JPH0444938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of cutting a temporary gas conduit that is mainly buried underground and blocking the end of the pipe.

In the conventional construction method, as shown in Figures 5 and 6,
The end of the gas conduit 1 is closed through the following steps.

(a) An insertion hole 4 for a cutoff tool 3 made of a gas bag capable of temporarily blocking gas inside the gas pipe 1 is bored on the upper side in the gas flow direction than the planned cutting point a of the gas pipe 1. (See FIG. 5A) (B) Insert the shutoff tool 3 through the insertion hole 4 to shut off the inside of the gas conduit 1.

(c) Cut the gas conduit 1 at the above-mentioned planned location. (See FIG. 5B) (d) Short pipes 21 with caps 20 are disposed on the open end side of the gas conduit 1 so as to be coaxial and facing each other at appropriate intervals. (See Figure 5 C) (E) Inner peripheral surface portions 22a, 22 on both sides in the tube axis direction between the gas conduit 1 and the short tube 21 with a cap.
A between a cylindrical body 22 having an outwardly expanding tapered surface 22a, one tapered inner peripheral surface 22a of this cylindrical body 22 and the outer peripheral surface of the gas conduit 1, and the other parts of the cylindrical body 22. and elastic seals 23, 23 interposed between the Taber inner circumferential surface 22a and the outer circumferential surface of the short pipe 21 with a cap, and
Due to the relative proximity movement of the bolt 24 and nut 25, which are held through the cylindrical body 22, by the tightening operation from the tube axis direction, the elastic seals 23, 23 are connected to the tapered inner circumferential surfaces 22a, 22.
A pair of pressing plates 26, 26 that press against the small diameter side of a.
Fit the closure jig B provided with the above, and tighten the bolts and nuts 24 and 25 of this closure jig B to tightly seal the elastic seals 23 and 23 to the outer circumferential surface of the tube and the inner circumferential surface of the cylindrical body 22. let (Refer to FIG. 5D) (f) The blocking device 3 is taken out of the pipe 1, and after the inside of the pipe is air purged, the insertion hole 4 is closed with the plug 28. (See FIG. 5E) (G) Weld a half-shaped protective case 27 that covers the entire closure jig B between the gas conduit 1 and the cap short tube 21. (See Figure 5) (H) Weld the plug 28. (See Figure 5-G) (I) A special test gas such as N ₂ gas is sealed in the space between the protective case 27 and the cylindrical body 22 to perform an airtightness test on the elastic seal portion.

This conventional construction method had the following problems.

[] Since the closing jig B for closing the end of the gas pipe 1, the protective case 27, and the short pipe with cap 21 protrude largely in the pipe axis direction and the pipe diameter direction, it is difficult to cut the gas pipe when cutting the gas pipe. It is necessary to cut on the side of the existing pipe rather than the desired cutting point, and not only does the amount of material used increase, but the excavation area and welding work time also increase, and the overall construction requires a lot of time and effort. , which can easily lead to a rise in construction costs.

[] It is not possible to reliably purge air to the end of the pipe.

[] If the elastic seals 23, 23 have poor adhesion to the outer circumferential surface of the tube and the inner circumferential surface of the cylindrical body 22, a test gas such as N ₂ gas different from the gas in the gas conduit 1 may be inserted between them. There is a high risk of it entering the conduit 1.

The present invention has an object to improve the drawbacks of the conventional construction methods as described above.

A feature of the method for blocking the end of a gas conduit according to the present invention, which has been adopted to achieve the above object, is that the end of the pipe is blocked through the following steps.

(b) An operation hole is drilled on the upper side of the gas flow direction than the planned cutting point of the gas pipe, and further above this operation hole in the gas flow direction, it is possible to temporarily shut off the gas inside the gas pipe. Drill an insertion hole for a shutoff device consisting of a gas bag.

(b) Insert a shutoff device through the insertion hole to shut off the inside of the gas pipe.

(c) Cut the gas pipe at the planned cutting location.

