Single-Ferrule Tube Fittings: Stainless & High-Nickel Alloy, US-Serving
A single-ferrule tube fitting is an instrumentation compression tube fitting where one ferrule, pushed forward by the drive nut, does two jobs at once: it grips the tube's outside diameter and forms the metal-to-metal seal against both the tube and the fitting body. Crestflo makes single-ferrule compression tube fittings in 316/316L through duplex, high-nickel and titanium alloys. Sizes run imperial and metric, up to 2" (50 mm) OD, and every fitting is qualified to ASTM F1387. Hardened and non-hardened ferrules are both available.
Standard items ship from ready stock. Specials are made to order, with delivery running 6-8 weeks.
Request a quote · request a sample
Scope note: in this document, "ferrule" refers specifically to a fluid-system compression ferrule, the metal ring that grips and seals tubing inside an instrumentation fitting. It doesn't mean an electrical wire-end ferrule. Nor does it cover a hose or cable ferrule, or a sanitary tri-clamp ferrule.
What Is a Single-Ferrule Tube Fitting? One-Piece Ferrule Grip & Seal
In a single-ferrule design, one ferrule handles both mechanical jobs of the joint. As the nut is drawn up, it pushes the ferrule forward along a tapered bore in the body. The ferrule contracts radially onto the tube OD to grip it, and at the same time seats against the body to form the seal. So one component delivers both the tube hold and the leak-tight seal. The result is a compact, low-part-count connection, no welding, no flaring, no soldering required.
The joint has four elements:
The machined fitting shell, called the Body, carries the tapered ferrule seat and leads to the onward connection, whether a tube socket or a thread.
- Nut, the drive nut that converts turning force into axial travel.
- Ferrule, the single ring that grips the tube OD and seals against tube and body.
- Tube, the instrumentation tube being connected.
This one-ferrule design is what sets it apart from double-ferrule fittings, which split grip and seal between a back ferrule and a front one. Want a plain-language definition of the ferrule itself? Check the instrumentation fittings glossary.
Also Known As: Single-Ferrule Compression Fitting, One-Piece Ferrule Fitting & More
Buyers and specifiers call this connection by several names. It is commonly written as a single ferrule tube fitting, single-ferrule fitting, single ferrule compression fitting, or single-ferrule compression tube fitting. Engineering drawings and MRO catalogs may list it as a one-ferrule fitting, one-piece ferrule fitting, mono-ferrule fitting, 1-ferrule fitting, single ferrule tube connector, or simply a single ferrule instrumentation fitting. The component itself is variously a compression ferrule, tube-fitting ferrule, or ferrule ring. All describe the same one-ferrule instrumentation joint covered on this page.
Single-Ferrule Tube Fitting Specifications: Ferrule, Size, Material & Certification
Below is a summary of the single-ferrule fitting as Crestflo supplies it. The ratings shown reference the applicable published standard, and they can be adjusted to what's required.
| Attribute | Single-ferrule tube fitting |
|---|---|
| Working principle | One ferrule, driven axially by the nut, radially grips the tube OD and forms a metal-to-metal seal against tube and body |
| Fitting class | Instrumentation compression tube fitting, single-ferrule design (double-ferrule also offered) |
| Ferrule count | 1 |
| Ferrule condition | Hardened or non-hardened, to requirement |
| OD size range | To 2" (50 mm) OD; imperial and metric |
| Imperial sizes | 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 1" |
| Metric sizes | 6, 8, 10, 12 mm and additional sizes to 50 mm |
| End connections | Tube × tube and tube × thread (via connection-shape pages) |
| Thread standards | NPT per ASME B1.20.1; NPTF; BSPT; BSPP; ISO parallel; JIC 37°; SAE-ORB |
| Stainless grades | 304/304L, 316/316L, 904L |
| Duplex / super-austenitic | Duplex 2205, Super Duplex 2507, 254 SMO, AL-6XN, Alloy 20 |
