Every so often a buyer asks me whether they really need electropolished tubing or whether standard bright annealed stainless will do. It's a fair question, because electropolished (EP) tubing costs more and can take longer to get. After 20 years in the instrumentation valve and fitting business, my answer is simple: it depends on what's flowing through the line and how clean it has to stay.
What Electropolishing Does
Electropolishing is an electrochemical process that removes a thin layer of metal from the inside surface of the tube. It takes the peaks off the surface, so the bore ends up smoother and brighter than standard tubing. It also leaves a chromium-rich passive layer that helps the stainless resist corrosion.
A smoother bore has fewer places for particles, moisture and process residue to hide. It cleans up faster, purges faster and sheds fewer particles into the flow stream. That's the whole point of paying for it.
When EP Tubing Is Worth It
- High-purity gas systems. Semiconductor and specialty gas lines, where a stray particle or trace of moisture can ruin product.
- Pharmaceutical and biotech. Lines that get cleaned in place and need a surface that drains and rinses well.
- Analytical sample lines. When you're measuring small concentrations, a rough bore can hold onto the sample and throw off readings or slow the analyzer's response.
For instrument air, hydraulic lines, most process impulse lines and general utility service, standard 316/316L tubing is usually the right call. If you're not sure, follow the process spec or ask the engineer who owns the system.
Handle It Like It's Clean, Because It Is
The EP finish only helps if you keep it clean during installation. Leave the end caps on until you're ready to cut. Wear clean gloves. Don't drag lengths across the floor or set them down open-ended in a dusty work area. Store it off the ground and away from carbon steel work, where grinding dust can land on it.
Cutting and Prep
Use a sharp cutter made for stainless, like our RIDGID tube cutter, and keep the wheel clean so it doesn't drag contamination into the cut. The GRIP-IT TOOL locks onto the tubing while you cut so the tube doesn't spin in your hand. It fits 1/8", 1/4", 3/8", 1/2", 3/4" and 1" OD tubing. Point the open end down while you cut and deburr so chips fall out instead of into the bore.
Take off the burr with a deburring tool, lightly, inside and out. Then blow the tube clean with clean, dry gas per your site procedure and recap it until it goes in. All of these tools are on our tools page.
Fittings and Leak Testing
Match the fittings to the job. Some high-purity systems call for welded or face-seal connections; others use two-ferrule compression fittings. Follow the system spec. Where compression fittings are used, DK-Lok tube fittings are 100% interchangeable and intermixable with Swagelok and Parker A-Lok for like size and material, properly assembled per the DK-Lok catalog. In ASTM F1387 testing witnessed by TÜV Rheinland, 14 combinations of intermixed DK-Lok and Swagelok nuts, front ferrules, back ferrules and bodies passed every test, with "No failure observed." See also the Parker A-Lok interchangeability letter.
Once the line is pressurized per your site procedure, apply Gator Leak Detector all the way around each joint you touched and watch for bubbles or foam. On male connectors and other NPT-to-tube fittings, check the pipe-thread joint as well as the tube nut, since the NPT side is often skipped. If your system's cleanliness spec limits what can touch the outside of the joints, follow it. If something leaks, isolate and depressurize before putting a wrench on it. Never tighten a fitting under pressure.
We're Here to Help
A-Best Industrial Inc. Fittings, Valves, and Tubing stocks electropolished tubing along with 316/316L and 304/304L stainless (DFARS compliant), Inconel, Teflon and nylon tubing. See our tubing page, or call 310-833-3353 or email sales@abesttube.com. We're open Monday–Friday, 8:00 AM–5:00 PM Pacific, with after-hours emergency service.