Mechanically Lined Pipes (MLPs) are engineered to combine carbon steel's structural strength with Corrosion-Resistant Alloys (CRAs) corrosion resistance, offering a cost-effective solution for transporting corrosive fluids in various industries.
MLPs consist of an outer carrier pipe, typically carbon or low-alloy steel, and an inner liner pipe composed of CRA materials such as stainless steel, duplex stainless steel, or nickel alloys. The selection of these materials depends on factors like fluid composition, operating temperature, pressure, and environmental conditions. Proclad offers MLPs in sizes ranging from 4" to 20" in diameter, with wall thicknesses between 6mm and 45mm, accommodating various project specifications.
Proclad utilises a 38,000-ton hydroforming press to expand the CRA liner within the carbon steel pipe, achieving 100% residual contact between the liner and the outer pipe. This process applies pressures typically between 400 to 900 bar on pipes up to 12 meters long, ensuring a robust mechanical bond that enhances grip strength and overall performance.
Mechanically Lined Pipes (MLPs) are engineered to provide a cost-effective and durable solution for transporting corrosive fluids across various industries. Their unique construction, combining a carbon steel outer pipe with a corrosion-resistant alloy (CRA) inner liner, makes them particularly suitable for the following applications:
The versatility and robust performance of MLPs across these applications highlight their importance in modern pipeline infrastructure, especially in sectors where corrosion resistance and mechanical strength are paramount.
Selecting appropriate materials for MLPs is crucial and should align with international standards such as those from the American Petroleum Institute (API), the American Society for Testing and Materials (ASTM), Det Norske Veritas (DNV), and the International Organization for Standardization (ISO).
Proclad adheres to these standards, offering base material grades from API 5L X52 to X70, with various CRA liners to meet specific project requirements.
Proclad conducts rigorous testing and inspection procedures to ensure MLPs meet industry standards and client specifications. These procedures include hydrostatic testing, dimensional inspection, visual inspection, and non-destructive testing methods such as ultrasonic testing or radiographic examination.
The reel-lay method involves spooling pipes onto a reel for transportation and unspooling them during installation. This process subjects the pipes to plastic deformation, impacting the bond between the carbon steel backing pipe and the CRA liner in MLPs. Ensuring this mechanical bonding remains intact is crucial for the pipe's fatigue performance.
TWI conducted a comprehensive program to assess the fatigue performance of reeled MLPs. The study involved full-scale resonance fatigue testing and non-destructive examinations, such as dye penetrant inspection (DPI) and eddy current testing (ECT), on MLP specimens with a nominal outer diameter of 8.625 inches and a total wall thickness of 32.1mm, featuring Alloy 625 liners, clad overlay, and girth welds.
Key Findings:
The successful qualification of reeled MLPs for fatigue service demonstrates their viability for dynamic applications in the subsea oil and gas sector. This advancement offers a cost-effective alternative to solid CRA or metallurgically clad pipes without compromising performance.
Enhancing pipeline integrity with Mechanically Lined Pipes requires meticulous material selection, precise manufacturing processes, and stringent testing protocols. Proclad's expertise in MLP technology ensures the delivery of high-quality, cost-effective, and durable pipeline solutions across various industries.