| Nickel / CRA grades | Inconel 600/601/625/718/825, Incoloy 800/800H/825, Monel 400/K500, Hastelloy C-276/C-22/B-2/B-3/X, Nickel 200/201 |
| Titanium | Titanium Gr 2 |
| Working pressure | Determined by tube OD, wall and alloy per ASME B31.3; values per applicable standard, customizable to requirement |
| Temperature | Limited by the selected alloy and seal per applicable standard; customizable to requirement |
| Finishes | Material finish, electropolish, passivation, silver anti-galling plating, custom |
| Sour service | NACE MR0175 / ISO 15156-compliant material options |
| Performance qualification | ASTM F1387 |
| Certifications | ISO 9001 / 14001 / 45001 & PED certified |
| Traceability | Heat/lot number on every part; EN 10204 MTC 3.1 standard, 3.2 on request |
| Origin | Indian origin; US / European melt available on request, with full material traceability |
| Lead time | Ready stock for standard items; made-to-order for specials; 6–8 week delivery |
Single-Ferrule Fitting Materials: 316/316L, Duplex, Inconel, Hastelloy & Titanium
Crestflo makes single-ferrule stainless steel tube fittings in 304/304L, 316/316L and 904L, and it carries that same one-piece ferrule design over to corrosion-resistant duplex, high-nickel and titanium alloys. No brass. Each grade below links out to its own material page, where you'll find the full rundown on composition and properties. The complete range lives within the tube fittings hub, and Crestflo supplies these alloys as instrumentation fittings, valves and tubing.
| Family | Grades | Representative UNS | Material page |
|---|---|---|---|
| Austenitic stainless | 304/304L, 316/316L, 904L | S30400/S30403, S31600/S31603, N08904 | 316/316L · 904L |
| Duplex / super-austenitic | Duplex 2205, Super Duplex 2507, 254 SMO, AL-6XN, Alloy 20 | S31803/S32205, S32750, S31254, N08367, N08020 | Duplex 2205 · Super Duplex 2507 · 254 SMO |
| Nickel / CRA | Inconel 625, Incoloy 825, Monel 400, Hastelloy C-276 | N06625, N08825, N04400, N10276 | Inconel 625 · Inconel 825 · Monel 400 · Hastelloy C-276 |
| Titanium | Titanium Gr 2 | R50400 | Titanium Gr 2 |
UNS designations are standard published values. For grade selection, check the full instrumentation fitting materials hub on Crestflo's site.
Single-Ferrule Fitting Sizes: Imperial (1/8"–1") & Metric (6–12 mm)
Single-ferrule fittings come in sizes up to 2" (50 mm) OD, offered in both imperial and metric. That means you can connect tube from either system using a single line card.
| System | Sizes | Size page |
|---|---|---|
| Imperial fractional | 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 1" OD | 1/4" · 1/2" · 1" |
| Metric | 6, 8, 10, 12 mm and up | 6 mm · 10 mm · 12 mm |
Check out the metric tube fittings and imperial-fractional tube fittings ranges. For the complete OD listing, Crestflo's tube fitting size chart has what you need.
Single-Ferrule Fitting End Connections & Threads: NPT, BSPP, JIC & SAE-ORB
Single-ferrule fittings come in tube-to-tube and tube-to-thread configurations, covering the full range of connection shapes. Thread ends meet their published standards, with NPT following ASME B1.20.1, and you'll pick them from the shape and thread pages below.
| End type | Standard | Owner page |
|---|---|---|
| Tube × tube union | — | union |
| Connector (male / female) | NPT, BSPT, BSPP, ISO parallel | connector · male connector · female connector |
| Elbow / tee / cross | — | elbow · tee · cross |
| NPT / BSPP threads | ASME B1.20.1; BS EN ISO 228 | NPT · BSPP |
| JIC 37° / SAE-ORB | SAE J514 / SAE J1926 | JIC-37 · SAE-ORB |
Hardened vs Non-Hardened Single Ferrules & Finish Options
Ferrules come hardened or non-hardened, whichever the job calls for. A harder ferrule digs in more aggressively on heavier-wall or harder tube, while a softer one works better with thinner-wall or softer alloy tube. For the metallurgical trade-off, see hardened vs non-hardened ferrules. Ferrules are also sold as components and as nut-and-ferrule sets. Standard finishes include material finish, electropolish, passivation, and silver anti-galling plating; custom finishes are available on request.
