike a seat or elbow and spark.
- Rapid pressurization. Snapping a valve open can compress gas downstream so fast that it heats up enough to ignite soft seats or contaminants.
Every habit below goes after one of those three.
Start with cleaned components and keep them sealed
Use tubing, fittings and valves that are cleaned for oxygen service and arrive capped and bagged. Leave the caps on until the moment you make the connection. If a part has been sitting open on a bench or got handled with bare hands, it's no longer clean. Wear clean, lint-free gloves when you handle it.
Your system owner or engineer should spell out the cleaning standard the job requires. If nobody has, ask before you build, not after.
Cut clean and deburr every end
Chips and burrs are fuel and ignition sources in the same package. Cut stainless tubing with a tube cutter made for stainless, like our RIDGID tube cutters, instead of a hacksaw that throws chips everywhere. Lock a GRIP-IT TOOL onto the tube while you cut so the tube doesn't spin in your hand and you get a square cut.
Then deburr the inside and outside of every end with a deburring tool. Point the tube end down while you deburr so chips fall out instead of in, and blow it out with clean, dry, oil-free gas before you assemble. You'll find all of these on our tools page.
Watch what goes on the threads
Standard petroleum-based thread lubricants and anti-seize compounds have no place in oxygen service. If threads need a sealant or lubricant, use only a product that's specifically rated for oxygen service, and use the least amount that does the job. Keep it off the first thread so it can't migrate into the flow path. Tube fittings seal metal to metal, so they don't need any sealant on the tube connection.
Use fittings you can trust and assemble them right
Follow the manufacturer's installation instructions every time: tube fully bottomed, correct turns, and a gap inspection gauge check where it applies. If you're mixing brands on a job, DK-Lok's ASTM F1387-99(2005) test report, witnessed by TÜV Rheinland, covered 14 combinations of intermixed DK-Lok and Swagelok nuts, ferrules and bodies in 1/4" through 1" OD. Across tests including hydrostatic burst, impulse, vibration and thermal cycling, the result was "No failure observed," and DK-Lok backs the intermix of properly assembled, same-size, same-material components in writing. Read the ASTM F1387 test report, or see our DK-Lok page.
Open valves slowly
When you pressurize an oxygen line, crack the valve and bring pressure up slowly. Fast opening is what drives the compression heating described above. Ball valves and other quarter-turn valves open fast by nature, so check your system's design before you use one as an isolation valve on high-pressure oxygen.
Related reading: Building a Hydrogen Line? Tubing and Fitting Tips Before You Start and Thread Sealant vs. Anti-Seize: Which One Goes on Your Threads?.
We're here to help
Oxygen work rewards slow, careful habits. If you want your crew to build those habits, ask about the free Safety training course from A-Best Industrial Inc. Fittings, Valves, and Tubing on our training page.
Questions about tubing, fittings or tools for an oxygen job? Call A-Best Industrial Inc. Fittings, Valves, and Tubing at 310-833-3353 or email sales@abesttube.com. We're open Monday through Friday, 8:00 AM to 5:00 PM Pacific, with after-hours emergency service.