LSAW steel pipe physical tolerance

LSAW (Longitudinal Submerged Arc Welded) steel pipes are manufactured to precise standards, with strict physical tolerances to ensure consistency in dimensions, performance, and safety. These tolerances refer to permissible deviations from specified dimensions such as diameter, wall thickness, length, and out-of-roundness, as well as straightness and end finishing.

Here are some common physical tolerances for LSAW steel pipes based on industry standards such as API 5L, ASTM A252, or EN10219.

1. Outside Diameter Tolerance

Nominal Diameter (D):

For D≤406.4 mm (16 inches):

Tolerance:±0.75% of the specified outside diameter.

For D > 406.4 mm (16 inches):

Tolerance:±0.5% of the specified outside diameter.

These tolerances ensure that the pipe's external diameter remains within acceptable limits for fitment and performance.

2. Wall Thickness Tolerance

Wall thickness tolerances vary depending on the pipe's size and grade but typically follow these guidelines:

For wall thickness≤12.5 mm:±12.5% of the specified thickness.

For wall thickness > 12.5 mm:±10% of the specified thickness.

This tolerance is critical for maintaining the strength and pressure ratings of the pipe.

3. Out-of-Roundness (Ovality) Tolerance

Out-of-roundness is the difference between the maximum and minimum diameters of the pipe cross-section:

For D≤508 mm (20 inches): Tolerance is typically≤1% of the outside diameter.

For D > 508 mm: The tolerance is generally≤0.75% of the outside diameter.

Ovality is essential to ensure the pipe's structural integrity and fitment, particularly during installation.

4. Straightness Tolerance

The straightness of LSAW pipes is measured by the deviation per unit length:

The permissible deviation is usually around 0.2% of the total length, ensuring that the pipe does not warp or bend excessively during production.

For example, in a 12-meter long pipe, the maximum deviation would be about 24 mm.

5. Length Tolerance

Standard lengths: Typically 6 to 12 meters, but custom lengths are available depending on customer requirements.

Length tolerances:

For standard-length pipes:±500 mm.

For fixed-length pipes:±5 mm.

Accurate length tolerance ensures the pipe meets the project specifications, especially when several pipes need to be connected.

6. End Tolerance (Beveling or Squareness)

Bevel angle: Standard bevel angle for welding is 30° ±5°with a 1.6 mm±0.8 mm root face (land).

Squareness of cut: For pipes that are not beveled, the cut should be perpendicular to the pipe axis, with a tolerance of±1°from a 90°cut.

7. Weight Tolerance

Weight tolerance is based on the pipe's actual weight compared to the theoretical weight calculated from its nominal dimensions:

For individual pipes:±10% of the theoretical weight.

Maintaining weight tolerance is crucial for ensuring the correct material strength and density.

8. Weld Seam Deviation

The weld seam is critical for LSAW pipes, and tolerance is maintained for weld reinforcement height:

Internal and external weld seam height: Typically≤3 mm for pipes larger than 406.4 mm.

Smooth and consistent weld seams ensure proper performance, especially under pressure.

9. End Squareness

The pipe ends should be cut straight or beveled according to the standard, with a typical tolerance for end squareness:

The maximum allowed deviation from square cut is 0.2% of the outside diameter.

Conclusion

The physical tolerances for LSAW steel pipes ensure dimensional accuracy, performance reliability, and structural integrity in various applications such as oil and gas transportation, structural supports, and pressure pipelines. These tolerances are strictly regulated to maintain the pipe's ability to meet the demands of its intended environment and ensure proper fitment with other components.