JPH041320A - Steel pipe cutting method in water - Google Patents

Abstract

PURPOSE:To efficiently cut a steel pipe in a submerged condition, by cutting the pipe periphery at a partially processed part of the cutting position of the periphery of the pipe by means of a plasma are cutting. CONSTITUTION:A cutter B is inserted into a steel pipe A and a contact member is closely pressed at the inside face of the periphery wall of the steel pipe A and then the cutter B is fixed at the inside face of the periphery wall of the steel pipe A. Next, a grinding wheel cutter is fixed and rotated and then a slide box 18 is moved forward to the inner face of the periphery wall of the steel pipe A by the actuation of a reciprocal hydraulic cylinder 17 for the grinding wheel cutter. Next, the grinding wheel cutter 19 is brought near the inner face of the periphery wall of the steel pipe A and a part of the periphery wall of the steel pipe A is cut to pierce it. And the plasma arc cutting device 5 is pushed to the inner face side of the periphery wall of the steel pipe A to supply high frequency and high tension current thereto to generate a pilot arc. And further, plasma main arc is generated between the plasma torch 22 and the steel pipe A to perform cutting in the peripheral direction of the periphery wall of the steel pipe A.

Description

[Detailed description of the invention] "Field of industrial application" The present invention is applicable to quay underwater structures, bridge pier erection work, reclamation work,
Particularly thick steel pipe piles used in artificial island construction work, etc.
This invention relates to a method for cutting steel pipes such as steel pipe sheet piles after completion of construction.

``Prior art'' Conventionally, methods for cutting steel pipe piles and steel pipe sheet piles (hereinafter referred to as steel pipes) used in, for example, underwater quay structures, bridge pier erection work, reclamation work, artificial island construction work, etc., after completion of construction, include: For example, it is known to use a rotary cutter, typically a push-cut disk cutter or a grindstone cutter, either alone or in combination.

For example, a cutting device capable of cutting the peripheral wall of a steel pipe using a whetstone cutter equipped with a revolution and rotation drive device was developed in
It is disclosed in Japanese Patent No. 0-32139.

Furthermore, a cutting device for cutting the peripheral wall of a steel pipe using high-pressure fluid using a water jet nozzle is disclosed, for example, in Japanese Patent Application Laid-Open No. 61-870.
It is disclosed in Publication No. 20.

``Problems to be Solved by the Invention'' In the technique described in Japanese Patent Publication No. 50-32139, which cuts the peripheral wall of a steel pipe with a grindstone cutter, the cutting edge body of the blade is inserted into the peripheral wall of the steel pipe. Immediately before cutting is completed, the cuffer blade becomes stuck due to residual stress or the tube's own weight, so the cutter is easily damaged, resulting in problems such as lower cutting costs and poor workability. There was a problem in that the cutting efficiency of steel pipes was extremely reduced.

Furthermore, in the technique described in Japanese Patent Application Laid-Open No. 61-87020, the circumferential wall of the steel pipe is cut using high-pressure fluid, so cutting takes a considerable amount of time and there is a problem in cutting cost.

Furthermore, a method of using plasma arc cutting means alone is already known, but this plasma arc cutting means exhibits unparalleled cutting efficiency in (t) when the wall thickness of the steel pipe to be cut is thin.

In other words, when the plasma arc first transfers to the surrounding wall of the steel pipe, the high-temperature plasma melts the immediate surrounding wall, and after the molten dross is removed by scattering outward from the outer surface of the surrounding wall. , by moving the plasma torch along the circumferential direction of ff[, stable cutting can be achieved.

However, when the wall thickness of the steel pipe becomes large, once the plasma arc moves to the peripheral wall, it becomes difficult for the plasma arc to penetrate the peripheral wall, and the molten dross cannot escape from the inside of the peripheral wall to the outside, and it remains inside the peripheral wall. It solidifies and eventually swells in parts.

If this situation progresses, dross will eventually build up at the tip of the plasma torch, leading to damage to the pipe.
Unlike cutting thin-walled steel pipes, this is extremely difficult.

