Most fitting leaks I've chased over the years didn't start at the fitting. They started at the tube end. A crooked cut, a burr left on the ID, or a scratch where the ferrule needs to seal will beat the best fitting in the world. Here's how to prep stainless tubing so your compression fittings seal the first time.
Start with the Right Cutter
Stainless is tougher than copper, and a cutter made for soft tubing will dull fast, walk on the tube, and leave a spiral instead of a square end. Use a tube cutter with a wheel made for stainless steel, like the RIDGID tube cutters we carry.
Avoid a hacksaw unless you have no other choice. If you must use one, use a fine-tooth blade and a guide block to keep the cut square, and plan on extra deburring time.
Keep the Tube From Spinning
This is where a lot of techs fight the job. You tighten the cutter a little, rotate, and the tube starts spinning in your hand instead of the cutter going around it. That leads to an uneven cut and sometimes a scratched tube surface, right where the ferrules need to bite.
The GRIP-IT TOOL solves that. It locks onto 1/8", 1/4", 3/8", 1/2", 3/4" and 1" OD stainless tubing so you can hold the tube steady while you work the cutter around it.
Cut With Patience
- Mark your length and set the cutter wheel right on the mark.
- Snug the wheel lightly, then make two full rotations.
- Tighten a small amount every two turns. Cranking it down hard deforms the tube and makes a bigger burr.
- Keep going until the tube parts cleanly.
Look at the end when you're done. It should be square to the tube and round, not oval or flattened.
Deburr Inside and Out
Every cut leaves a burr. On the ID, it restricts flow and can break loose into your system, where it can end up in a valve seat or an instrument. On the OD, it can keep the tube from bottoming in the fitting body or damage the ferrules.
Use a deburring tool on both the inside and outside edges. Take off the burr and nothing more. You're not trying to put a big chamfer on the tube.
Clean It and Check It
After deburring, blow out or wipe out any chips and filings. In clean service, like instrument air, analyzer lines or oxygen service, follow your plant's cleaning requirements before the tube goes in.
Then run your fingers and eyes along the last inch or so of the tube. Scratches, dents or drag marks in the area where the ferrules seal are a leak waiting to happen. If you see them, cut that section off and start again. Tubing is cheaper than a callback.
Then Make Up the Fitting
With a good tube end, bottom the tube in the fitting body and follow the manufacturer's make-up instructions. Our Fitting Tool holds stainless tube fittings from 1/16" to 1/2" steady while you work on them, and a gap inspection gauge is a quick way to confirm proper make-up on the fittings designed for one.
You can find the cutters, the GRIP-IT TOOL, deburring tools and the rest of our install tools on our tools page. Need tubing to go with them? See our stainless steel tubing.
We're Here to Help
If your crew could use a refresher, ask about the free Safety training course A-Best Industrial Inc. Fittings, Valves, and Tubing offers to new and existing customers. Call us at 310-833-3353 or email sales@abesttube.com. We're glad to help you get it right the first time.