Connector Tube Fittings: Stainless Steel & Alloy Instrumentation Connectors

A connector tube fitting is an instrumentation compression fitting. On one end, one or two ferrules grip and seal against the tube's outside diameter. The other end is something else entirely: a male thread, a female thread, a weld prep, or a system port. Crestflo builds these connectors in 316/316L, duplex, and nickel alloys, ranging from 1/16″ to 2″ (50 mm) OD, in single- or double-ferrule versions. Every one is tested to ASTM F1387 and dimensioned to drop straight in as a replacement for the major brands.

Reviewed by the Crestflo Engineering Team

A connector, in this context, is a stainless-steel or alloy instrumentation compression tube fitting. It joins tubing to a threaded, welded, or ported connection. It isn't an electrical or wire connector, not a plastic or lab tubing connector, and not a barbed or garden-hose connector.

Connector Tube Fitting: Also Known As

Across drawings, catalogs, and RFQs, the same part goes by many names. Buyers call it a tube fitting connector, a tube connector fitting, a compression tube connector, or a compression fitting connector. Some specify a stainless steel tube connector (shortened on drawings to SS tube fitting connector), and others just write instrumentation tube connector. The straight tube-to-thread version usually gets labeled a straight connector. Sealing style is what separates the two-ferrule or double-ferrule connector from the single-ferrule connector. Every one of these names points to the same connector family covered on this page. The sub-types below split that family by the non-tube end.

What Is a Connector Tube Fitting? (Compression Tube Connector Working Principle)

A connector caps off a tube run and ties it into a fixed connection point. The ferrule end swages onto the tube's outer diameter, forming a leak-tight compression seal that also grips the tube so it can't pull out. The other end carries the mating connection: a male or female pipe thread, a weld end, or a straight-thread port. That's the feature separating a connector from its relatives. A union joins tube to tube (both ends are ferrule ends). An adapter joins thread to thread and has no tube end at all. A connector, by contrast, is the tube-to-thread, tube-to-weld, or tube-to-port member of the family. It's the part you reach for when tubing needs to meet a gauge, valve, manifold, transmitter, or bulkhead. When a specifier says "tube-to-pipe connector," they mean a male- or female-thread connector that lands the tube onto a threaded pipe run.

Types of Connector Tube Fittings: Male, Female, Weld, Port & Bulkhead

Connectors are one of the core tube fitting families found on an instrumentation manifold. What defines each one is the second end, the non-tube side. Every configuration listed below is either stocked as a standard item or built to order, and each has its own dedicated page.

For the pure tube-to-tube case see the union tube fitting; for thread-to-thread transitions, the tube adapter case, see the adapter fitting.

Connector Design & Ferrule Technology: Single vs Double Ferrule

Crestflo connectors are built in both double- (two-) ferrule and single-ferrule designs. The two-ferrule geometry separates the sealing and gripping functions so the seal holds under vibration, pressure cycling, and thermal movement, while the single-ferrule design offers a simpler, lower-part-count alternative for suited services. Ferrules are supplied hardened or non-hardened to requirement, and a heat/lot number is marked on every part for full traceability. Explore the single-ferrule design, the ferrule-less option, and matching nut-and-ferrule sets or replacement ferrules; the trade-offs are compared in our single vs double ferrule and hardened vs non-hardened ferrules guides.

Connector Materials: 316/316L Stainless, Duplex & Nickel Alloys

316 and 316L stainless make up the standard offering for general instrumentation service. When conditions turn corrosive, sour, high-temperature, or high-chloride, the full alloy ladder is available. Grades come supplied to ASTM A269, A276, and A479, with values set per the applicable standard, and they're customizable to requirement. Threads can also be finished with a silver anti-galling plating, which keeps stainless-on-stainless make-up from seizing.

Not sure which grade the job needs? Start with our material selection by service guide, or try the alloy selector.

Connector End & Thread Connections: NPT, BSPT, BSPP, ISO, JIC 37° & SAE-ORB

Every threaded and ported end meets its published standard, in both imperial and metric: NPT follows ASME B1.20.1, JIC 37° flare follows SAE J514, and the SAE straight-thread O-ring boss follows SAE J1926. Pick the end that matches your equipment port:

Connector Sizes: 1/16″ to 2″ OD, Imperial and Metric

Connectors come in tube OD sizes from 1/16″ all the way up to 2″ (50 mm), available in both fractional/imperial sizes and their metric equivalents. The most requested sizes get their own landing pages, so you can jump straight to what you need.

