JP2000217216A - Connecting cable force feed pipeline adapter therefor, and method for force-transporting and laying cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and easily detect the leakage from an airtightly sealed part and specify the spot where the leakage occurs, by connecting a pressure gauge to an adapter for connecting cable force feed pipeline and constituting the adapter in a split cylindrical body which can be divided into two half cylindrical bodies in the longitudinal direction. SOLUTION: An adapter 1 for connecting cable force-transporting pipeline is constituted in the form of a split cylindrical pipe 1c, which can be divided into two half cylindrical bodies having inside diameters which are equal to the outside diameter of a cable force feed pipe 10. Flange sections 1b are provided at the half-divided cross section of each half cylindrical body so that the flange sections 1b may be protruded in the lateral direction in the same plane as the divided plane of each half cylindrical body. When the adapter 1 is connected to the pipe 10 while a pressure gauge 1a is connected to the side face of the split cylindrical pipe 1c, the half- cylindrical bodies of the pipe 1c are respectively put on the outer periphery of the joint and the flanges 1b of the half-cylindrical bodies are brought into contact with each other and fixed to each other with screws. Therefore, the leakage from an airtightly sealed part can be detected quickly and easily and the spot where the leakage occurs can be specified quickly and easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable pressure line connecting adapter used at a connection portion of a cable pressure line for feeding and laying a cable by gas flow.

[0002]

2. Description of the Related Art Conventionally, as exemplified in FIG. 4, there is a method of laying an optical cable such as an optical fiber cord having a relatively small outer diameter by a gas flow through a previously laid cable pressure feeding pipeline. Are known. That is, compressed air of about 5 kgf / cm 2 to 10 kgf / cm 2 is supplied from the compressor 13 through the cable guide tube 14 to the outside diameter of 6 kgf / cm 2.
mm of plastic such as polyethylene,
It is fed into a cable pumping line consisting of a cable pumping tube 10 called a so-called sheath tube to form a pressure gradient of the compressed air flow, and the pumping force due to this pressure gradient and the not shown provided at the pumping start end 11 are provided. Due to the pushing force applied by the cable pushing mechanism, the optical cable wound around the drum 60 is fed through the cable pressure feeding conduit to its pressure feeding end 12.
Pump up to The optical cable pressure-fed to the pressure-feeding end 12 is pulled out through the cable lead-out tube 15 and connected to an external cable network to complete the installation.

Prior to pressure feeding of an optical cable, a cable pressure feeding pipe line including a cable pressure feeding pipe 10 is laid, but a connection is required about every 250 m which is the unit length of the cable pressure feeding pipe 10. At this connection point, a handling hole 50 is provided, and a pressure feeding pipeline connection portion is formed therein. In this press-fitting pipe line connecting portion, the insertion pipes 2 having the same inner diameter and outer diameter are inserted into the intermittent portions between the open ends of the pair of cable press-feeding pipes 10 facing each other, and the two abutting portions are connected. It is formed by mounting a cylindrical joining member 100 of pressure-resistant design on each outer periphery and connecting them airtightly.

[0004] An airtightness test is performed after laying the cable pumping pipeline and immediately before pumping the optical cable. In this airtightness test, a closing valve provided with a pressure gauge is attached to the pumping end 12 of the cable pumping line, and air is pumped by the compressor 13 from the pumping start end 11 to make the internal pressure a predetermined pressure. The airtightness is checked by checking whether or not the airtightness can be maintained. When an airtight leak is detected, a pressure measurement is performed for each connection portion to identify an airtight leak location. In addition to the above-mentioned publications, Japanese Patent Laid-Open No. 4-229006 is a prior art document showing a general technical level.

[0005]

Conventionally, the cable laying by the optical cable pumping method is utilized exclusively for laying a small diameter optical fiber cord having an outer diameter of about 1 mm to 3 mm. The connection portion is relatively small, about 6 mm, and the connection portion is connected to the cable-feeding pipe 10 using the cable-feeding-pipe connection adapter 100 having a simple cylindrical structure. In this case, the gas flow rate is 100 l
/ Min, and the pipe cross-sectional area is as small as 28 mm2. Therefore, even if the pumping pressure is about 10 kg / cm2, which is the maximum, the force exerted on the cable pumping pipe due to the compressed air pressure is relatively small. There were almost no damage accidents.

