Cross-section of a high-tech sandwich pipe underwater

Sandwich Pipe Revolution: How New Tech Can Protect Our Deep-Sea Pipelines

Mira Elwood in Tech & Innovation September 2025 • 4 min read.

"Explore how innovative sandwich pipe technology is transforming the safety and efficiency of underwater hydrocarbon transportation."

As the demand for hydrocarbons rises, exploration ventures deeper into ultra-deep-water areas. Traditional single-walled steel pipes often fall short due to challenges such as high external pressure, buoyancy, and low temperatures, restricting their use to limited depths.

To combat these limitations, innovative concepts like pipe-in-pipe (PIP) and sandwich pipe (SP) systems have emerged, offering promising solutions for flow assurance and operational requirements in deep and ultra-deep waters. Unlike PIP systems, where the annulus's structural attributes are sometimes overlooked, SP systems offer a lightweight alternative that enhances thermal insulation and structural resistance.

Sandwich pipe systems, composed of two metal tubes with a polymer or cement-based core, allow the tubes and core to jointly withstand ambient pressure. Especially suitable for ultra-deep-water applications, SP systems are now the focus of research aimed at enhancing their resilience against collapse and buckle propagation, ensuring safer and more reliable hydrocarbon transport.

Buckle Up: Understanding How Sandwich Pipes Resist Deep-Sea Collapse

Cross-section of a high-tech sandwich pipe underwater

The collapse of offshore pipelines, triggered by external pressure or bending, poses a significant risk in deep-sea environments. If the ambient pressure exceeds the propagation pressure, a local collapse can rapidly spread, flattening or even destroying the entire pipeline. Recent studies have explored the behavior of single-walled pipes and PIP systems under such conditions, but sandwich pipes present a more complex scenario due to the interactions between the tubes and core layer.

Critical factors influencing the pressure-bearing capacity of SP systems include the inter-layer adhesion and the properties of the core layers. To better understand these factors, researchers have conducted experiments and numerical analyses, focusing on the impact of inter-layer adhesion on ultimate bearing capacity under combined external pressure and bending.

Experimentation: Small-scale tests to observe buckle propagation in SP specimens with varied interface bonding.
Simulation: Finite element models in ABAQUS to replicate collapse scenarios.
Analysis: Study effects of inter-layer adhesion on stress, deformation, and buckle propagation.
Optimization: Comprehensive correlation analyses to assess geometric and material properties.

The results of these studies indicate that effective interface bonding markedly enhances buckle propagation pressure, improving energy dissipation and structural deformation capacity. The thickness of the core layer and the ratio of wall thicknesses between the inner and outer tubes significantly affect buckle propagation pressure. Moreover, empirical design expressions have been developed to estimate buckle propagation pressure conservatively, particularly in cases lacking inter-layer adhesion.

Engineering a Safer Future for Deep-Sea Hydrocarbon Transport

Ongoing research into sandwich pipe systems promises to enhance the safety and efficiency of deep-sea hydrocarbon transport. With a focus on improving interface bonding, optimizing core layer properties, and refining design parameters, engineers are paving the way for more reliable and robust pipeline solutions. These advancements not only address current challenges but also ensure the sustainability of future offshore operations, balancing economic needs with environmental responsibility.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.1016/j.engstruct.2018.08.033, Alternate LINK

Title: Buckle Propagation Of Sandwich Pipes Under External Pressure

Subject: Civil and Structural Engineering

Journal: Engineering Structures

Publisher: Elsevier BV

Authors: Shunfeng Gong, Xipeng Wang, Tao Zhang, Chengbin Liu

Published: 2018-11-01

Everything You Need To Know

What are sandwich pipes, and how do they differ from traditional pipelines used in deep-sea hydrocarbon transport?

Sandwich pipes (SP) are innovative pipeline systems designed for deep-sea hydrocarbon transport, particularly in ultra-deep waters. They consist of two metal tubes with a polymer or cement-based core, working together to withstand ambient pressure. Unlike traditional single-walled steel pipes, which are limited by high external pressure, buoyancy, and low temperatures, sandwich pipes offer enhanced structural integrity, thermal insulation, and resistance to collapse. Pipe-in-pipe (PIP) systems are another alternative, but SP systems are often preferred for their lightweight design and improved performance characteristics.

Why is the inter-layer adhesion in sandwich pipes so crucial for their performance in deep-sea environments?

Inter-layer adhesion in sandwich pipes is critical because it significantly influences the pressure-bearing capacity and overall structural integrity of the system. Effective bonding between the metal tubes and the core layer of the sandwich pipe markedly enhances buckle propagation pressure. This, in turn, improves energy dissipation and structural deformation capacity, vital for withstanding the extreme conditions in deep-sea environments. Without proper adhesion, the pipe is more susceptible to collapse and buckle propagation.

How does the core layer in sandwich pipes contribute to their resilience against deep-sea collapse and what are the key factors to consider?

The core layer in sandwich pipes plays a crucial role in enhancing their resilience against deep-sea collapse. It provides structural support, aids in withstanding external pressure, and influences the way the tubes interact under stress. Key factors include the core layer's thickness and material properties (polymer or cement-based), as well as the ratio of wall thicknesses between the inner and outer metal tubes. Research focuses on optimizing these factors to improve the sandwich pipe's ability to resist buckle propagation and ensure safer hydrocarbon transport.

What are the primary challenges that sandwich pipe technology addresses in deep-sea hydrocarbon transportation, and how are these challenges overcome?

Sandwich pipe technology primarily addresses the challenges posed by high external pressure, buoyancy, and low temperatures encountered in deep-sea hydrocarbon transportation, especially in ultra-deep waters. These challenges restrict the use of traditional single-walled steel pipes. Sandwich pipes overcome these limitations by combining two metal tubes with a polymer or cement-based core. This design enhances structural integrity, provides thermal insulation, and increases resistance to collapse. Ongoing research, including experimentation, simulation, and analysis, focuses on improving inter-layer adhesion, optimizing core layer properties, and refining design parameters to further enhance safety and efficiency.

What advancements are being made in the research of sandwich pipe systems, and what impact will these have on the future of offshore hydrocarbon transport?

Current research in sandwich pipe systems focuses on enhancing the safety and efficiency of deep-sea hydrocarbon transport. Key areas of advancement include improving inter-layer adhesion, optimizing core layer properties, and refining design parameters. Researchers utilize experimentation (small-scale tests), simulation (finite element models), and comprehensive analyses to understand and improve sandwich pipe performance. These advancements will lead to more reliable and robust pipeline solutions, ensuring the sustainability of future offshore operations. This, in turn, will balance economic needs with environmental responsibility by providing a safer and more efficient means of transporting hydrocarbons from ultra-deep-water locations.