The Rise of Bimetal Pipes
In the demanding depths of the ocean and the corrosive heart of industrial plants, a quiet revolution in pipeline technology is taking place.
Explore the TechnologyImagine a pipeline that is both incredibly strong and highly resistant to corrosion—a combination that has long been a holy grail for engineers in the oil, gas, and chemical industries. This is not a fantasy but a reality made possible by seamless two-layer bimetal pipes2 8 .
These engineering marvels are transforming how we transport valuable and often dangerous resources under extreme conditions. By marrying the robust strength of carbon steel with the superior corrosion resistance of alloys like stainless steel, bimetal pipes offer a cost-effective and reliable solution for some of the world's most challenging engineering projects.
This composite structure is particularly crucial as industrial activities move into more extreme environments, such as offshore oil and gas fields with high concentrations of carbon dioxide and hydrogen sulfide. In these settings, traditional single-material pipelines face unprecedented challenges, with corrosion being a primary factor affecting service life and safety2 .
Carbon steel base pipe withstands immense pressures, axial forces, and bending moments2 .
Among the various manufacturing techniques, hydraulic expansion has emerged as a leading, industrially mature process for creating mechanically lined pipes (MLPs). It is prized for its convenience, lower production costs, and high product quality stability2 .
The corrosion-resistant alloy liner, slightly undersized, is inserted into the carbon steel base pipe, leaving a small initial gap between the two2 .
High-pressure fluid is pumped into the liner. The pressure is carefully controlled and gradually increased2 .
As the pressure rises, the liner first expands plastically, moving outward to contact the base pipe. With continued pressure increase, the base pipe itself begins to deform elastically and then plastically2 .
When the hydraulic pressure is released, the elastic recovery of the base pipe is greater than that of the now-plastically deformed liner. This differential recovery creates a powerful residual contact pressure, mechanically locking the two layers together2 .
Visual representation of the hydraulic expansion process showing liner insertion, pressure application, and bond formation.
To understand the reliability of this process, researchers conduct meticulous experiments. One such study used full-scale industrial equipment to manufacture MLPs and then analyzed the resulting bond2 .
The study confirmed that the residual contact pressure has a direct, predictable relationship with the design forming hydraulic pressure. This allows manufacturers to precisely control bonding strength by adjusting hydraulic pressure2 .
| Designed Forming Hydraulic Pressure (MPa) | Measured Residual Contact Pressure (MPa) | Liner Material State |
|---|---|---|
| Low | Low | Partially yielded |
| Medium | Medium | Fully yielded |
| High | High | Strain-hardened |
The standard diameters mentioned—530, 550, 610, 630, 720, and 820 mm—are not arbitrary. They align with global standards (like ASME B36.10) and are tailored for major projects9 . Their application is diverse:
Used in high-pressure boiler systems and nuclear power plants under high temperatures and pressures4 .
| Base Pipe Material | Liner Material | Key Properties | Typical Applications |
|---|---|---|---|
| X65 Carbon Steel | 2205 Duplex Stainless Steel | High strength, excellent chloride corrosion resistance | Offshore oil and gas pipelines, chemical transport3 |
| Carbon Steel (AISI 1045) | Copper (Grade T2) | Good strength, high thermal conductivity, corrosion resistance | Heat exchanger tubes, specific process lines8 |
| Carbon Steel | Nickel-Based Alloys (Alloy 625) | Exceptional resistance to high temperatures and severe corrosion | Downhole tubing, HT/HP wells, flare systems |
The innovation pipeline is far from dry. The future of bimetal pipe technology is being shaped by advanced manufacturing processes and digital technologies.
As global infrastructure pushes into ever more challenging frontiers, the silent, robust reliability of seamless bimetal pipes will undoubtedly play a starring role, ensuring that the "blood vessels" of modern industry remain healthy and secure for decades to come.