Inconel 825 Tube Fittings (Alloy 825 / Incoloy 825, UNS N08825)

Inconel 825 tube fittings are mechanical-grip compression fittings, machined from nickel-iron-chromium Alloy 825 (UNS N08825). One or two ferrules swage onto the tube's outside diameter, forming a leak-tight, gas-tight seal along with a firm grip on the tube itself. That combination is what makes 825 fittings the practical pick for sulfuric and phosphoric acid lines, chloride and seawater service, and sour (H₂S) hydrocarbon instrumentation. Crestflo carries these fittings from 1/8-inch through 2-inch (50 mm) tube OD, in both single and double (twin) ferrule versions. They're qualified to ASTM F1387 and offered to NACE MR0175 / ISO 15156 for sour service. Standard items ship from stock; specials are built to order, with delivery running 6-8 weeks. Request a quote to price out your configuration.

Reviewed by the Crestflo Engineering Team

Incoloy® and Inconel® are registered trademarks of Special Metals Corporation.

What Inconel 825 Compression Tube Fittings Are

An Alloy 825 compression tube fitting is built for fluid-system instrumentation work: a body, a nut, and one or two ferrules that bite into the tube's outer diameter as the nut is torqued down. The result is a joint you can take apart and put back together without losing integrity. No flaring, no welding, no elastomer seal in the leak path. The seal is metal-to-metal, so the joint's service window comes from the alloy, not from an O-ring giving out first.

Scope matters here. These are instrumentation compression tube fittings in alloy 825, not plumbing pipe fittings, and not electrical wire ferrules. They tie into small-bore instrument tubing on analyzers, transmitters, sample lines, chemical-injection systems, and process taps, wherever sulfuric or phosphoric acid, chlorides, or H₂S push 316 stainless out of the running.

Also Known As: Incoloy 825, Alloy 825, N08825, Werkstoff 2.4858

Buyers and specifiers write the same alloy several ways, but they all point to the same Ni-Fe-Cr-Mo-Cu material. The technically correct trade name is "Incoloy® 825," because 825 is a nickel-iron-chromium alloy rather than one of the nickel-chromium grades that carry the true Inconel name. The market still searches for it as "Inconel 825," so we use that term here, but the material is the same one. "Alloy 825" and "825" are the common generic forms. It is registered as UNS N08825 and Werkstoff 2.4858 (NiCr21Mo), with the descriptive designation NiFe30Cr21Mo3 and the British designation BS NA16. Fitting feedstock is covered by the wrought nickel-alloy specifications ASTM B425 (rod and bar) and ASTM B366 (wrought fittings).

Because these names all point to the same product, asking for "alloy 825 tube fittings," "Incoloy 825 ferrule fittings," or "N08825 fittings" gets you exactly what's described on this page. The terms are interchangeable.

Why Choose Inconel 825 for Instrumentation Tube Fittings

Alloy 825 is a titanium-stabilized nickel-iron-chromium alloy, strengthened in solid solution rather than by age hardening. Its roughly 40% nickel content drives resistance to chloride stress-corrosion cracking, the failure mode that limits austenitic stainless in seawater and brine. The deliberate copper-plus-molybdenum pairing is the alloy's signature: it gives 825 its standout resistance to sulfuric and phosphoric acid, both reducing environments where a plain Ni-Cr grade would struggle. Chromium at about 21% handles the oxidizing side and supports pitting and crevice resistance, and the titanium addition keeps the material from sensitizing after welding.

For a compression fitting, that chemistry translates directly into where you can put it: acid-plant and pickling lines, phosphoric and sulfuric acid service, chloride-bearing seawater and produced-water systems, and sour oil-and-gas duty. Alloy 825 is not a high-temperature strength alloy the way 625 is, and its mechanical service ceiling sits lower, so where the governing risk is heat or oxidizing halogens, a different grade is the better call. For the full metallurgical picture, composition, mechanical and physical properties, PREN, and corrosion-by-media data, see the Alloy 825 grade page. We've summarized the reference composition below for convenience when writing specs. The values follow the applicable alloy standard, and Crestflo verifies actual heat chemistry on the material test certificate.

For a head-to-head against the alloy most often weighed against it, see Inconel 625 vs 825 and the Inconel 625 grade page, where higher strength and broader oxidizing and high-temperature capability govern the choice.

Inconel 825 Tube Fitting Sizes (1/8-inch to 2-inch OD): Imperial & Metric

Crestflo machines Alloy 825 tube fittings in both imperial fractional and metric tube-OD series, with end connections up to 2-inch (50 mm) OD. The size chart below covers the standard imperial and metric range. Working pressure for any given fitting depends on size, wall thickness, and temperature. It comes from standard tube-fitting pressure data for the tube OD and wall, following ASTM/ASME practice, and the exact rated pressure for your configuration is confirmed on the quotation. Values follow the applicable standard and can be customized to requirement.

Inconel 825 Tube Fitting End & Thread Connections: NPT, BSPP, JIC & Weld

Fittings come with tube-OD compression ends, tapered or parallel threads, or weld ends. All fittings are available in national, international, and custom thread types.

Single vs Double Ferrule & Hardened vs Non-Hardened Options

Alloy 825 fittings come in single-ferrule and double (twin) ferrule designs, and hardened or non-hardened ferrules are supplied depending on what the job calls for. This choice shapes gripping action, vibration resistance, and how many times the fitting can be reassembled.

