WO2020138145A1 - Crushing test method for steel pipe for pipeline, manufacturing method for steel pipe for pipeline, and crushing test device - Google Patents

Abstract

A cylindrical deformation body (3), which has been made from a synthetic resin and is longer in the axial direction than a test steel pipe (2) consisting of a portion of a steel pipe for a pipeline that has been cut off so as to be formed into a ring shape, is fit onto the outer periphery of the test steel pipe. Next, the test steel pipe and deformation body are disposed such that the axes thereof extend along the space between a pair of opposing walls (10, 11) disposed so as to oppose each other. The pair of opposing walls sandwich the deformation body such that both axial-direction end surfaces (3a, 3b) of the deformation body are in close contact with the pair of opposing walls. Subsequently, a fluid is supplied to a pressure chamber (16) formed by surrounding the outer peripheral surface of the deformation body with the pair of opposing walls and a peripheral wall (12a) opposing the outer peripheral surface of the deformation body, and the fluid is pressurized and made to act on the outer peripheral surface of the deformation body. Next, the inner diameter of the test steel pipe is measured, the pressure of the fluid in the pressure chamber is measured, and the crushing limit pressure of the crushed test steel pipe is calculated on the basis of these measured values.

Description

Crush test method for steel pipe for pipeline, manufacturing method of steel pipe for pipeline, and crush test apparatus

The present invention relates to a crush test method for a pipeline steel pipe (outer diameter of about 300 to 1500 mm) laid on the deep sea floor, a method for manufacturing a pipeline steel pipe, and a crush test apparatus.

In recent years, along with the increase in energy demand, the importance of pipelines as a long-distance transportation method for crude oil and natural gas has increased. When a part of the pipeline between the oil field or gas field and the supply base is provided on the deep sea floor, it is necessary to select a steel pipe for a pipeline that can withstand the water pressure even if it is submerged at a depth of about 2000 to 3000 m. As one of the means for selecting a steel pipe for a pipeline, there is a test for evaluating and predicting a crush resistance performance in which crushing does not occur even if a fluid pressure similar to the water pressure of the seabed acts on the outer circumference of the steel pipe (for example, Patent Document 1).

In the pipe test described in Patent Document 1, a part of the steel pipe for pipeline is cut to form a ring-shaped test steel pipe, and this test steel pipe is attached to the pressure generating part. The pressure generating portion includes a pair of opposing walls arranged to face each other by sandwiching the test steel pipe from the axial direction so as to be in close contact with both end surfaces in the axial direction of the test steel pipe, and one outer peripheral edge portion of the pair of opposing walls. A peripheral wall extending to the other side and surrounding the outer peripheral surface of the test steel pipe is provided, and a pair of opposing walls and the peripheral wall form a pressure chamber surrounding the outer periphery of the test steel pipe.

Then, the fluid is supplied to the pressure chamber of the pressure generating part, and the pressurized fluid acts on the outer peripheral surface of the test steel pipe to deform the test steel pipe inward in the radial direction, and the strain sensor attached to the test steel pipe. The crushing limit pressure until the test steel pipe is crushed is measured based on the change of the fluid pressure and the fluid pressure, and the crushing performance of the pipeline steel pipe is evaluated and predicted. Here, since the test steel pipe is sandwiched from the axial direction so that the pair of opposing walls are in close contact with both end faces in the axial direction of the test steel pipe, even if the pressure chamber becomes high in pressure, the pressure chamber is forced from between the end face and the opposing wall. It is sealed without fluid leakage to the outside.

Japanese Patent No. 5123327

However, in the pipe test of Patent Document 1, when the test steel pipe is deformed inward in the radial direction, a frictional force is generated on both axial end faces of the test steel pipe that is in close contact with the pair of opposing walls. There is a risk that the crushing limit pressure until the crushing will show a high value. Therefore, in the pipe test of Patent Literature 1, there is a possibility that the pressure crushing performance of the steel pipe for a pipeline may be overestimated because the crushing limit pressure shows a high value.

The present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and when the test steel pipe is deformed inward in the radial direction by the action of the pressurized fluid, it is formed on both end faces in the axial direction of the test steel pipe. Provided are a crushing test method for a steel pipe for a pipeline, a method for manufacturing a steel pipe for a pipeline, and a crushing test apparatus that can reproduce the crushing limit pressure of a steel pipe for a pipeline with high accuracy without generating frictional force. The purpose is to

In order to achieve the above object, the crushing test method for a pipeline steel pipe according to an aspect of the present invention is a ring-shaped test steel pipe formed by being cut from a part of the pipeline steel pipe, and a test steel pipe. On the other hand, a step of mounting a cylindrical deformable body made of synthetic resin with a long axial length set, and a test steel pipe and deformable body so that the axis extends between a pair of opposing walls arranged to face each other. And a step of sandwiching the deformable body between the pair of opposing walls in a state where both end faces in the axial direction of the deformable body are in close contact with the pair of opposing walls, and a peripheral wall facing the outer peripheral surface of the pair of opposing walls and the deformable body. The step of supplying fluid to the pressure chamber formed surrounding the outer peripheral surface of the deformable body and causing the pressurized fluid to act on the outer peripheral surface of the deformable body, the step of measuring the inner diameter of the test steel pipe, and the pressure of the fluid in the pressure chamber And a step of calculating the crushing limit pressure of the crushed test steel pipe based on the inner diameter measurement value of the test steel pipe and the pressure measurement value of the fluid in the pressure chamber.

The method for producing a steel pipe for a pipeline according to an aspect of the present invention is a method for producing a steel pipe for a pipeline through the steps of performing the crushing test method for a steel pipe for a pipeline described above.

Further, the crushing test apparatus for a steel pipe for a pipeline according to an aspect of the present invention is a test steel pipe formed by cutting a part of a steel pipe for a pipeline to form a ring shape, and an axial length of the test steel pipe is increased. It is a cylindrical member that is set and formed of synthetic resin.The deformable body mounted on the outer circumference of the test steel pipe and the deformable body are clamped from the axial direction so that both axial end surfaces of the deformable body are in close contact with each other. An apparatus main body that forms a pressure chamber that surrounds the outer periphery of the deformable body by including a pair of opposed walls that are arranged to face each other and a peripheral wall that extends from the pair of opposed walls and that surrounds the outer peripheral surface of the deformable body, Fluid supply means for supplying fluid to the pressure chamber, inner diameter measurement means for measuring the inner diameter of the test steel pipe, fluid pressure measurement means for measuring the pressure of the fluid in the pressure chamber, and inner diameter measurement value and fluid measured by the inner diameter measurement means And a calculating means for calculating the crush limit pressure of the crushed test steel pipe based on the pressure measurement value of the fluid measured by the pressure measuring means.

