JPS63265511A - Hollow pipe for and method of preventing cable duct freezing trouble - Google Patents

Abstract

PURPOSE:To obtain a method which is effective also for a cable already provided in a duct, by taking a pipe having a nonselfstanding pipe wall into said duct and thereafter by filling a hollow granular material, which absorbs a cubical expansion pressure of water due to its freezing, into said pipe through air pressure. CONSTITUTION:First, an internal pressure is applied by a compressor 10 to a pipe 9 folded and taken into a duct and composed of a high strength member 7 and a flexible member 8 so that said pipe 9 is formed into a hollow pipe shape in said duct. After that, a hollow granular material 11 is sent into the hollow pipe 9 through compressed air. In this manner, when water enters the duct in a cold area, a gap 4 is filled with water, of which volume increases at the time of its freezing. However, a freezing pressure can be reduced by compression and deformation of said hollow granular material 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technique for preventing damage due to freezing of communication cables housed in underground conduits in cold regions.

(Conventional technology) In cold regions, when water that has entered the pipes freezes,
Expansion pressure caused by freezing was applied to the cables, causing problems such as destruction of the cables and severe loss of transmission characteristics. Conventionally, a method to prevent this was to pull in a hollow plastic pipe at the same time as the cable was pulled in.

FIG. 9 is a diagram illustrating an example of a conventional freezing prevention method, in which 1 is a cable, 2 is a plastic hollow pipe continuous in the longitudinal direction for freezing prevention, 3 is a conduit, and 4 is a This is a void within the pipe.

In this method, when water enters the pipe and the water that fills the void 4 freezes, the volumetric expansion pressure at the time of freezing causes the hollow pipe to 2
This had the effect of preventing expansion pressure from being applied to the cable by compressing and deforming it. However, the diameter of this pipe is 20
Since the pipe is as thick as ~30 mm+, if the cable is already accommodated in the conduit, it is extremely difficult to add and draw in the pipe as the frictional force increases significantly. For this reason, there was a drawback that it could not be applied to communication cables housed in conduits.

(Problems to be Solved by the Invention) The present invention provides a method for preventing freezing damage even for existing cables in conduits.

(Means for Solving the Problems) The present invention has a non-self-supporting pipe wall composed of a high-strength tα member that is not continuous in the radial direction and a flexible member such as a sheet that connects the members in the radial direction. This pipe is drawn into the conduit using the Zurupai 11M structure, and then the pipe is filled with air pressure with hollow granules that absorb the residual expansion pressure of water due to freezing.

The conventional technology is to create a free-standing pipe wall in the longitudinal direction: instead of using a continuous pipe, a small-diameter pipe is drawn in. The difference is that the friction resistance can be reduced.

Figure 1 shows an example of Akira Kino's hollow tube for preventing freezing of cable routes, which has a non-self-supporting pipe wall that can be folded. (b) is a cross-sectional view when internal pressure is applied to make it into a pipe shape.

In FIG. 1, 5 is a high-strength member such as FRI (III reinforced plastics), nylon, etc., and 6 is a flexible member such as PE (polyethylene) sheet, which interconnects the high-strength members 5. Since it has this structure, when it is drawn into the pipe, it is folded into the shape shown in <a> and has a small cross-sectional area, so F? ! It is possible to reduce the friction resistance and draw the pipe into the existing pipe, and by applying air pressure or the like after drawing it in, the pipe shape can be maintained as shown in (b). In addition, the retraction tension is 1 little more than 1. It can be shared by the II member 5.

Figure 2 shows another embodiment of the hollow pipe of the present invention for preventing freezing damage in a Gaeple pipeline with a non-self-supporting pipe wall. (b) is a cross-sectional view when the pipe is shaped into a pipe by applying internal pressure.

In FIG. 2, J3 indicates a high-strength member such as steel wire or FRP, and 8 a flexible member such as a PE sheet.

Since it is M43a like this, when drawing it into the pipe, it can be folded as shown in (a) to reduce the cross-sectional area and reduce the frictional resistance, and after drawing it in, it is possible to apply internal pressure such as air pressure. This allows the pipe shape to be maintained as shown in (b).

In another embodiment, a lubricant such as silicone oil may be applied to the surface of these pipes.

