JPH0758284B2 - Pipe insertion method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe insertion method applicable to thermal power plants, nuclear power plants and heat exchangers in general, water pipelines and the like. More specifically, the present invention relates to a method of pressure-inserting a cable having a plurality of floats at predetermined intervals into a thin tube by providing a probe at the tip, and the probe can be extended to a far distance without being blocked. The present invention relates to a method for inserting into a tube that enables transportation.

2. Description of the Related Art FIG. 5 shows a conventional tube insertion method. That is, conventional IS
In the I (In-Service Inspection) device, the probe 9 is transported to a distance inside the heat transfer tube (narrow tube) 8 and is wound around the drum 4 and is inserted into the tube by the pusher device 5 with a seal. Using the inserted transport cable 6 and the probe 9 attached to the end of this cable, high-pressure water from the pump 3 is used to apply thrust to the front and rear of a plurality of floats 7 attached to the cable 6 at predetermined intervals. A method of transporting by generating is used. In addition, 14
Indicates a valve.

Problems to be Solved by the Invention However, such a conventional method of carrying by a constant high-voltage source has the following problems. That is,
Since the force applied to the float portion does not change with time, if there is an obstacle on the inner wall of the pipe or if the float is caught at the bent portion, it cannot be conveyed further deeper immediately. The conditions for the heat transfer tube for gas are more severe, and the float contacts the bottom of the heat transfer tube due to the action of gravity to generate a frictional force, which makes it more difficult to convey the heat transfer tube to a deep part.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to provide an in-tube insertion method capable of transporting a probe to a distant place without being blocked. .

Means for Solving the Problems In order to solve the above problems, the present invention is a method of pressure inserting a cable having a plurality of floats at a predetermined interval with a probe at its tip, into a thin tube, A liquid is used as a carrier fluid to be fed from the proximal end of the thin tube, and a gas is mixed into this liquid, or two kinds of gases having different densities are used as the carrier fluid, and these gases are caused to flow alternately. Is.

Action According to the above-mentioned means, floats are attached to the transport cable at regular intervals, and by adding flow fluctuations to each float, a varying thrust force acts on the floats, so that the probe is moved to a distance. Can be transported up to.

In this case, the thrust generated in each float is proportional to the pressure before and after the float, and also to the density difference.Therefore, by using a liquid as a carrier fluid and mixing gas into this liquid, the density Since a gas having a significantly smaller value is alternately sent, the probe can be transported over a long distance even with a long thin tube.

Also, if only gas can be used as the carrier fluid,
By alternately flowing two kinds of gas having different densities, it is possible to change the thrust generated in the float and convey the probe to a distant place.

Example Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 4. In these figures, the same parts as those shown in FIG. 5 are designated by the same reference numerals, and the duplicated description will be omitted.

First, FIG. 1 shows a first embodiment of the present invention, in which a gas mixing device 11 connected to a compressor 10 is provided at an outlet of a pump 3 for injecting pressurized water (liquid) from a tank 2 into a heat transfer tube (narrow tube) 8. It is provided. Then, the air (gas) from the compressor 10 is mixed into the pressure water from the pump 3 via this gas mixing device 11,
The gas-liquid two-phase flow is sent into the heat transfer tube 8.

FIG. 2 shows the operation of the first embodiment, where A is thrust F (medium) when passing through the liquid phase, B is thrust F (small) when approaching the gas phase,
C indicates the thrust F (large) when the liquid phase arrives, and the thrust F
Varies with time depending on the condition of the fluid passing through the float.

As described above, when the gas-liquid two-phase flow is applied to the transport cable 6, the flow pattern of the slag flow in which the gas phase and the liquid phase alternately exist due to the restriction of the float 7, and therefore the float 7 has the same shape as when the gas phase passes. The thrust acting on the passage of the liquid phase changes. Due to the thrust that fluctuates in the longitudinal direction, the transport cable 6 makes a peristaltic motion. By this action, the probe 9 can be transported to a distant place without being blocked by the projection on the inner surface of the bent pipe.

