Double Ferrules Union Fitting: High-Integrity Tube Connector

Stop system leaks, vibration loosening, and thread galling—the three most common failures in high-pressure fluid and gas lines. The Stark Double Ferrules Union is engineered for critical instrumentation and control systems where zero-leakage is non-negotiable. Our forged 316/316L stainless steel design delivers a robust mechanical grip, ensuring long-term system stability under extreme process conditions.

[Request a Quote in 24h] [Apply for Free Samples]

✓ 24h Engineering Support| ✓ Trusted by 1,200+ Global Enterprises| ✓ Zero-Leak Performance Guarantee

🔧 Find Your Size in 3 Clicks

1. Select Your System:○ Imperial (Fractional) ○ Metric

🔥 Most Popular Sizes (In Stock - Same Day Shipping)

1/4"	3/8"	1/2"	3/4"
SS-TU-FT4	SS-TU-FT6	SS-TU-FT8	SS-TU-FT12
6mm	10mm	12mm	16mm
SS-TU-MT6	SS-TU-MT10	SS-TU-MT12	SS-TU-MT16
[Add to Quote]	[Add to Quote]	[Add to Quote]	[Add to Quote]

Part Number Format: [Material]-TU-[Size] (e.g., INC625-TU-FT4)

(TU = Union)

(FT / MT = Sizing System (Fractional Tube / Metric Tube))

🛠 The Engineering Advantage

Reliable performance engineered for versatile industrial service, from standard instrumentation to specialized project requirements.

Dual-Ferrule Mechanical Grip: The front ferrule creates a gas-tight seal against the body, while the back ferrule provides a vibration-resistant grip on the tube, distributing stress to prevent tubing damage.

Optimized Compatibility: Designed for full dimensional and functional interchangeability with Swagelok® and Parker A-LOK®—an ideal solution for MRO and system upgrades.

Anti-Galling Silver-Plated Nuts: All internal nut threads are silver-plated as standard to prevent thread seizing (galling), ensuring reliable reassembly and extending the service life of the fitting.

Quality Controlled Surface Finish: Machined to a high-quality internal finish (Ra 15-32 µin), suitable for general industrial, gas, and fluid service.

📈 Technical Specifications

Feature	Stark Standard Specification	Optional Advanced Upgrades
Material Grade	316/316L Stainless Steel	Duplex 2205, Super Duplex 2507, Inconel 625, Hastelloy C276, Monel 400, etc.
Pressure Rating	Up to 10,000 PSI (689 bar)	Custom High-Pressure Configurations
Internal Finish	Ra 15-32 µin (Standard Industrial)	Ra 5-10 µin (Electropolished for High-Purity)
Testing	100% Pneumatic Tested at 1.1x Working Pressure	Helium Leak Testing (1 x 10⁻⁹ sccs)
Compliance	MTR to EN 10204 3.1 & PMI Verified	NACE MR0175 / NORSOK M-650

📌 Targeted Application Support

Industrial Gas & Oil: Reliable sealing for process instrumentation and control panels.

Extreme Corrosion Service: Alloy 625 and C-276 options for sour gas (NACE) and aggressive chemical processing.

AI Data Center Cooling: Zero-leak performance for high-density liquid cooling systems.

Water Treatment & Desalination: Corrosion-resistant connections for reverse osmosis and filtration skids.

🎯 Why Choose Stark? A Head-to-Head Comparison

Feature	Standard Commodity Fittings	Stark Union
Thread Protection	❌ None (Prone to galling/seizing)	✅ Silver-Plated Standard (Anti-Galling)
Leak Rate	~10⁻⁶ sccs (Typical)	<10⁻⁹ sccs (Helium Leak Tested)
Reassembly Cycles	3-5 times before potential failure	20+ Cycles with No Degradation
Material Traceability	⚠️ Often not provided or incomplete	✅ MTR + PMI Verification with Every Order
Lead Time (Standard 316SS)	1-2 Weeks	3-5 Days (Popular sizes ship same-day)

❓ Frequently Asked Questions (FAQ)

Q1: Are Stark fittings truly interchangeable with Swagelok®?

