The efficient operation of boilers hinges on the reliability of their associated piping systems. Bending pipes with a pipe bender is a crucial step in creating these systems, allowing for navigation around obstacles and connection to various boiler components.

2. Literature Review

Previous research has explored wall thinning in pipe bending, focusing on factors like bend radius, pipe material. bending angle, and bending machine type. Studies have shown that smaller bend radii and higher bending angles generally result in increased wall thinning. Additionally, different materials exhibit varying susceptibility to wall thinning, with softer materials tend to experience more pronounced thinning.

3. Experimental Methodology

3.1 Materials and Specimens

This study utilized seamless steel pipes commonly employed in boiler systems. The pipes had an outer diameter (OD) of 2 inches, a wall thickness of 0.1 inches, and were made from ASTM A106 Grade B material. Specimens were cut to suitable lengths for bending.

3.2 Bending Process

A hydraulic pipe bender, capable of applying precise bending forces and controlling bend radius, was used for the experiments. Bending pipe with the pipe bender was performed at different bend radii (3D, 4D, and 5D, where D represents the pipe OD) and bending angles (90°, 120°, and 150°). Each combination was repeated three times to ensure data consistency.

3.3 Wall Thickness Measurement

Wall thickness measurements were taken at various locations along the bend region using a high-precision caliper. Measurements were concentrated near the inner and outer bend radii, where maximum thinning is expected.

4. Results and Discussion

The experimental results clearly demonstrated the influence of both bend radius and bending angle on wall thinning. As expected, smaller bend radii resulted in more significant wall thinning. This can be attributed to the increased strain concentration at tighter bends.

Similarly, higher bending angles led to increased wall thinning.

4.1 Wall Thinning Mechanisms

The observed wall thinning is primarily attributed to two mechanisms:

• Plastic deformation: The bending process induces plastic flow of the pipe material, particularly in the inner bend region, leading to irreversible thickness reduction.
• Crack formation and propagation: Severe bending can initiate microcracks in the pipe wall, which may propagate and contribute to overall wall thinning.

4.2 Implications for Boiler Piping Design

This study’s findings have important implications for designing boiler piping systems:

• Bend radius selection: Choosing appropriate bend radii is crucial to minimize wall thinning. Where possible, larger bend radii should be preferred.
• Bending angle optimization: Limiting bending angles can help reduce the extent of wall thinning.
• Material selection: Considering alternative materials with improved formability and resistance to cracking may mitigate wall thinning.