Introduction to Stainless Steel Double-Wall Pipes

A stainless steel double-wall pipe is a coaxial pipeline system composed of two concentric stainless steel tubes – an inner pipe that carries the medium and an outer pipe that provides secondary protection.

Between them lies an enclosed or open interstitial space, which can be vacuum-insulated, ventilated, or filled with inert gas depending on the application.

At Ganyeah Group, we specialize in designing and manufacturing high-performance stainless steel double-wall pipes for LNG transport, chemical processing, and aerospace fuel systems – where safety, precision, and reliability are paramount.

1. Structure Design and Types

Basic Structure:

The stainless steel double-wall pipe features an inner carrier pipe and an outer containment pipe. The interlayer can be engineered in three primary ways:

• Vacuum Insulation:
  A high-vacuum layer minimizes heat transfer — ideal for cryogenic liquids and LNG fuel systems on ships or storage facilities.
• Ventilated Jacket:
  Used for toxic or flammable gases, where active ventilation removes any leakage.
• Pressurized Inert Gas:
  Filling the gap with nitrogen or argon prevents air ingress and enhances explosion resistance, commonly used in chemical and nuclear plants.

stainless steel pipes supply by Ganyeah Group

Material Selection:

Typical materials include 304, 316L, and 2205 duplex stainless steel. Duplex stainless steel offers twice the yield strength (~450 MPa) of 304 and exceptional resistance to chloride stress corrosion cracking.

Size Range:

Diameters typically range from DN15 to DN550, with pressure ratings up to 1000 bar. High-pressure gas transport pipes and vacuum-insulated stainless steel double-wall pipes employ precision supports to maintain coaxial alignment.

2. Manufacturing Process and Key Technologies

Core Techniques:

• Wax Injection Molding:
  Molten wax is injected between the inner and outer pipes, solidified to maintain alignment during bending. This method — widely used in aerospace fuel lines — ensures perfect coaxiality without deformation.
• Advanced Welding:
  The inner pipe is TIG welded under argon shielding with 100% radiographic inspection, while the outer pipe undergoes liquid penetrant testing. Interlayer temperature is kept below 150°C to prevent distortion.
• Vacuum Processing:
  Vacuum-insulated stainless steel double-wall pipes require multi-stage evacuation (vacuum ≤10⁻³ Pa) and helium leak detection for guaranteed thermal performance.

Quality Control:
Manufacturing follows a four-tier quality system:

• Intergranular corrosion test (ASTM A262 Practice E) for incoming materials.
• Inner pipe roundness ≤1% of nominal diameter.
• Coaxiality ≤2 mm/m during assembly.
• Hydrostatic or pneumatic testing before delivery.

3. Applications and Case Studies

Energy and Chemical Industries:

In LNG carriers, vacuum-insulated stainless steel double-wall pipes are used for cryogenic fuel transfer. For instance, CSSC’s LNG systems use pipes certified by the China Classification Society (CCS) for -163°C operation.

In refineries and petrochemical plants, duplex stainless steel double-wall pipes transport corrosive media such as acids or alkalis safely. The Oman 24-inch duplex gas pipeline has run for over 25 years without corrosion.

Aerospace:

Aircraft fuel systems (e.g., C919 and Airbus A320) utilize stainless steel double-wall pipes formed by wax-assisted bending and flexible welded joints, ensuring leak-free performance under vibration and temperature extremes.

Municipal and Construction:

• Exhaust Systems: Double-wall flue pipes filled with rock wool or PU foam minimize heat loss.
• Drinking Water Projects: Stainless-steel–carbon steel composite double-wall pipes have been adopted in Fuzhou’s urban water supply, reducing stainless steel consumption by 85% and overall cost by 45%.

4. Advantages and Limitations

Core Advantages:

• High Safety: Outer pipe acts as a containment barrier and can house sensors for leak detection.
• Superior Corrosion and Temperature Resistance: 316L resists chloride pitting, while duplex grades tolerate temperatures from -50°C to 250°C.
• Energy Efficiency: Vacuum-insulated types reduce heat loss by over 90% compared to single-wall systems.

Limitations:

• Higher Cost: Manufacturing is complex, typically 30–50% more expensive than single-wall pipes.
• Installation Challenges: Requires specialized welding and vacuum sealing tools; alignment must be precisely maintained.

5. Industry Standards and Specifications

International Standards:

• ASTM A813/A813M: Welding and performance requirements for austenitic stainless steel double-wall pipes.
• ISO 13628-7: Design and testing guidelines for subsea double-wall pipelines.

Chinese Standards:

• T/CANSI 18-2020: National specification for marine LNG and LPG double-wall piping systems.
• T/SDSS 001-2024: Standard for welded stainless-steel composite pipes for municipal and building applications.

6. Maintenance and Safety Management

Routine Maintenance:

• Clean with neutral detergents; inspect weld seams for cracks or corrosion.
• Conduct hydrostatic or pneumatic pressure tests every 3–5 years (1.5× design pressure for nuclear-grade systems).
• Internal inspection via endoscopes ensures no degradation inside the pipe.

Safety Measures:

• Leak Monitoring: Sensors or gas detectors in the interspace trigger alarms upon leakage.
• Environmental Protection: Apply epoxy zinc-rich coatings for outdoor exposure and avoid acid or salt environments.

7. Market Trends and Future Outlook

The global stainless steel double-wall pipe market is expected to grow at a CAGR of 4.4% (2024–2029), driven by LNG expansion, hydrogen energy, and seawater desalination projects.
For instance, Qatar’s 2030 LNG capacity plan will significantly boost demand for cryogenic double-wall piping.

Technological innovations include:

• Smart Monitoring: Optical fiber sensors for real-time pressure, strain, and temperature feedback.
• Lightweight Design: Use of thin-wall duplex materials and advanced supports for reduced weight without compromising strength.

The stainless steel double-wall pipe combines dual containment, superior corrosion resistance, and durability for critical fluid transport.

Despite higher costs and complex fabrication, its long-term safety, energy efficiency, and reliability make it the preferred choice for high-risk applications in energy, aerospace, and chemical sectors.

With Ganyeah Group’s expertise in advanced pipe manufacturing and precision welding, our stainless steel double-wall piping systems deliver unmatched performance in the world’s most demanding environments – from LNG terminals to next-generation clean energy infrastructure.