JPS6154477B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a construction method for existing pipes such as water pipes and gas pipes, in which a coating agent is applied to the inner wall of the pipe during the process of moving the pig.

As a method for repairing this type of pipe inner surface, the method shown in FIG. 1 is known. That is, a pair of front and rear pigs 1 and 2, which are connected to each other by a connecting pipe 3, is installed inside the existing pipe A, with the coating agent B filled between the two pigs, and the rear pig 2 is exposed to air pressure.
By applying _P1 , while moving the pigs 1 and 2, the coating agent is pushed out from the circumferential surface of the rear pig 2, and the coating film C is applied to the inner circumferential surface of the existing pipe A.

In this case, the problem is that pigs 1 and 2
When the amount of coating agent B filled between the two pigs decreases due to the movement of the coating agent B, a gap D is created above the gap D, which results in an uncoated portion at the top of the inner surface of the tube. Also, apply pressure to the treatment area where coating agent B has already been applied and coating film C has been formed.
Due to P ₁ working, when there are corrosion holes etc. on the inner surface of the existing pipe A, uncured coating agent may leak from there and the coating C may be torn or thinned, and the inner surface treatment may be necessary. This may lead to the loss of its original meaning.

Therefore, even if the filling amount of the coating agent decreases due to the movement of the pig, a void will not be created above the filled part, and even if pressure is not applied to the pig from the coated side, the coating agent will be able to absorb the required amount. A construction method for existing pipes has already been proposed in which a coating film of coating agent can be accurately formed over the entire inner surface of the pipe by applying the necessary pressure for extrusion.

Here, the front and rear pigs are connected by a connecting rope, and a movable pig that can be moved between the pigs through the connecting rope is provided, a coating agent is filled between the movable pig and the rear pig, and the front pig is connected with a towing rope and a movable pig that can be moved between the pigs through the connecting rope. The desired pressure is applied to the coating agent via the movable pig when it is moved under the negative pressure applied to the front space.

The present invention aims to eliminate the inconvenience that the coating agent flows into the branch pipe branching from the existing pipe and blocks the branch pipe in the above construction. By focusing on the point at which negative pressure is applied and detecting the change in air pressure inside the branch pipe, the resin between the pigs is at least lower than the filling pressure applied to the resin while it finishes passing through the branch communication part of the branch pipe. The present invention aims to provide a construction method for existing pipes in which high atmospheric pressure is applied to the branch pipes to prevent resin from entering the branch pipes.

For this purpose, the present invention fills the space between the movable pig and the rear pig with resin, passes the pig through the required existing pipe, applies negative pressure to the space in front of the front pig, and moves it within the existing pipe by towing it. However, when repairing the inside of a pipe, a small atmospheric communication part is installed in the branch pipe that branches from the existing pipe to the supply destination, and the negative pressure state before the front pig passes through the branch pipe connection part of the branch pipe is removed. When the pressure changes to atmospheric pressure, this is detected and the required pressure is applied to the branch pipe, and this state is maintained at least until the rear pig has passed.

Hereinafter, one embodiment of the present invention will be described in FIGS. 2 to 4.
This will be explained in detail with reference to the drawings. Here, a pair of front and rear pigs 11 and 12 inserted into the existing pipe A are as follows:
It is connected by a connecting rope 13, and the front pig 11
is towed forward by a tow rope 14 or by negative pressure. In addition, the above pig 11,1
A movable pig 16 is arranged between the movable pig 1 and the movable pig 16, the movable pig 16 having an insertion hole 15 through which the cable 13 is inserted in the center so as to be slidable relative to the connecting cable 13.
6 and the rear pig 12 is filled with a coating agent B such as a thermosetting resin, for example, an epoxy resin. The above front pig 11 and movable pig 1
6 has an outer diameter that allows it to move airtightly against the inner surface of the existing pipe A, whereas the rear pig 12 has a slightly smaller outer diameter and has a gap G for coating agent B to flow out between it and the inner surface of the pipe. is formed.

In the existing pipe A, the front and rear pigs 11 and 12 are moved by the traction of the tow rope 14 and negative pressure. At this time, due to the movement of pigs 11 and 12,
The movable pig 16 moves rearward due to its movement resistance P ₃ and applies a pressing force P ₃ to the coating agent B filled between the movable pig 16 and the rear pig 12. B is pushed out from the circumferential gap G of the rear pig 12 and applied to the inner surface of the existing pipe A after the pig 12 has passed, forming a coating film C on the inner surface of the pipe.

In this case, coating agent B includes pig 11,
Since the pressing force P ₃ is applied via the movable pig 16 during the movement of the coating agent 12, even if the amount of coating agent filled decreases as the coating process progresses, no void will be created above the filled portion. A coating film C having a uniform thickness can be formed over the entire inner surface of the tube. Furthermore, since no positive pressure is applied inside the existing pipe A after the pig 12 has passed, even if there is a corrosion hole on the inner surface of the existing pipe A, the coating film C
Since the coating film C is cured with the corrosion pores closed, the coating film C will not be torn or thinned.