In order to solve this problem, even if the capacity of the power supply device of the plasma arc cutting means is increased and the plasma arc current is increased, in the case of thick inner steel pipes, the current must be extremely large. This results in a significant increase in equipment costs for the entire device, which is undesirable in terms of cutting costs and safety.6 The present invention aims to solve the conventional problems of cutting thick internal steel pipes as described above. shall be.

``Means for Solving the Problems'' The method for underwater cutting of steel pipes according to the present invention involves performing processing such as drilling, cutting, grinding, grooving, etc. on a part of the peripheral wall of the steel pipe at the location to be cut, and then The purpose of this method is to cut the peripheral wall of the steel pipe from the site using plasma arc cutting means.

"Operation" As mentioned above, on a part of the steel pipe peripheral wall at the 1w point to be cut,
After drilling, cutting, grinding, grooving, etc. are performed, the peripheral wall of the steel pipe is cut from this processed area using a plasma arc cutting means, so that the molten dross of the processed area due to the plasma arc is removed from the inside of the peripheral wall of the steel pipe. Therefore, even if the steel pipe is thick, there is no swelling of molten dross on the inner surface of the peripheral wall, and the peripheral wall of the steel pipe can be cut in a stable and efficient manner.

"Example" Next, an example of the underwater cutting method of steel pipe according to the present invention will be described below based on the drawings.

11th! As shown in FIG. The HE shaft 3 is rotatably loosely fitted around the center in the vertical direction, and the swing shaft 3 can be moved up and down in the axial direction, and can be controlled to move forward and backward in the direction perpendicular to the axis of the swing shaft 3. A grindstone cutter device that can be controlled to rotate in the circumferential direction of 3! ! 4 and a plasma arc cutting bag W5.

The casing 1 includes an upper part 1 having a cylindrical shape.
a and a lower casing 1b, and a suitable hanging hand 6 is provided on the upper part of the upper casing 1a.

The holding means 2 holds the abutting member 7, which is movable in a direction perpendicular to the axis of the casing 1, against the toe caning 1.
Each contact member 7 is driven by each contact hydraulic cylinder 8, and is provided at three locations (120 degree position) on each of the lower soil stages. It is located.

The swing shaft 3 is loosely fitted into a lift bearing 9 and a swing bearing 10 which are disposed in the center of the upper casing [a] and at upper and lower positions thereof, and is connected to a swing shaft lift disposed in the upper casing la. Hydraulic pressure roller 11 for the flywheel (also provided on the opposite stool 1 as shown in FIG. 2), slide guide 12, swing drive bag W13, and each control device (
(not shown) so as to be able to rise and fall and turn 111M, and the lower end of the swing shaft 3 is connected to a circular plate lc fitted to the lower canong 1b.

Note that the swing drive device 13 includes a motor 14, a pinion 15, and a gear 16.

As shown in FIGS. 1 and 3, the grindstone cutter device 4 is arranged in a slide box 18 so as to be controllable in advance and retreat by the operation of a hydraulic cylinder 17 for advancing and retreating the grindstone cutter and a control device (not shown). and a whetstone cutter 19,
It consists of a motor 20 that rotationally drives the grindstone cutter 19, and is disposed within the lower casing lb.

The plasma arc cutting bag W5 is placed on the slide box 18 so as to be controllable in advance and retreat by the operation of a hydraulic cylinder 21 for advancing and retreating the plasma torch and a control bag W (FI!J not shown), and a plasma torch is attached to the tip of the bag W5. 22, and cables and hoses 23 such as external plasma arc cables, high-frequency high-voltage current cables, and cooling water hoses are connected to the rear.

Next, a method for cutting nine thick-walled steel pipes according to the present invention will be explained.

First, the cutting device B, which is suspended by hanging a wire or the like on the hanging handle 6, is gradually inserted from the upper end of the steel pipe A, and when the grindstone cuffer 19 is lowered to the intended cutting position, each of the contact members constituting the holding means 2 7 is pushed out by each abutting hydraulic cylinder 8 and pressed against the inner surface of the circumferential wall of the steel pipe, whereby the cutting device B is fixed to the inner surface of the circumferential wall of the steel pipe and is maintained in that state until the cutting operation is completed. Ru.

