Superior Fluid Solutions · Cross-Reference
Hy-Lok® vs Swagelok®: What to Check Before You Cross-Reference Either One
Both are twin-ferrule instrumentation fittings, and both end up on drawings that somebody else has to source. Here is the buying checklist, and the one thing you must never do.
A drawing names one brand because an engineer picked it years ago, and from then on everyone downstream lives with it. When the part is back-ordered, or the line was built by a contractor who used whatever was on the truck, somebody has to work out what actually goes back in. This is a sourcing guide for that job: what separates these two on paper, what to confirm before you order, and where buyers get burned.
What the two have in common
Both are twin-ferrule compression fittings for instrument tubing, built in stainless steel, sold in inch and metric sizes, and specified for the same kind of work: instrument hookups, sample lines, panels, hydraulic and gas service. Both use a front ferrule that seals against the tube and a back ferrule that grips it, so the seal is not also holding the tube in place.
That shared description is exactly why a cross-reference is possible at all. It is also why a cross-reference has to be checked rather than assumed. A shared design principle is not a shared part.
The one rule that is not negotiable
Do not build a connection from more than one brand. Not a nut from one and a body from another, and not one brand’s ferrules dropped into another brand’s fitting. The parts are designed, hardened and tested as a set, and no manufacturer stands behind a mixed joint. If you are converting a panel, convert complete connections and keep spare ferrule sets with the fittings they belong to.
What to confirm before you order
Every one of these can be answered before anything ships, and each one is a real reason orders come back:
| Check | Why it matters when you buy |
|---|---|
| Tube OD, inch or metric | 1/4 inch is 6.35 mm and 6 mm is 0.2362 inch. Measure the tube rather than trusting the callout, because mixed panels are common. |
| Ferrule design | Match twin ferrule to twin ferrule. If part of the line is single ferrule, note it, because those joints need a different plan. |
| End connection | NPT, BSPT, tube stub and straight-thread ports are easy to confuse on a parts list. Confirm the port on the instrument. |
| Material grade | Corrosion-resistant 316 stainless steel covers most service. An aggressive process may need something else, and that is a different conversation than a cross-reference. |
| Pressure and temperature | Check the rating against real service conditions, including heated or traced sections. |
| Documentation | If the spec calls for a material test report, say so on the order so it ships with the parts. |
Superlok® fittings are listed in 316 stainless steel. Send the part numbers from your drawing and each one can be confirmed before you buy.
Converting a panel without stopping the job
Take the connections in whole units. Work from the instrument back toward the tap, replace complete joints, and keep a short list of what was converted and when, so the next person is not guessing which brand is behind which nut. Where a line has to stay in service, do the isolation points first: needle valves for flow setting, ball valves for isolation, and inline filters where the instrument needs protecting.
Build the rest of the order from tube fittings, unions where the line needs to open for maintenance, and pipe fittings at the process end. If you are weighing brands more broadly, our page on the Swagelok alternative covers the wider comparison, and we have written about cross-referencing under deadline for oil and gas and for a chemical turnaround.
Cross-reference questions
Are Hy-Lok® and Swagelok® fittings interchangeable?
As complete fittings they cross-reference by form, fit, and function once tube size, ferrule design, end connection, grade and rating are confirmed. Their individual parts are not interchangeable, and a joint should never be built from two brands.
How do I work out what is already on the line?
Measure the tube OD, look at the end connection on the instrument, and note whether the fitting is single or twin ferrule. Send us that, with a photo if it is easier, and we will work back to a part number.
Do you carry both inch and metric?
Tell us the tube OD for each line and we will confirm the matching part and whether it is available. Mixed inch and metric panels are more common than people expect.
Can I order without waiting on a quote?
Yes. Fittings and valves are listed with pricing and availability so you can order directly. If you would rather have the cross-reference confirmed first, send the part numbers before you buy.
Can I get material certification with the order?
Ask for it when you order. If your specification requires a material test report, say so up front so it can be confirmed before the parts ship.
Send the drawing, get the part numbers back
Superlok® instrumentation fittings in corrosion-resistant 316 stainless steel, listed with pricing and availability.
Superior Fluid Solutions
Corrosion-resistant Superlok® fittings and valves, cross-referenced by form, fit, and function to your Hy-Lok®, Swagelok® and Parker® part numbers.
Sources
- Jon Kestner (Swagelok Company), “Using Tube Fittings from Different Manufacturers May Lead to Leaks,” Stainless Steel World Americas, 18 July 2024, on the risks of intermixing components between brands. ssw-americas.com
Technical note: the source above is authored by an employee of a fitting manufacturer and publishes no test data. It is cited for the engineering reasoning. Tube size, material grade and pressure rating are confirmed per order. Shipping note: most in-stock orders placed during business hours ship the same day; orders placed after hours or on weekends ship the next business day.
Swagelok®, Hy-Lok® and Parker® are registered trademarks of their respective owners. Superior Fluid Solutions and Superlok® are not affiliated with, authorized by, or endorsed by those companies. Cross-references are made by form, fit, and function only.