According to the crushing test method of a pipeline steel pipe, the manufacturing method of a pipeline steel pipe and the crushing test apparatus according to the present invention, when the test steel pipe is deformed radially inward by the action of the pressurized fluid, No frictional force is generated on both end faces in the axial direction, and the crushing limit pressure of the pipeline steel pipe can be reproduced with high accuracy using the test steel pipe.

It is sectional drawing which shows the crushing test apparatus of the steel pipe for pipelines of 1st Embodiment which concerns on this invention. It is a figure which shows the principal part of the crushing test apparatus of the steel pipe for pipelines of 1st Embodiment. It is a block diagram which shows the structure of the calculating part which comprises the crushing test apparatus of the steel pipe for pipelines of 1st Embodiment. It is a figure which shows the principal part of the crushing test apparatus of the steel pipe for pipelines of 2nd Embodiment. It is a figure which shows the principal part of the crushing test apparatus of the steel pipe for pipelines of 3rd Embodiment. It is a figure which shows the principal part of the crushing test apparatus of the steel pipe for pipelines of 4th Embodiment. It is a graph which shows inner diameter displacement of the test steel pipe which reproduced plastic crushing when a crushing test was performed.

Next, first to third embodiments according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar reference numerals are given to the same or similar parts. However, it should be noted that the drawings are schematic and different from the actual ones. Therefore, the specific thickness and dimensions should be determined in consideration of the following description. Further, it is needless to say that the drawings include parts in which dimensional relationships and ratios are different from each other.
Further, the following first to fourth embodiments exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is as follows: The shape, structure, arrangement, etc. are not specified below. Various changes can be added to the technical idea of the present invention within the technical scope defined by the claims described in the claims.

[Crush Test Apparatus of First Embodiment]
1 and 2 show a crushing test apparatus for steel pipes for pipelines according to a first embodiment of the present invention.
As shown in FIG. 1, a crushing test apparatus 1 for pipeline steel pipes according to the first embodiment sandwiches a test steel pipe 2, a deformable body 3 mounted on the outer periphery of the test steel pipe 2, and the deformable body 3 from an axial direction. In the state, the apparatus main body 4 in which the test steel pipe 2 and the deformable body 3 are arranged, the pressurized water supply unit 5, the strain gauge 6, the pressure gauge 7, and the arithmetic unit 8 are provided.

The test steel pipe 2 is a member formed by cutting a part of a steel pipe for a pipeline for evaluating and predicting crush resistance performance to form a ring shape. The test steel pipe 2 cut from the pipeline steel pipe is cut such that both axial end faces thereof are flat.
The deformable body 3 is a cylindrical member that is attached to the outer circumference of the test steel pipe 2 and is made of synthetic resin. Examples of the synthetic resin of the deformable body 3 include a nylon resin called NC nylon. The thickness of the deformable body 3 is set to about 3 mm. The inner diameter of the deformable body 3 may be the same as the outer diameter dimension of the test steel pipe 2 so as to be in close contact with the outer peripheral surface of the test steel pipe 2, but it is about 5 mm larger than the outer diameter dimension of the test steel pipe 2. However, it does not significantly affect the crush test.

As shown in FIG. 2, the axial length Lc1 of the deformable body 3 is set longer than the axial length Lt1 of the test steel pipe 2, and the difference ΔL1 (in the axial length between the deformable body 3 and the test steel pipe 2). Lc1-Lt1) is set in the range of 0.3 mm to 5.0 mm (0.3≦ΔL1≦5.0).

As shown in FIG. 1, the device main body 4 includes a doughnut-shaped bottom plate 10 having a penetrating part 10a, a top plate 11 having the same outer peripheral shape as the bottom plate 10 and having a penetrating part 11a, and a bottom plate 10. And a ring-shaped intermediate plate 12 arranged coaxially between the roof 11 and the roof 11. The intermediate plate 12 is arranged in a state of being fitted in annular step portions 10b and 11b provided on the outer peripheries of the surfaces of the bottom plate 10 and the top plate 11 facing each other. Although not shown, grooves for inserting a sealing material are formed on the step surfaces extending along the axial direction of the step portions 10b and 11b and the inner wall surface of the intermediate plate 12 facing the step surfaces. A packing is attached to maintain liquid tightness between the step portions 10b and 11b and the intermediate plate 12. The shape of the groove and the shape of the rubber packing can be arbitrarily selected, and for example, the structure may be such that a rubber packing having a circular cross section or a rectangular cross section is mounted.

The apparatus main body 4 is provided with a ring-shaped test space ST surrounded by an upper surface 10h of the bottom board 10, a lower surface 11h of the top board 11, and an inner peripheral surface 12a of the intermediate board 12. In this test space ST, the test steel pipe 2 and the deformable body 3 are arranged so that the axis extends between the upper surface 10h of the bottom plate 10 and the lower surface 11h of the top plate 11.
A plurality of first connecting bolts 14 and second connecting bolts 15 are attached to the device body 4. The plurality of first connecting bolts 14 pass through the through holes 11c, 12c which penetrate the axial direction at predetermined intervals in the outer circumferential side of the roof 11 and the intermediate plate 12, and the predetermined intervals in the circumferential direction of the bottom plate 10. The threaded portion is screwed into the threaded hole 10c provided by opening. The plurality of second bolts 15 pass through the through-holes 11d that penetrate through the axial direction in the circumferential direction on the inner circumferential side of the roof 11 at predetermined intervals, and set the predetermined intervals in the circumferential direction on the inner circumferential side of the bottom plate 10. The screw portion is screwed into the screw hole 10d provided as above.

By mounting the plurality of first and second connecting bolts 14 and 15, the bottom surface of the deformable body 3 in a state where both end surfaces 3a and 3b in the axial direction are in close contact with the lower surface 11h of the top 11 and the upper surface 10h of the bottom board 10. It is sandwiched between 10 and the roof 11. A pressure chamber 16 is formed in a space surrounded by the outer peripheral surface of the deformable body 3, the inner peripheral surface of the intermediate plate 12, the lower surface 11h of the roof 11 and the upper surface 10h of the bottom plate 10.
A water supply passage 11e and a pressure measurement passage 11f, which communicate with the outside of the pressure chamber 16 and the apparatus body 4, are formed in the roof 11, and the pressurized water supply unit 5 is connected to the water supply passage 11e. The pressure gauge 7 is connected to 11f. Further, a plurality of strain gauges 6 are attached to the inner peripheral surface of the test steel pipe 2.