In order to cut a part of the peripheral wall of the steel pipe A at the location to be cut, after fixing the grindstone cutter device 4 at a predetermined position, the grindstone cutter 19 is rotated, and the hydraulic cylinder 17 for advancing and retreating the grindstone cutter is rotated. The operation pushes the slide box 18 toward the inner surface of the circumferential wall of the steel pipe A, brings the grindstone cutter 19 close to the inner surface of the circumferential wall of the steel pipe A, and then inserts a part of the circumferential wall into the steel pipe, as shown in FIG. 4(A). Cut through.

In this case, as shown in Figure 4 (b), it is possible to limit the grinding (grooving) to only a part of the thickness of the peripheral wall (when moving on to cutting by plasma arc, plasma arch FA scratches due to molten dross splashing Grooving can be done by machining to an extent that prevents troubles from occurring), or instead of using the grindstone cutter device 4, for example, a drill, water jet (
A part of the peripheral wall may be perforated as shown in FIG.

As described above, after penetrating a part of the peripheral wall of the steel pipe A, the grindstone cutter 19 is retreated to the fixed position, the hydraulic cylinder 11 for raising and lowering the rotating shaft is operated, and the height of the rotating shaft 3 is adjusted by the plasma torch. After adjusting the height difference between the plasma torch 22 and the grindstone cutter 19 to make the height of the plasma torch 22 match the height of the part cut by the grindstone cutter 19, the hydraulic cylinder 21 for advancing and retracting the plasma torch is adjusted. When activated, the plasma cutting device 5 is pushed toward the inner surface of the circumferential wall of the steel pipe A, the plasma torch 22 is brought close to the inner surface of the circumferential wall of the steel pipe A, and the plasma torch 22 is moved through the cable hoses 23 while rotating the turning shaft 3. A high-frequency high-voltage current is supplied to generate a pyroelectric arc, and then a plasma main arc is generated between the plasma torch 22 and the steel pipe A to cut the circumference of the peripheral wall of the steel pipe that was not cut by the grindstone cutter 19. Make directional cuts.

When the cutting of the peripheral wall of the steel pipe A is completed in this way, the plasma arc cutting device 5 is returned to its original position and all operations are returned to their original state.

"Effects of the Invention" As described above, according to the method of the present invention, thick-walled steel pipe piles,
Steel pipes such as steel pipe sheet piles can be efficiently cut underwater.

In particular, plasma arc cutting equipment is easy to operate,
Moreover, since the cutting speed is fast, cutting costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the cutting device used in the method of the present invention, and FIG.
jl sectional view, Figure @3 is the front view of the grindstone cutter device, No. 4
Figures (a), (b), and (c) are cross-sectional views showing examples of processing a part of the peripheral wall of the steel pipe at the location to be cut. A... Steel pipe B... Cutting device l... Casing 2... Holding means 3... Rotating shaft 4... Grindstone cutter device 5... Plasma arc cutting device 7... Contact member 8 ...Hydraulic pressure cylinder for contact 11...Hydraulic pressure cylinder for lifting and lowering the rotating shaft 13...
・Swivel drive device 17... Hydraulic solinder 18 for advancing and retreating the grindstone cutter...
・Slide box 19...Whetstone cutter 20...
・Motor 21 ・Hydraulic cylinder for plasma torch advancement and retreat 22 ・・
・Plasma torch 23... Cables and hoses Figure 2 Figure 3 Figure 1 Figure 4 Processing section

Claims (2)

[Claims] (1) A steel pipe characterized in that a part of the steel pipe peripheral wall at the location to be cut is subjected to processing such as drilling, cutting, grinding, grooving, etc., and then the steel pipe peripheral wall is cut from this processed region by plasma arc cutting means. underwater cutting method. (2) As the processing means for drilling, cutting, grinding, grooving, etc., a perforating tool such as a drill, a grooving tool such as a grindstone cutter, a water jet, a metal saw, or an end mill is used. The described underwater cutting method for steel pipes.