[0006] However, the inventor of the present invention has proposed that the gas flow rate be reduced to the conventional 100 mm in order to develop a technique for pumping an extremely large cable having an outer diameter of several tens mm or more compared to the conventional 3 mm.
As a result of repeating a pumping test in which the pumping force was increased from about 1 / min to about 15 cubic meters / min to increase the pumping force, it was found that there was a danger that the connection portion of the cable pumping pipe 10 was damaged and fragments were blown off.

Conventionally, airtight leaks may occur in the cable pumping line even during cable pumping.
If this discovery is delayed, the cable may meander and be damaged. This is caused by the fact that when the airtight leak occurs, a sufficient pumping force is lost and the leading end of the cable stops, while the pushing of the cable continues from the rear end. Incidentally, the position of the cable tip during conventional pressure feeding is measured by a pressure feeding management counter (not shown) at the pressure feeding start end 11, but lacks a function of detecting meandering. Also,
Even if an airtight leak can be detected at an early stage, it may take a long time to lay out the labor-saving cable to identify the place where the airtight leak is occurring.

Further, as for the connecting portion of the cable pumping pipe 10, the cable pumping pipe 10 is connected by adopting a simple cylindrical cable pumping pipe connection adapter 100 which is easier to withstand pressure design than before. For example, when a branch portion is formed after the installation of
Zeros must be removed by cutting, which may damage the cable.

[0009]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems, the present invention provides a method for connecting a cable-pumping line for pressure-feeding and laying a cable by a gas flow between an open end of the opposing cable-pumping pipe. A member connecting the abutting portions of the insertion tube inserted into the intermittent portion and the cable pumping tube, comprising a cylinder having a pressure gauge and having a half-split structure that can be divided in the longitudinal direction. This is a cable compression pipe connection adapter.

[0010] The present invention is also characterized in that the cable pressure pipe connection adapter includes a speed meter for measuring the speed of the cable for pressure feeding and a gas flow meter for measuring the flow rate of the gas to be pumped. Further, the present invention is a cable pumping pipeline having a connection portion using the cable pumping pipeline connection adapter, and a cable pumping method for pumping a cable using the cable pumping pipeline.

[0011] The inventor of the present invention has a problem that the connection portion of the cable pumping line is broken due to an increase in the diameter of the cable pumping line required for realizing the gas pumping of the large-diameter cable and an increase in the gas flow rate accompanying this. In order to solve the problem, it was found that if the leak was detected and repaired at a small stage, this problem could be solved, and for this purpose, the pressure measurement at each connection of the cable pumping pipeline was extremely effective Thus, the present invention has been completed.

More specifically, according to the present invention, it becomes possible to measure the pressure at each connection portion of the cable pumping pipeline before and during the pumping of the cable. The location can be quickly and easily specified, and it is possible to take a precautionary measure by detecting a precursor to the breakage of the connection portion. In addition, early detection of meandering of the cable in the cable pressure feeding pipeline is realized, and damage to the cable due to this can be avoided.

According to the present invention, it is possible to realize a large-diameter cable-pumping line and the accompanying gas-pumping by a high-flow-rate and high-pressure pumping gas.
It is possible to feed and lay heavy cables, and it is possible to extend the feeding distance for each time. In addition, it is possible to significantly reduce the cable laying pipeline and cable laying period.

Further, according to the present invention, since the cable pressure feeding pipeline connection adapter has a half-split structure which can be divided in the longitudinal direction, the cable can be easily removed after the cable is laid, and the work time required for this can be greatly reduced. At the same time, it can be reused including the pressure gauge part, which contributes to a reduction in installation cost.

By the way, in the conventional method, a cylindrical cable pressure feeding line connection adapter which is easy to withstand pressure design is used. Therefore, when a cable branch is formed, the cable pressure feeding line connection adapter is cut and removed. In this case, the cable cannot be reused, and the cable may be damaged in this case. However, according to the present invention, the cable pressure line connection adapter has a half-split structure. There is no need to remove and there is no risk of damaging the cable.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that the same parts are assigned the same numbers, and duplicate descriptions are omitted.

