JPH0676838B2 - Old pipe rehabilitation pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Object of the Invention” The present invention relates to the creation of an old pipe rehabilitation pipe, and an object thereof is to provide a pipe material suitable for performing old pipe rehabilitation on an existing pipeline such as a water supply.

Industrial application field Old pipe rehabilitation technology for existing pipelines.

Conventional technology In order to implement the pipe-in-pipe method as a method of rehabilitating the old Seki for existing pipelines such as waterworks, the diameter of the new pipeline should be as close as possible to the old pipeline in order to maintain the water distribution capacity of the existing pipeline. It is necessary to do.

Therefore, as one conventionally proposed for such a purpose, there is JP-A-60-196485, and this method is to attach a pipe expanding jig to one end of the rolled steel pipe to be inserted, and to use this pipe expanding jig. While expanding the rolled-up steel pipe by pulling it in until it comes into contact with the protrusion at the center of the fixed rib attached to the expanding pipe jig, after temporarily welding the seam of the rolled-up steel pipe, It is characterized in that the seam of the rolled-in steel pipe is main welded while being removed and adjusting the roundness.

Problems to be Solved by the Invention However, the above-mentioned conventional ones involve a large expansion amount because they are pre-wound in order to increase the circumferential length of the pipe and expand the overlapped one. It is difficult to form into the required pipe dimensions, and sufficient ductility (elongation at break) cannot be secured in the pipe material after pipe expansion.

Further, the pipe expanding load is inevitably large, and it is affected by the initial strain distribution, or the centering is difficult in welding by the seam or the butt circumference.

"Structure of the invention" Means for solving the problem C has a yield point lower than the predetermined yield point required for the target pipeline in the pipe making stage of 0.008% or less of ultra-low carbon steel or austenitic stainless steel. In addition, a material that has a ductility of 30% or more and that exhibits a yield point of the predetermined yield point or higher and ductility of the predetermined elongation value or higher required for the target pipeline after pipe expansion in the old pipe should be applied. An old pipe rehabilitation pipe characterized by having an outer diameter smaller than the inner diameter of the pipe by 5% or more.

The pipe can be appropriately carried into the target old pipe by being pipe-molded with an outer diameter smaller than the inner diameter of the old pipe to be applied by 5% or more.

It has a ductility of 30% or more, and has a yield point lower than the prescribed yield point required for the target pipeline during pipe making, so pipe expansion after setting it at the prescribed position is relatively simple and equipment is relatively low. It can be easily achieved by load.

After the pipe expansion process, it exhibits a yield point of a predetermined yield value or more required for the target pipeline and a ductility of a predetermined elongation value or more, so that the characteristics required as a rehabilitating pipe can be properly provided.
The pipe expanding process can be performed by any of fluid pressure and mechanical processing.

Examples To further explain the present invention as described above, what is conventionally used as an existing pipeline for water supply is
It is similar to JIS G3457's arc welded carbon steel pipe for piping (STPY41), and in the past, a material of a material conforming to this has been used, but on the other hand, this is for regeneration without the disadvantages of the prior art described above. In order to use it as a pipe, it is necessary to carry in a pipe material with a smaller diameter than the old pipe into the old pipe and expand the diameter. However, as a result of examining the mechanical properties of a steel pipe of the above-mentioned material that has been expanded by 15% as an example, the results show that it has the characteristics shown in Fig. 1 and the standard lower limit elongation δ specified in such a pipeline is obtained. : I learned that the ratio that is well over 18% and 30% is as shown in Fig. 2. That is, the steel pipe after such working has a yield point of 15
Although the tensile strength is almost unchanged with the increase of about kgf / mm ² , the elongation is remarkably reduced and the value is close to half of the value before processing shown in Fig. 1. It was confirmed that the elongation does not satisfy the lower limit elongation value δ: 18% or more required by the standard, and the construction purpose as a rehabilitating pipe cannot be achieved.

Therefore, as a result of further study by the present inventors, for example, C
Ultra-low carbon steel of 0.008 or less or austenitic stainless steel has the characteristics shown in Fig. 3 at the time of pipe forming, that is, the yield point is about 20 kgf / mm ² as described above. It is considerably lower than the standard lower limit value (23 kgf / mm ² ) required for piping such as water, but it has a high breaking elongation (high ductility) of more than 50% and more than twice the yield point. As shown in FIG. 4, the steel pipe having a high degree of hardening is subjected to a pipe expanding process corresponding to 15% of the pipe diameter in the same manner as described above.