(d) An elastic seal that elastically adheres to the inner circumferential surface of the pipe due to bulging outward in the radial direction when the gas pipe is tightened in the direction of the pipe axis, and an elastic seal that contacts the inner circumferential surface on the downstream side in the direction of gas flow than this elastic seal. A closing jig is provided with a stopper member that can be used as a stopper, and an on-off valve is attached to the cut-side end of the fluid pipe that is held through the elastic seal and the stopper member.
The elastic seal is inserted into the gas conduit portion between the two holes so as to be in close contact with the inner circumferential surface of the tube.

(E) Take out the shutoff device outside the pipe, purge the inside of the pipe with air, and then plug the insertion hole.

(F) Weld the retaining member of the closing jig to the inner peripheral surface of the pipe to fix the closing jig.

(g) Weld a cap to the end of the gas pipe to close off the end of the pipe.

(H) Open the on-off valve through the operation hole, purge air to the end of the pipe, and then plug the operation hole while keeping the on-off valve open.

The functions and effects of the present invention having the above characteristics are as follows.

[] A closing jig, which is a structural member for closing the end of the gas pipe, is inserted into the gas pipe, and a cap is directly fixed to the cut end of the gas pipe, so it is not possible to use conventional construction methods. The amount of protrusion of the closing component in the tube axis direction and tube radial direction can be reduced as much as possible. Therefore, not only the amount of material used is reduced, but the construction length and excavation area in the direction of the pipe axis are also small.
In addition, since the welding work time can be significantly shortened, the overall time and effort required for construction can be reduced as much as possible, and construction costs can also be reduced.

In addition, since the pipe line is blocked by the gas bag blocking device and then the pipe line is further blocked by the blocking jig, intermediate pressure or high pressure gas can also be reliably blocked by the blocking jig.

[] The removal movement of the closing jig is controlled not only by the frictional force between the inner circumferential surface of the gas conduit and the elastic sealing material, but also by the tensioning action of a retaining member located on the downstream side of the elastic seal in the direction of gas flow. Since this is utilized to prevent leakage due to removal and movement of this closing jig, it is possible to prevent leakage.

[] Since a fluid pipe with an on-off valve is held through the elastic seal and the retaining member,
By guiding the gas in the gas conduit into the cap through the fluid and the on-off valve, the air in the gas conduit is passed through the fluid conduit and the operation hole, and
Ensure that the air inside the cap passes through the operation hole.
Not only is it possible to purge smoothly, but by guiding the gas in the gas pipe into the cap as described above, the required pressure of the gas in the gas pipe can be used to conduct the necessary airtightness test of the welded part. Because it can be performed directly, for example, it is possible to prevent the risk of a test gas such as _N2 gas, which is different from the gas inside the gas pipe, entering the gas pipe as in the past, and it also helps reduce construction costs. However, it has now become possible to conduct airtightness surveys accurately, easily, and safely.

Hereinafter, embodiments of the construction method of the present invention will be described based on the drawings.

(b) After reducing the internal pressure of the gas pipe 1 to a low pressure state (less than 1 Kg/cm ² ), cut the gas pipe 1 at the cutting position a and position b of the operation hole 2 relative to the on-off valve 9 of the closing jig A (described later) (for example, A hole of 1 inch or less is drilled at a position 50 mm or more from the pipe end and directly above the on-off valve 9), and a gas bag (gas This is an example of a shutoff device that can temporarily shut off gas inside the conduit 1.) Hole forming position c for inserting 3 and 3.
(For example, the distance from the operation hole 2 is 650 mm or more). (See Figure 1 A) (B) Based on the above decision, open the operation hole 2 in the gas pipe 1.
Then, a gas pack operation hole 4 is bored. After drilling, plug plugs 5 and 6 respectively. (See Figure 1B) (c) Remove the plug 6 from the insertion hole 4, insert the first bag 3 and the second bag 3 while being careful not to burr when drilling, and shut off the inside of the gas conduit 1. (See Figure 1 C) (d) Cut the gas conduit 1 at the planned location. After cutting, be careful not to burr the cut end (blade edge) and clean the inner surface of the tube near the insertion of the closing jig with a rag, etc. (See Figure 1 D) (E) Remove the plug 5 from the operation hole 2. Be careful of burrs when drilling.