For guidance on making the right choice, see single vs double vs ferrule-less fittings and hardened vs non-hardened ferrules. Replacement nuts and ferrules are stocked separately, and so are single-ferrule fittings and double-ferrule fittings.

Available Inconel 825 Fitting Shapes & Connectors

Alloy 825 covers the full geometry range, so you can build a complete instrument run in a single material:

• Union, elbow, tee, cross, and reducer fittings
• Male connectors, female connectors, and adapters for joining mismatched threads
• Bulkhead unions, port connectors, caps, and plugs for sealing off unused lines
• Weld connectors (socket, butt, and orbital)

825 comes in related fitting families too, including 37° JIC flare fittings and DIN 2353 bite-type fittings, all combinable within the same instrument tubing system. For the geometry range and ferrule design, start at the tube-fittings product hub.

Corrosion & Service: Sulfuric/Phosphoric Acid, Chlorides & Sour (H₂S) Duty

What a fitting actually sees in service is the whole reason to specify 825 over stainless. The table below sums up how Alloy 825 behaves against the media that drive fitting selection. These are the alloy's published, standard-referenced characteristics, not a per-fitting rating; the corrosion allowance and suitability for a specific stream stay the specifier's call.

Where a stream runs strongly oxidizing, carries hot hydrochloric acid, or needs higher-temperature strength, look instead to Hastelloy C-276 for aggressive reducing acids or Inconel 625 for oxidizing and high-temperature sour service.

Standards, Testing & NACE MR0175 Sour-Service Compliance

Crestflo qualifies its compression tube fittings to ASTM F1387, the performance standard for mechanically attached fittings. That's the basis for dimensional interchange and mechanical-integrity claims. For sour service, Alloy 825 fittings are offered to NACE MR0175 / ISO 15156. Alloy 825 is among the well-established corrosion-resistant alloys covered by the standard, accepted in the solution-annealed condition; confirm the certified hardness limits and any environmental restrictions on H₂S partial pressure, temperature, and chloride content in the standard against your application. We hold the standard approvals that apply to instrumentation tube fittings.

These fittings go through a wide battery of tests. Hydraulic proof, burst, and impulse come first. Then there's pneumatic, flexure-fatigue, rotary-flex, vibration, and thermal-cycling work, plus pull-out and vacuum checks. Positive material identification (PMI) confirms the alloy on every piece, which matters for a high-nickel grade where substitution is a real risk. NDT is standard and done in-house. Destructive testing goes out to labs accredited under ISO/IEC 17025. Third-party inspection is available on request.

Material Traceability & Certification

Every Alloy 825 part is marked with its own heat/lot number. Each shipment comes standard with an EN 10204 MTC 3.1 certificate, and 3.2 is available on request. PMI confirms grade at the part level, every time. That documentation backs solid audit trails for offshore, subsea, acid-plant, and sour-service work, the kind of jobs where a mis-specified alloy is not a small problem.

Drop-In Interchange with Swagelok, Parker & Hy-Lok

Crestflo Alloy 825 fittings are built as dimensional interchange / equivalent fittings for the major instrumentation brands, and that claim rests on ASTM F1387 performance qualification, not on marketing language. These aren't "compatible" or "intermix" parts. Brand names such as Swagelok®, Parker®, and Hy-Lok® remain trademarks of their respective owners, and Crestflo is not affiliated with them; the interchange is strictly dimensional. We don't publish a part-number table. Instead, we prepare interchange references per project: request your cross-reference, and our engineering team will map your existing part numbers to Crestflo 825 equivalents.

Origin & US-Serving Positioning

Crestflo manufactures for the US market. Standard product comes from India; US or European melt is available on request, with full material traceability. Parts are engineered as US drop-in replacements and ship in 6-8 weeks. TAA/DFARS and domestic-melt requirements are handled straight, no hedging, on our US-origin compliance page. If a project calls for a specific melt origin, just specify it on the RFQ.

Why Crestflo for Inconel 825 Tube Fittings

Crestflo operates as the instrumentation division of an export house with four decades behind it and formal recognition from the Government of India. That parent company has a proven delivery record across the Middle East. Its backing grounds a new, focused instrumentation brand built on a handful of clear advantages:

• Lead time of 6-8 weeks versus 20+ weeks typical of the majors.
• ASTM F1387 drop-in interchange proof that mill and trading suppliers rarely publish.
• Small MOQ and private label for distributors and OEMs.
• Both imperial and metric on every fitting, single or double ferrule, hardened or non-hardened.
• Heat-number marking plus MTC 3.1/3.2 on every order, PMI-confirmed.
• Cost-competitive after US duties and tariffs, ISO 9001 / 14001 / 45001 & PED certified.

We Engineer Confidence.

Request a Quote for Inconel 825 Fittings

Give us the details: size, shape, ferrule, thread, and quantity. We'll price it out and get your order scheduled:

• Request a quote, the fastest path to pricing and lead time.
• Request a sample for qualification.
• Become a distributor for line-card and stocking programs.

Datasheets and CAD models are available to customers on request. Reach Crestflo's US sales desk at sales@crestflousa.com or +1 346 594 9005 (Houston, TX). Round out your system with the related Alloy 825 instrumentation valves and Alloy 825 tubing, and serve the corrosion-critical lines in oil and gas and petrochemical and chemical plants.

Frequently Asked Questions

Related Pages

• Alloy 825 alloy grade & corrosion data
• Alloy 825 instrumentation valves
• Alloy 825 tubing
• Inconel 625 vs 825 · Inconel 625 · Hastelloy C-276
• Tube-fittings product hub · ASTM F1387 standard