Spare Ferrules & Nuts for Instrumentation Tube Fittings
Spare ferrules and nuts are the replaceable sealing parts of a compression tube fitting, the front ferrule, back ferrule, single ferrule, and nut that are consumed or replaced when instrumentation fittings are serviced, remade, or restocked. Crestflo supplies these as individual spare and replacement service parts, not only as complete fittings, in stainless through high-nickel and CRA alloys and titanium, hardened or non-hardened, in imperial and metric sizes, with a heat/lot number on every part and an EN 10204 material test certificate. In this context, "ferrule" means the fluid-system compression ferrule inside an instrumentation tube fitting, not a wire-rope, electrical wire-crimp, walking-stick, or column/distilling ferrule.
What Spare Ferrules & Nuts Are: Replacement Service Parts for Compression Fittings
Spare ferrules and nuts let you re-order just the sealing components of a compression tube fitting instead of buying complete fitting bodies. In a gaugeable compression fitting, the ferrule swages onto the tube outside diameter as the nut is pulled up, forming the leak-tight mechanical grip and seal; the nut supplies the make-up force. Because these parts do the sealing and gripping work, they are the items most often reordered, after a make-and-break service, when a ferrule or nut is lost or damaged, or when a distributor or panel shop keeps a spares and kitting program stocked. The aftermarket reorder is served here; the ferrule and nut as primary fitting components are detailed on the tube fitting ferrules and nut and ferrule pages.
Also Known As: Replacement Ferrules, Ferrule Kit, Ferrule Repair Kit & Nut Set
Maintenance and procurement buyers specify these parts under many names. They are searched as spare ferrules and nuts, replacement ferrules and nuts, replacement ferrules, or replacement nuts for tube fittings; as a ferrule kit, ferrule set, ferrule replacement kit, ferrule repair kit, tube fitting repair kit, ferrule service kit, or ferrule pack; and as a nut and ferrule set (nut & ferrule set) or, in reversed forms, ferrules and nuts and nuts and ferrules. The individual pieces appear as front ferrule, back ferrule (rear ferrule), single ferrule (two-piece), and the nut, also called a tube nut, gland nut, drive nut, or compression nut. Stainless items are searched as stainless steel ferrules and stainless steel tube nuts. For the aftermarket reorder of any of these, this is the spare-parts line.
Spare Ferrule & Nut Components: Front Ferrule, Back Ferrule, Single Ferrule & Nut
A double-ferrule (two-ferrule) service set has three pieces; a single-ferrule set has two. The nut supplies the make-up force, the front ferrule forms the primary seal against the tube and body, and the back ferrule grips and holds the tube through a colleting action.
| Component | Role | Sold as | Typical reorder reason |
|---|---|---|---|
| Front ferrule | Primary seal against tube OD and fitting body seat | Individual part or in a set/kit | Damaged or lost during service; kitting |
| Back ferrule (rear ferrule) | Grips and holds the tube (colleting action) | Individual part or in a two-ferrule set | Remake after break-out; spares stocking |
| Single ferrule (two-piece) | One-piece ferrule that both grips and seals | Individual part or with nut | Replacement on single-ferrule designs |
| Nut (tube / gland / drive / compression nut) | Threads onto the fitting body and advances the ferrule(s) on pull-up | Individual part or with ferrule(s) | Thread wear, galling, loss; kitting |
For the deeper component geometry, see tube fitting ferrules; for the assembled sealing group, see nut and ferrule sets.
When to Reorder Ferrules & Nuts, Not Whole Fittings
You can order just the ferrules and nuts, not complete fitting bodies, when a joint is being retightened or remade after break-out, when a ferrule or nut is lost or damaged, when a fitting is being converted to a different tube alloy, or when a distributor or OEM keeps a spare-parts, kitting, or VMI program stocked. The fitting bodies stay in service; only the consumed sealing parts are replaced. Parts are supplied in bulk or kitted, with private-label packaging and kitting/VMI available for stocking programs.
Spare Ferrules & Nuts Specifications at a Glance
The ferrule set and nut complete a compression tube fitting, so pressure and temperature capability is a property of the assembled fitting rather than of the loose parts. Ferrules and nuts are machined from bar stock and marked for traceability.
