Hot Roll Bonded Clad Pipe Vs Mechanical Lined Pipe

With advancements in technology and a drive to reduce capital and operational costs, the demand for lined and clad materials has risen in the oil & gas and petrochemical industries. By combining two materials with distinct characteristics, the resulting product can offer the advantages of both at a reduced cost.

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This article provides insights into hot roll bonded clad pipes and mechanical lined pipes based on personal experience and limited knowledge. Both types of pipes are industrially accepted and broadly utilized, with no significant issues noted. Therefore, the focus here is on their strength, weaknesses, and applicability rather than questioning their integrity.

Understanding the Differences

Hot Roll Bonded Clad Pipe

Hot Roll Bonded (HRB) Clad Pipe is made using CRA Clad Plate, which is then formed into pipe using rolling or pressing methods and "seamed" through welding. The CRA Clad Plate is manufactured by rolling CRA Plate onto C-Mn Steel Plate under hot conditions, forming a metallurgical bond. While disbondment can occur, it is generally accepted within industry standards.

Due to the metallurgical bonding, HRB clad pipes are often considered as reliable as solid pipes with some advantages. They can be cut and used in sections without much special treatment, are compatible with attachments like o-lets, and can be made in various sizes. However, HRB clad pipes can be costly, have longer delivery times compared to solid or lined pipes, and pose challenges during installation such as diameter variance and potential disbondment propagation.

Mechanical Lined Pipe

Mechanical Lined Pipe (MLP) is produced by mechanically attaching a CRA layer to a C-Mn Steel Pipe, with both ends sealed using CRA weld. This is done by inserting a CRA pipe into the C-Mn Steel pipe and expanding it mechanically or hydrostatically to fit the inner surface, creating grip forces.

Since both pipes are manufactured and inspected separately according to industry standards prior to the lining process, their individual integrity is maintained. This can be seen as a strength of MLP over HRB clad pipes. Other benefits include lower procurement costs, quicker delivery, better fit-up matching, and the flexibility of mixing and matching lining-end seal materials.

However, MLP has limitations when it comes to extreme length corrections, cutting, or installing attachments like o-lets. These factors make it less suitable for piping spools or manifolds. Though recent technologies have addressed cutting issues, attachment installation often requires supplementary clad pipe or pup pieces. MLP size limits generally follow the C-Mn pipe size limits, with the largest lined pipe currently being 24” NPS.

Common Misconceptions

There is a misconception that MLP is weak due to the lack of a metallurgical bond between the two materials, resulting in different thermal expansion rates and potential failure. While this may be true at extremely high temperatures, proper material selection can mitigate this risk. The belief that MLP may fail due to natural bending during installation is also unfounded, as MLP has been successfully installed in extreme conditions using the S or J lay method.

Conclusion

In summary, both HRB clad and MLP pipes have their respective strengths and weaknesses. The choice between them depends on the specific requirements of the application. For more information on materials and processes used in pipelines, click here to understand better what is a wear plate and to explore various Hardfacing Machine options. For further discussion or inquiries, feel free to comment or share this article if you find it beneficial.

Jakarta, 29 November 2019

Fatkhy Baridwan