Measuring method of end cut of steel pipe

Long-distance oil and gas pipelines are connected by a large number of single steel pipes. To facilitate the on-site butt joint construction, the steel pipe manufacturer needs to machine the designed welding groove and blunt edge on the pipe end of each steel pipe and ensure the cutting accuracy of the pipe end. At present, the measurement methods of pipe end cut in the industry mainly include straightedge measurement, vertical measurement, and special platform measurement.

1. Square measurement

A square ruler used to measure the cut slope of the pipe end generally has two legs. One leg is about 300mm in length and is used to close to the outer wall surface of the pipe end; the other leg is slightly longer than the pipe diameter and is used as a measuring leg against the pipe mouth. . When measuring the pipe end incline, the feet should be close to the outer wall of the pipe end and the nozzle, and the pipe end incline value an in this direction should be measured with a feeler gauge.

The measurement method adopts simple tools and easy measurement. However, the measurement error is affected by the flatness of the outer wall of the tube end during measurement. Also, when the diameter of the steel pipe to be tested is large, a large square should be used, which is heavy and inconvenient to carry.

2. Vertical measurement

Using two pairs of rotating rollers, the steel pipe is placed on it, and the steel pipe does not need to be leveled. Place a bracket with a wire hammer on the upper surface of the outer wall of the pipe end to be tested. The bracket is fixed on the upper surface of the outer wall of the pipe end. The wire hammer hangs at the mouth of the pipe and is a distance away from the pipe end, and keeps its position during measurement on both sides constant.

First, measure the distance between the end surface and the lower vertex of the pipe and the vertical line, and then rotate the steel pipe 180°, and measure the distance between the end surface and the lower vertex of the pipe and the vertical line in the same way. After taking the sum of the differences of the corresponding points, take the average value, and the absolute value is the chamfer value.

This method eliminates the influence of the vertical line is not perpendicular to the axis of the steel pipe. When the steel pipe is inclined, the tangential value of the steel pipe end can still be measured more accurately. However, tools such as a rotating shaft and a wire hammer are needed in the measurement process, which is troublesome.

3. Special platform measurement

The principle of this measurement method is the same as the vertical method. The measuring platform is composed of a platform, a rotating roller, and a measuring square. There is no need to adjust the perpendicularity between the steel pipe axis and the measuring square during measurement. Place the measuring square against the mouth of the pipe and the distance from the mouth of the pipe is 10-20mm. The chamfer value is the sum of the differences of the corresponding points, then the average value, and then the absolute value.

This method is easy to measure the distance between the upper and lower vertices and the square, and the accuracy is better than the vertical measurement. However, auxiliary tools are more expensive and the measurement cost is high.

Among the three methods, the dedicated platform measurement method has the best accuracy and is recommended for online steel pipe production; the vertical measurement method has better accuracy, and it is recommended to use the offline measurement of small batches of large diameter steel pipes; the square measurement method has the lowest accuracy, and it is recommended to measure Used for steel pipes with smaller diameters.