If you cover it like this, it will be 1 when pulling in the pipe or pulling out the cable. Since the frictional resistance is reduced, the vibrator can be pulled in and the cable removed with even lower tension.

Fig. ff13 is a practical example of the freezing damage prevention method of the present invention, in which 1 is an existing cable, 3 is a conduit, 9 is a pipe drawn into the conduit, and 10 is a compressed air 11 is a hollow granular body; 12 is a container for supplying the hollow granular body 11; and 13 is a connecting portion for introducing compressed air into the pipe line 3.

With this configuration, the bones in Figure 1 (a) or Figure 2 (Figure 2) are broken and drawn into the pipe 3.
A compressor 10 applies internal pressure to the pipe 9 made of the high-strength member 5 or 7 and the flexible member 6 or 8 shown in a) to form the pipe 9 into a hollow pipe shape within the conduit, and then into a hollow granular shape. The body 11 can be fed into the hollow pipe by means of compressed air. At the other end of the pipe, the length of the hollow granules 11 coming out is measured by X1, and the distribution of the hollow granules fed into the hollow pipe can be determined from the relationship between the discharge amount and the supply amount per hour. The supply may be terminated when a predetermined amount of the granular material 11 is filled into the hollow pipe. Also,
By covering the discharge side of the hollow pipe with a mesh having a mesh size smaller than the size of the hollow granules, it is possible to further increase the number of filling ports into the hollow pipe.

FIG. 4 is a cross-sectional view of a conduit filled with hollow particles, in which 1 is a cable, 3 is a conduit, 4 is a void in the conduit, and 9
1 is the pipe explained in FIG. 2, and 11 is a filled hollow granule.

When water enters the pipe in a cold region, the void 4 is filled with water and its volume increases when frozen, but the freezing pressure can be reduced by compressing and deforming the hollow granules 11. Furthermore, even if water flows into the pipe at one time, the hollow particles are housed within the pipe, so they will not be washed away by the water flow and will remain evenly within the pipe.

FIG. 5 is a sectional view of another example of a conduit filled with hollow particles, in which 1 is a cable, 3 is a conduit, 4 is a gap, and 9
' is the pipe explained in FIG. 1, and 11 is a filled hollow granule. The operation and effect of the example shown in FIG. 5 are the same as in the case of FIG. 4. When water flows into the pipe and also enters the pipe through pinholes and freezes, assuming that the strength of the shell of the hollow granule is easily deformed by the pressure caused by the freezing of the water, The volumetric expansion rate due to freezing of water is approximately 10%.
Therefore, when ρ is the volume ratio of the total volume of the granules to the air contained in the hollow granules, and β is the filling ratio of the hollow granules to the pipe, ρβ>0.1(1 −
β) If the pipe is filled with hollow particles so as to satisfy (1), no pressure due to freezing will be applied to the cable.

The coefficient of thermal expansion of ice is approximately 5X10-'/'C,
The change in volume due to ice temperature can be ignored because it is extremely small compared to the volume expansion due to freezing.

FIG. 6 is a cross-sectional view of an example of a hollow granule used in the present invention, where 14 is a shell of the hollow granule, 15 is a hollow portion, and the hollow granule can be made of plastic, rubber, or the like. Buckling stress P of such a hollow granular body due to external pressure is expressed by the following equation.

P=4Et'/(3r2(7-shi)15(23-
ν) (1-ν') ) (kg/ms')...
(2) Here, E and ν are the Young's modulus and Poisson's ratio of the material constituting the hollow granule, and r and t are the inner radius and wall thickness of the hollow granule. FIG. 7 shows a calculation example of the relationship between t/r and buckling stress when hollow granules are made of low-density polyethylene with E = 20 kg/sv+'. Further, the buckling stress Pc of a cylinder such as a cable jacket is expressed by the following equation.

Pc = E (t/r)3/4 (1-ν2) (kg
/gi*2) ・ ・ ・
(3) Here, E and ν are the Young's modulus and Poisson's ratio of the material constituting the cylinder, and , and are the radius and wall thickness of the cylinder. In the example of r -1011 and t-211, the buckling stress is 0.18 (kg/1 m''). in this case,
As can be seen from FIG. 7, if t/r is set to 0.04 or less, the hollow granules buckle before any abnormality occurs in the cable, making it possible to absorb the volumetric expansion pressure of water due to freezing.

