Double Ferrule Tube Fitting Manufacturer, Supplier & Exporter
A double ferrule compression fitting joins metal tubing using two ferrules: a front ferrule that forms the seal and a back ferrule that grips the tube. Raaj Fittings manufactures and exports double ferrule tube fittings in SS 316L, SS 304, duplex, super duplex and nickel alloys, in metric tube sizes from 3 mm to 25 mm OD and imperial sizes from 1/8" to 1" OD.
Double ferrule fittings are the most widely specified connection in high-integrity instrumentation tubing. The two-ferrule design gives a gas-tight seal and a firm grip that resists vibration, pressure surges and thermal cycling, and the joint can be disconnected and remade many times without losing its seal.
Our double ferrule fittings are dimensionally compatible with Swagelok® standard connections. All fittings are supplied with EN 10204 3.1 mill test certificates and full material traceability.
We export double ferrule compression fittings to instrumentation contractors, OEMs and distributors across the Middle East and GCC, Europe and the Americas, in metric and imperial tube sizes with NPT or BSP ends to suit each market.
Double Ferrule Fittings Specifications
3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 25 mm
1/8", 3/16", 1/4", 5/16", 3/8", 1/2", 5/8", 3/4" and 1"
Up to 413 bar (6,000 psi) in small tube ODs with suitable wall thickness; rating depends on tube OD, wall, material and temperature
Tube compression ends; NPT (ASME B1.20.1), BSPT and BSPP (BS 21 / ISO 7-1) threaded ends
Body, nut, front ferrule and back ferrule
Dimensionally compatible with Swagelok® standard connections
Precision-machined from bar stock on CNC machines
EN 10204 3.1 mill test certificate; EN 10204 3.2 on request
Materials & Grades
We supply double ferrule compression fittings in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Double Ferrule Compression Fittings
Stainless steel is the standard material for instrumentation tube fittings across oil and gas, petrochemical, pharmaceutical, and offshore applications. SS 316L is the most widely specified grade.
The industry default for instrumentation tube fittings — low carbon content prevents sensitisation; molybdenum addition provides superior chloride and acid resistance versus 304 grades.
Superior chloride and acid resistance — used where chloride exposure, marine atmosphere, or mild chemical service requires better corrosion resistance than 304.
General corrosion resistance at lower cost than 316L — suitable for water, steam, mild chemical, and food-grade applications where chloride exposure is limited.
Duplex & Super Duplex Stainless Steel Double Ferrule Compression Fittings
Duplex and super duplex grades provide approximately twice the yield strength of 316L with excellent resistance to chloride stress corrosion cracking — the preferred choice for offshore and subsea instrumentation where standard 316L may be susceptible to SCC.
(UNS S31803 / S32205) Offshore topsides instrumentation, seawater injection, and chemical injection systems
(UNS S32750) Subsea instrumentation, high-chloride offshore service, and FPSOs — PREN ≥ 42
Nickel Alloy Double Ferrule Compression Fittings
For aggressive chemical, sour gas, and high-temperature service where duplex stainless steel is insufficient — specified in chemical injection, downhole instrumentation, and severe process environments.
(UNS N06625) Outstanding corrosion resistance in offshore, subsea, and chemical service; widely specified for downhole instrumentation and subsea chemical injection tubing
(UNS N10276) Broad-spectrum resistance to aggressive acids, chlorides, and oxidising media; chemical and FGD process sample systems
(UNS N04400) Hydrofluoric acid service, seawater, and marine instrumentation systems
(UNS N08020) Sulfuric acid and aggressive chemical process sample and instrumentation systems
Special Grades & High-Purity Double Ferrule Compression Fittings
For semiconductor, pharmaceutical, and high-purity gas applications requiring electropolished internal surfaces and ultra-low extractable contamination.
Pharmaceutical and biotech grade — electropolished internal surface for sterile process piping, pure steam, WFI, and clean compressed air systems in GMP-compliant facilities.