Further, when incompressible water or the like is used as the carrier fluid, it is possible to convey the probe to a distant place by applying a time-varying pressure to the water to create a pulsating flow, as in the first embodiment. However, in the method using the pulsating flow, it is difficult to convey the probe for a long distance in a long thin tube because of the tube resistance and the attenuation of the water pressure at the float.

On the other hand, in the above-described first embodiment, the pressure difference (pulsation difference) of water is not used, but water (liquid) and gas are caused to flow alternately. Therefore, long-distance conveyance of the probe in the long thin tube is performed. Is possible. That is, since the thrust generated in each float is proportional to the pressure before and after the float and also to the density difference (see Fig. 2), water (liquid) is used as the carrier fluid and air (gas) is mixed with this water. By doing so, since water and air whose density is significantly smaller than that of water are alternately sent, it becomes possible to carry the probe over a long distance even with a long thin tube.

Next, FIG. 3 shows a second embodiment of the present invention. As a device for injecting gas as a carrier fluid into the heat transfer tube 8, a gas switching device 31 and two types having different densities, that is, a gas source A12 and a gas source. A gas supply device with B13 is provided. The gas switching device 31 allows gases having different densities to periodically pass through the transfer cable 6 inside the heat transfer tube 8.

In order to increase the difference in buoyancy applied to the float 7 due to this difference in density, the difference in density between the two types of gas should be selected as large as possible, and the float 7 should be filled with helium gas for transportation. It is advisable to make the entire cable 6 as light as possible.

FIG. 4 shows the operation of the second embodiment, in which the acting force (the resultant force of gravity and buoyancy) changes in each float due to the effect that the buoyancy changes with time from large to medium to small to medium to large. To do.

As described above, when gases having different densities periodically pass through the float 7 of the transport cable 6, the buoyancy applied to the float 7 periodically changes depending on the position. For this reason, a portion having a large buoyancy and a portion having a small buoyancy are generated in the transport cable 6, and the cable 6 as a whole performs peristaltic motion. By this action, even if there are projections, bends, etc. on the inner surface of the tube, the probe 9 can be transported to a distant place without being obstructed by them.

Further, depending on the plant, only gas may be used as the carrier fluid, and in this case, it is difficult to create the above-mentioned pulsating flow because the gas has compressibility, but in the second embodiment, it has compressibility. Even if the gas is a gas, the thrust generated in the float is changed by alternately flowing two kinds of gases having different densities, so that the probe can be transported to a distant place.

EFFECTS OF THE INVENTION As described above, according to the present invention, in a method of inserting a cable having a probe at its tip and having a plurality of floats attached at predetermined intervals into a capillary by pressure, a proximal end of the capillary is provided. Since a liquid is used as a carrier fluid to be fed from the gas and a gas is mixed into the liquid, or two kinds of gases having different densities are used as the carrier fluid, these gases are caused to flow alternately. Even if it is, the probe can be transported for a long distance, and even if only gas can be used as the transport fluid, the probe can be transported for a long distance.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing its operation, FIG. 3 is a system diagram showing a second embodiment of the present invention, and FIG. 4 is its action. FIG. 5 is a system diagram showing a conventional example. 2 ... Tank, 3 ... Pump, 4 ... Drum, 5 ... Sealing pusher device, 6 ... Transport cable, 7 ...
Float, 8 ... Heat transfer tube, 9 ... Probe, 10 ... Compressor, 11 ... Gas mixing device, 12 ... Gas source A, 13 ... Gas source B, 14 ... Valve, 31 ... Gas switching apparatus.

Claims (1)

[Claims] 1. A method of pressure-inserting a cable having a plurality of floats at a predetermined interval and having a probe at a tip thereof, wherein a liquid is used as a carrier fluid to be fed from the base end of the tube. A pipe insertion method, characterized in that a gas is mixed in the lever liquid, or two kinds of gases having different densities are used as the carrier fluid, and the gases are alternately flowed.