Single-Ferrule Fitting Pressure & Temperature Ratings
For a compression tube fitting, the working pressure of the joint tracks the tube it grips, set by tube OD, wall thickness and alloy per ASME B31.3 allowable-stress tables rather than by the fitting body alone. Temperature capability is bounded by the selected alloy. Both are stated per the applicable standard and are customizable to requirement. Where a service exceeds the range of a single-ferrule compression fitting, that duty moves to purpose-built high-pressure tube fittings such as cone-and-thread fittings rated to higher working pressures. Certified per-service ratings and the ordering-code guide are available on request from the engineering team.
Single-Ferrule vs Double-Ferrule vs Ferrule-Less: Which to Choose
Crestflo builds all three, and here's what actually separates them: single-ferrule, double-ferrule and ferrule-less fittings each split the grip-and-seal job differently. A single ferrule handles both tasks in one piece. Double-ferrule designs divide the labor: a back ferrule grips, a front ferrule seals. Ferrule-less fittings skip the ring entirely, gripping and sealing without a separate ferrule at all.
| Design | Ferrules | Grip & seal | Typical selection |
|---|---|---|---|
| Single-ferrule | 1 | One ferrule grips and seals | Compact joints, lower part count, general instrumentation |
| Double-ferrule | 2 | Back ferrule grips, front ferrule seals | Vibration, thermal cycling, frequent re-make |
| Ferrule-less | 0 | Grip and seal without a ferrule ring | Where a ferrule-free connection is specified |
For the full decision, read single vs double ferrule and single vs double vs ferrule-less, or view the ferrule-less range. For installation and gauging, see ferrule installation and gauging.
Standards, Testing & Traceability: ASTM F1387, NACE & MTC 3.1
Crestflo compression tube fittings meet ASTM F1387, the performance spec for mechanically attached fittings. That's the interchange basis letting a single-ferrule fitting stand in dimensionally for the majors. For sour service, material options comply with NACE MR0175 / ISO 15156. Need help choosing? See sour-service selection.
| Item | Basis | Availability |
|---|---|---|
| Performance qualification | ASTM F1387 | Standard |
| Sour service | NACE MR0175 / ISO 15156 | Material option |
| Quality & safety | ISO 9001 / 14001 / 45001 & PED certified | Standard |
| Testing | Hydraulic proof/burst/impulse, pneumatic, flexure fatigue, rotary flex, vibration, thermal cycling, pull-out, vacuum; PMI | Standard regime |
| NDT | In-house; destructive testing at ISO/IEC 17025-accredited labs | Standard |
| Third-party inspection | Witnessed inspection | On request |
| Traceability | Heat/lot number on every part; EN 10204 MTC | 3.1 standard, 3.2 on request |
You'll find certificates in the quality section, and material test certificates fall under traceability. Need datasheets or CAD files? Customers can request them directly.
Order Single-Ferrule Tube Fittings: RFQ, Samples & Private Label
Set up your single-ferrule fittings by size, alloy, end connection and ferrule condition, then pass the requirement along to our engineering team. We support small MOQ, private-label and made-to-print programs for distributors, OEMs and end users alike.
- Request a quote, send size, alloy and connection detail.
- Request a sample, evaluate before you commit.
sales@crestflousa.com · +1 346 594 9005 · Houston, TX. Contact the engineering team at Crestflo.
Need to match an existing brand? Request your Swagelok®, Parker® or Hy-Lok® cross-reference from the cross-reference desk. Crestflo returns single-ferrule interchange guidance, not a part-number table.
Why Crestflo for Single-Ferrule Tube Fittings
Crestflo sits as the instrumentation division of an export house that's been in business for four decades and carries Government-of-India recognition, with a delivery record across the Middle East to back it up. As a US-serving single-ferrule tube fitting supplier and manufacturer, we build single-ferrule tube fittings engineered as dimensional drop-in replacements for Swagelok, Parker, Hoke, Hy-Lok and Fitok. That work rests on ASTM F1387 qualification, a performance basis most competitors don't publish. When engineers benchmark the best single-ferrule tube fittings for a demanding service, that published F1387 qualification is the objective yardstick they measure against.
