In harsh upstream and downstream oil and gas environments across the UK and Ireland, managing hydrogen sulfide (H₂S) is a critical challenge. In wet or humid conditions, H₂S can cause sulfide stress cracking (SSC) and stress corrosion cracking (SCC). During these corrosion processes, atomic hydrogen diffuses into high-strength metals, leading to brittle fractures at stress levels well below the material’s yield strength.

To help prevent costly failures and ensure long-term reliability, equipment used in sour service applications must comply with stringent NACE standards. At NVFCL, we supply FITOK Super Duplex 2507 Tube Fittings, engineered to meet and exceed these demanding corrosion resistance requirements.

Understanding NACE Standards

Material selection for sour service environments is guided by two internationally recognised standards developed by the National Association of Corrosion Engineers (NACE):

• NACE MR0175 / ISO 15156 – The industry standard for upstream oil and gas production, where H₂S concentrations are typically highest.
• NACE MR0103 / ISO 17945 – Designed for downstream refining and petrochemical facilities, where corrosion and cracking risks remain despite lower H₂S concentrations.

Compliance matters: Using fully certified NACE-compliant materials is one of the most effective ways to reduce the risk of hydrogen-induced cracking and extend the lifespan of critical process systems.

FITOK Super Duplex 2507 Double Ferrule Tube Fittings

FITOK manufactures a wide range of NACE-compliant tube fittings in corrosion-resistant materials including 316 Stainless Steel, 6Mo, Alloy 625, Alloy 825, Alloy C-276, and Super Duplex 2507.

The Super Duplex 2507 Series is engineered with component-specific materials to optimise both corrosion resistance and mechanical performance.

A standard double ferrule fitting consists of:

In contact with the process medium

• Fitting Body – Super Duplex 2507
• Front Ferrule – Super Duplex 2507

Isolated from the process medium

• Nut – Super Duplex 2507 Bar Stock
• Rear Ferrule – 6Mo Alloy

Why This Design Matters

NACE MR0175 places strict requirements on components that come into direct contact with wet H₂S.

FITOK optimises each component accordingly:

• Body and Front Ferrule – Manufactured from Super Duplex 2507 to provide exceptional corrosion resistance where the process media flows.
• Rear Ferrule and Nut – Manufactured from 6Mo alloy and Super Duplex 2507 bar stock respectively. Once the front ferrule creates a secure seal against the tube, these components are isolated from the process media. This allows them to meet NACE requirements while delivering excellent mechanical strength and tube gripping performance.

This intelligent material selection provides the ideal balance of corrosion resistance, sealing integrity and mechanical reliability.

A Complete NACE-Compliant Product Range

In addition to Super Duplex tube fittings, NVFCL supplies FITOK’s full range of NACE-compliant instrumentation products, including:

• Medium and high-pressure fittings (20M and 60H Series)
• PMH and AMH adapters and pipe fittings
• T20M and T60H instrumentation tubing
• Ball valves
• Needle valves
• Check valves
• Relief valves
• Gauge valves

Source Certified FITOK Products from NVFCL

Selecting non-certified materials for H₂S service can significantly increase safety risks, maintenance costs and the likelihood of premature equipment failure.

As the only authorised FITOK distributor in the UK and Ireland, NVFCL combines FITOK’s engineering expertise with local stock availability, giving customers access to fully traceable, certified components with fast regional delivery.

If you’re designing fluid systems for upstream oil and gas production or downstream petrochemical applications where H₂S is present, our team can help you select the right solution.

Contact NVFCL to request a NACE compliance certificate, technical data sheets, or more information on the FITOK Super Duplex 2507 range.