JPH0676691B2 - Underwater cutting method for thick steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Industrial field of application” The present invention relates to an underwater structure for a quay, pier erection work, landfill work,
Especially thick steel pipe piles used in artificial island construction work,
The present invention relates to a method of cutting a steel pipe such as a steel pipe sheet pile after completion.

"Prior art" Conventionally, for example, as means for cutting steel pipe piles and steel pipe sheet piles (hereinafter referred to as steel pipes) used in underwater quay structures, bridge pier construction work, landfill work, artificial island construction work, etc. after completion, For example, it is known to use a disc cutter for push-cutting or a rotary cutter, which is a preferable example of a grindstone cutter, alone or in combination.

For example, a cutting device capable of cutting a steel pipe peripheral wall with a grindstone cutter equipped with a revolution and rotation drive device is disclosed in
-32139 publication.

Further, a cutting device for cutting the peripheral wall of the steel pipe with a high-pressure fluid by a water jet nozzle is disclosed in, for example, JP-A-61-87020.

"Problems to be solved by the invention" By the way, in the technique described in Japanese Patent Publication No. 50-32139, which cuts the steel pipe peripheral wall with a grindstone cutter, the blade itself of the cutter is inserted into the steel pipe peripheral wall, and the cutting is completed. Immediately before, the cutter blade is caught by residual stress or the weight of the pipe itself, so the cutter is easily damaged, resulting in poor cutting cost and workability. There was a problem of causing an extreme decrease.

Further, in the technique described in Japanese Patent Laid-Open No. 61-87020, the peripheral wall of the steel pipe is cut by the high-pressure fluid, so that the cutting takes a considerably long time and there is a problem in cutting cost.

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

That is, at the time when the plasma arc first migrates to the steel pipe peripheral wall, the high temperature plasma arc melts the nearest peripheral wall portion, and after the molten dross is scattered and removed from the outer surface of the peripheral wall, the plasma torch is removed. By moving along the circumferential direction of the peripheral wall, stable cutting is performed.

However, when the wall thickness of the steel pipe becomes large, when the plasma arc moves to the peripheral wall, it becomes difficult for the plasma arc to penetrate the peripheral wall, and molten dross does not escape from the inside of the peripheral wall to the outside, and remains inside the peripheral wall. It solidifies and finally rises partially.

When such a state progresses, finally the dross rises at the tip part of the plasma torch, which causes damage to the torch.
It is extremely difficult, unlike the case of cutting thin steel pipes.

In order to solve such a 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, the current must be extremely increased in the case of a thick-walled steel pipe. However, the equipment cost of the entire apparatus is significantly increased, which is not preferable in terms of cutting cost and safety.

The present invention aims to solve the conventional problems of cutting such thick steel pipes.

"Means for Solving the Problem" The underwater cutting method for a steel pipe according to the present invention is to perform a drilling process, a cutting process, a grinding process, or a grooving process on a portion of a peripheral wall of a thick steel pipe at a cut point. After that, the peripheral wall of the steel pipe is cut from this processed portion by the plasma arc cutting means.

[Operation] As described above, after a part of the peripheral wall of the thick-walled steel pipe at the portion to be cut is processed by punching, cutting, grinding, or grooving, the steel pipe is cut from this processed portion by the plasma arc cutting means. Since the peripheral wall is cut, the molten dross at the processing area due to the plasma arc can be regularly scattered from the inside to the outside of the steel pipe peripheral wall. Therefore, even with a thick steel pipe, the molten dross swelling phenomenon on the inner surface of the peripheral wall Not,
The peripheral wall of the steel pipe can be cut efficiently in a stable state.

[Example] Next, an example of an underwater cutting method for a steel pipe according to the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 to 3, a cutting device B for a steel pipe A used in the method of the present invention comprises a casing 1 and a holding means 2 for holding and fixing the casing 1 on the inner surface of the peripheral wall of the steel pipe A.
A swivel shaft 3 which is freely rotatably fitted in the longitudinal center of the casing 1, and an up-and-down control in the axial direction of the swivel shaft 3, and a forward and backward control in a direction orthogonal to the axial line of the swivel shaft 3. In addition, it comprises a grindstone cutter device 4 and a plasma arc cutting device 5 which are held so as to be controllable to rotate in the circumferential direction of the rotating shaft 3.

The casing 1 is an upper casing formed in a tubular shape.
1a and lower casing 1b, upper casing 1a
An appropriate hanging hand 6 is provided on the upper part of the.

The holding means 2 includes an abutting member 7 which can move forward and backward in a direction perpendicular to the axis of the casing 1, and is provided in the upper casing 1a
The contact members 7 at the upper and lower positions in the outer peripheral direction of the
Is driven by each contact hydraulic cylinder 8 and is arranged at each of three upper and lower positions (120 degree positions).

The swivel shaft 3 is loosely fitted to a lifting bearing 9 and a swivel bearing 10 disposed in the central portion of the upper casing 1a and at the upper and lower positions thereof to lift the swivel shaft disposed in the upper casing 1a. A hydraulic cylinder 11 (which is also provided on the opposite side as shown in FIG. 2), a slide guide 12, a swing drive device 13, and control devices (not shown) hold the swivel shaft 3 so that it can be raised and lowered and swung.
The lower end of the circular plate 1c fitted to the lower casing 1b
Have been serialized.

