JPS6255456B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling expansion of a large diameter pipe.

One of the methods for manufacturing large diameter pipes is the UOE pipe manufacturing method. This UOE pipe manufacturing method involves edge-cutting a steel plate cut to predetermined dimensions, and then using a U press to process the steel plate.
Form it into a shape, then use an O press to form it into an O shape.
After tack welding the butt portions of the formed tubes, welding the inner and outer surfaces is performed to form a welded blank tube, and this welded blank tube is expanded to a predetermined outer diameter. A mechanical expander or a hydraulic expander is used in this tube expansion step.

The pipe expansion process originally involves finishing the welded raw pipe to the specified outer diameter, adjusting the roundness and straightness,
The purpose is to remove residual stress. However, in the case of using a mechanical expander, if there is a defect in supporting and guiding the welded blank pipe, accurate roundness may not be obtained and dimensional accuracy may deteriorate. This situation often occurs due to a defective V-roller in front of the expander head. Hereinafter, the mechanism of defective tube expansion will be explained with reference to the drawings.

As shown in FIG. 1, in the conventional pipe expansion process, a welded raw pipe 1 is guided and supported by lower rollers 2 and V rollers 3, and the expander head 5 of a mechanical expander 4 is moved by the rollers. 2 and 3
The welded raw pipe 1 was expanded from the inside.

A pair of cantilever type V rollers 3 located in front of the expander head 5 (on the upstream side in the direction of movement of the welded raw pipe)
is conventionally of a fixed type, and its outer periphery is coated with polyurethane or the like so as not to damage the outer surface of the welded raw pipe 1. When the welded raw pipe 1 is bent or distorted, the welded raw pipe 1 is biased on one side of the V roller 3, causing wear and tear on the coating of the V roller 3. As a result, the tube is expanded in a state where the center of the expander head 5 and the center of the welded blank tube 1 are shifted from each other, resulting in a decrease in the dimensional accuracy of the finished product.

Conventionally, in order to prevent this, the interval between the V rollers was adjusted by manually inserting and removing shims into the brackets of the V rollers, thereby adjusting the center position of the welded blank pipe. However, it is actually difficult to perform such position adjustment for each welded raw pipe, and dimensional defects are inevitable.

Furthermore, in the case of a high expansion rate, when the welded raw pipe is bent or distorted, one or both of the V rollers 3
There is no immediate contact, and dimensional accuracy further deteriorates.

Therefore, an object of the present invention is to eliminate as much as possible the functional defects of the V rollers that cause dimensional defects in the tube expansion process of the large-diameter pipe manufacturing method, reduce man-hours, and improve quality and production efficiency. The aim is to achieve this goal.

The method of the present invention includes supporting a pair of cantilevered V rollers so that their positions can be adjusted separately, and attaching a load detector to the support end side of the support shaft of the V rollers.
It is characterized in that the bending moment acting on each V roller of the welded blank pipe is detected, and the position of each V roller is adjusted so that each bending moment is equal to a set value.

Next, the method of the present invention will be explained with reference to FIG. A lifting platform 10 is provided at a predetermined position on the transport line for the welded blank pipe 1. The lifting platform 10 is normally raised, but can be lowered when necessary. A pair of holders 20 are slidably attached on a lifting platform 10. The holder 20 is moved on the lifting table in a direction perpendicular to the longitudinal direction of the welded blank pipe 1 by a screw shaft 11 rotatably supported on the lifting table 10.

A support shaft 30 is horizontally supported in a cantilever manner on the upper end of the holder 20, a load detector 31 is attached to the support end side, and a V roller 3 is rotatably attached to the free end.

The detection signal from the load detector 31 is transmitted to the control device 40.
Further, a control signal from the control device 40 is sent to each motor 50 connected to each screw shaft 11.

When the shape and transportation position of the welded raw pipe 1 are correct, the cross-sectional center O of the welded raw pipe 1 is at the normal position as shown in FIG. 3, and its weight W is equal to the left and right V.
It acts equally (W/2) on the same position of the roller 3. That is, the distance l between the contact point P between the V roller 3 and the welded pipe 1 and the inner end surface of the load detector 31 is as follows:
The left and right V rollers are the same. At this time, the bending moment M detected by the left and right load detectors 31 is Wl/2.

However, due to a defect in the shape of the welded raw pipe 1 or a defect in the V roller 3, the conveyance position of the welded raw pipe 1 may be incorrect.
For example, as shown in Figure 3, when the center moves from point O to point O', which is shifted by Δx to the left,
Each contact point P of the left and right V rollers 3 moves to point P'. The amount of movement is approximately Δx for both. At this time, the bending moment M _L detected by the load detector 31 on the left side is W(l−Δ
x)/2, and load detector 3 on the right side
The bending moment M _R detected by 1 is W
(l+Δx)/2.

The control device 40 controls the bending moment M during normal operation.
(set value) and each bending moment M _L and M _R at the time of abnormality are compared, and a control signal is sent to each motor 50 so that Δx becomes zero.

As is clear from the above explanation, according to the method of the present invention, by simply improving existing equipment,
The pipe expansion accuracy can be improved, work efficiency can be improved, and failures of the V rollers can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a conventional method for expanding a large diameter pipe. FIG. 2 is a front view taken from the - line in FIG. 1. FIG. 3 is a schematic explanatory diagram showing the method of the present invention. 1: Welded raw pipe, 2: Lower roller, 3: V roller, 4: Mechanical expander, 5: Expander head, 10: Lifting platform, 11: Screw shaft,
20: Holder, 30: Support shaft, 31: Load detector, 50: Motor.

Claims (1)

[Claims] 1 In the mechanical pipe expansion process of the UOE pipe production line, a pair of cantilevered V rollers is supported so that their positions can be adjusted separately, a load detector is attached to the support end side of the support shaft of the V roller, and welded. A method for controlling the expansion of a large-diameter pipe, characterized by detecting the bending moment of the raw pipe acting on each V-roller, and adjusting the position of each V-roller so that each bending moment becomes equal to a set value.