(Cable Compression Line Connection Adapter) FIG. 1 shows a cable compression line connection adapter according to an embodiment of the present invention. Reference numeral 1 denotes a cable pressure feeding pipe connection adapter, which is composed of a half cylinder pipe 1c having a half structure having the same inner diameter as the outer diameter of the cable pressure pipe 10, and a pressure gauge 1a connected to a side surface of the half cylinder pipe 1c. Become.

This cable pressure feeding line connection adapter 1
As illustrated in FIG. 4, in each of the handling holes 50 of the cable pumping pipeline, the intervening pipes 2 having the same outer diameter and inner diameter are provided at intermittent portions between the open ends of the pair of opposing cable pumping pipes 10. It is used to hermetically connect two seams that can be inserted.

A flange section 1b is formed on a half section of each of the pair of half cylinders of the half cylinder tube 1c so as to have the same plane as that of the half cylinder and project laterally. At the time of connection of the cable feed pipe 10, the half cylindrical pipe 1c is put on the outer periphery of each joint position, and the flange portions 1b are fixedly connected to each other by screwing them together.

As the pressure gauge 1a, a small pressure gauge used for measuring ordinary oil pressure, air pressure, vacuum, and the like can be used. An analog system or a digital system that directly displays numbers may be used. In the embodiment of the present invention, the maximum scale is 15 kg / cm 2, and the minimum scale is 0.5 kg / cm 2.
A pressure gauge 1a having an outer diameter of a gauge part of 40 mm of a diaphragm type of kg / cm2 is connected to a side surface of a half-cylindrical pipe 1c as illustrated in FIG.

In particular, when the pressure gauge 1a is small, it can be mounted so as to be embedded in the side surface of the half cylindrical tube 1c. The material of the half cylindrical tube 1c is not limited to a metal such as stainless steel as long as a predetermined strength can be secured, and may be a high-strength engineering plastic such as polycarbonate.

(Connection of Cable Pressure Feeding Pipeline by Cable Pressure Feeding Pipeline Connection Adapter) First, the cable pressure feeding pipe line is laid by connecting a cable pressure feeding pipe 10 made of a polyethylene pipe having an inner diameter of 50 mm, a wall pressure of 3.5 mm, and a length of 250 m. It is laid over 1 km (see step (1) in FIG. 2).

In this case, as shown in FIG.
Each of the three handling holes 50 is provided, and a connection portion is formed inside the inside using the cable pressure pipe connection adapter 1 as described above (see the step (2) in FIG. 2). An airtightness test is performed with a closing valve with a pressure gauge attached to the pressure-feeding end 12 after the cable pressure-feeding pipe is laid (see step (3) in FIG. 2).

In general, it is rare that the cable is pressure-fed immediately after the cable pressure-feeding pipeline is laid. Therefore, an airtight test is usually performed immediately after the cable-pressure-feeding pipeline is laid and immediately before the cable pressure-feeding. (See step (4) in FIG. 2). In this airtight test, air was pumped from the pumping start end 11 by the compressor 13 to
The pressure is increased to kgf / cm 2, and it is detected that the pressure can be maintained, and airtightness is confirmed (see step (4) in FIG. 2).

When airtightness is confirmed, a ball-through test is performed in which a ball having an outer diameter larger than the outer diameter of the cable to be pumped is passed by using compressed air. Is larger than the cable outer diameter (see step (5) in FIG. 2). If a leak is detected, the location of the leak is identified and repaired. In this case, according to the present invention, the pressure inside the cable pumping line can be actually measured by the pressure gauge 1a for each connection portion.
In addition to the presence / absence of an airtight leak, it is possible to specify a leak location more quickly than ever before and repair it.

That is, if there is an airtight leak, there is a difference in any one of the pressure of the compressor 13, the display pressure of the pressure gauge 1a attached to each connection portion, and the display pressure of the pressure gauge of the closing valve. An airtight leak point can be specified in units between each position where the pressure gauge is attached. As a result, the work of laying the cable pressure feed pipe 10 can be significantly shortened as compared with the related art.

(Cable laying method) The method of feeding the cable is basically the same as that of the prior art. However, in the present invention, the cable is fed by the pressure gauge 1a of the cable feeding pipe connection adapter 1 at each connection. As a result of being able to estimate the pressure gradient in the pumping line with high accuracy, it is possible to quickly and accurately grasp the airtight leak and the cable pumping state occurring during the pumping operation. In the embodiment of the present invention, as the cable to be pressure-fed, an optical cable having an outer diameter of 20 mm, which is about 7 times larger than the conventional maximum of 3 mm, is selected.