Standard items ship from stock, specials are made to order, and delivery runs six to eight weeks, well under the twenty-week industry norm. We cover single-ferrule needs across the country, from Gulf Coast refineries to Northeast pharma plants and West Coast semiconductor fabs. A buyer looking for a nearby source gets factory-direct supply instead of a distributor markup.
Origin is Indian, though US or European melt is available on request, and every part comes with full material traceability. Each one carries a heat number along with EN 10204 MTC 3.1. Both imperial and metric sizes sit on a single line card, and small MOQ and private-label options are available.
The Crestflo Engineering Team reviews every fitting. We Engineer Confidence.
Single-Ferrule Tube Fitting FAQ
What is a single-ferrule tube fitting?
A single-ferrule tube fitting is a compression tube fitting that relies on one ferrule to grip the tube's outer diameter and form the seal at the same time, with the nut driving against the fitting body to make that happen. It joins instrumentation tubing without any welding or flaring involved.
What is a ferrule fitting used for?
Ferrule fittings create a leak-tight, gaugeable mechanical joint between metal tubing and instrumentation, no welding, brazing or flaring required. They're used across process, analytical, hydraulic and pneumatic sensing and impulse lines.
Single-ferrule vs double-ferrule, which should I use?
A single-ferrule fitting relies on one component to grip the tube and seal it at once, which keeps the joint compact with fewer parts. The double-ferrule design splits those two jobs between a back ferrule and a front ferrule, and it holds up better under vibration, thermal cycling and repeated re-making. Which one's right depends on the application. Crestflo builds both.
What is the difference between a flange and a ferrule?
A flange is a bolted rim that joins two components face-to-face, with a gasket sandwiched between them. Inside a compression tube fitting, though, you'll find something different: a ferrule, the small ring that grips and seals the tube itself. Different scales, different jobs. These aren't related joint types at all.
What alloys are single-ferrule fittings available in?
We stock 304/304L, 316/316L and 904L stainless, along with Duplex 2205, Super Duplex 2507, 254 SMO, AL-6XN and Alloy 20. Add to that Inconel, Incoloy, Monel, Hastelloy and Nickel 200/201, plus Titanium Gr 2. Brass isn't part of the lineup.
What sizes do single-ferrule fittings come in?
OD tops out at 2" (50 mm). Sizes span both imperial (1/8"–1") and metric (6, 8, 10, 12 mm and up). One range handles both, so imperial and metric tube can be served without separate lines.
Are single-ferrule fittings NACE-compliant for sour service?
NACE MR0175 / ISO 15156-compliant materials, yes, Crestflo does offer those for single-ferrule fittings used in sour or corrosive service.
Are single-ferrule fittings performance-tested?
Yes. Crestflo's compression tube fittings are qualified to ASTM F1387. That qualification includes hydraulic, pneumatic, vibration, thermal-cycle and pull-out testing, along with PMI verification and EN 10204 MTC 3.1 traceability.
Can single-ferrule fittings replace Swagelok, Parker or Hy-Lok fittings?
Crestflo single-ferrule fittings are built for dimensional interchange, and they're ASTM F1387-qualified. If you need interchange guidance, request your brand cross-reference from our engineering team.
What is the lead time and minimum order?
Standard items ship straight from stock. Specials are made to order, and delivery on those runs 6 to 8 weeks. MOQs stay small, and private-label options are available too.
Where are single-ferrule fittings made?
Crestflo sources these fittings from India, though US and European melt is available on request, and full material traceability comes standard. As a US-serving manufacturer, Crestflo engineers its fittings for drop-in replacement in the US market.
Can I get hardened or non-hardened ferrules?
Yes. We supply ferrules hardened or non-hardened, whichever the job calls for, and match them to your tube wall and alloy.
Related Tube Fittings & Resources
- Tube fittings hub, the full instrumentation tube fitting range.
- Ferrule-less tube fittings, the nut and ferrule assembly, and tube fitting ferrules sold on their own
- For comparisons: single vs double ferrule, and if you want the fuller picture, single vs double vs ferrule-less
- On materials and standards, see instrumentation fitting materials, the ASTM F1387 standard, and the Swagelok cross-reference guide