As shown in FIG. 3, the calculation unit 8 includes an input unit 8a, a crushing pressure calculation unit 8b, a display unit 8c, and the like. The input unit 8a, the crushing pressure calculation unit 8b, and the display unit 8c are specifically realized by a general-purpose information processing device such as a personal computer or a workstation, and have, for example, a CPU, a ROM, a RAM, etc. as main components. In addition to being parts, they are connected by a network and are configured to exchange data.

The pressure value of the pressure chamber 16 measured by the pressure gauge 7 is input to the input section 8a of the calculation section 8, and the test steel pipe 2 measured by the plurality of strain gauges 6 mounted on the inner peripheral surface of the test steel pipe 2 is measured. The displacement amount of is input.
The crushing pressure calculation unit 8b calculates the pressure when the test steel pipe 2 is crushed (crushing limit pressure) based on the change in the pressure value of the pressure chamber 16 input to the input unit 8a and the displacement amount of the test steel pipe 2.
The display unit 8c displays the value of the crush limit pressure of the test steel pipe 2 calculated by the crush pressure calculation unit 8b.

The pair of opposing walls described in the present invention correspond to the lower surface 11h of the top 11 and the upper surface 10h of the bottom board 10, and the fluid supply means described in the present invention corresponds to the pressurized water supply unit 5. The inner diameter measuring means described in the present invention corresponds to the strain gauge 6, the fluid pressure measuring means described in the present invention corresponds to the pressure gauge 7, and the arithmetic means described in the present invention. , Corresponding to the calculation unit 8.

Next, a crushing test procedure for a steel pipe for a pipeline using the crushing test apparatus 1 of the first embodiment will be described together with its operation.
First, the deformable body 3 is attached to the outer circumference of the test steel pipe 2.
Next, as shown in FIG. 1, the test steel pipe 2 and the deformable body 3 are arranged in the test space ST of the apparatus main body 4 so that the axis extends between the upper surface 10h of the bottom plate 10 and the lower surface 11h of the top plate 11. To do.
Next, the plurality of first connecting bolts 14 and the second connecting bolts 15 are attached to the apparatus body 4, and both axial end surfaces 3a and 3b of the deformable body 3 are attached to the lower surface 11h of the roof 11 and the upper surface 10h of the bottom board 10. The deformable body 3 is sandwiched between the bottom plate 10 and the top plate 11 in a state of being in close contact with each other. As a result, the pressure chamber 16 is formed in the space surrounded by the outer peripheral surface of the deformable body 3, the inner peripheral surface of the intermediate plate 12, the lower surface 11h of the top 11 and the upper surface 10h of the bottom plate 10.

At this time, as shown in FIG. 2, in the test steel pipe 2, one end surface 2b in the axial direction is placed on the upper surface 10h of the bottom plate 10 and the other end surface 2a in the axial direction contacts the lower surface 11h of the roof 11. It is arranged inside the deformable body 3 in a state where it is not.
Next, the pressurized water is supplied from the pressurized water supply unit 5 to the pressure chamber 16 via the water supply passage 11e. When the water pressure in the pressure chamber 16 is increased by the supply of the pressurized water from the pressurized water supply unit 5, the water pressure acts on the outer peripheral surface of the deformable body 3 and the deformable body 3 is plastically deformed radially inward. With the plastic deformation of the deformable body 3, the test steel pipe 2 mounted inside the deformable body 3 also plastically deforms radially inward.

Since the deformable body 3 is made of synthetic resin, even if the deformable body 3 is in close contact with the lower surface 11h of the roof 11 and the upper surface 10h of the bottom board 10, a large frictional force is not generated between the lower surface 11h and the upper surface 10h.
Since the water pressure of the pressure chamber 16 acts on the outer circumference of the test steel pipe 2 via the deformable body 3, the test steel pipe 2 is likewise plastically deformed radially inward. At this time, in the test steel pipe 2, one end surface 2b in the axial direction is placed on the upper surface 10h of the bottom plate 10 and the other end surface 2a in the axial direction is not in contact with the lower surface 11h of the roof 11, so that the bottom plate 10 is not in contact. Since it is not sandwiched between the roof 11 and the roof 11, frictional force is not generated between the axial end surfaces 2a and 2b and the lower surface 11h and the upper surface 10h.

Then, the calculation unit 8 inputs the pressure value of the water pressure of the pressure chamber 16 acting on the outer circumference of the test steel pipe 2 to the input unit 8a from the pressure gauge 7, and the displacement amount of the test steel pipe 2 plastically deformed radially inward. Since input is made from a plurality of strain gauges 6, the crush pressure calculation unit 8b calculates the crush limit pressure when the test steel pipe 2 is crushed based on the change in the pressure value of the pressure chamber 16 and the displacement amount of the test steel pipe 2. .. Then, the display unit 8c displays the value of the crushing limit pressure of the test steel pipe 2.
Here, the test steel pipe 2 which is plastically deformed radially inward is also plastically deformed in the direction in which the axial length increases. In the present embodiment, the difference ΔL1 between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 is set to 0.3 mm or more, but this difference ΔL1 (0.3 mm or more) is Even if the test steel pipe 2 is plastically deformed in the direction in which the axial length increases, the axial end surface of the test steel pipe 2 does not come into contact with the lower surface 11h of the roof 11. As a result, even if the test steel pipe 2 is plastically deformed in the direction in which the axial length increases, there is no possibility of generating a frictional force between the top plate 11 and the bottom plate 10.

If the difference ΔL1 between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 is less than 0.3 mm, the end surface of the test steel pipe 2 comes into contact with the lower surface 11h of the roof 11, so the test A frictional force may be generated between the steel pipe 2 and the top 11 and the bottom 10.
Further, if the difference ΔL1 between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 is too large, the deformable body 3 is excessively deformed by the action of water pressure in the pressure chamber 16, and the deformable body is deformed. The liquid-tightness of the contact position between the axial end surface 3a of 3 and the lower surface 11h of the roof 11 and the contact position between the axial end surface 3b of the deformable body 3 and the upper surface 10h of the bottom plate 10 may deteriorate. Therefore, in the first embodiment, by setting the difference ΔL1 to a value of 5.0 mm or less, excessive deformation of the deformable body 3 is prevented, and the liquid at the contact position between the bottom board 10 and the roof 11 and the deformable body 3 is prevented. The tightness is secured.