In this way, within the existing pipe A, the pigs 11,1
Coating is achieved by moving pipes 2 and 16, while branching pipes such as supply pipes branched from the existing pipe A (the above supply pipe is branched into many branches and connected to the gas meter of each customer) ) 17, the following measures are taken. That is, the branch pipe 17 is provided with an atmosphere communication section 18 having a restriction on the side, and is communicated with a compressor 20 via a valve 19.
A pressure sensor 21 is provided opposite to. The pressure detector 21 does not issue a signal to open the valve 19 at the stage of indicating negative pressure, and the pressure sensor 21 does not issue a signal to open the valve 19 at the stage of indicating a negative pressure, but at the stage of changing from a predetermined negative pressure indicated value to an atmospheric pressure specified value, the pressure sensor 21 does not issue a signal to open the valve 19.
The valve 19 is connected to a regulator 22 which issues a signal to close the valve 19 when the pressure decreases to a predetermined atmospheric pressure. Also, after receiving this valve closing signal,
A timer 23 operates to operate the regulator 22 after a certain time delay, thereby delaying the closing timing of the valve 19.

Therefore, in a situation where the branch communication part of the branch pipe 17 is connected to the existing pipe A in front of the pig 11 (see Fig. 2), negative pressure is applied to the branch pipe 17, and the atmosphere communication part Since the amount of air introduced from 18 is extremely small, the required negative pressure is applied. Therefore, since the pressure sensor 21 is detecting negative pressure, the valve 19 is in a closed state.

Next, when the pig 11 passes through the branch communication section, the negative pressure applied in front of the pig 11 does not reach the branch pipe 17, so the residual negative pressure is removed by the atmosphere from the atmosphere communication section 18. Valve 19 is opened by regulator 22, and positive pressure P ₄ is supplied from compressor 20. This positive pressure P ₄ is preferably slightly larger than or equal to the pressure P ₃ applied to the resin.
Therefore, when the movable pig 16 and the rear pig 12 pass through the branch communication section (see FIG. 3), the resin B will not enter the branch pipe 17.

When the rear pig 12 finishes passing through the branch communication section (see Fig. 4), the pressure inside the branch pipe 17 drops significantly to atmospheric pressure as air is released into the existing pipe A. be done. The pressure detector 21 detects this and sends a signal to the regulator 22.
At this time, the timer 23 works, and the regulator 22
The operation instruction is delayed and acts on the valve 19, and until the valve 19 is closed, the air flow is blown out from the branch pipe 17 into the existing pipe A, completely connecting the branch communication part to the existing pipe A. It is possible to promote the curing of the coating agent around the coating agent and ensure a reliable communication state.

In the above embodiment, the construction method of the present invention is applied when coating the inner surface of the pipe, but it is also possible to apply the method of the present invention, such as penetrant penetration into the sealing material at the pipe joint, filling of the putty into the pipe joint, etc. Of course, this method can also be used when applying resin filling pressure using a pig.

As described in detail above, the present invention involves towing the pig while applying negative pressure to the space in front of the pig, and applying filling pressure to the resin filled between the front and rear pigs during this moving process to coat the inner surface of the pipe or coat the pipe. When repairing a joint, etc., resin can be prevented from entering a branch pipe branched from an existing pipe, and the branch pipe can be completely prevented from being blocked by resin.

[Brief explanation of the drawing]

Fig. 1 is a vertical side view showing an example of conventional internal coating work for existing pipes, and Figs. 2 to 4 show an example in which the construction method of the present invention is applied to internal pipe coating work, in order of work procedure. FIG. 11...Front pig, 12...Back pig, 13...
... Connecting cable, 15 ... Insertion hole, 16 ... Movable pig,
17...branch pipe, 18...atmospheric communication section, 19...
... Valve, 20 ... Compressor, 21 ... Pressure detector, 22 ... Regulator, 23 ... Timer, A ... Existing pipe, B ... Coating agent, C ...
...paint film.

Claims (1)

[Claims] 1 In a system in which resin is filled between a pair of front and rear pigs, the pig is passed through the required existing pipe, negative pressure is applied to the space in front of the front pig, and the pipe is repaired while being towed and moved within the existing pipe. , a small-diameter atmospheric communication section is provided in a branch pipe branching from the existing pipe to the supply destination, and when the pressure changes from a negative pressure state to atmospheric pressure before the front pig passes through the branch communication section of the branch pipe, This construction method for existing pipes is characterized by detecting this, applying the required pressure to the branch pipe, and maintaining that state at least until the rear pig finishes passing.