We carry both metric and imperial/fractional tube connectors. For exact dimensions, check the tube fitting size chart.

Connector Specifications, Pressure Rating & Standards Conformance

Working pressure comes from the tube itself. It's set by tube OD, wall thickness, and alloy on the allowable-stress basis of ASME B31.3, so a correctly matched connector holds the rated pressure of the tubing it grips. A thick-wall, small-OD assembly gives you a high-pressure tube connector without any change to the fitting body. Values follow the applicable standard and can be customized to requirement.

The seal is all-metal, with no elastomer, so service temperature comes down to the alloy you choose rather than a soft seal. Size the assembly with our tube-pressure calculator, then check the limits against the pressure-temperature derating guide.

Swagelok & Parker Connector Interchange, Backed by ASTM F1387

Crestflo connectors are engineered as dimensional drop-in equivalents for Swagelok, Parker, Hoke, Hy-Lok, and Fitok connectors. The interchange isn't a look-alike claim; it's backed by ASTM F1387 performance qualification. We publish it as an engineered equivalence, not as a compatibility or intermix statement. Rather than post a static part-number table, we build the mapping for your bill of materials directly: request your Swagelok® or Parker® cross-reference, and our engineering team sends back the matched Crestflo equivalents. If you're specifying a Swagelok alternative, our Swagelok alternative page lays out the F1387-backed equivalence before you commit an RFQ. Start at the Swagelok cross-reference, the Parker A-Lok cross-reference, or the interchange lookup. Swagelok® and Parker® are trademarks of their respective owners.

Installing a Tube Connector

Push the tube all the way into the fitting until it seats firmly against the shoulder. Finger-tighten the nut, then pull it up to the marked position so the ferrule, or ferrules, bite into the tube's outer diameter and form the seal. Get the gauging right and consistent, and you'll get a joint that's repeatable and leak-tight every time. For the full method, along with gauge checks, see our ferrule installation and gauging guide.

Why Buy Connector Tube Fittings From Crestflo

Crestflo is the instrumentation division of an export house with four decades behind it, recognized by the Government of India, with a proven record of delivery across the Middle East, established supply discipline standing behind a focused instrumentation brand. For connectors, that means:

• ASTM F1387-qualified drop-in interchange for Swagelok, Parker, Hoke, Hy-Lok, and Fitok. It's the kind of interchange proof most competitors won't publish.
• Ready stock on standard items, made-to-order for specials, 6-8 week delivery. Compare that to the 20+ weeks you'll wait with the majors.
• Both imperial and metric on every connector, single or double ferrule.
• Small MOQ and private-label/OEM programs for distributors and equipment builders.
• Certified to ISO 9001, 14001 and 45001, and compliant with PED. Every part ships with an EN 10204 MTC 3.1 (3.2 available on request) and carries its own heat/lot number.
• NACE MR0175 / ISO 15156 compliance available for sour service.
• Indian origin, with US and European melt available on request, backed by full material traceability, TAA and domestic-melt options are there when your specification calls for them.

We'll send datasheets and CAD models to customers on request. For more detail, see the Crestflo Engineering Team page, our stance on US-origin & compliance, and how we handle material traceability.

Request a Connector Quote or Sample

Tell us the connector type, size, thread or end, and alloy, and we'll match the part and confirm delivery. Request a quote, request a free sample, take a look at the private-label program, or become a distributor. For US inquiries, reach Crestflo at sales@crestflousa.com, +1 346 594 9005, in Houston, TX.

Connectors support oil & gas, petrochemical, offshore, hydrogen, semiconductor, and analytical sampling systems. Learn more about oil and gas, analytical sampling systems, and instrument air.

Connector Tube Fitting FAQ

Related Connector Resources

• Connector types worth knowing: male connector, female connector, weld connector, port connector, and bulkhead connector.
• A few related fittings round out the family: union, adapter, reducer.
• These parts are built to recognized standards, including ASTM F1387, ASTM A269, ASME B1.20.1, NACE MR0175, and EN 10204 MTC.
• Pillar: tube fittings