| Attribute | Specification |
|---|---|
| Component types | Front ferrule, back ferrule, single ferrule, nut |
| Ferrule design served | Single-ferrule and double-ferrule (front + back) |
| Ferrule hardening | Hardened or non-hardened, supplied to requirement |
| Tube OD range | 1/16"–2" imperial and 3–50 mm metric |
| Bar stock | Machined per ASTM A276 / A479 (values per applicable standard; customizable to requirement) |
| Materials | 304/304L, 316/316L, 904L stainless; duplex/super-duplex; high-nickel/CRA alloys; titanium Gr2 |
| Nut finish | Material finish, electropolish, passivation, silver anti-galling plating, custom |
| Interchange basis | Dimensional interchange qualified per ASTM F1387 |
| Testing | Fitting performance qualified per ASTM F1387; PMI on material |
| Traceability | Heat/lot number on every part; EN 10204 MTC 3.1 (3.2 on request) |
| Certification | ISO 9001 / 14001 / 45001 & PED certified |
| Compliance | NACE MR0175 / ISO 15156 for sour service, where specified |
| Origin | Indian origin; US / European melt available on request, with full material traceability |
| Availability | Ready stock for standard items · made-to-order for specials · 6–8 week delivery |
Spare Ferrule & Nut Materials: 316/316L Stainless, Duplex, Inconel, Monel, Hastelloy & Titanium
Crestflo supplies stainless steel ferrules and nuts plus corrosion-resistant alloy (CRA) parts across a far wider grade range than the 316-only listings common in the aftermarket, and the ferrule and nut can be matched to the tube and fitting-body alloy. Each grade is covered in depth on its dedicated material page; here it is offered only in instrumentation ferrule and nut form.
| Family | Grades | Grade reference |
|---|---|---|
| Austenitic stainless | 304/304L, 316/316L, 904L | 316/316L stainless ferrules, 904L |
| Duplex / super-austenitic | Duplex 2205, Super Duplex 2507, 254 SMO, AL-6XN, Alloy 20 | super duplex 2507 |
| Nickel alloys | 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 | Inconel 625, Hastelloy C-276, Monel 400 |
| Titanium | Titanium Gr2 | all material options |
Brass is not offered on the US instrumentation line; the scope here is stainless and high-nickel/CRA alloys plus titanium.
Hardened vs Non-Hardened Ferrules: Both Supplied to Requirement
Crestflo supplies both hardened and non-hardened ferrules to your requirement. A hardened ferrule keeps a tough gripping edge over a ductile core, which helps grip on harder tube alloys, while non-hardened ferrules suit softer or thin-wall tube. Select the condition to match the tube material and service, see hardened vs non-hardened ferrules for the decision.
Single-Ferrule vs Double-Ferrule Spares: Which Parts to Order
Order the spare parts that match your fitting design. A single-ferrule (two-piece) fitting uses one ferrule that both grips and seals, so its spares are the single ferrule and nut. A double-ferrule (two-ferrule) fitting separates the jobs, front ferrule seals, back ferrule grips, so its spares are the front ferrule, back ferrule, and nut. Crestflo supplies spares for both. For the full comparison, see single vs double ferrule and the single-ferrule tube fittings family page.
Spare Ferrule & Nut Sizes: 1/16"–2" Imperial & 3–50 mm Metric
Spare ferrules and nuts are offered across the full imperial and metric tube-OD range of the compression fittings line, from 1/16" through 2" fractional and 3 mm through 50 mm metric, covering the common 1/8", 1/4", 3/8", 1/2", 5/8", 3/4", and 1" sizes and the 6 mm, 8 mm, 10 mm, and 12 mm metric sizes. Sizes and dimensions are per the applicable standard and customizable to requirement.
| Tube OD system | Sizes offered | Ferrule configurations |
|---|---|---|
| Imperial (fractional) | 1/16", 1/8", 1/4", 3/8", 1/2", 5/8", 3/4", 1", up to 2" | Single or double ferrule |
| Metric | 3, 6, 8, 10, 12 mm through 50 mm | Single or double ferrule |
For dimensional selection by tube OD, see the tube fitting size chart and per-size pages such as 1/4-inch tube fittings.
Nut Finishes & Anti-Galling Plating for Ferrules & Nuts
Nuts are available with silver anti-galling plating to reduce thread galling on repeated make-up, alongside material finish, electropolish, passivation, and custom finishes. Ferrules are supplied in material finish with electropolish or passivation on request, and oxygen-clean handling is available for high-purity service, see oxygen and UHP cleaning. Finishes are specified to the standard cleanliness or plating target for the service and customizable to requirement.
Drop-In Interchange for Swagelok®, Parker® & Hoke® Fitting Bodies
Crestflo ferrules and nuts are engineered for dimensional interchange with major-brand fitting bodies, and that interchange is backed by ASTM F1387 performance qualification rather than assertion alone. Swagelok® is a trademark of Swagelok Company; Parker® is a trademark of Parker-Hannifin Corporation; Hoke® is a trademark of its respective owner; and Crestflo is not affiliated with, sponsored by, or endorsed by these companies. Part-level mapping is handled in the cross-reference layer, request your Swagelok® cross-reference or work from the master interchange chart with our engineering team.
Standards, Certification & Traceability: ASTM F1387, NACE MR0175 & EN 10204 MTC
Spare ferrules and nuts complete a compression tube fitting that Crestflo qualifies to ASTM F1387, the performance standard covering hydraulic proof, burst and impulse, pneumatic, flexure and rotary-flex fatigue, vibration, thermal cycling, pull-out, and vacuum testing. Sour-service parts are supplied to NACE MR0175 / ISO 15156 where specified. Every part carries a heat/lot number, and each order ships with an EN 10204 MTC 3.1 certificate (3.2 on request), backed by positive material identification and in-house NDT. Crestflo is ISO 9001 / 14001 / 45001 & PED certified; certificates are held in the quality documentation, and origin/TAA questions are handled on US origin compliance.