(Measurement of Cable Tip Pressure and Detection of Airtight Leakage During Cable Pumping) First, when a cable is pumped, the pressure Pi at the pumping start end 11 is first placed in the cable pumping line.
n = 10 kg / cm 2, pressure P at the end 12 of the pumping
A pressure gradient of 1 atm is formed as o and the cable is pumped through this pressure gradient. At the stage before the cable is pumped, the cable tip pressure P at the tip of the cable being pumped is
1 can be estimated by the empirical formula expressed by the formula (1).

[0029]

(Equation 1)

Here, P1: cable tip pressure (kgf / cm2) X: cable traveling length (m) L: cable pressure feeding line length (m) d1: cable pressure feeding line inner diameter (cm) d2: cable pressure feeding line Effective inner diameter (cm) Pin: Pressure at the end of pumping (kgf / cm2) Po: Pressure at the end of pumping (kgf / cm2) m: Adjustment coefficient (d2 / d1) 19/14 Also, FIG. Shown in Here, “v” indicates the cable feeding speed, and “du” indicates the outer diameter of the cable to be pumped.

Based on the equation (1), the cable tip pressure P when the cable is pressure-fed in the cable pressure-feeding pipeline
A value of 1 can be estimated over its entire length. In addition, at the stage before the pressure feeding of the cable, the respective pressure distributions from the pressure feeding start end 11 to the tip of the cable being pressure fed and from the cable tip of the cable being pressure fed to the pressure feeding end 12 are determined in advance. An empirical formula is obtained by an experiment under the same conditions as when the cable is pumped, and it can be estimated using this.

After the start of pressure feeding of the cable, the actual pressure value P1 at the time when the distal end of the cable passes through each connection is measured by the pressure gauge 1a at each connection. The time at which the end of the cable passes through each connection part can be specified from the fact that the display of the pressure gauge 1a rapidly rises to the cable end pressure P1.

At each connection, if the estimated value of P1 based on equation (1) and the actual value of P1 measured by the pressure gauge 1a match, there is no abnormality in the pressure gradient. Conversely, when the latter is smaller than the former, it is airtight. There is a risk of leakage. More specifically, the pressure gradient estimated by the equation (1) and the empirical equation over the entire length of the cable pumping line is compared with the actually measured value of the pumping pressure at each connection obtained by the pressure gauge 1a. Thereby, the presence or absence of the airtight leak and its location can be specified easily and with high accuracy.

Therefore, when an airtight leak is recognized, the location of the airtight leak is specified, and the pumping of the cable is stopped to repair the airtight leak. In this case, the process returns to the airtightness test step (see the step (4) in FIG. 2) before the start of the pumping.

(Detection of cable meandering) Further, in the present invention, the passage of the end of the cable can be detected by the pressure gauge 1a of the cable pressure feeding line connection adapter 1 at each connection portion by a sudden rise in pressure. This passing time and the length of the cable that has passed through the pumping start end 11 by the same time as measured by the pumping length management counter at the pumping start end 11 (hereinafter, simply referred to as the pushing length) can be specified. it can.

As a result, each time the leading end of the cable passes through each connecting portion, this pushing length and the cable pressure feeding pipe from the starting end of the pressure feeding to the connecting portion corresponding to the length of the actually pressure fed cable are used. The length of the road (hereinafter, simply referred to as the traveling length) is compared, and if they match, it occurs when the cable is pushed in while the pumping force is insufficient.
It can be determined that the cable does not meander.

This makes it possible to avoid the problem that the cable is meandered and damaged during the pressure feeding. If the pressure gradient is properly controlled by the above-mentioned method, it is considered that there is almost no problem of meandering of the cable. However, the method of comparing the traveling length and the pushing length is a cause other than the lack of the pressure gradient. It is significant that the cable can be prevented from meandering and the cable from being damaged.

More specifically, when the respective travel lengths of the cable passing through the connection portion do not match the corresponding pushing lengths (see the process in FIG. 2), the cable may be meandering. Stop and correct the cable meandering, determine the cause and take corrective action.

