JPS6137014B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to the technical field of manufacturing double pipes such as oil country tubular goods using hydraulic pipe expansion.

Accordingly, the present invention provides a structure in which a stainless steel inner tube is relatively layered within a carbon steel outer tube for oil country tubular goods, one end of the inner tube is fixed by a seal clamp of a fixed stand,
This relates to a hydraulic pipe expansion device whose other end is movably provided to another fixed stand and which is fixed to a seal clamp to which an axial load is applied by a pressing device, and which is hydraulically expanded by a hydraulic device. In particular, the sealing clamp for the other end of the inner tube is provided as a sleeve piston that is slidable with respect to the tube expansion liquid conduction fixing stand, and an elastic spring is interposed between the sleeve piston and a device that moves the sleeve piston back and forth to reset. The present invention relates to a double pipe manufacturing device that is capable of applying an axial pressing force.

As is well known, in order to provide corrosion resistance in addition to pressure and heat resistance to pipes used for transporting corrosive fluids, such as oil country tubular goods, so-called double-walled pipes are constructed in which the outer pipe is a carbon steel pipe and the inner pipe is a stainless steel pipe. Tubes are increasingly being used.

In order to prevent cracking and implosion during operation over time, it is necessary to tightly fit the inner and outer tubes in the type double tube. The fitting method and tube expansion method were not satisfactory.

To deal with this, in the thermal tube expansion method newly developed in the applicant's earlier invention, the inner and outer tubes are heated or cooled to create a diameter difference before expansion, and the inner and outer tubes are expanded using hydraulic pressure. Expand the tube, yield it, and continue expanding the outer tube integrally.
The outer tube was also subjected to yield plastic deformation, the tube expansion pressure was released after the set strain, and the temperature was naturally raised or cooled after tube contraction to obtain a high degree of fit.

By the way, in double pipe manufacturing based on pipe expansion, the inner pipe yields, plastically deforms, and is shortened in the axial direction as the diameter increases until it comes into contact with the outer pipe. It is necessary to simultaneously apply axial pushing force during the tube expansion process.

Up until now, this has been dealt with by changing the diameter of the sliding cylinder that holds the seal clamp against the inner tube and applies the axial pushing force, but this problem has been solved by initially reducing the expansion resistance of the inner tube. There is a drawback that no device has been obtained that satisfies the contradictory functions that the axial pushing force must be increased as the initial pressure increases. If the control mechanism is designed to obtain pushing force through sequence design, it is necessary to prevent the pushing force from becoming excessive in the expanded state after both pipes are joined, but there is also the problem that it is difficult to control accordingly. In any case, the disadvantage was that the equipment became extremely complicated and the plant cost increased.

The purpose of the present invention is to solve the problem of the axial pushing force of the inner tube in the conventional double tube manufacturing process that includes the tube expansion process, and to press the inner tube seal clamp with an elastic spring. It is an object of the present invention to provide an excellent double-pipe manufacturing device in which the axial pushing force can be easily adjusted.

The structure of the present invention in accordance with the above object is such that the inner tube is relatively stacked on the outer tube, one end of the inner tube is fixed to a seal clamp of a fixed stand, and the other end is fixed to a seal clamp of a movable sleeve piston, The initial pushing force is adjusted and applied using an elastic spring, and a predetermined hydraulic pressure is applied between both seal clamps to expand the inner tube, yield, and contact the outer tube, while the axial contraction occurs as the tube expands. is guaranteed by the pushing force of the elastic spring, and in the tube expansion process after integrating the inner and outer tubes, the elastic spring prevents unnecessary axial force from being applied, and after a certain strain, the hydraulic pressure is released to contract the tube, and the seal clamp The main idea is to remove the spring and move the compression spring backward.

Next, one embodiment of the present invention will be described below based on the drawings.