How to Order Spare Ferrules & Nuts: What to Specify, Kits & CAD
Specify spare parts by tube OD (imperial or metric), ferrule design (single or double ferrule), ferrule material, nut material and plating, ferrule condition (hardened or non-hardened), quantity, the mating fitting brand and series to interchange, and MTC grade. To pin down the exact ordering code for your requirement, request the ordering-code guide from our engineering team or build a part number with the configurator. Datasheets and CAD models are available to customers on request. For related components, see the parent instrumentation accessories line, tube installation tools, and the tube fitting ferrules detail. Request a quote, email sales@crestflousa.com or call +1 346 594 9005 (Houston, TX). Distributors can review the line card, and samples are available via request a sample.
Why Buy Spare Ferrules & Nuts from Crestflo
Crestflo is the instrumentation division of a four-decade-old, Government-of-India-recognized export house with a Middle-East delivery track record, engineering heritage behind a focused US-serving instrumentation brand. Spare parts pair genuine alloy breadth (stainless plus high-nickel/CRA and titanium, not 316 only) with an ASTM F1387 interchange basis, heat-number traceability and EN 10204 MTC, both imperial and metric sizing, hardened or non-hardened ferrules, and small-MOQ, kitting, and private-label programs. Availability is ready stock for standard items, made-to-order for specials, and 6–8 week delivery, see lead time. We Engineer Confidence.
Spare Ferrules & Nuts: Frequently Asked Questions
What is the purpose of a ferrule in a tube fitting?
The ferrule swages onto the tube's outer diameter as the nut is tightened, forming the mechanical grip and leak-tight seal between the tube and the fitting body. The nut supplies the make-up force, and the result is a gaugeable, remakeable joint made by controlled pull-up rather than by flaring, brazing, or welding.
What is another name for a ferrule?
In fluid-system fittings the ferrule is also called a sleeve, gripper, or bite ring, and in UK usage an olive or compression ring; a two-piece set has a front ferrule and a back ferrule. This is not the same as a wire-rope, electrical wire-crimp, or walking-stick ferrule.
Can I order just spare ferrules and nuts, not the whole fitting?
Yes. Front ferrules, back ferrules, single ferrules, and nuts are supplied as individual spare and replacement service parts, in bulk or kitted, so you replace only the consumed sealing components while the fitting bodies stay in service.
What materials are available for ferrules and nuts?
304/304L, 316/316L, and 904L stainless; duplex and super-duplex (2205, 2507), 254 SMO, AL-6XN, and Alloy 20; Inconel, Incoloy, Monel, Hastelloy, and Nickel 200/201; plus Titanium Gr2. Brass is not offered on the US instrumentation line.
Do you offer hardened ferrules?
Both hardened and non-hardened ferrules are supplied to requirement. Hardening keeps a tough gripping edge over a ductile core, which helps grip on harder tube alloys; see the hardened vs non-hardened ferrules guide for selection help.
When should you not reuse or use a ferrule?
Do not reuse a ferrule that shows visible damage, cracking, or scoring, and do not use a ferrule in the wrong alloy for the media. For sour service, select a NACE MR0175 / ISO 15156-compliant alloy, and confirm the correct hardness and finish for the application before make-up.
Should I make my own ferrules?
No. Ferrule geometry and hardness are dimensionally controlled and qualified for interchange and sealing under ASTM F1387; a self-made ferrule cannot be relied on to grip and seal correctly. Source qualified parts in the required alloy, size, and hardness rather than fabricating them.
How do I remove a stuck ferrule?
Use the correct ferrule and tube-fitting service procedure and tools rather than forcing the joint, which can damage the tube or fitting body. See the ferrule installation and gauging guide for the make-up and removal procedure, and the tube installation tools line for the service tooling.
Will your ferrules interchange with Swagelok® or Parker® fittings?
Crestflo ferrules are engineered for dimensional interchange with major-brand fitting bodies, backed by ASTM F1387 performance qualification. Swagelok® is a trademark of Swagelok Company and Parker® of Parker-Hannifin Corporation; Crestflo is not affiliated with or endorsed by these companies. Request your cross-reference for part-level confirmation.
Do parts come with material certification?
Yes, a heat/lot number on every part and an EN 10204 MTC 3.1 certificate as standard (3.2 on request), backed by positive material identification, plus ISO 9001 / 14001 / 45001 & PED certification and NACE MR0175 compliance where specified.
What is the lead time and minimum order?
Availability is ready stock for standard items, made-to-order for specials, and 6–8 week delivery, with small MOQ. Private-label and kitting programs are available for distributors and OEMs.
Where are they made? Are they TAA-compliant?
Standard parts are of Indian origin, with US or European melt available on request and full material traceability. Standard product is not TAA-compliant; where domestic-melt or TAA is required, US/European-melt options are offered as a capability, see the US origin compliance page for details.