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Guidelines and Considerations for Pipe Bending in China’s Marine Industry

In the marine industry, the bending of pipes plays a critical role in the construction and maintenance of various systems aboard ships and offshore structures. Whether for conveying fluids, supporting structures, or accommodating complex layouts, the bending of pipes must adhere to strict technical conditions to ensure reliability, efficiency, and safety. In China’s marine sector, specific guidelines govern the process of pipe bending, emphasizing the preference for cold bending while allowing for exceptions under certain circumstances.

Rotary Draw Bending
Stretch Forming

Cold Bending vs. Hot Bending

Pipe bending in the marine industry primarily favors cold bending, a process that involves bending pipes at room temperature without the application of added heat. Cold bending is preferred for its ability to maintain the structural integrity and material properties of the pipe while achieving precise bends. However, there are situations where hot bending, which involves heating the pipe before bending, may be necessary to overcome limitations posed by cold bending.

Conditions Permitting Hot Bending

  • Smaller Bending Radius: Hot bending becomes necessary when the required bending radius is smaller than what cold bending can achieve or exceeds the capability of existing cold bending molds. In such cases, the controlled application of heat allows for tighter bends without compromising the integrity of the pipe.
  • Complex Shapes: Pipes with intricate shapes or those lacking straight sections between elbows may pose challenges for cold bending. Hot bending offers a solution by enabling the formation of complex bends and configurations that are difficult to achieve through cold bending alone.
  • Thin-Walled Tubes: Cold bending may result in significant collapse or wrinkling for pipes with excessively thin walls. In such instances, hot bending can be utilized to avoid deformation and ensure the structural integrity of the pipe.
  • Lack of Suitable Molds: For pipes with larger diameters or those that are infrequently used, suitable molds for cold bending may not be readily available. Hot bending provides a viable alternative, allowing for the creation of bends without the need for specialized tooling.
  • Thick-Walled Tubes: Cold forming thick-walled pipes can be challenging due to the material’s properties. Hot bending offers a solution by softening the material, making it more pliable and easier to form into the desired shape.

Guidelines and Considerations

When determining the appropriate method for pipe bending in the marine industry, several factors must be considered to ensure compliance with technical standards and safety regulations:

  • Material Properties: The material composition and thickness of the pipe influence the suitability of cold bending versus hot bending. Cold bending is preferred for most applications, but hot bending may be necessary for materials that are difficult to deform at room temperature.
  • Bend Radius and Angle: The required bend radius and angle dictate the feasibility of cold bending. Smaller radii and more acute angles may necessitate hot bending to achieve the desired configuration without compromising the pipe’s structural integrity.
  • Equipment and Expertise: Cold bending typically requires specialized machinery and skilled operators to ensure accurate and consistent bends. Hot bending may involve additional equipment for heating and handling the pipe, as well as expertise in temperature control and bending techniques.
  • Quality Assurance: Regardless of the bending method used, quality assurance measures must be in place to verify the integrity of the bends and ensure compliance with technical specifications. Non-destructive testing methods, such as ultrasonic testing, may be employed to assess the integrity of the bent pipes.


In conclusion, pipe bending in China’s marine industry follows stringent guidelines aimed at achieving precise bends while maintaining the structural integrity of the pipes. While cold bending is the preferred method for most applications, hot bending serves as a viable alternative under specific conditions where cold bending is impractical or insufficient. By adhering to these guidelines and considerations, marine engineers and manufacturers can ensure that pipe bending processes meet the highest standards of quality, safety, and efficiency.