As the continuation condition of the cable pressure feeding, it is necessary at least to confirm that the actually measured value of the pressure P1 at the cable tip and the estimated value based on the empirical formula (1) match, but it is preferable. Further confirms that each travel length as the cable passes through the connection and the corresponding push-in length.

(Removal of the cable pressure feeding line connection adapter and the insertion tube, extra length of cable) After the cable pressure feeding is completed (see step (7) in FIG. 2), the cable pressure feeding line connection adapter 1 is removed. It is removed (see step (8) in FIG. 2). Conventionally, this connection member was cylindrical and could not be removed without cutting or the like. However, in the present invention, since the connection member has a half-split structure, it can be easily removed and used repeatedly.

The cutting pipe 2 is cut and removed (see step (9) in FIG. 2). In this case, the break tube 2 is usually made of plastic and can be easily cut, so that damage to the cable does not matter. In order to secure a surplus length of the cable, a part of the cable is pulled out by a predetermined length from the intermittent portion between the open ends of the cable pressure feeding tube 10 in preparation for forming a branch of the laid cable (FIG. 2). Step (10)). Repeat the above steps until the specified installation distance is reached.
Repeat every 00m.

(Processing Method of Measured Pressure Data, etc.)
Note that the pressure P1 when the cable passes through each of the above-mentioned connection portions is used.
The centralized control device is provided with the measured values and the data of the passing time of the data, and the data are transmitted to this device, for example, wirelessly together with various data at the pumping start end 11 and the like. Estimation of the pressure gradient using the empirical formula, comparison with the transmitted measured pressure value, and the necessary command can be issued to the related equipment based on the result.

Further, various data such as the actually measured value of the pressure P1 when the cable of each connection portion passes and the passing time thereof are as follows:
The worker can record it or record it by himself, and in the event of a pumping trouble, etc., after the fact, whether or not there is an airtight leak by the above method, identification of the airtight leak location, presence or absence of cable meandering, etc. You can also consider.

(Detection of Cable Meandering by Measuring Cable Speed) In the embodiment of the present invention, the pressure gauge 1a is attached to the cable pressure feeding line connection adapter 1, but the invention is not limited to this. It is also possible to attach a speedometer.

As a result, the cable speed at each connection portion is compared with the cable speed at the same time at the pumping start end 11, and
If the former is smaller than the latter, it can be determined that some kind of meandering of the cable has occurred in the cable pumping line. In the method of measuring the cable speed, the method of measuring the pressure P1 is limited to one measurement when the end of the cable passes through each connection portion, but continuous measurement can be performed. It is characterized in that the meandering of the cable can be detected earlier than in the method of measuring the pressure P1 and the breakage of the cable can be avoided.

Specifically, for example, Japanese Patent Application Laid-Open No. Hei 6-23023
As described in Japanese Patent Laid-Open Publication No. 2 (1994), a transparent window is provided in the cable pressure pipe connection adapter 1, and a running cable is irradiated with a laser beam through this window, whereby a bright and dark pattern is generated on the surface of the cable. It is also possible to detect the movement of a certain so-called speckle pattern by a sensor and measure the pumping speed of the cable.

The measurement data such as the cable speed and the cable passage time is transmitted to a central control device (not shown).
In this centralized control device, the cable speed at each connection part is compared with the cable speed at the same time at the pumping start end 11, and if the former speed is lower than the latter, some kind of cable is sent in the cable pumping line. When it is determined that the meandering has occurred, a command to automatically stop the pressure feeding is issued to a pressing device (not shown) at the pressure feeding start end 11 so that the operation can be stopped.

Of course, the reliability of the measurement result can be further enhanced by using the above-described method of measuring the pressure together with the method of measuring the cable speed.

(Attaching the flow meter to the cable pressure pipe connection adapter) Also, by attaching the gas flow meter to the cable pressure pipe connection adapter 1, in the airtightness test step (see step (4) in FIG. 2), By detecting the gas flow rate and the direction of the gas flow caused by the leak, the location of the leak can be more easily specified.