Next, effects of the crushing test apparatus 1 for a steel pipe for a pipeline according to the first embodiment will be described.
According to the first embodiment, the pressure chamber 16 that applies water pressure to the outer peripheral surface of the test steel pipe 2 to be subjected to the crush test includes the outer peripheral surface of the deformable body 3 mounted on the outer peripheral surface of the test steel pipe 2, the inner peripheral surface of the intermediate plate 12, It is formed in a space surrounded by a lower surface 11h of the top 11 and an upper surface 10h of the bottom 10. Then, the water pressure of the pressure chamber 16 acts on the test steel pipe 2 via the deformable body 3 and plastically deforms inward in the radial direction. However, in this test steel pipe 2, one end surface 2b in the axial direction is the bottom plate. 10, the other axial end surface 2a is not in contact with the lower surface 11h of the roof 11, and the axial end surfaces 2a and 2b generate a frictional force between the lower surface 11h and the upper surface 10h. do not do.

Therefore, since no frictional force is generated in the test steel pipe 2 to be subjected to the crushing test, the crushing limit pressure of the pipeline steel pipe can be reproduced with high accuracy in the test steel pipe 2, and the pressure crushing performance of the pipeline steel pipe is highly accurate. Can be evaluated.
Further, since the difference ΔL1 (Lc1-Lt1) between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 is set to 0.3 mm or more, the test steel pipe 2 has an increased axial length. Even if it is plastically deformed in the direction in which it does not contact the lower surface 11h of the roof 11 and no frictional force is generated between it and the roof 11, the pressure crushing performance of the pipeline steel pipe can be evaluated with higher accuracy. You can
Further, by setting the difference ΔL1 (Lc1-Lt1) between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 to a value of 5.0 mm or less, the liquid tightness of the pressure chamber 16 can be improved. Since it is possible to sufficiently secure the property, the crushing limit pressure of the test steel pipe 2 can be calculated with high accuracy.

[Crush Test Apparatus of Second Embodiment]
Next, FIG. 4 shows a main part of a crushing test apparatus 17 for pipeline steel pipes according to a second embodiment of the present invention. The same components as those of the crushing test apparatus 1 for a steel pipe for a pipeline according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
In the device body 4 of the crushing test device 17 of the present embodiment, ring grooves are formed on the step surfaces along the axial direction of the step portions 10b and 11b shown in the first embodiment and on the inner wall surface of the intermediate plate 12 facing the step surfaces. Instead, instead, a ring groove having a quadrangular cross section is formed on the step surfaces orthogonal to the axial direction of the step portions 10b and 11b and the axial surface of the intermediate disk 12 facing the step surfaces. An annular packing 23 having a rectangular cross section is attached to the ring grooves formed on the surfaces of the step portions 10b and 11b and the intermediate plate 12 that face each other in the axial direction.

According to the second embodiment, the axial force generated in the first and second connecting bolts 14 and 15 by passing through the roof 11 and being screwed into the bottom plate 10 causes a step difference perpendicular to the axial direction of the step parts 10b and 11b. Since a large adhesion force acts on the annular packing 23 mounted between the surface and the surface of the intermediate plate 12 facing the surface and orthogonal to the axial direction, the water pressure in the pressure chamber 16 is increased as compared with the first embodiment. It is possible to greatly increase it.
Therefore, the crushing test apparatus 17 for steel pipes for pipelines of the second embodiment measures the crushing limit pressure of the test steel tube 2 by significantly increasing the water pressure of the pressure chamber 16 as compared with the crushing test apparatus 1 of the first embodiment. Therefore, the crushing limit pressure of a significantly high value of the pipeline steel pipe can be reproduced with high accuracy in the test steel pipe 2.

In the second embodiment, the annular packing 23 is attached to the ring groove provided on the step surface orthogonal to the axial direction of the step portions 10b and 11b and the surface orthogonal to the axial direction of the intermediate plate 12 facing the step surface. Even if an arc-shaped ring groove is formed and an O-ring is attached to this ring groove, the same effect can be obtained.

[Crush Test Apparatus of Third Embodiment]
Next, FIG. 5 shows a main part of a crushing test apparatus for steel pipes for pipelines according to a third embodiment of the present invention. The same components as those of the crushing test device for pipeline steel pipes according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
In the crushing test device 20 of the third embodiment, a cylindrical rubber packing 21 is attached to the outer periphery of the deformable body 3.

The rubber packing 21 is a member in which thick portions 21a and 21b are provided at both ends in the axial direction, and the thickness other than the thick portions 21a and 21b is 3 mm, and the axial length in the free length is It is set to be longer than the axial length Lc2 of the deformable body 3. Further, the thick portions 21a and 21b are not always necessary, and the effect of the present invention can be exhibited without the thick portions.
Further, the axial length Lc2 of the deformable body 3 is set longer than the axial length Lt2 of the test steel pipe 2, and the difference ΔL2 (Lc2-Lt2) between the axial lengths of the deformable body 3 and the test steel pipe 2 is , 1.0 mm or more and 1.3 mm or less (1.0≦ΔL2≦1.3).
The cylindrical elastic body described in the present invention corresponds to the rubber packing 21.

Next, a crushing test procedure of a steel pipe for a pipeline using the crushing test device 20 of the third embodiment will be described together with its operation.
First, the deformable body 3 is attached to the outer periphery of the test steel pipe 2, and the rubber packing 21 is attached to the outer periphery of the deformable body 3.
Next, in the test space ST of the apparatus body 4, the test steel pipe 2, the deformable body 3, and the rubber packing 21 are arranged so that the axis extends between the upper surface 10h of the bottom plate 10 and the lower surface 11h of the roof 11.