(f) The operation hole 2 and the insertion hole 4 of the gas conduit 1
Insert the closing jig A into the pipe section located between the (See Fig. 1 E) As shown in Figs. 2 to 4, this closing jig A is caused by bulging outward in the radial direction accompanying the tightening operation of the gas conduit 1 from the pipe axis direction. An elastic seal 7 that elastically adheres to the inner circumferential surface of the tube end, and a tube of the elastic seal 7 that contacts the inner circumferential surface on the downstream side in the gas flow direction at two points in the circumferential direction of the elastic seal 7. A member 8 that prevents the extraction movement toward the opening side is provided, and a cylindrical tightening operation shaft 7A that is a constituent member of the elastic seal 7 and extends in the axial direction of the gas conduit 1 is provided to prevent the elastic seal 7 and the extraction movement. A fluid pipe passing through the stop member 8 is also used, and a valve 9 which can be opened and closed is provided at the end of the operating shaft 7A on the pipe opening side.

The elastic seal 7 includes circular clamping plates 7C and 7D that can clamp two rubber rings 7B and 7B, which can be elastically tightly attached to the inner circumferential surface of the gas conduit 1, from both sides in the tube axis direction, respectively, on the operating shaft 7A. and 7D,
7D, and fix only the clamping plate 7C located on the uppermost side in the gas flow direction to the operating shaft 7A, and O-rings 7E, 7E are attached to the end of the operating shaft 7A on the tube opening side. By tightening and pressing the movable clamping plate 7D to the fixed clamping plate 7C side through the provided cylindrical members 7F, 7F and the sleeve 7G, a nut 7H is activated to bulge the rubber rings 7B, 7B outward in the radial direction. It is constructed by screwing together.

The retaining member 8 is externally fitted and held on a portion of the operating shaft 7A located between the sleeve 7G and the nut 7H of the elastic seal 7, and has a portion 8a that comes into contact with the inner circumferential surface of the gas conduit 1. , 8a are formed in a dogleg shape so that they are located on the lower side in the gas flow direction than the external fitting holding portion 8b.

In addition, when inserting this closure jig A, return the nut 7H and remove the rubber rings 7B, 7B.
After inspecting and cleaning, lift jig A slightly and insert it slowly.

(G) Set the closing jig A in the proper position and tighten the nut 7.
By tightening H, the rubber rings 7B, 7B are brought into strong elastic contact with the inner peripheral surface of the gas conduit 1. In this case, the on-off valve 9 is removed. Further, the knob of the on-off valve 9 is positioned directly below the operation hole 2, and the retaining member 8 is set in a horizontal or almost horizontal position.

(H) Grasp the retaining member 8 and pull it toward you to check if jig A does not move. If it moves, tighten the nut again.

(li) Install the on-off valve 9. In this case, check to see if the knob is in the "closed" position. (Refer to Fig. 1) In addition, in this way, after blocking the pipe line with both bags 3, using a closing jig to close the pipe line is generally done at medium pressure or with only both bags 3. This is because it is unreliable to shut off high-pressure gas, and even if you try to block the pipe only with a blocking jig that is highly reliable for medium and high-pressure gas,
This is because the closing jig cannot be inserted through the insertion hole drilled in the hole.

(N) Bleed out a little air from the second bag 3 and check for overflow gas. Note that the overflow gas refers to gas that leaks from between the elastic seal 7 and the inner surface of the gas conduit 1 beyond the elastic seal 7.
If there is any leakage in the closing jig, press air into the second bag 3 again, remove the plug, and tighten the nut 7H again.

