Cross Tube Fittings: Instrumentation Union Cross (4-Way), Stainless Steel & High-Nickel Alloy

A cross tube fitting is a four-port instrumentation compression fitting. It joins four tubes of the same outside diameter at 90°, forming a single leak-tight "+" junction. Each of the four ends grips its tube with a mechanical ferrule set and seals metal-to-metal on the tube's outside diameter. That lets a run branch into four directions from one machined body: supply, return and two takeoffs. When a tee's three ports just aren't enough, this is the fitting an instrument panel or sampling loop reaches for.

A quick note on scope. On this page, "cross" refers to an instrumentation compression tube fitting with four tube-fitting ends. It's not a threaded or socket-weld pipe cross, and it isn't the Crestflo cross-reference / interchange tool.

Crestflo is the instrumentation division of an export house with four decades behind it and formal recognition from the Government of India. These crosses ship as drop-in replacements built for the US market, delivered in 6-8 weeks. We Engineer Confidence.

Cross Tube Fitting: Also Known As

This fitting goes by a lot of names, and buyers and specifiers use them interchangeably: union cross, tube fitting cross, tube cross fitting, cross union, cross connector, cross tube connector, cross fitting. Since all four ends take the same tube size, some just call it an equal cross. Function gives it other labels too: 4-way cross, four-way tube fitting, instrumentation cross. Sealing method adds a couple more: compression cross fitting, double-ferrule cross.

When a job calls for a two-ferrule brand pattern of union cross, Crestflo supplies its crosses as a dimensional interchange. That's the instrumentation compression form, not a threaded pipe cross.

What Is a Cross Tube Fitting?: Union Cross vs Tee vs Union

Crestflo makes crosses, tees and straight unions as one family of compression tube fittings, and all three seal the same way. What changes is the number of ports and how they're arranged. A cross is the four-port "+" piece: reach for it when an instrument line has to feed and branch in four directions at one node, a distribution header, say, or a manifold takeoff, or a multi-stream analytical sampling junction. If three ports will do the job, the tee tube fitting costs less and weighs less. Need a plain in-line join instead? Check the union tube fitting. Standard Crestflo crosses come as equal (union) crosses, with all four ends sized the same; reducing and thread-branch versions get built to spec.

Cross Fitting Design & Ferrule Configuration: Single vs Double Ferrule

Each port on the cross seals when a nut advances and drives a ferrule set onto the tube OD. That action creates a mechanical grip and a metal-to-metal seal, with no gaskets, elastomers or thread sealant involved. Crestflo makes both single-ferrule and double-ferrule crosses, with hardened or non-hardened ferrules available to match your requirement. The double-ferrule arrangement splits the sealing and gripping functions apart, and it's the configuration most instrumentation specifications call for. All four ends come as tube-fitting ends standard. Looking for the ferrule set itself, or spares? See tube fitting ferrules, along with the single vs double ferrule and hardened vs non-hardened ferrules explainers.

Cross Tube Fitting Sizes (1/8″–2″ / 3–50 mm): Both Imperial and Metric

Tube-fitting ends go up to 2″ (50 mm) OD, and that holds across the whole line in both imperial and metric sizes. On an equal cross, all four ends match in size.

Nominal sizes and their corresponding tube OD track the standard imperial and metric OD tables. Values follow the applicable standard, though they're not locked in; customization to the requirement is available.

For sizing across the system, browse metric tube fittings or imperial-fractional tube fittings. Crestflo's size chart covers the complete range.

Cross Tube Fitting Materials: 316/316L Stainless, Duplex, Inconel, Monel & Titanium

The default build ships as a 316/316L stainless steel cross fitting. Most systems call it out as an SS cross tube fitting. Machining covers the full instrumentation alloy range, though; brass and aluminum aren't part of that. Every part gets a heat/lot number, along with EN 10204 MTC 3.1 (3.2 if you ask for it). You'll find grade compositions published against their ASTM standards on each material page.

For sour-service duty, we supply crosses that meet NACE MR0175 / ISO 15156 requirements. Composition, PREN and mechanical properties by grade are all listed in the full materials library, check there for details specific to your grade.

Connections & Ratings: Tube Ends, Thread Options & Pressure–Temperature

All four ends come as tube-fitting ends by default. When a branch needs to land on a thread, the cross points to the connection-type pages instead of repeating them: NPT per ASME B1.20.1, BSPP, BSPT and ISO parallel. A cross carries no elastomer seat, so its temperature limit follows the alloy and tube rather than a seal material. Working pressure isn't a single fixed number either; it's set port by port, based on tube OD, wall thickness and alloy. That's why working pressures come from the standard tube pressure-allowable tables, for instance ASTM A269 / A213 tube data evaluated per ASME B31.3. Values follow the applicable standard and can be customized to requirement. Need a rated build for a specific OD, wall and alloy? Request it from Crestflo's engineering team, and check the pressure-temperature derating and tube sizing and wall thickness guides. Finishes include material finish, electropolish, passivation and silver anti-galling plating, with oxygen cleaning available.