That is, in the airtightness test step before the cable feeding, if there is no airtight leak, there is no gas flow, and if there is airtight leak, the gas flow in the direction of the airtight leak caused by the airtight leak is caused. Since this flow is detected, the location of the airtight leak can be more accurately and easily detected by detecting this flow. The flow meter is preferably a small one capable of detecting the flow rate and the direction of the gas, and is, for example, a flow meter of a type in which a propeller bypass is provided in the inner wall surface of the cable pressure pipe connection adapter 1 and the propeller is rotated. You may.

In the embodiment of the present invention, an optical cable having a pumping pressure of 10 kg / cm 2 at the maximum, a pumping distance of 1 km each time, and an outer diameter of 20 mm was used, but the present invention is not limited to this. It is also possible to adopt pressure and to set the distance of each pumping to 1 km or more, or to pump cables whose outer diameter exceeds 20 mm.

[0052]

According to the present invention, pressure measurement at each connection portion of the cable pressure feeding pipeline and high-precision pressure management are realized, and the detection of the airtight leak and the identification of the airtight leak point during the cable pressure feeding become quick and easy. Thus, it is possible to detect a precursor of the damage of the connection portion and take preventive measures. As a result, it is possible to realize a large-diameter cable-pumping line and the accompanying high-pressure and high-pressure gas-pumping, thereby enabling pressure-feeding and laying of a cable having a larger outer diameter and weight than ever before, and The pumping distance can be extended. Further, it is possible to significantly reduce the cable laying pipeline and the cable laying period.

Further, according to the present invention, since the cable pressure feeding pipeline connection adapter has a half-split structure which can be divided in the longitudinal direction, it is easy to remove the cable after the cable is laid, and the working time required for this is greatly reduced. At the same time, it can be reused including the pressure gauge part, which contributes to a reduction in installation cost. Further, there is no need to cut and remove the cable pressure pipe connection adapter after the cable pressure feeding is completed, and therefore the cable is not damaged.

[Brief description of the drawings]

FIG. 1 is a side view and a cross-sectional view showing the structure of a cable pressure-feeding pipeline connection adapter of the present invention. FIG. 1A shows a side view, and FIG. 1B shows a cross-sectional view.

FIG. 2 is a flow chart showing a process of laying a cable pressure feed line using the cable pressure feed line connection adapter of the present invention, and pressure feeding and laying a cable using the cable pressure feed line.

FIG. 3 is a diagram for explaining the positional relationship of the signs of Expression (1).

FIG. 4 shows the present invention and a conventional cable pressure feeding pipeline. However, the difference between the present invention and the conventional cable pumping pipeline is that the cable pumping pipeline connecting adapter 1 in the present invention has the structure shown in FIG. They differ in that they are cylindrical.

[Explanation of symbols]

 1, 100: Cable pressure pipe connection adapter 1a: Pressure gauge 1b: Flange 1c: Half cylindrical pipe 2: Split pipe 10: Cable pressure pipe 11: Pressure start end 12: Pressure end 13: Compressor 14: Cable Guide tube 15: Cable draw-out tube 50: Handling hole 60: Cable drum

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 6/46 F16L 55/00 B H02G 9/06 G02B 6/00 351

Claims (7)

[Claims] At each connecting portion of a cable pumping line for pressure-feeding and laying a cable by a gas flow, an interrupting tube inserted into an intermittent portion of an open end of a facing cable pumping tube and the cable pumping tube are connected to each other. A cable pressure-feeding pipeline connection adapter, which is a connection member for hermetically connecting the abutting portions, comprising a cylindrical body provided with a pressure gauge. 2. The adapter according to claim 1, further comprising a speedometer for measuring a speed at which the cable is pumped. 3. The cable pressure pipe connection adapter according to claim 1, further comprising a flow meter for measuring a flow rate of the gas flow. 4. The cable pressure line connection adapter according to claim 1, wherein the adapter has a half-split structure that can be divided in the longitudinal direction. 5. A cable pumping line having a connection portion using the cable pumping line connection adapter according to any one of claims 1 to 4. 6. A method for laying a cable under pressure using the cable pressure-feeding pipeline according to claim 5. 7. The cable continues to be pumped on condition that the measured value and the estimated value of the pressure at the distal end of the cable during the pressure feeding by the pressure gauge at each connection portion of the cable pressure feeding line match. 7. The method according to claim 6, wherein the pressure feeding of the cable is stopped when there is a mismatch.