Flattening test of ERW welded pipe

The flattening test is a crucial quality assurance procedure for Electric Resistance Welded (ERW) pipes. This test evaluates the material's ductility and the quality of the weld seam by subjecting a sample of the pipe to compressive deformation. The goal is to ensure that the pipe can withstand mechanical stresses during its intended application without failure.

Purpose of the Flattening Test

The primary objectives of the flattening test are to:

Verify the mechanical integrity of the weld seam.

Assess the pipe's ability to resist cracking or other defects under compressive stress.

Ensure the overall quality and uniformity of the pipe.

Test Procedure

- Sample Preparation

Selection: Cut a representative sample from the ERW welded pipe. The sample length is typically three times the pipe's outer diameter.

Cleaning: Ensure the sample is free from dirt, oil, and other contaminants.

- Test Setup

Equipment: Use a flattening test machine equipped with parallel plates that can apply a uniform compressive force.

Positioning: Place the sample horizontally between the flattening plates, ensuring the weld seam is oriented perpendicular to the direction of compression.

- Flattening Process

Compression: Gradually apply compressive force to the sample. The rate of compression should be controlled to prevent sudden deformation, typically at a rate not exceeding 25 mm per minute.

Observation: Monitor the sample as it flattens, paying close attention to the behavior of the weld seam and the pipe walls.

- Evaluation Criteria

Crack and Defect Inspection: Inspect the sample for any signs of cracking, especially along the weld seam and pipe walls. Use visual inspection and, if necessary, magnification tools.

Deformation Measurement: Measure the distance between the flattened plates when the sample reaches a specific degree of compression, as defined by applicable standards (e.g., ASTM, ISO).

Acceptance Criteria: The sample passes the test if it does not exhibit cracks or other defects and meets the specified deformation limits.

Standards and Specifications

The flattening test should adhere to industry standards such as:

ASTM A370: Standard Test Methods and Definitions for Mechanical Testing of Steel Products.

API 5L: Specification for Line Pipe, which includes criteria for flattening tests on welded pipes.

Safety Considerations

Protective Gear: Operators should wear appropriate protective equipment, including safety glasses, gloves, and protective clothing.

Equipment Maintenance: Ensure the flattening test machine is regularly inspected and maintained to prevent malfunction during testing.

Conclusion

The flattening test is an essential procedure for ensuring the quality and reliability of ERW welded pipes. By following the proper test procedures and adhering to relevant standards, manufacturers can verify the integrity of their products, ensuring they meet the necessary mechanical and safety requirements for their intended applications.