Next, the plurality of first connecting bolts 14 and the second connecting bolts 15 are attached to the apparatus body 4, and both axial end surfaces 3a and 3b of the deformable body 3 are attached to the lower surface 11h of the roof 11 and the upper surface 10h of the bottom board 10. The thickened portions 21a and 21b at both ends of the rubber packing 21 in the axial direction are elastically deformed in a compressed state so as to sandwich the deformable body 3 between the bottom plate 10 and the top plate 11. As a result, the pressure chamber 16 is formed in a space surrounded by the outer peripheral surface of the rubber packing 21, the inner peripheral surface of the intermediate plate 12, the lower surface 11h of the top 11 and the upper surface 10h of the bottom plate 10.
At this time, in the test steel pipe 2, one end surface 2b in the axial direction is placed on the upper surface 10h of the bottom plate 10 and the other end surface 2a in the axial direction does not contact the lower surface 11h of the roof 11, and the deformable body 3 is deformed. Placed inside.

Next, the pressurized water is supplied from the pressurized water supply unit 5 to the pressure chamber 16 via the water supply passage 11e. When the water pressure in the pressure chamber 16 increases due to the supply of the pressurized water from the pressurized water supply unit 5, the water pressure acts on the outer peripheral surface of the deformable body 3 via the rubber packing 21, and the deformable body 3 is plastically deformed radially inward. It transforms. Then, along with the plastic deformation of the deformable body 3, the test steel pipe 2 mounted inside the deformable body 3 also plastically deforms radially inward.
In the test steel pipe 2 which is plastically deformed inward in the radial direction, one end face 2b in the axial direction is placed on the upper face 10h of the bottom plate 10, and the other end face 2a in the axial direction contacts the lower face 11h of the roof 11. Since it is not sandwiched between the bottom plate 10 and the top plate 11, no frictional force is generated between the axial end faces 2a and 2b and the lower face 11h and the upper face 10h.

The test steel pipe 2 is plastically deformed inward in the radial direction and is also plastically deformed in a direction in which the axial length is increased. In the second embodiment, the difference ΔL1 between the axial length Lc2 of the deformable body 3 and the axial length Lt2 of the test steel pipe 2 is set to 1.0 mm or more, but this difference ΔL2 (1.0 mm or more) is set. Even if the test steel pipe 2 is plastically deformed in the direction in which the axial length increases, the axial end surface of the test steel pipe 2 does not come into contact with the lower surface 11h of the roof 11. As a result, even if the test steel pipe 2 is plastically deformed in the direction in which the axial length increases, there is no possibility of generating a frictional force between the top plate 11 and the bottom plate 10.
Further, in the third embodiment, by setting the difference ΔL2 to a value of 1.3 mm or less, excessive deformation of the deformable body 3 is prevented, and the liquid at the contact position between the bottom plate 10 and the roof 11 and the deformable body 3 is prevented. The tightness is secured.

Next, the effect of the steel pipe crushing test apparatus 20 of the third embodiment will be described.
The water pressure of the pressure chamber 16 acts on the test steel pipe 2 via the deformable body 3 and plastically deforms inward in the radial direction. However, in the test steel pipe 2, one end face 2b in the axial direction is the top face 10h of the bottom plate 10h. The other end surface 2a in the axial direction is not in contact with the lower surface 11h of the roof 11, and the axial end surfaces 2a and 2b do not generate frictional force between the lower surface 11h and the upper surface 10h. Therefore, since no frictional force is generated in the test steel pipe 2 to be subjected to the crushing test, the crushing limit pressure of the pipeline steel pipe can be reproduced with high accuracy in the test steel pipe 2, and the pressure crushing performance of the pipeline steel pipe is highly accurate. Can be evaluated.

Further, in the crushing test apparatus 20 of the third embodiment, the rubber packing 21 is attached to the outer periphery of the deformable body 3, and when the deformable body 3 is sandwiched between the bottom plate 10 and the top plate 11, the rubber packing 21 moves in the axial direction of the rubber packing 21. The thick portions 21a and 21b at both ends are elastically deformed in a compressed state on the lower surface 11h of the top board 11 and the upper surface 10h of the bottom board 10. Thereby, the crushing test apparatus 20 of the third embodiment has higher liquid-tightness at the contact position between the bottom plate 10 and the roof 11 and the deformable body 3, as compared with the crushing test apparatus 1 of the first embodiment. The water pressure in the pressure chamber 16 can be increased. Therefore, the crushing test apparatus 20 of the third embodiment can measure the high value of the crushing limit pressure of the test steel pipe 2 by increasing the water pressure in the pressure chamber 16, and the high value of the crushing limit pressure of the pipeline steel pipe can be measured. Can be reproduced with high precision using a test steel pipe.

Further, since the difference ΔL2 (Lc2-Lt2) between the axial length Lc2 of the deformable body 3 and the axial length Lt2 of the test steel pipe 2 is set to 1.0≦ΔL2≦1.3, the test steel pipe 2 Even if is plastically deformed in the direction of increasing the axial length, the lower surface 11h of the roof 11 does not come into contact with the roof 11 and no frictional force is generated between the roof 11 and the pressure crushing performance of the pipeline steel pipe. It can be performed with high accuracy, and the crush limit pressure of the test steel pipe 2 can be calculated with high accuracy.

[Crush Test Apparatus of Fourth Embodiment]
Next, FIG. 6 shows an essential part of a crushing test apparatus for pipeline steel pipes according to a fourth embodiment of the present invention. The same components as those of the crushing test apparatus 20 for pipeline steel pipes according to the third embodiment shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.
In the crushing test device 30 of the fourth embodiment, annular notches 3c and 3d are formed on the outer peripheral sides of the axially opposite end faces 3a and 3b of the deformable body 3, and the notches 3c and 3d have O Rings 31 and 32 are attached.

Although not shown in FIG. 6, the difference ΔL2 (Lc2-Lt2) between the axial length Lc2 of the deformable body 3 and the axial length Lt2 of the test steel pipe 2 is 1.0≦ΔL2≦1.3. Is set to.
The annular recesses described in the present invention correspond to the annular notches 3c and 3d, and the O-rings described in the present invention correspond to the O- rings 31 and 32.

In the crush test apparatus 30 of the fourth embodiment, the deformable body 3 is mounted on the outer circumference of the test steel pipe 2, and the O- rings 31, 32 are provided in the annular cutouts 3c, 3d provided on both end faces 3a, 3b of the deformable body 3. Put on. Then, in the test space ST of the apparatus body 4, the deformable body 3 in which the test steel pipe 2 and the O- rings 31, 32 are mounted is arranged so that the axis extends between the upper surface 10h of the bottom plate 10 and the lower surface 11h of the top plate 11. To do.