Yes. Our fittings are designed to be dimensionally and functionally compatible with leading brands like Swagelok® and Parker A-LOK®. They can be safely mixed in existing systems for maintenance and upgrades.

Q2: How do silver-plated nuts prevent thread galling?

Silver provides a permanent solid lubricant that prevents the stainless-on-stainless seizing common in standard fittings. This enables high-torque installation for a secure seal and allows for repeated reassembly without thread damage.

Q3: Are material certificates included with every order?

Absolutely. Every shipment is accompanied by a Material Test Report (MTR) according to EN 10204 3.1 and our internal PMI verification results to ensure 100% material traceability and compliance.

📦 Complete Size & Cross-Reference Chart

Tube O.D. (in)	Stark Part No.	Swagelok® Ref	Parker A-LOK® Ref
1/16"	SS-TU-FT1	SS-100-6	1SC1
1/8"	SS-TU-FT2	SS-200-6	2SC2
3/16"	SS-TU-FT3	SS-300-6	3SC3
1/4"	SS-TU-FT4	SS-400-6	4SC4
5/16"	SS-TU-FT5	SS-500-6	5SC5
3/8"	SS-TU-FT6	SS-600-6	6SC6
1/2"	SS-TU-FT8	SS-810-6	8SC8
5/8"	SS-TU-FT10	SS-1010-6	10SC10
3/4"	SS-TU-FT12	SS-1210-6	12SC12
7/8"	SS-TU-FT14	SS-1410-6	14SC14
1"	SS-TU-FT16	SS-1610-6	16SC16
1-1/8"	SS-TU-FT18	SS-1810-6	18SC18
1-1/4"	SS-TU-FT20	SS-2000-6	20SC20
1-1/2"	SS-TU-FT24	SS-2400-6	24SC24

Tube O.D. (mm)	Stark Part No.	Swagelok® Ref	Parker A-LOK® Ref
2 mm	SS-TU-MT2	SS-2M0-6	SCM2
3 mm	SS-TU-MT3	SS-3M0-6	SCM3
4 mm	SS-TU-MT4	SS-4M0-6	SCM4
6 mm	SS-TU-MT6	SS-6M0-6	SCM6
8 mm	SS-TU-MT8	SS-8M0-6	SCM8
10 mm	SS-TU-MT10	SS-10M0-6	SCM10
12 mm	SS-TU-MT12	SS-12M0-6	SCM12
14 mm	SS-TU-MT14	SS-14M0-6	SCM14
15 mm	SS-TU-MT15	SS-15M0-6	SCM15
16 mm	SS-TU-MT16	SS-16M0-6	SCM16
18 mm	SS-TU-MT18	SS-18M0-6	SCM18
20 mm	SS-TU-MT20	SS-20M0-6	SCM20
22 mm	SS-TU-MT22	SS-22M0-6	SCM22
25 mm	SS-TU-MT25	SS-25M0-6	SCM25
28 mm	SS-TU-MT28	SS-28M0-6	SCM28
30 mm	SS-TU-MT30	SS-30M0-6	SCM30
32 mm	SS-TU-MT32	SS-32M0-6	SCM32
38 mm	SS-TU-MT38	SS-38M0-6	SCM38

Can't find your size?[Request Custom Configuration]

💬 Still Have Questions?

Our engineering team is ready to assist with technical selection, system design, or material recommendations.

[Chat with an Engineer] [Email: sales@starkvalve.com] [Call: +86-13917221881]

🔒 Disclaimer

Swagelok® and Parker A-LOK® are registered trademarks of their respective holders. Stark is not affiliated with, endorsed by, or sponsored by these companies. Part numbers and brand names are provided for cross-reference and compatibility purposes only.