The turning drive device 13 includes a motor 14 and a pinion 15
And consists of gears 16.

As shown in FIGS. 1 and 3, the grindstone cutter device 4 is arranged in a slide box 18 so that the grindstone cutter device 4 can be moved back and forth by operating a hydraulic cylinder 17 for moving the whetstone cutter and a control device (not shown). It is composed of a grindstone cutter 19 and a motor 20 that rotationally drives the grindstone cutter 19, and is arranged in the lower casing 1b.

The plasma arc cutting device 5 is mounted on the slide box 18 so that the plasma torch advance / retreat hydraulic cylinder 21 and a control device (not shown) can be operated to advance / retreat, and has a plasma torch 22 at its tip. , Cables and hoses such as plasma arc cables, high-frequency high-voltage current cables, and cooling water hoses from the outside 23
Are connected.

Next, a method for cutting a thick steel pipe of the present invention will be described.

First, the cutting device B in which the hanging hand 6 is lifted with a wire or the like is gradually inserted from the upper end of the steel pipe A, and when the grindstone cutter 19 descends to the planned cutting position, each contact member that constitutes the holding means 2. 7 is pushed out by each abutting hydraulic cylinder 8 and pressed against the inner surface of the peripheral wall of the steel pipe A, whereby the cutting device B is fixed to the inner surface of the peripheral wall of the steel pipe A, and the state is maintained until the cutting operation is completed. .

Then, in order to cut a part of the peripheral wall of the steel pipe A at the cut point, after fixing the grindstone cutter device 4 at a predetermined position, the grindstone cutter 19 is rotated and slid by the operation of the hydraulic cylinder 17 for advancing and retracting the grindstone cutter. Box 18 for steel pipe A
Of the peripheral wall of the steel pipe A, and a part of the peripheral wall of the steel pipe A is cut through as shown in FIG. 4A.

In this case, as shown in FIG. 4 (b), it may be limited to only grinding (groove receiving) of a part of the peripheral wall thickness (when cutting to plasma arc, plasma torch damage due to rebound of molten dross is caused. Grooving may be performed to the extent that troubles can be prevented) or grindstone cutter device 4
Regardless of the method, grooving and cutting means with a metal saw is used, or, for example, a drill, end mill, water jet (preferably containing abrasive material) is used to punch a part of the peripheral wall as shown in FIG. You may.

As described above, after cutting through a part of the peripheral wall of the steel pipe A, the grindstone cutter 19 is retracted to the fixed position, the swivel shaft lifting hydraulic cylinder 11 is operated, and the height of the swivel shaft 3 is adjusted to the plasma torch. 22 and the height of the grinding wheel cutter 19 is adjusted to match the height of the plasma torch 22 with the height of the portion cut by the grinding wheel cutter 19, and the operation of the hydraulic cylinder 21 for advancing and retracting the plasma torch. The plasma arc cutting device 5 is extruded toward the inner surface of the peripheral wall of the steel pipe A by the above, the plasma torch 22 is brought close to the inner surface of the peripheral wall of the steel pipe A, and the plasma torch 22 is rotated through the cables and hoses 23 while rotating the turning shaft 3. Supply high frequency high voltage current to
Generate a pilot arc, then plasma torch 22
And a plasma main arc between the steel pipe A and
The circumferential wall of the steel pipe A, which has not been cut by the grindstone cutter 19, is cut in the circumferential direction.

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 the initial state.

[Advantages of the Invention] As described above, according to the method of the present invention, a thick steel pipe pile,
A steel pipe such as a steel sheet pile can be efficiently cut in water.

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

[Brief description of drawings]

1 is a longitudinal sectional view showing an embodiment of a cutting device used in the method of the present invention, FIG. 2 is a sectional view taken along line XX in FIG. 1, FIG. 3 is a front view of a grindstone cutter device, and FIG. (A), (B), (C) is a cross-sectional view showing each working example of a part of the steel pipe peripheral wall in the cut portion. A ... Steel pipe, B ... Cutting device 1 ... Casing, 2 ... Holding means 3 ... Swivel shaft, 4 ... Whetstone cutter device 5 ... Plasma arc cutting device 7 ... Abutting member 8 ... Abutting Hydraulic cylinder 11 …… Swivel shaft lifting hydraulic cylinder 13 …… Swivel drive 17 …… Grinding wheel cutter advance / retreat hydraulic cylinder 18 …… Slide box, 19 …… Grinding wheel cutter 20 …… Motor 21 …… Plasma torch Advance hydraulic cylinder 22 …… Plasma torch, 23 …… Cables and hoses

Claims (2)

[Claims] 1. A part of a peripheral wall of a thick-walled steel pipe at a portion to be cut is subjected to any one of drilling, cutting, grinding and grooving, and then a plasma arc cutting means is used to cut the peripheral wall of the steel pipe. Method for underwater cutting of thick-walled steel pipe, characterized by cutting. 2. A drill, a grindstone cutter, a water jet, a metal saw, or an end mill is used as any one of the boring, cutting, grinding, and grooving processing means. The underwater cutting method for a thick steel pipe according to 1.