Reference numeral 1 denotes a double pipe manufacturing apparatus which constitutes the gist of the present invention, in which fixing stands 4 and 4' having water guide holes 3 and 3' are provided at positions separated by a predetermined distance on the head 2, and the water guide holes 3 and 3' are respectively provided with fixed stands 4 and 4'. , 3' are connected to a high-pressure water source and drainage facility (not shown) via valves 5, 5' and water conduit pipes 6, 6'.

In the former, a pressure boosting plunger 8 provided on a hydraulic cylinder 7 serving as a hydraulic device faces the cylinder 9 of the water introduction hole 3 so as to be able to advance and retreat, and a seal clamp 11 is provided on the tapered tip portion 10. It is provided so that it can be opened and closed.

On the other hand, in the latter, a sleep piston 8' which is slidably provided via a seal packing 12 with the water introduction hole 3 as a cylinder 9' is used as a seal clamp 11'.

Further, a hydraulic cylinder 7' as an advance/retreat device is fixedly installed at the rear of the fixed stand 4', and its rod 13 is connected to a crosshead 14 and moved forward from the crosshead 14 in a position and posture that does not interfere with the fixed stand 4'. A plurality of guide rods 15, 15 extending
... are the holes 16, 16... of the sleeve piston 8'.
Loosely insert the stoppers 17, 17... at their front ends.
have.

Between the crosshead 14 and the flange 18 of the sleeve piston 8', elastic springs 19, 19, .
15... is exteriorized and interposed.

Note that 20 is a carbon steel outer tube, and 21 is a stainless steel inner tube that is installed inside the outer tube 20, so that a double tube 22 is formed by both. Further, 23 is a support cart, which supports the double pipe 22 midway.

In the above configuration, in the stress-strain curve (horizontal axis strain ε, vertical axis tube expansion stress F) graph in Figure 2, the diameter D ₀ of the outer tube 20 is heated to a predetermined temperature in the natural temperature state.
At _D0 ', the diameter is increased from A' to B', and at the same time, the inner tube 21 is cooled from natural temperature with cold water, and its diameter is decreased from _D1 to _D1 ' from A to B ( _D1 > _D0 , D ₀ '> _D1 '), the two are fitted in a relatively overlapping manner with a difference in diameter, and the front end of the inner tube 21 is fastened and fixed to the seal clamp 11 of the stand 4.

Further, the rear end operates the hydraulic cylinder 7' in a predetermined manner to move the sleeve piston forward and backward via the crosshead 14 and the elastic spring 19, and the seal clamp 1
1', and is set so as to apply and maintain a set amount of pushing force in the initial direction to the inner tube 21 via the elastic spring 19 by operating the hydraulic cylinder.

Therefore, the valve 5' is closed and the valve 5 is opened to supply cooling water from a cooling water source (not shown) to the water guide pipe 6 and the water guide hole 3.
Water is introduced into the inner pipe 21 through the inner tube 21, and the water introduction hole 3 is filled with water.

Next, when the water is full, the valve 5 is closed and the plunger 8 is pushed forward by the hydraulic cylinder 7 to increase the pressure of the full water and apply an expansion force to the inner pipe 21.

In this case, the cross section is designed so that the axial pressing force applied to the cross section of the proximal step of one sleeve piston 8' relative to the cylinder 9', which is shown for convenience of illustration, is not substantially applied.

In this way, the inner tube 21 is cooled and expanded, and as shown in FIG. 2, yields and plastically deforms while following the graph C and coming into contact with the outer tube 20.

In this tube expansion process, the elastic-plastic expansion of the inner tube 21 is accompanied by axial shortening, but from the initial set state in FIG. 3 to the inner and outer tube contact in FIG. , is pushed in by the initial set pushing force of the elastic spring 19, and on the other hand, the elastic spring 19 loses its positional energy and becomes smaller than the initial pushing force by the set strength.

