The Pipe Mill is the core equipment in the welded pipe production line. Its proper operation plays a vital role in improving production efficiency, economic benefits, and product quality. Therefore, precise adjustments and timely troubleshooting are essential. This chapter details the adjustment methods.

Alignment of the Upper Horizontal Rolls

The upper horizontal rolls are aligned based on the lower horizontal rolls. Steps include:

1. Calculation of Axial Spacing:

The axial spacing for open roll passes and closed roll passes is calculated as follows:

Open Roll Pass:

Closed Roll Pass:

Parameters:

D lower: Bottom diameter of the lower roll (mm)
D upper: Outer diameter of the upper roll (mm)
t: Thickness of the pipe blank (mm)
R: Radius of the sizing roll pass (mm)
a: Reduction coefficient (0.1～0.5)

Reduction Adjustment:
The reduction amount depends on factors such as pipe blank thickness, pipe diameter reduction, specifications, and shaft elasticity. Cold rolling must be avoided during forming. The correctness of the reduction can be verified by the solder mark method, where a solder wire, bent to match the roll pass, is fed slowly into the rolls to observe the impression.

Leveling and Centering of the Upper Rolls:
After leveling the upper rolls, a template gauge can be used to check whether the side gaps between upper and lower roll passes are uniform. For closed roll passes, manual touch methods can confirm proper alignment.

4. Alignment of Vertical Rolls

The alignment of vertical rolls includes three steps:

1. Determining Roll Opening Clearance:
Based on roll pass deformation width, a reduction of about 5mm is recommended. Excessive reduction increases roll edge wear and equipment load.

2. Center Alignment:
Center alignment of vertical rolls must be synchronized with horizontal rolls to ensure all rolls are aligned on the same centerline.

3. Height Adjustment:
Adjust the lower edge of the vertical roll pass to align with the baseline steel wire. The initial vertical roll heights are determined based on process parameters and roll trimming amounts.

The opening gap of the vertical roller is based on the deformation opening width during hole design, and then it is appropriate to shrink by about 5 mm. If the shrinkage is too large, it will accelerate the wear of the upper edge of the vertical roller hole, and also increase the load of the equipment. The center of the vertical roller should be aligned with the flat roller at the same time to ensure that the center positions of the flat roller and the vertical roller are on the same center line. After the center line of the vertical roller hole is found, the steel wire can be dropped on the bottom diameter position of the flat roller hole to start finding the height of the vertical roller. The height of the vertical roller is based on the height of the lower edge of the vertical roller hole and the steel wire.

The height of the vertical rollers in the first few forming passes should be determined according to the process parameters of the roller ring removal amount under the vertical roller (the mesh part in the figure is the roller ring removal part).

5. Alignment of other hole types

Alignment methods of other hole types

Refer to the alignment principle of flat rollers and vertical rollers, except that the bottom diameter of the guide roller should be slightly higher than the reference line by 0.5-2 mm (depending on the diameter and wall thickness of the produced pipe). The burr roller should be 0.5 mm higher than the reference line to make the force more stable when planing the external burrs and prevent planing jumps.