Semiconductor grade — ultra-high-purity electropolished finish for process gas delivery, specialty gas distribution, and wet chemistry in semiconductor fabs.
Exceptional corrosion resistance in seawater and oxidising media at low density — used in desalination and marine instrumentation where weight is a factor.
How a Double Ferrule Fitting Seals
When the nut is tightened, it pushes the back ferrule against the front ferrule. The front ferrule is driven into the tapered seat of the body and against the tube, forming the primary seal. At the same time the back ferrule hinges inwards and grips the tube surface. The result is two independent functions — seal and grip — carried by two parts, which is why the joint stays tight under vibration.
- Dual seal and grip — the front ferrule seals, the back ferrule holds the tube.
- Vibration resistance — the back ferrule isolates the seal from tube movement.
- Gas-tight — suitable for gases, light hydrocarbons and vacuum service.
- Remakeable — can be disconnected and retightened for maintenance.
Double or Single Ferrule?
A single ferrule fitting uses one ferrule to do both jobs; it has fewer parts and is quick to assemble, and suits general instrumentation and process service. Double ferrule fittings are preferred where dual-seal redundancy is wanted — critical instrumentation, high pressure, sour service and offshore systems.
Configurations
The double ferrule design is available in every common configuration, including union connectors, male connectors, female connectors, union elbows and tees, bulkhead unions and reducing unions. Do not mix ferrules or nuts from different manufacturers in one joint; use matched components throughout.
Swagelok® is a registered trademark of Swagelok Company. Our products are not manufactured by or affiliated with Swagelok Company.
Applications & Industries
- Instrument impulse lines to pressure, flow and level transmitters
- Analyser and sample systems in refineries and chemical plants
- Chemical injection and hydraulic control lines offshore
- Gas distribution panels and calibration gas systems
- Pharmaceutical and semiconductor process gas lines (electropolished 316L)
- Power plant instrumentation and steam sampling
When ordering, give the fitting type, tube OD (metric or imperial), any thread size and form, and the material grade. See all tube fittings we manufacture.
Testing, Inspection, Marking & Packing
Double ferrule fittings are produced under our quality assurance process:
- Bar stock verified by PMI testing, with full chemical and mechanical traceability
- Dimensional inspection of body seat, ferrule profiles, nut threads and hex sizes
- Thread gauging of NPT, BSPT and BSPP ends
- Pressure testing on request
- Marking with material grade and heat code for traceability
Supplied with EN 10204 3.1 mill test certificates; EN 10204 3.2 certificates and third-party inspection on request.
Fittings are capped and bagged to keep ports clean, then boxed and packed in seaworthy wooden cases for export; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Double Ferrule Compression Fittings?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures tube fittings at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Double ferrule compression fittings are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Double Ferrule Compression Fittings — FAQs
It is a tube fitting with two ferrules. When the nut is tightened, the front ferrule seals against the body and tube, and the back ferrule grips the tube, giving a dual seal and grip.
Our double ferrule fittings are dimensionally compatible with Swagelok® standard connections. For best results, use matched ferrules and nuts from one manufacturer in each joint.
SS 316L double ferrule fittings reach up to 413 bar (6,000 psi) in small tube ODs with suitable wall thickness. The rating falls as tube OD and temperature increase; ask for size-specific tables.
Metric tube ODs from 3 mm to 25 mm and imperial ODs from 1/8" to 1".
SS 316L is the usual minimum. Where chloride stress corrosion cracking is a risk, duplex 2205 or super duplex 2507 is recommended, and Inconel 625 is often used for chemical injection and subsea service.
Yes. We supply double ferrule compression fittings for projects under the European Pressure Equipment Directive (PED 2014/68/EU), with EN 10204 3.1 certificates as standard and 3.2 on request. NACE MR0175 / ISO 15156 compliant material is available for sour service in the Middle East and the Americas.
