JPH035231B2 - - Google Patents

Description

[Detailed description of the invention]

purpose of invention

[Industrial application field]

The present invention relates to a method of lining the inner surface of a tube.

[Conventional technology]

For example, when connecting steel pipes whose inner surfaces are lined with rubber or synthetic resin by welding, the joint must be lined after welding. If the diameter of the pipe is small and it is not possible for a person to enter the pipe, this lining is carried out by the leaf spring coil method or the expander method. In the leaf spring coil method, a leaf spring is rolled into a coil and placed inside a pipe, then unwound to increase the diameter.
This is a method in which a lining material is injected into the space formed between the pipe and the connecting part and then hardened. This method inevitably has the problem of insufficient sealing at the overlapping portions of the leaf springs, resulting in leakage of the liquid lining material. The expander method, in which a rubber core is placed inside the pipe and blown to make it adhere tightly to the lining surface, prevents the lining material from leaking, but it also seals the contact surface between the existing lining surface and the core. When the necessary internal pressure is applied to the core, the surface of the core bulges out, narrowing the space into which the lining material is to be injected, resulting in an insufficient lining thickness. Another problem is that when the internal pressure of the core is released, if the force that causes the core to return to its original shape is strong, it will act as a large peeling force against the lining layer, which will reduce the strength of the lining layer. The core must be kept inflated until it reaches its full potential, which results in poor workability and poor core utilization. Although a mold release agent is applied to the surface of the core to prevent peeling, the mold release agent may get caught up in the lining material and cause defects. If the existing lining surface contacts the core, the lining material will penetrate and form a thin layer at the edges of the lining layer.
It is a common experience that delaminations that originate from this thin layer grow and often lead to larger delaminations.

[Problems to be solved by the invention]

The purpose of the present invention is to solve the above-mentioned problems and to obtain a lining layer superior to that obtained by conventional methods while adopting the principle of the expander method.
An object of the present invention is to provide a method for lining the inner surface of a pipe. Composition of the invention

[Means to solve the problem]

The method for lining the inner surface of a tube of the present invention comprises injecting a lining material into the gap formed between the inner surface of the tube and the outer surface of the core and curing it. A core outer cylinder that is slightly smaller than the inner diameter of the pipe lining and expands due to internal pressure but does not significantly exceed the inner diameter of the pipe lining, and a core outer cylinder that is inflatable and has a length that exceeds both ends of the core outer cylinder. It is characterized by using a product formed by combining a core body.

[Effect]

To explain with reference to the drawings, first, as shown in FIG. 1, the core body 12 attached to the air supply pipe/operating rod 13 is inserted into the core outer cylinder 11 at the connection part of the pipe 21, and the core body 12 is integrated. Insert the one you made. If necessary, apply a mold release agent to the surface of the core outer cylinder. Next, blow air into the core to inflate it.
As shown in FIG. 2, the diameter of the core outer cylinder 11 is increased, and its surface is brought into close contact with the existing lining layer 22. At this time, even if the necessary internal pressure is applied to ensure a sufficient seal on the contact surface, the outer cylinder does not expand significantly beyond the inner diameter of the pipe lining, so the space 3 into which the lining material is injected is hardly narrowed. , the required thickness of the lining layer is ensured. Therefore, lining material 4A is injected into gap 3,
Let it harden. When the core body 12 is almost cured, the air pressure is released and the core body 12 is contracted. The diameter of the core outer cylinder also decreases as the internal pressure is released, and it is removed together with the core. When the adhesive force of the lining part is strong or when the effect of the mold release agent is low, the core outer cylinder 11 remains. In the remaining core outer cylinder 11, the lining material has completely hardened, and
After becoming the hardened lining material 4B, for example, the third
As shown in the figure, use a key stick 5 or the like to remove it. At this time, the peeling force acting on the lining surface is negligible. If there is no problem in using the tube, the outer cylinder may be left inside the tube as it is.

[Embodiment]

The core outer cylinder is made from a material that expands slightly due to internal pressure. Rubber is usually sufficient, but it is also possible to provide a reinforcing layer of woven fabric or non-woven fabric that can be expanded and contracted to some extent inside. The length of the core outer cylinder should be selected so that the overlap with the existing lining surface is in the range of 5 to 75 mm. Needless to say, if the overlap is too small, the necessary sealing effect cannot be obtained, and if it is too large, the core will become unnecessarily large. Particularly preferred is 10 to 50 mm. Thickness is 0.5
~5 mm, especially 1~3 mm is suitable. Both ends of the core outer cylinder may be tapered to some extent so that the thickness becomes thinner toward the ends. This ensures close contact with the existing lining. The core body may be made of a material that can be inflated by blowing air into it, usually soft rubber. Injection and curing of the lining material may be performed according to known techniques. If it is desired to accelerate curing, the lining portion may be heated by an appropriate method, such as hot air or a band heater. Effects of the Invention According to the method of the present invention, a lining can be obtained that has a required lining thickness and is well bonded to an existing lining layer and is difficult to peel off. After the lining material is injected, the core can be removed once it has hardened, resulting in a high core utilization rate and improved workability.

[Brief explanation of the drawing]

The drawings are cross-sectional views illustrating the process of lining the inner surface of a tube according to the present invention, in which FIG. 1 shows the core inserted into the connecting part of the tube, and FIG. The core outer cylinder is brought into close contact with the inner surface of the tube, and the lining material is injected into the space thus formed, and Figure 3 shows the core outer cylinder being removed after the lining material has hardened.
are shown respectively. 1... core, 11... core outer cylinder, 12... core body, 21... tube, 22... existing lining layer,
4A...Lining material, 4B...Hardened lining material.

Claims (1)

[Claims] 1. In a method for lining the inner surface of a tube, which consists of injecting a lining material into the gap formed between the inner surface of the tube and the outer surface of the core and curing it, the outer diameter of the core is normally slightly smaller than the inner diameter of the tube lining part; A core outer cylinder that expands due to internal pressure but does not significantly exceed the inner diameter of the pipe lining, and a core body that is inflatable and has a length that exceeds both ends of the core outer cylinder. A method for lining the inner surface of a tube, characterized by using.