(l) Take the bags 3, 3 out of the tube, purge the inside of the tube with air, and then plug the insertion hole 4 with the plug 6. Inspect the plug for leaks, and if there is any leak, stop it with clay. (See Figure 1.) (e) Open the on-off valve 9 to purge the remaining air between the gas bag operation position and the rubber rings 7B, 7B, and then close it again. Thereafter, a leak test is performed on the rubber ring 7B and the opening/closing valve portion through the cut opening of the gas conduit 1 using soapy water and a gas leak detector.

If there is any leakage, insert the first bag 3 and the second bag 3 through the insertion hole 4, remove the on-off valve 9, retighten the nut 7H, and return to step (R).

(W) After fillet welding the retaining member 8 to the inner peripheral surface of the gas conduit 1 in a horizontal position, the cap 10 is butt welded to the cut open end of the gas conduit 1.
(See Figure 1, H) In this case, be sure to remove any burrs when cutting the gas pipe 1.

(f) After 10 minutes have passed since the end of welding, open the on-off valve 9 through the operation hole 2, and open the cap 10.
After purging the air, open the on-off valve 9.
The operation hole 2 is closed with the plug 5 while maintaining the state. (Refer to Figure 1) In this case, use a purge checker to confirm replacement, and check for leaks at the plug.

(Y) Each plug 5 of the operation hole 2 and insertion hole 4,
Weld 6. If the insertion hole 4 is to be reused, a special screw plug or flanged short pipe should be welded to it.

(T) After increasing the gas pressure in the gas pipe 1 from a low pressure state to the holding pressure (medium pressure), perform an airtightness test on each welded part of each plug and cap using soapy water, a gas leak detector, etc. .

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the method for closing the end of a gas pipe according to the present invention, Figures 1A to 4 are process diagrams of the process for closing the end of the gas pipe, and Figure 2 is a part of the closing jig. A cutaway plan view, Figure 3 is a view taken along the - line in Figure 2,
FIG. 4 is a view taken along the - line in FIG. 2. Fifth
Figures 6 and 6 show the conventional process for blocking the end of a gas pipe, and Figures 5A to 5C show the process of blocking the end of the pipe,
FIG. 6 is an enlarged sectional view of the closure jig. A... Closing jig, 1... Gas conduit, 2... Operation hole, 3... Blocker, 4... Insertion hole, 7... Elastic seal, 7A... Fluid pipe, 8... Removal prevention member, 9...
...Opening/closing valve, 10...Cap.

Claims (1)

[Claims] 1. A construction method in which the end of the gas conduit 1 is blocked through the following steps. (b) Drill an operating hole 2 on the upper side in the gas flow direction than the planned cutting point a of the gas pipe 1, and temporarily cut the inside of the gas pipe 1 on the upper side in the gas flow direction than the operation hole 2. An insertion hole 4 for a shutoff device 3 made of a gas bag capable of shutting off gas is bored in the hole. (b) Insert the shutoff tool 3 through the insertion hole 4 to shut off the inside of the gas conduit 1. (c) Cut the gas conduit 1 at the planned cutting point a. (d) An elastic seal 7 that elastically adheres to the inner circumferential surface of the pipe due to bulging outward in the radial direction when the gas pipe 1 is tightened from the pipe axis direction, and an inner periphery on the downstream side of the elastic seal 7 in the direction of gas flow. A shut-off valve 9 is attached to the cut-side end of the fluid pipe 7A, which is provided with a retaining member 8 that can come into contact with a surface, and is held through the elastic seal 7 and the retaining member 8. The closing jig A is inserted into the portion of the gas conduit 1 between the holes 2 and 4 in such a manner that the elastic seal 7 is brought into close contact with the inner peripheral surface of the pipe. (e) Take out the blocking device 3 outside the pipe 1, purge the inside of the pipe with air, and then plug the insertion hole 4. (f) The closure jig A is fixed by welding the retaining member 8 of the closure jig A to the inner peripheral surface of the pipe. (G) Weld the cap 10 to the end of the gas conduit 1 to close the end of the pipe. (h) Opening the on-off valve 9 through the operation hole 2;
After air purging to the end of the pipe, the operation hole 2 is plugged while the on-off valve 9 is kept open.