Standards, Testing & Traceability: ASTM F1387 & NACE MR0175

Crestflo compression tube-fitting crosses carry performance qualification to ASTM F1387, the standard that governs compression-tube-fitting testing and lets a cross stand in as a dimensional drop-in for the major two-ferrule systems. That's backed by actual test data, not matching shapes. Each cross is ISO 9001, ISO 14001, and ISO 45001 certified, along with PED certification, and ships compliant with NACE MR0175 and ISO 15156 for sour service. We hold every standard approval that applies to compression tube fittings.

Testing covers hydraulic proof, burst and impulse, pneumatic, flexure and rotary flex, vibration, thermal cycling, pull-out and vacuum, along with PMI and in-house NDT. Destructive testing happens at ISO/IEC 17025-accredited labs, and third-party inspection is available on request. Crestflo marks every part with its heat/lot number, see material traceability.

Drop-In Interchange: Swagelok®, Parker A-LOK® & Other Union Crosses

Because they're qualified to ASTM F1387 and machined to standard two-ferrule geometry, Crestflo union crosses serve as a dimensional interchange for the major brands' union crosses. An equivalent, not a copy. Never marketed as "compatible" or "genuine." Swagelok® is a trademark of Swagelok Company. A-LOK® and Parker® are trademarks of Parker Hannifin. Hy-Lok®, Ham-Let®, FITOK® and DK-Lok® belong to their respective owners, and Crestflo isn't affiliated with or endorsed by any of them. Part-level interchange sits on the cross-reference layer instead of a published chart here. Request your Swagelok® or Parker® cross-reference from our engineering team through the Swagelok cross-reference or Parker A-LOK cross-reference pages.

Ordering a Cross Fitting & Part-Number Cross-Reference

Configure a cross by tube OD, alloy, ferrule type (single or double, hardened or non-hardened) and finish. For a branch on a thread, add the thread form and size on that port. Crestflo doesn't publish its ordering-code series or the competitor part-number equivalents; you have to ask for them. Request the ordering-code guide, or your part-number cross-reference, from the engineering team through a direct RFQ. Datasheets and CAD models go out to customers on request as well. There's no PDF or CAD download to hunt down: the full size, alloy and standard data already sits in the tables above, all on one screen.

Why Crestflo for Cross Tube Fittings

• ASTM F1387 drop-in. It matches the majors' union crosses dimension for dimension, and that's not a resemblance claim. It's proven through test qualification.
• 6-8 week delivery. Standard items ship from ready stock; specials are made to order. Incumbents typically run 20+ weeks.
• Full alloy range. We cover 316/316L, Duplex, Inconel, Monel, Hastelloy and Titanium. Most tube-fitting suppliers stop at stainless.
• Both imperial and metric, single and double ferrule, hardened or non-hardened.
• Heat-number traceability + MTC on every part; NACE compliance for sour service.
• Small MOQ and private label: this is the instrumentation division of an export house recognized by the Government of India, and it's built a delivery record across the Middle East.

Origin is straightforward: Indian origin as standard; Crestflo can supply US or European melt on request, backed by full material traceability. Need domestic melt or have TAA requirements? See US-origin compliance.

Applications

Cross tube fittings serve as four-way branch nodes. They appear across oil and gas, offshore and subsea work, petrochemical, hydrogen, semiconductor, power generation and nuclear, analytical sampling systems, instrument air and hydraulics systems.

Request a Cross Fitting Quote

Tell us the specification: tube OD, alloy, ferrule type, finish, and any thread branch. From there, Crestflo returns a quoted, drop-in build. The fastest route is to request a quote. If you'd rather test the fit first, request a sample. Need to see the full range? Ask for the line card. Distributors and manufacturers can also look into the private-label program, or speak directly with an engineer through OEM support. Reach US sales at sales@crestflousa.com, +1 346 594 9005, Houston, TX.

Reviewed by the Crestflo Engineering Team

Frequently Asked Questions

Related Pages

• All tube fittings
• Tee tube fitting · Union tube fitting · Elbow tube fitting
• Tube fitting ferrules · Single vs double ferrule
• Swagelok cross-reference · Request a quote