GB2244537A - Lining underground branch pipe with rigid plastics tube - Google Patents

Description

METHOD OF LINING BRANCH PIPE PORTION OF UNDERGROUND MAIN PIPE WITH RIGID PLASTICS TUBE TECHNICAL FIELD The present invention relates to a method of lining branch pipe portions of underground main pipes with a rigid plastics tube, and more particularly to a method of forming a rigid plastics tube lining over the inner surface of the branch pipe portion as connected at its one end to the underground main pipe through the opening at the other end thereof, i.e., from the surface of the ground.

BACKGROUND ART A method of lining pipes is already known wherein a rigid plastics tube inserted in the pipe and having a smaller diameter than the pipe is inflated radially of the pipe by applying heat and pressure to the tube from inside and thereby line the pipe with the rigid plastics tube (see, for example, Unexamined Japanese Patent Publication No.88281/1983).

The rigid plastics tube lining is hard, therefore retains itself in the pipe lining state and is more excellent in quality than the soft tube lining which is bonded with an adhesive to the pipe for lining.

No particular problem is experienced in using the rigid plastics tube lining method for lining underground main pipes such as water supply pipes, gas pipes and sewer pipes, whereas a problem arises when a branch pipe portion extending from the main pipe to the surface of the ground is to be lined by this method. Since the branch pipe portion has one end connected to the main pipe, it is very difficult to carry out lining work through the opening of the other end which only is usable as a work opening.

In this case, the problem can be eliminated by excavating the ground and cutting off the branch pipe portion from the main pipe to form another work opening and line the pipe portion through both ends as in the usual work condition. However, this requires much labor and time for excavating the ground, cutting off the branch pipe portion and restoring the piping to the original state, hence an undesirable solution.

DISCLOSURE OF THE INVENTION The main object of the present invention is to provide a method of lining a branch pipe portion of an underground main pipe with a rigid plastics tube easily and reliably through one end of the branch pipe portion from the surface of the ground.

Other features of the invention will become apparent from the following description.

The present invention, which is defined in the appended claims, provides a method of forming a rigid or semirigid plastics tube lining over the inner surface of a branch pipe portion joined at its one end to an underground main pipe.

The method of the present invention is used for lining branch pipe portions branching toward the surface of the ground from underground main pipes such as water supply main pipes, gas main pipes and sewer main pipes.

The method of the invention is practised for the branch pipe portion as joined at its one end to the underground main pipe through the branch pipe other end which is substantially open to the surface of the ground as a work opening.

When the main pipe is a water main or gas main, the branch pipe other end is removed at the portion where a meter is mounted for the user so that the branch pipe portion is opened to the surface of the ground. When the main pipe is a sewer, the branch pipe other end is joined to a gully in a gutter formed in the ground surface and left open to the ground surface at the junction. The branch pipe other end thus open to the ground surface is utilized as a work opening.

The rigid or semirigid plastics tube to be used for lining by the method of the invention must be thermo-plastic so as to be inflatable by the heat and pressure applied thereto by a fluid from inside. The rigid plastics tube is usually made of polyvinyl chloride, polyethylene, polypropylene or like material which is 60 to 100"C, preferably about 70 to about 95"C, in softening point.

The rigid plastics tube made of the above material is circular in cross section and has an outside diameter smaller than the inside diameter of the branch pipe portion, for example, an outside diameter corresponding to about 50 to about 90% of the inside diameter.

The rigid plastics tube has such a wall thickness that the resulting lining is capable of retaining its shape and strength for use as such without application of any adhesive. Usually, the thickness is in the range of about 1 to about 10 mm and is determined according to the inflation ratio, outside diameter, material, etc.

The fluid to be used for applying heat and pressure to the rigid plastics tube from inside is not limited specifically but is preferably steam which has a great heat capacity, becomes water on condensation and is dischargeable as it is without entailing any pollution.

The fluid has a temperature higher than the softening point of the rigid plastics tube and a pressure which overcomes the tensile strength of the rigid plastics tube as softened by heating.

The rigid plastics tube is inserted into the branch pipe portion to position the forward end of the rigid plastics tube in coincidence with one end (joined to the main pipe) of the branch pipe portion without projecting the tube end into the main pipe.

Heat and pressure are applied indirectly to the rigid plastics tube inserted in the branch pipe portion through a soft tube inserted through the rigid plastics tube to inflate the rigid plastics tube and line the branch pipe portion with the rigid plastics tube.

According to this method, the rigid plastics tube does not project into the main pipe, so that no surplus end portion of the rigid plastics tube lining remains within the main pipe.

The soft tube to be used for inflating the rigid plastics tube is made, for example, of heat- and pressure-resistant rubber, free to inflate and collapse and recovered by being drawn out from the rigid plastics tube lining to above the ground after the lining operation.

Before practising the method, it is necessary to measure the length of the branch pipe portion to position the forward end of the rigid plastics tube in coincidence with the above-mentioned one end of the branch pipe portion. The length can be measured, for example, by measuring the overall length of the branch pipe portion inclusive of the diameter of the main pipe with a piano wire inserted through the branch pipe portion through the other end thereof and substracting the diameter of the main pipe from the measurement.