In addition, a plurality of first connecting bolts 14 and second connecting bolts 15 are attached to the device body 4, and both axial end faces 3a and 3b of the deformable body 3 are closely attached to the lower surface 11h of the roof 11 and the upper surface 10h of the bottom board 10. Then, the O- rings 31 and 32 are elastically deformed to the lower surface 11h and the upper surface 10h in a compressed state, and the deformable body 3 is sandwiched between the bottom plate 10 and the top plate 11. As a result, the pressure chamber 16 is formed in the space surrounded by the outer peripheral surface of the deformable body 3, the inner peripheral surface of the intermediate plate 12, the lower surface 11h of the top 11 and the upper surface 10h of the bottom plate 10. At this time, in the test steel pipe 2, one end surface 2b in the axial direction is placed on the upper surface 10h of the bottom plate 10 and the other end surface 2a in the axial direction does not contact the lower surface 11h of the roof 11, and the deformable body 3 is deformed. Placed inside.

Then, similarly to the crushing test apparatus 20 of the second embodiment, when pressurized water is supplied from the pressurized water supply unit 5 to the pressure chamber 16 via the water supply passage 11e, the deformable body 3 is plastically deformed and the deformable body 3 is deformed. The test steel pipe 2 mounted on the inside of the plastic also plastically deforms inward in the radial direction.
Therefore, also in the crushing test apparatus 30 of the fourth embodiment, no frictional force is generated in the test steel pipe 2 on which the crushing test is performed, so that the crushing limit pressure of the pipeline steel pipe can be reproduced with high accuracy in the test steel pipe 2, It is possible to highly accurately evaluate the pressure crushing performance of a steel pipe for a pipeline.

Further, in the crushing test device 30 of the fourth embodiment, the O- rings 31 and 32 are attached to both end surfaces 3a and 3b of the deformable body 3, and when the deformable body 3 is sandwiched between the bottom plate 10 and the top plate 11, The O- rings 31 and 32 are elastically deformed on the lower surface 11h of the top 11 and the upper surface 10h of the bottom 10 in a compressed state. Thereby, the crushing test apparatus 30 of the fourth embodiment also has higher liquid-tightness at the contact position between the bottom plate 10 and the roof 11 and the deformable body 3, as compared with the crushing test apparatus 1 of the first embodiment. The water pressure in the pressure chamber 16 can be increased.

Therefore, the crushing test apparatus 30 of the fourth embodiment can measure the high value of the crushing limit pressure of the test steel pipe 2 by increasing the water pressure in the pressure chamber 16, and the high value of the crushing limit pressure of the pipeline steel pipe can be measured. Can be reproduced with high precision using a test steel pipe.
Further, by performing a crush test using the crush test devices 1, 17, 20, 30 of the first to fourth embodiments, it is possible to manufacture a steel pipe for pipeline in which a crush limit pressure with high accuracy is set. it can.

[Example 1]
Next, the measurement of the crush limit pressure by the crush test method using the crush test device for pipeline steel pipe according to the present invention, and the measurement of the crush limit pressure by the crush test method using the conventional crush test device, The effects of the present invention were verified by making a comparison as shown in Table 1 above.

Inventive Example 1 to Inventive Example 5, and Comparative Examples 1 and 2, the nominal pipe thickness is 39 mm, the nominal outer diameter is 812.8 mm, and the steel pipe for pipeline having the same outer diameter shape and the same steel pipe characteristics is used. did.
Inventive Example 1 to Inventive Example 3 are measurement results using the crushing test apparatus 1 of the first embodiment in which the deformable body 3 is mounted on the outer circumference of the test steel pipe 2. The present invention 1 has a difference ΔL1=0.3 mm in the axial length between the deformable body 3 and the test steel pipe 2, the invention 2 has ΔL1=0.5 mm, and the invention 3 has ΔL1=3.0 mm. ..

In addition, Examples 4 and 5 of the present invention are measurement results using the crushing test apparatus 20 of the second embodiment in which the deformable body 3 is mounted on the outer circumference of the test steel pipe 2 and the rubber packing 21 is mounted on the outer circumference of the deformable body 3. is there. In the invention example 4, the difference in axial length between the deformable body 3 and the test steel pipe 2 was ΔL2=1.0 mm, and in the invention example 5, ΔL2=1.3 mm.
Further, Comparative Example 1 uses the crushing test apparatus 1 of the first embodiment in which the deformable body 3 is attached to the outer circumference of the test steel pipe 2, and the difference ΔL1=0.0.5 in the axial length between the deformable body 3 and the test steel pipe 2. It was set to 1 mm. Furthermore, Comparative Example 2 uses the crushing test apparatus 1 of the first embodiment in which the deformable body 3 is attached to the outer circumference of the test steel pipe 2, and the difference ΔL1=6.6 in the axial length between the deformable body 3 and the test steel pipe 2. It was set to 0 mm.

The crushing limit pressures of Inventive Example 1 to Inventive Example 5 and Comparative Examples 1 and 2 are the result of measuring the actual pipe without cutting a part of the pipeline steel pipe (actual pipe test result) and the pipeline. The result (crushing device result) measured by the crushing test device of the first and third embodiments using the test steel pipe 2 obtained by cutting a part of the steel pipe for use is shown, and the actual pipe test result and the crushing device result are compared. The measurement accuracy was shown.
As is clear from Table 1, in the present invention examples 1 to 3 the frictional force is not generated in the test steel pipe 2 when the crushing test is performed by mounting the deformable body 3 on the outer periphery of the test steel pipe 2. Since the difference ΔL1 between the axial length Lc1 of the deformable body 3 and the axial length Lt1 of the test steel pipe 2 is set to 0.3 mm≦ΔL1≦5.0 mm, the measurement accuracy error is 0.5%. It is within.

In addition, in Examples 4 and 5 of the present invention, the deformable body 3 was attached to the outer circumference of the test steel pipe 2, and the rubber packing 21 was attached to the outer peripheral side of the deformable body 3, so that the test steel pipe 2 was not subjected to the crush test. Since no frictional force is generated and the difference ΔL2 between the axial length Lc2 of the deformable body 3 and the axial length Lt2 of the test steel pipe 2 is set to 1.0 mm≦ΔL2≦1.3 mm, The error is less than 1.0%.
On the other hand, Comparative Example 1 uses the crushing test apparatus 1 of the first embodiment in which the deformable body 3 is mounted on the outer circumference of the test steel pipe 2, but the difference ΔL1 in the axial length between the deformable body 3 and the test steel pipe 2 is used. = Less than 0.3 mm, the test steel pipe 2 is plastically deformed in the axial direction and comes into contact with the lower surface 11h of the top 11 and the upper surface 10h of the bottom 10 to generate frictional force, and the crushing limit pressure of the test steel pipe 2 Showed a high value, and the measurement error was as large as 5.8%.

