CRA Clad Pipes vs. Mechanically Lined Pipe (MLP) Selection: Balancing Performance, Cost, and Application Needs
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CRA Clad Pipes vs. Mechanically Lined Pipe (MLP) Selection: Balancing Performance, Cost, and Application Needs
In offshore and onshore energy projects, the choice of pipeline material is one of the most critical design decisions. Corrosion-Resistant Alloy (CRA) clad pipes and Mechanically Lined Pipes (MLPs) are two leading technologies designed to provide reliable protection against corrosion in aggressive service conditions. Each offers unique advantages, trade-offs, and application niches.
This article examines the differences between CRA clad and MLP, evaluates their technical and economic considerations, and provides guidance for operators, EPCs, and project managers making pipeline selection decisions.
Table of Contents
Understanding CRA Clad Pipes
Definition and Manufacturing Process
Key Strengths of CRA Clad Pipe
Understanding Mechanically Lined Pipe (MLP)
Definition and Structure
Key Strengths of MLP
Head-to-Head Comparison
Cost and Material Efficiency
Corrosion Resistance and Reliability
Manufacturing and Supply Chain Considerations
Installation Methods and Technical Performance
Case Studies and Industry Adoption
Future Outlook in Energy Transition Projects
Conclusion – Key Takeaways
References
Understanding CRA Clad Pipes
Definition and Manufacturing Process
CRA clad pipe consists of a carbon steel backing pipe metallurgically bonded to an internal layer of corrosion-resistant alloy. The cladding is applied using welding techniques such as hot-roll bonding or weld overlay. This metallurgical bond ensures the CRA layer becomes an integral part of the pipe, offering long-term durability even under severe conditions (DNV-ST-F101, 2021).
Key Strengths of CRA Clad Pipe
Full metallurgical bond: Superior resistance to liner disbondment or slippage.
High reliability in hostile environments: Particularly effective in sour service (high H₂S, CO₂).
Track record: CRA clad pipes have decades of operational history in offshore fields worldwide.
Understanding Mechanically Lined Pipe (MLP)
Definition and Structure
MLP is a bi-metallic pipeline with a carbon steel outer pipe and a corrosion-resistant inner liner. The liner is mechanically bonded, often via hydraulic expansion, to the host pipe. Unlike CRA cladding, the bond is mechanical rather than metallurgical.
Key Strengths of MLP
Cost efficiency: Uses a thinner CRA liner, reducing material costs significantly.
Flexible production: Capable of large-volume manufacturing and shorter delivery times.
Proven offshore use: DNV-qualified for reel-lay, S-lay, and J-lay installations.
Lightweight: Lower pipe weight can simplify handling and installation.
Head-to-Head Comparison
Cost and Material Efficiency
CRA clad pipes require substantial CRA usage, which can drive costs up, especially during periods of nickel price volatility. In contrast, MLPs reduce CRA consumption by using only a thin liner, often providing up to 30–40% savings (Proclad, 2024).
Corrosion Resistance and Reliability
CRA Clad Pipe: Offers robust, metallurgical bonding with minimal risk of disbondment. Excellent choice for high-pressure, high-temperature sour service.
MLP: Provides reliable protection against corrosion in most subsea and onshore conditions. However, specific qualification testing is required to validate liner performance in fatigue-critical environments (ASME OMAE, 2024).
Manufacturing and Supply Chain Considerations
CRA Clad Pipe: Requires more complex fabrication and welding, which can lead to longer lead times.
MLP: Faster production rates—BUTTING and Proclad report outputs of up to 20–24 km/month—making it an attractive solution for large-scale projects.
Installation Methods and Technical Performance
CRA Clad Pipe: Fully compatible with standard S-lay and J-lay installation methods.
MLP: Compatible with S-lay, J-lay, and reel-lay. Qualification programs (e.g., Brazilian Pre-Salt projects) have proven its integrity under repeated spooling and unspooling cycles (Stainless Steel World, 2022).
Case Studies and Industry Adoption
Brazilian Pre-Salt: BUTTING’s BuBi® MLP used successfully for subsea SCR risers and flowlines, DNV-qualified for reel-lay.
North Sea Projects: CRA clad pipes chosen where sour service and extremely high pressure require maximum reliability.
Global Operators: Both technologies coexist, with selection dependent on service conditions, economics, and project specifications (OnePetro, 2019).
Future Outlook in Energy Transition Projects
Both CRA clad and MLP technologies are expected to play roles beyond oil and gas.
Hydrogen Transport: CRA materials and MLP liners are under evaluation for hydrogen embrittlement resistance.
Carbon Capture and Storage (CCS): MLP offers cost-efficient CRA lining for CO₂ pipelines, where corrosion protection is essential.
Conclusion – Key Takeaways
CRA clad pipe remains the gold standard for the most severe service conditions requiring maximum integrity.
MLP delivers a cost-effective alternative, especially for large-diameter subsea flowlines and risers.
Selection should balance service environment, cost, fatigue performance, and supply chain factors.
Both technologies are evolving, with roles extending into hydrogen and CCS pipelines as the energy transition accelerates.
Alloy Liner Being Inserted Into Carbon Steel Pipe Prior to Hydroforming