In other words, the yield limit of the above-mentioned steel pipes that had not reached the standard lower limit yield point (23kgf / mm ² ) required for such water pipes before processing and was therefore difficult to adopt for such water pipes as it was the points in the post-processing 30 kgf / mm ² or more, has reached to 40 kgf / mm ^2, it was confirmed that sufficiently satisfies the above-mentioned standard lower yield point. Also in the tensile strength is not changed to the value before processing shown in FIG. 3 and 45 kgf / mm ² or 52kgf / mm ² degree, even after processing with respect to elongation
It was known that it was about 35 to 40%, and the lower limit elongation (δ: 18%) was sufficiently secured.

That is, in the present invention, the old pipe is rehabilitated by utilizing the mechanical properties of the steel pipe such as the ultra low carbon steel or the austenitic stainless steel as shown in FIGS. If such a steel pipe is introduced into the old pipe and expanded, it has a low yield point as shown in FIG. 3, so that the load during expansion can be low, and the pipe can be easily processed. Moreover, after pipe expansion, as shown in FIG. 4, all the standard values required for this kind of water pipe etc. are sufficiently satisfied.

At the time of pipe making, it is introduced into the old pipe as an outer diameter smaller than the inner diameter of the old pipe to be applied, and generally has an outer diameter smaller than the inner diameter of the old pipe by 3% or more, preferably 5% or more. The upper limit of the degree of small diameter may be about 30%, but is preferably 20% or less, and it goes without saying that the one having such a small outer diameter can be easily introduced into the old pipe. 3 to 35% for pipe expansion, especially
It is appropriate to carry out in the range of 10 to 20%.

A concrete production example of the device according to the present invention is as follows.

Various ultra low carbon steels having the composition as shown in Table 1 below were prepared by decarburization refining.

The mechanical properties of these ultra-low carbon steels during pipe forming are as shown in Table 2 below.

However, by introducing such ultra low carbon steel pipe into the old pipe, 15%
Typical mechanical properties of the expanded tube are shown in Fig. 4a-
It is as shown by the curve a and sufficiently satisfies all the standard values required for water pipes.

Separately from the above, the composition of the composition prepared by the present inventors as austenitic stainless steel is as shown in Table 3 below.

However, the mechanical properties of these austenitic stainless steels during pipe forming were as shown in Table 4 below.

An example of the mechanical properties when such an austenitic stainless steel pipe is introduced into the old pipe and expanded by 15% is shown in Fig. 4b ... b curve. It is clear that all of the standard values are sufficiently satisfied.

"Effects of the Invention" In the case of the present invention as described above, when rehabilitating an existing old pipe such as a water pipe, the object inserted into the old pipe can be expanded and easily and advantageously achieved. In other words, since it has a low yield point in the pipe making stage, the pipe expansion process itself is easy, and it can be constructed without centering and other process disadvantages as in the conventional method, and after the pipe expansion the yield point and elongation It is an invention having a great industrial effect because it can sufficiently satisfy the predetermined standard value in any of the values and the tensile strength and the rehabilitation purpose can be sufficiently achieved.

[Brief description of drawings]

The drawings show the technical contents of the present invention. Fig. 1 is a table showing a stress-strain relationship for a conventional water pipe for water supply, and Fig. 2 is a stress-strain curve after expanding the pipe by 15%. The chart shown in FIG. 3, FIG. 3 is a chart of the stress-strain curve at the time of pipe making of the steel pipe used in the present invention, and FIG. 4 is a chart showing the stress-strain curve after the tube is expanded by 15%. However, the curves a ... a in FIGS. 3 and 4 are extremely low carbon steel,
b ... b shows the case of austenitic stainless steel.

Claims (1)

[Claims] 1. A pipe having a yield point lower than a predetermined yield point required for a target pipeline in a pipe making stage such as an ultra low carbon steel or an austenitic stainless steel having a C content of 0.008% or less.
An old pipe that has a ductility of 30% or more and that has a yield point above the specified yield point and ductility above the specified elongation value required for the target pipeline after the pipe is expanded in the old pipe. An old pipe rehabilitation pipe characterized by being molded with an outer diameter smaller than the inner diameter by 5% or more.