In Comparative Example 2, the measurement error is 10% or more. This comparative example 2 uses the crushing test apparatus 1 of the first embodiment in which the deformable body 3 is mounted on the outer circumference of the test steel pipe 2, but the difference ΔL1 in the axial length between the deformable body 3 and the test steel pipe 2 is used. It exceeds 5.0 mm. As a result, when the water pressure in the pressure chamber 16 is rising, the deformable body 3 is deformed in a state of entering between the end surface of the test steel pipe 2 and the lower surface 11h of the roof 11 and the liquid tightness of the pressure chamber 16 is increased. Became impossible, and the maximum pressure of the pressure chamber 16 was greatly reduced before the test steel pipe 2 was crushed.
Therefore, the method using the crushing test apparatus 1 according to the first embodiment of the present invention and the method using the crushing test apparatus 20 according to the third embodiment are highly accurate in determining the crushing limit pressure of the steel pipe for pipeline with the test steel pipe. It was confirmed that it can be reproduced. The method using the crushing test apparatus 30 of the fourth embodiment can also accurately reproduce the crushing limit pressure of the pipeline steel pipe with the test steel pipe.

[Example 2]
Next, the crushing limit pressure is measured by the crushing test method using the crushing test device for pipeline steel pipes according to the present invention, and the crushing limit pressure is measured by the crushing test method using the conventional crushing test device. The effect of the present invention was verified by determining whether crushing was reproduced.
Whether or not the plastic crush is reproduced is determined from the elastic deformation line of the test steel pipe 2 and the inner diameter displacement ΔR (average value of the measured inner diameter change) of the test steel pipe 2 subjected to the crush test calculated by the following formula (1). Judgment is made by comparison with the amount of separation, and when the inner diameter displacement ΔR of the test steel pipe 2 is more than 0.2% from the elastic deformation line, it is judged that the plastic indentation is reproduced.
ΔR =-(PR ² )/(tE) ……… (1)
Note that P is the pressure (Mpa), R is the initial inner diameter (mm) of the test steel pipe 2, t is the thickness (mm) of the test steel pipe 2, and E is the Young's modulus (Mpa).

Inventive Example 6 and Comparative Example 3 used steel pipes for pipelines having a nominal pipe thickness of 40 mm, a nominal outer diameter of 691 mm, the same outer diameter shape, and the same steel pipe characteristics.
In the invention example 6, the deformable body 3 is mounted on the outer circumference of the test steel pipe 2, and the shaft generated in the first and second connecting bolts 14 and 15 by penetrating the roof 11 and being screwed into the bottom 10 The force exerts a large adhesion force on the annular packing 23 mounted between the step surfaces of the step portions 10b and 11b which are orthogonal to the axial direction and the surface of the intermediate plate 12 which faces the step surfaces and which is orthogonal to the axial direction, and the pressure is applied. It is a measurement result which used the crushing test apparatus 17 (refer FIG. 4) of 2nd Embodiment which can raise the water pressure of the chamber 16 significantly. Then, in Inventive Example 6, the difference in axial length between the deformable body 3 and the test steel pipe 2 was ΔL1=1.0 mm. On the other hand, Comparative Example 3 uses the crushing test apparatus 17 of the second embodiment in which the deformable body 3 is attached to the outer circumference of the test steel pipe 2, and the difference ΔL1=6.x in the axial length between the deformable body 3 and the test steel pipe 2. It was set to 0 mm.

FIG. 7 shows the relationship between the water pressure change and the inner diameter displacement of the pressure chamber 16 for the test steel pipe 2 of the present invention example 6. The test steel pipe 2 of the present invention example 6 plastically deforms as the water pressure of the pressure chamber 16 increases. It was verified that the plastic indentation was reproduced when the distance from the elastic deformation line was 0.8%. It was also verified that when the plastic indentation of Inventive Example 6 was reproduced, a crushing test at an ultrahigh pressure exceeding 50 MPa could be reproduced.
On the other hand, in Comparative Example 3 in which the difference ΔL1=6.0 mm in the axial length between the deformable body 3 and the test steel pipe 2, when the water pressure in the pressure chamber 16 increases, the deformable body 3 causes the end face of the test steel pipe 2 and the roof 11 to rise. It deformed in a state of entering between the lower surface 11h and the lower surface 11h, making liquid tightness of the pressure chamber 16 impossible, and the maximum pressure of the pressure chamber 16 greatly decreased before the test steel pipe 2 was crushed. At this time, the inner diameter displacement ΔR of the test steel pipe 2 is 0.05% from the elastic deformation line, and the water in the pressure chamber 16 leaks to the outside in the elastically deformed state, so that the crush test can be reproduced. Can not.

1, 17, 20, 30 Crush test device 2 Test steel pipe 2a Another end face 2b of test steel pipe in the axial direction One end face 3 of test steel pipe in the axial direction 3 Deformation bodies 3a, 3b End face 4 of the deformation body 4 Device body 5 Pressurized water supply unit 6 Strain gauge 7 Pressure gauge 8 Calculation unit 8a Input unit 8b Crush pressure calculation unit 8c Display unit 10 Bottom plate 10a Penetration part 10b Steps 10c, 10d Screw hole 10h Top surface 11 Top 11a Penetration part 11b Step part 11c Penetration hole 11d Through hole 11e Water supply path 11f Pressure measurement path 11h Lower surface 12 Intermediate board 12a Inner peripheral surface 12c Through hole 14 First connecting bolt 15 Second connecting bolt 16 Pressure chamber 21 Rubber packing 21a, 21b Thick portion 22 O-ring 23 Ring Packing ST Test space Lc1 Axial length Lt1 of deformable body of first embodiment Axial length ΔL1 of test steel pipe of first embodiment Difference Lc2 between axial length of deformable body and test steel pipe of first embodiment Axial Length Lt2 of Deformed Body of Second Embodiment Axial Length ΔL2 of Test Steel Pipe of Second Embodiment Difference in Axial Length of Deformed Body and Test Steel Pipe of Second Embodiment

Claims (11)