FIG. 8 is a cross-sectional view of another example of the hollow granules used in the present invention, where 14 is a shell of the hollow granules, and 15' is a plurality of independent cells, which can be realized by foamed urethane foam or the like. can. Since it is composed of independent air bubbles, even if water enters the pipe, water will not fill the air bubbles, and since it is spongy, it easily deforms when frozen and has no resilience. It has excellent properties and has a rough eaves, making it easy to fill pipes.

In addition to the shapes shown in FIGS. 6 and 8, the shape of the hollow particles may be cylindrical, ellipsoidal, spherical, etc.

(Effects of the Invention) As explained above, the hollow pipe for preventing cable conduit freezing damage and the cable conduit freezing damage prevention method according to the present invention utilizes hollow granules filled in the pipe to absorb compressive force on the cable due to freezing. Because it can be applied to existing cable pipelines, the hollow granules do not move when flooded, and the effect of evenly absorbing freezing pressure can be expected.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show the frozen cable conduit Fll of the present invention.
An embodiment of a hollow pipe for damage prevention; FIG. 3 is an embodiment of the freezing prevention method of the present invention; FIGS. 4 and 5 are cross-sections of the pipe line filled with hollow granules according to the present invention. Figure, 6th
The figure is a sectional view of an example of a hollow granule used in the present invention, FIG. 7 is a diagram showing buckling stress of the hollow granule, and FIG. FIG. 9 is a diagram illustrating an example of a conventional freezing prevention method. 1... Cable 2... Plastic hollow pipe 3... Conduit 4... Gap in the conduit 5
... High-strength member such as FRP, nylon 6 ... Flexible member such as PE sheet 7 ... High-strength member such as FRP, steel wire 8 ... Flexible member such as PE sheet 9... - Pipe 9' Pipe 10... Compressed air generator such as a compressor 11... Hollow granules 12... Container 13 for supplying hollow granules...
Connecting portion 14 for guiding compressed air to the pipe line... Shell of hollow granular body 15... Hollow part 15 of hollow granular body... Hollow part 15' of hollow granular body... Bubbles in Figure 1 ( , a) (b) Fig. 2<1) 8 = -PE ent mushroom V - ability to drink (b) Fig. 3 Figure 4 Figure 5 4-11! Meat “gF!”
9-00.7.4. . Fig. 6 f5 ---- East 9 Genki (No. -1:t! Figure 9

Claims (1)

[Claims] 1. The wall of the pipe is continuous in the longitudinal direction, but is not continuous in the radial direction. One or more high-strength members are connected in the radial direction, and the high-strength members are connected in the longitudinal direction. consisting of a flexible non-self-supporting member that is continuous with the pipe, and that extends over the entire length of the pipe.
A hollow pipe for preventing freezing damage in cable conduits, which is characterized by being able to be folded in the radial direction. 2. The hollow pipe for preventing freezing damage in a cable conduit according to claim 1, wherein a lubricant is attached to the surface of the hollow pipe. 3. A flexible pipe in which the wall of the pipe is continuous in the longitudinal direction and one or more high-strength members that are not continuous in the radial direction, and the high-strength members are connected in the radial direction and are continuous in the longitudinal direction. consisting of non-self-supporting members, and spanning the entire length of the pipe,
A radially foldable hollow pipe for preventing freezing damage in a cable conduit is drawn into a conduit accommodating the cable, and a plurality of hollow granules are pneumatically fed into the hollow pipe from one end of the hollow pipe. A method for preventing freezing damage in a cable conduit, characterized by filling the cable conduit. 4. When filling the hollow pipe with hollow particles,
The volume ratio of the enclosed air to the volume of the hollow granules is ρ, and the filling rate of the hollow granules to the space inside the pipe is β, and the characteristic is that ρβ>0.1(1−β) is satisfied. A method for preventing freezing damage in a cable conduit according to claim 3. 5. The method for preventing freezing damage in a cable conduit according to claim 3 or 4, wherein the granular material filled in the hollow pipe is formed of a foam having a plurality of closed cells. .