Troubleshooting guide › Cutting problems › Pipe and profile cutting problems
The hand-torch faults (slag, gouging, backfire) are on the gas cutting page. This page is about what the machine adds on pipe and profile work: a chain or magnet that must track, a radius that must be locked, a template that must be traced with the right offset, and a cut that must come back to where it started. Each of those has two or three usual causes.
Reviewed by the Cruxweld technical team, October 2026. Settings are starting points to confirm on a test piece; acceptance is decided by the code or drawing the job is built to. Checks marked “call” are for our technical team.
The machine drifted along the pipe: chain slack or twisted, chain links wrong for the diameter, wheels not square to the pipe, body not clamped (spring over-compressed or under-tightened), pipe not round or has a weld seam the wheels ride over, hoses pulling the body sideways.
Torch holder loose; torch not following the wall as the machine rides a seam or a dent; nozzle height changing; speed changing as the hoses drag.
Chain rusty or distorted; chain fitted upside down (upper margin confused with the lower band); over-tightened so the machine lifts; dross on the sprocket.
Magnet face fouled with slag; pipe wall thin or heavily scaled; non-magnetic pipe; speed too high on a bend.
Clutch disengaged or its pin broken; reduction gear slipping; wheel loose.
Dross or foreign body on the rail or pipe; broken gear or clutch pin; loose axle or wheel; hoses disturbing the machine.
Supply voltage high or low; speed controller resistor.
Start point not preheated to white heat; piercing instead of edge starting; tip too small for the wall.
Radius rod not locked; machine rocking on its feet; centre point shifted during the cut; hoses pulling the arm.
Cross bar slide loose; torch clearing the column by rubbing; clutch slipping under drag.
Clutch lever disengaged; direction switch at stop.
Potentiometer worn or loose; motor brushes.
Wrong nozzle for the thickness; oxygen pressure low or speed high; nozzle bore blocked or damaged.
Template too thin or its edge not square; roller height wrong; template or roller dirty.
Template offset not applied or applied the wrong way; kerf changed with a different nozzle.
Dirty roller or edge; hoses or cable pulling on the arm; gearbox dry or worn.
Direction switch off; speed knob at zero; oxygen pressure low or the pressure switch not operating.
Residual oxygen in the pressure-switch line (normal for a moment).
Roller radius cannot follow a corner tighter than itself; template corner not relieved.
Acetylene nozzles are marked G02 (or ANM on some torches) and LPG nozzles G03 (PM / PNM); the LPG type has a stepped or slotted preheat face. Using an acetylene nozzle on LPG gives a weak, slow preheat and popping; an LPG nozzle on acetylene backfires. Check the marking before you light.
| Nozzle (acetylene) | Plate | Oxygen | Acetylene | Speed |
|---|---|---|---|---|
| 00 | 5-10 mm | 0.20-0.30 MPa | above 0.03 MPa | 450-600 mm/min |
| 0 | 10-20 mm | 0.20-0.30 MPa | above 0.03 MPa | 380-480 mm/min |
| 1 | 20-30 mm | 0.25-0.35 MPa | above 0.03 MPa | 320-400 mm/min |
| 2 | 30-50 mm | 0.25-0.35 MPa | above 0.03 MPa | 280-350 mm/min |
| 3 | 50-70 mm | 0.30-0.40 MPa | above 0.04 MPa | 240-300 mm/min |
| 4 | 70-90 mm | 0.30-0.40 MPa | above 0.04 MPa | 200-260 mm/min |
| 5 | 90-120 mm | 0.40-0.50 MPa | above 0.04 MPa | 170-200 mm/min |
Guide values for the G02 nozzles supplied with CIRCO and WING machines (1 MPa = about 10 kg/cm2). Stand-off 8-10 mm.
| Nozzle (LPG, PM type) | Plate | Oxygen | Fuel gas | Speed |
|---|---|---|---|---|
| 0 PM | 5-15 mm | 0.20-0.30 MPa | 0.02-0.03 MPa | 380-480 mm/min |
| 1 PM | 15-25 mm | 0.20-0.30 MPa | 0.02-0.03 MPa | 320-400 mm/min |
| 2 PM | 25-55 mm | 0.25-0.35 MPa | 0.02-0.03 MPa | 280-350 mm/min |
| 3 PM | 50-75 mm | 0.30-0.40 MPa | 0.02-0.04 MPa | 240-300 mm/min |
| 4 PM | 75-100 mm | 0.30-0.40 MPa | 0.02-0.04 MPa | 200-260 mm/min |
| 5 PM | 100-150 mm | 0.40-0.50 MPa | 0.02-0.04 MPa | 170-200 mm/min |
Guide values; stand-off 5-8 mm on LPG, 15-20 mm while piercing. Confirm the speed with a trial cut: the dial is a guide, not a measurement. Bevel cuts: one size larger nozzle, speed reduced 20-30 %.
Every six months in regular use: remove, wash out, re-grease, and replace a worn worm or wheel. Carbon brushes every three months or 1000 hours, replaced below 3 mm.
Yes, set the torch angle on the holder, up to 45 degrees in 5-degree steps, with one size larger tip and a slower speed. A compound bevel (two angles) needs two passes.
Each of these machines gives one thing a hand cannot: a constant speed on a fixed path. If the path (chain, rail, radius rod or template) is set up right and the torch data is right, the cut is right. Our gas cutting machines use standard G02 (acetylene) and G03 (LPG) nozzles, so the cutting data on this page applies across the range.
Send a photo of the weld or cut, your machine model, consumable and plate thickness. Our technical team replies on WhatsApp with the likely causes and the next checks to make.
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