1. On the outer circumference of a ring-shaped test steel pipe formed by being cut from a part of a pipeline steel pipe, a cylindrical deformable body formed of synthetic resin with an axial length set longer than that of the test steel pipe is mounted. Process,
   The test steel pipe and the deformable body are arranged so that an axis extends between a pair of opposing walls arranged to face each other, and the axial ends of the deformable body are in close contact with the pair of opposing walls. Sandwiching the deformable body between a pair of opposing walls,
   A fluid is supplied to a pressure chamber formed by surrounding the outer peripheral surface of the deformable body with a pair of opposing walls and a peripheral wall facing the outer peripheral surface of the deformable body, and the pressurized fluid acts on the outer peripheral surface of the deformable body. And the process of
   Measuring the inner diameter of the test steel pipe,
   Measuring the pressure of the fluid in the pressure chamber,
   Crushing a pipeline steel pipe, comprising: calculating a crushing limit pressure of the crushed test steel pipe based on an inner diameter measurement value of the test steel pipe and a pressure measurement value of the fluid in the pressure chamber. Test method.
2. When the axial length of the deformable body is Lc1 and the axial length of the test steel pipe is Lt1, the difference ΔL1 (Lc1-Lt1) in the axial length of the deformable body and the test steel pipe is 0.3 mm≦. The method for crushing a steel pipe for pipeline according to claim 1, wherein ΔL1≦5.0 mm.
3. A step of cutting a part of the steel pipe for a pipeline to form a ring-shaped test steel pipe,
   On the outer periphery of the test steel pipe, a step of mounting a cylindrical deformable body formed of synthetic resin by setting the axial length of the test steel pipe to be long,
   Mounting a seal member made of an elastic body on the outer periphery of the deformable body,
   The test steel pipe, the deformable body, and the seal member are arranged so that an axis extends between a pair of opposed walls arranged to face each other, and both axial end faces of the deformable body are closely attached to the pair of opposed walls. And sandwiching the deformable body with the pair of opposing walls in a state in which the seal member is elastically deformed and closely attached,
   A fluid is supplied to a pressure chamber formed by surrounding the outer peripheral surface of the deformable body with a pair of opposing walls and a peripheral wall facing the outer peripheral surface of the deformable body, and the pressurized fluid acts on the outer peripheral surface of the deformable body. Process,
   Measuring the inner diameter of the test steel pipe,
   Measuring the pressure of the fluid in the pressure chamber,
   Crushing a pipeline steel pipe, comprising: calculating a crushing limit pressure of the crushed test steel pipe based on an inner diameter measurement value of the test steel pipe and a pressure measurement value of the fluid in the pressure chamber. Test method.
4. When the axial length of the deformable body is Lc2 and the axial length of the test steel pipe is Lt2, the difference ΔL2 (Lc2-Lt2) in the axial length between the deformable body and the test steel pipe is 1.0 mm≦. The method for crushing a steel pipe for pipeline according to claim 3, wherein ΔL2≦1.3 mm.
5. A method for manufacturing a steel pipe for a pipeline, which comprises manufacturing the steel pipe for a pipeline through a step of performing the method for crushing a steel pipe for a pipeline according to any one of claims 1 to 4.
6. A test steel pipe formed by cutting a part of the steel pipe for a pipeline into a ring shape,
   A cylindrical member formed of synthetic resin by setting the axial length of the test steel pipe to be long, and a deformable body mounted on the outer periphery of the test steel pipe,
   A pair of opposing walls that are arranged to face each other by sandwiching the deformable body from the axial direction so that both axial end surfaces of the deformable body are in close contact with each other, and the deformable body extends from the pair of opposing walls. An apparatus main body having a peripheral wall surrounding an outer peripheral surface and forming a pressure chamber surrounding the outer periphery of the deformable body;
   Fluid supply means for supplying fluid to the pressure chamber,
   An inner diameter measuring means for measuring the inner diameter of the test steel pipe,
   Fluid pressure measuring means for measuring the pressure of the fluid in the pressure chamber,
   Arithmetic means for calculating a crushing limit pressure of the test steel pipe crushed based on the inner diameter measurement value measured by the inner diameter measurement means and the pressure measurement value of the fluid measured by the fluid pressure measurement means. Crush tester for steel pipes for pipelines.
7. When the axial length of the deformable body is Lc1 and the axial length of the test steel pipe is Lt1, the difference ΔL1 (Lc1-Lt1) in the axial length of the deformable body and the test steel pipe is 0.3 mm≦. 7. The crushing test apparatus for steel pipes for pipelines according to claim 6, wherein ΔL1≦5.0 mm.
8. A test steel pipe formed by cutting a part of the steel pipe for a pipeline into a ring shape,
   A cylindrical member formed of synthetic resin by setting the axial length of the test steel pipe to be long, and a deformable body mounted on the outer periphery of the test steel pipe,
   A seal member made of an elastic body attached to the outer periphery of the deformable body,
   A pair of opposed walls that are arranged to face each other by sandwiching the deformable body and the seal member from the axial direction so that both axial end surfaces of the deformable body are in close contact with each other and the seal member is in close contact while being elastically deformed. And a device main body that forms a pressure chamber that surrounds the outer periphery of the deformable body by including a peripheral wall that extends from the pair of opposing walls and that surrounds the outer peripheral surface of the deformable body,
   Fluid supply means for supplying fluid to the pressure chamber,
   An inner diameter measuring means for measuring the inner diameter of the test steel pipe,
   Fluid pressure measuring means for measuring the pressure of the fluid in the pressure chamber,
   Arithmetic means for calculating a crushing limit pressure of the test steel pipe crushed based on the inner diameter measurement value measured by the inner diameter measurement means and the pressure measurement value of the fluid measured by the fluid pressure measurement means. Crush tester for steel pipes for pipelines.
9. When the axial length of the deformable body is Lc2 and the axial length of the test steel pipe is Lt2, the difference ΔL2 (Lc2-Lt2) in the axial length between the deformable body and the test steel pipe is 1.0 mm≦. 9. The crushing test device for steel pipes for pipelines according to claim 8, wherein ΔL2≦1.3 mm.
10. The crush test apparatus for a pipeline steel pipe according to claim 8 or 9, wherein the seal member is a cylindrical elastic body having an axial length longer than that of the deformable body.
11. 10. The steel pipe for a pipeline according to claim 8 or 9, wherein the seal member is an O-ring fitted in an annular recess formed in a part of both end surfaces in the axial direction of the deformable body. Crush test device.

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