"We've got Hy-Lok all over the plant. Can we switch to DK-Lok?" I hear that question a lot at the counter. The short answer is yes, plenty of plants do. But there's a right way and a wrong way to make the switch, and the difference shows up as leaks. After 20 years in the instrumentation valve and fitting business, here's what I'd want you to know before you start ordering.
Hy-Lok vs. DK-Lok: Same Job, Different Brands
Hy-Lok and DK-Lok both make compression tube fittings and instrument valves for the same kind of work: process instrument lines, analyzer systems, hydraulics and gas service. On a drawing, a male connector is a male connector. When people search "Hy-Lok vs DK-Lok," what they usually want to know is three things: can I get the same part, will it work with what's already installed, and how fast can I get it.
Finding the DK-Lok Match for Your Hy-Lok Part Numbers
Start with your part list, not a catalog. Pull the Hy-Lok part numbers off your drawings, bill of materials or old POs and send them to us through our brand cross-reference page. We'll quote the DK-Lok equivalent line by line. Give us the tube OD, the material and the end connections, and flag anything metric, so we never guess on a thread or a size.
Can You Mix Hy-Lok and DK-Lok Parts?
Yes. DK-Lok and Hy-Lok tube fittings are compatible with each other and can be mixed, so you don't have to tear out a whole Hy-Lok run to start using DK-Lok. Keep to the same rules you'd follow with any brand: same tube size, same material, and every connection made up per the DK-Lok catalog.
One thing to know if your spec calls for test data: the formal intermix testing and written documentation for DK-Lok cover Swagelok and Parker A-Lok. 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, ferrules and bodies passed 100% of the testing, with "No failure observed." DK-Lok also confirms it in writing in its Parker A-Lok interchangeability letter.
How to Swap One Fitting the Right Way
- Isolate and depressurize the line per site procedure.
- Remove the old fitting. Ferrules are not reusable, so cut off the tube behind the old swaged ferrules and use new DK-Lok ferrules on clean, round tube.
- Make a square cut with a RIDGID tube cutter made for stainless steel. The GRIP-IT TOOL locks onto the tubing so it doesn't spin in your hand while you cut.
- Deburr the inside and outside with a deburring tool, and blow out the chips.
- Install the new DK-Lok fitting per the DK-Lok catalog, or pre-swage the ferrules with a pre-swaging tool when you're working in a tight spot. Check the make-up with a gap inspection gauge.
All of these tools are on our tools page.
Leak Test Every Joint You Touched
Once the line is pressurized per site procedure, apply Gator Leak Detector all the way around each joint you worked on 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 something leaks, isolate and depressurize before putting a wrench on it. Never tighten a fitting under pressure.
Ready to Cross Your Hy-Lok Parts?
A-Best Industrial Inc. Fittings, Valves, and Tubing is an authorized DK-Lok distributor in San Pedro, serving California and supporting customers nationwide and the U.S. Military. Learn more on our DK-Lok page or browse our compression tube fittings. Send us your part list, 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.
Hy-Lok, Swagelok and Parker A-Lok are trademarks of their respective owners. Brand names are used only to identify the parts customers ask us to quote.