BEST MODE OF PRACTISING THE INVENTION An embodiment of the invention will be described below with reference to the accompanying drawings, in which: Figure 1 is a view in vertical section schematically showing the step of inserting a rigid plastics tube into a branch pipe.

Figure 2 is a view in section taken along the line 111-111 in Figure 1; Figure 3 is a view in vertical section schematically showing the step of inflating the rigid plastics tube; Figure 4 is a view in vertical section schematically showing a rigid plastics tube lining formed; and Figure 5 is a vew in section taken along the line IV-IV in Figure 4.

Referring first to Figures 1 and 2, the rigid plastics tube 1 to be used in the present embodiment is circular in cross section and has an outside diameter corresponding to about 75% of the inside diameter of the branch pipe portion c to be lined.

Before the tube 1 is inserted into the pipe portion c, a collapsibly inflatable heat-resistant tube 9 is inserted through the rigid plastics tube 1 over the entire length thereof.

The forward end of the tube 9 is projected outward beyond the rigid plastics tube 1, and the end of the projection 9a is closed with a front plug 10. The outside diameter of the front plug 10 is smaller than the inside diameter of the rigid plastics tube 1 as inflated to form a lining. A heat-resistant hose 11 is inserted through the tube 9 and has a forward end secured to the inner end of the front plug 10 and the other end extending outward from the tube 9. The hose 11 is provided at its forward end with a metal member 12 having a communication opening 12a for holding the interior of the tube 9 in communication with the interior of the hose 11.

To line the branch pipe portion c with the rigid plastics tube, the rigid plastics tube 1 having the heat-resistant tube 9 inserted therethrough is inserted into the pipe portion c through a work opening, i.e., an opening at its outer end joined to the gully b in the gutter. When the inserted end of the rigid plastics tube 1 is positioned in coincidence with the open inner end of the branch pipe portion c, the insertion is discontinued. The inserted forward end of the rigid plastics tube 1 can be positioned in coincidence with the inner end of the branch pipe portion c by inserting the tube 1 by a length corresponding to the length of the pipe portion c which is measured in advance.

Alternatively, this can be accomplished by making the length of the projection 9a of the heat-resistant tube 9 equal to the diameter of the main pipe a.

When the branch pipe portion c has a bent portion, the rigid plastics tube 1 is inserted as softened by being internally heated with steam or the like. Since the softener tube is liable to collapse when not backed up from inside, it is inserted into the branch pipe portion c preferably while being supported from inside by the heat-resistant tube 9 inserted through the tube 1 by inflating the tube 9 to such an extent as will not inflate the rigid plastics tube 1. When desired, a steel strip may be used in combinaaion with the inflated tube 9.

After the tube 1 has been inserted into the branch pipe portion c along with the heat-resistant tube 9, the tube 9 is closed at the rear end with a rear stopper 13 as seen in Figure 3. The rear end of the rubber hose 11 is withdrawn from the pipe portion c and the tube 9 through the rear stopper 13, and a shutoff valve 14 is attached to the withdrawn end lla.

When steam is supplied from a boiler (not shown) to the interior of the heat-resistant tube 9 through a conduit 15 and then through a supply opening 13a in the rear stopper 13 in the state shown in Figure 3, the steam flows through the tube 9 from its rear end toward the front end thereof while heating the outside rigid plastics tube 1 through the tube 9 and is discharged via the communication opening 12a of the metal member 12 and then via the rubber hose 11. Instead of passing the steam through the rubber hose 11, the steam may be discharged through an outlet (not shown) formed in the front plug 10.

After the rigid plastics tube 1 is heated and softened by the steam, the opening of the valve 14 is adjusted to increase the steam pressure within the tube 9, causing the steam to inflate the tube 9 and therefore the outside rigid plastics tube 1 radially of the pipe portion to line the branch portion c with the tube 1.

After the branch pipe portion c has been lined with the rigid plastics tube 1, the steam is replaced by outside air with the internal pressure maintained in the tube 9, whereupon the rigid plastics tube 1 is cooled and solidified with the outside air. Subsequently, the pressure is released from the tube 9 to contract the tube 9 to recover the tube 9 from inside the rigid plastics tube 1, whereby the entire lining operation is completed.

Figures 4 and 5 show the branch pipe portion c formed with a rigid plastics tube lining l'-over its inner surface. The tube lining 1' is rigid, retains its shape and accordingly thereafter holds the pipe portion covered therewith stably and reliably.

With this method, there is no surplus end portion end left projections into the main pipe a and needing to be cutoff.

Claims (2)

1. A method of forming a rigid or semirigid plastics tube lining over the inner surface of a branch pipe portion joined at one end to an underground main pipe through the other end thereof substantially open to the surface of the ground as a work opening, the method being characterized by inserting a rigid or semirigid plastics tube into the branch pipe portion from the work opening with the forward end of the tube left open until the forward end reaches an opening at said one end of the branch pipe portion, subsequently applying heat and pressure to the rigid plastics tube with a fluid from inside through a collapsibly inflatable soft tube freely inserted in the rigid plastics tube over the entire length thereof to inflate the rigid plastics tube radially of the branch pipe and thereby line the branch pipe portion with the rigid plastics tube, and thereafter withdrawing the soft tube from inside the lining.

2. A method as defined in claim 1 wherein the fluid for applying heat and pressure to the rigid plastics tube is steam.