Therefore, the inner and outer tubes 20 and 21 are integrated, and as shown in FIG. 2, the inner tube 21 follows the graph C and the outer tube 200 follows the graph C', and the latter yields and deforms plastically, and the inner tube also deforms plastically. , the set distortion is reached, but during this time,
Since the amount of radial deformation in which the inner tube undergoes plastic deformation is small, the axial shrinkage margin is extremely small.Therefore, the state shown in FIG. The indentation force is relatively small, and the indentation force is only applied to the extent that it causes the formation of compressive residual stress.

In this way, when the set strain amounts C and C' in FIG. The tube contracts and reaches D ₀ ″ of D and N′, and the heated outer tube 20 cools by heat radiation, and from N′ to H′
The diameter of the inner tube ₂₁ increases from D to E, and the inner tube 21 increases in diameter from D to E, obtaining a large degree of fitting of ΔD, resulting in a self-locking double tube 22, and during this time the hydraulic pressure Due to the constant posture of the cylinder 7', compressive residual stress is formed due to the constant pushing force of the elastic spring 19.

After that, remove the seal clamps 11, 11', move the hydraulic cylinder 7' back, and move the guide rod 1
5 retreats, the sleeve piston 8' retreats via its stopper 17, and the double pipe 22 is removed.

It goes without saying that the embodiment of the present invention is not limited to the above-mentioned embodiment. For example, the hydraulic cylinder 7' may be an air cylinder, an elastic disc spring, etc., and axial pushing may be carried out during pipe expansion. Various modes can be adopted, such as pushing the hydraulic cylinder 7' as well.

Moreover, it goes without saying that the present invention is applicable not only to the thermal tube expansion method but also to general hydraulic tube expansion methods.

As described above, according to the present invention, for a fixed stand having a seal clamp that fixes one end of the inner and outer tubes that are layered relative to each other, a sleeve piston that is slidable on the other fixed stand is used as another seal clamp to secure both ends of the inner tube. By providing a pipe expansion hydraulic device for the inside of the inner pipe with a seal clamp, basically the sleeve piston has the effect of guaranteeing the axial shrinkage margin during the process of increasing the diameter of the inner pipe during hydraulic pipe expansion. .

By interposing an elastic spring between the sleeve piston and the advancing/retracting device, the initial pushing force during expansion of the inner tube can be freely adjusted by the advancing/retracting device, and the expansion resistance of the inner tube can be adjusted freely. Not only does this have an excellent effect of reducing the pressure, but by setting the initial pushing force, it is possible to prevent excessive pushing force from being applied during the process in which the inner tube contacts the outer tube and undergoes plastic deformation after yielding. Moreover, the excellent effect of being able to apply compressive residual stress is achieved, and there is the advantage that this can be done without interference between the two.

Furthermore, since the device can be designed with a simple mechanism such as an elastic spring and a hydraulic cylinder, it is easy to manufacture, avoids high costs, and has the advantage of being easy to maintain and manage.

[Brief explanation of the drawing]

The drawings are explanatory diagrams of one embodiment of the present invention; FIG. 1 is an overall schematic explanatory diagram, FIG. 2 is an explanatory diagram of tube expansion stress and strain, and FIGS. 3 and 4 are explanatory diagrams of an axial pushing process. 20... Outer tube, 21... Inner tube, 11, 11'... Seal clamp, 4, 4'... Fixing stand, 19... Pressing device, 7... Hydraulic device, 1... Manufacturing device, 8'... Sleeve piston, 7' ... Advancement/retraction device, 19... Repression spring.

Claims (1)

[Claims] 1. A fixed stand with a seal clamp for one end of the inner pipe layered on the outer pipe, and another fixed stand with a seal clamp on the other end movably provided with a pressing device, and provided on either of the two stands. A double pipe manufacturing apparatus having a hydraulic device, characterized in that the movable seal clamp is externally mounted on a corresponding fixed stand as a sleeve piston, and a pressure spring is interposed between the movable seal clamp and the advancing/retracting device. Heavy pipe manufacturing equipment.