JPS6027370B2 - Airtightness inspection method for plastic pipe terminal connections - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting a plastic pipe end connection for airtightness.

Some plastic pipes are not suitable for use with adhesives, depending on their use and material.

Conventionally, it was the first terminal connection for such plastic pipes.
Mechanical grounding as shown in the figure and butt welding connections as shown in FIG. 2 are known.

For mechanical connection, the metal tube 18 is inserted inside the plastic tube 10, the end of the plastic tube 10 is opened,
The flange of the metal tube 18 and the tightening flange 16 are tightened with bolts. In the butt welding connection, the plastic pipe 10 and the short collar tube 8 are butt welded. 7 is a loose flange.

In any case, an airtightness test is required, but the plastic pipe 10 is often the longest, and it takes time to test the airtightness of the entire pipe.

There is also a method of visually checking for leaks by flowing liquid, but this is inaccurate.

On the other hand, although the entire pipe is tested for airtightness as described above, a method has been considered in which only the inconvenient parts are sectioned and the airtightness test is performed on the partitioned pipe sections. However, in this case, it is necessary to close the tube end and provide an airtight blockage inside the tube to form a sealed compartment. For blockage in the pipe, it is necessary to insert a blocking member into the pipe.
Since the inner surface of the tube has unevenness due to the connection of the short-flange tube, insertion of the blocking member is difficult due to resistance, and it is difficult to insert the blocking member. When trying to select a material to facilitate insertion, there is a problem in that it is difficult to obtain sufficient airtightness between the inner surface of the tube and the closing member. In view of this situation, the present invention provides a method that allows the insertion of a blocking member into a pipe and the close contact of the blocking member to the inner surface of the pipe, thereby easily and accurately testing the airtightness of a terminal connection. The purpose is to provide

The configuration of the present invention will be specifically explained with reference to the drawings showing one embodiment.

In FIG. 3, a plastic tube 10 is butt welded to a flange tangent 8, and a welded portion 9 is raised on the inside and outside of the tube.

A push rod 11 and a pull rod 1 are connected to each other so that they can move relative to each other in the axial direction within this plastic tube end connection.
Insert 3.

The tip of the pull rod 13 protrudes from the tip of the push rod 11, and the tip of the push rod 11 and the tip of the pull rod 13 have surfaces that face each other in all axial directions, and the tip surface of the push rod 11 and the pull rod 13 have surfaces that face each other in all axial directions.

At least one of the corresponding surfaces of the pad 13 is an inclined surface that opens outward, thereby forming a V-shaped clamping surface, and the annular rubber is in contact with the inclined surface on the clamping surface. A packing 12 is sandwiched and arranged. The outer diameters of the pull rod 13 and push rod 11 are smaller than the inner diameter of the plastic tube 10, and the annular rubber packing 12
The outer diameter of the plastic tube 10 is approximately the same as the inner diameter of the plastic tube 10.

The end face of the short collar tube 8 is closed by a fixed flange 5, and the conduit 3 is attached to the fixed flange 5.

Conduit 3 is for introducing gas 1, and valve 2
is provided. The rear end (opposite the tip) of the pull rod 13 passes through the fixed flange 5 and is tightened with a nut 14 via a collar 15 so that it can move forward and backward in the axial direction.

The rear end of the push rod 11 may pass through the fixed flange 5, but does not need to.

If it is penetrated, there is an advantage that the annular rubber packing 12 can be attached vertically together with the pull rod 13, but it is necessary to devise ways to maintain airtightness. If there is no penetration, there is an advantage that airtightness with the fixed flange 5 can be easily ensured, but the vertical attachment of the circular rubber packing 12 relies only on the pull rod 13.

The pull rod 13 and push rod 11 are inserted into the plastic tube 10, closed with the end face by the fixed flange 6, and the loose flange 7 and the fixed flange 5, which are iron-fitted to the outside of the collar short tube 8, are tightened with bolts 6.

4 is a packing.

At this time, the pull rod 13 and push rod 11 are made of tubes that are made by loosening the nut 14 and relatively shifting them in the axial direction to increase the width of separation between the clamping surfaces, thereby increasing the degree of ironing of the annular rubber packing 12 with respect to the spherical holding surface. By inserting the gasket 12 into the tube 10, the gasket 12 can be easily deformed inwardly at the protruding portion within the tube and the insertion resistance can be kept low.

On the other hand, after the above-mentioned insertion work is completed, the pull rod 13 is retracted vertically with respect to the push rod 11, and the annular rubber packing 12 is held by the clamping surface with a narrower distance in the direction of the ball, or more specifically by the inclined surface forming that surface. By being pushed outward, it presses against the inner surface of the tube and seals it airtight. The valve 2 of the conduit 3 is opened to allow gas 1 to flow into this space.
The airtightness of the terminal connection is detected by detecting changes in gas pressure and leakage to the outside.

In other words, the annular rubber packing 12 is elastic and has a large inward elastic deformation escape, so even if there is a protrusion on the inner surface of the tube, it can be passed through by sufficient inward deformation, and the pull rod 13 By tightening, it is possible to press the plastic tube airtightly even if it is slightly smaller than the inner diameter of the plastic tube 10.

The explanation above has been given using the butt weld connection as shown in Fig. 2, but it can also be applied to the case of mechanical connection as shown in Fig. It is included.

Although FIG. 4 shows an example of the cross-sectional shape of the annular rubber packing 12 used in the present invention, it is not limited thereto. With the airtightness inspection method of the present invention, when performing an airtightness inspection of a tube end connection by airtightly closing each of the tube end and the inside of the tube, the insertion of the closing member into the tube can be performed with sufficient resistance, especially when airtightly closing the tube. It is small and easy to carry out, and after insertion, a simple tightening operation provides complete adhesion to the inner surface of the tube. Therefore, even if the end connection part has unevenness on the inner surface of the tube, it can be easily and accurately connected. It is possible to test airtightness.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 and 2 are cross-sectional explanatory diagrams showing a conventional plastic pipe end connection part, FIG. 3 is a cross-sectional explanatory diagram showing an embodiment of the present invention, and FIG. The figure is a sectional view showing an example of an annular rubber packing used in the present invention. 1: Gas, 2: Valve, 3: Conduit, 4: Packing, 5:
Fixed flange, 6: Bolt, 7: Loose flange, 8:
Short collar tube, 9: welded part, 10: plastic tube, 11: push rod, 12: annular rubber packing, 13: pull rod, 14: nut, 15: collar. 3 figures, 4 figures, 3 figures, 4 figures

Claims (1)

[Claims] 1. In a method for testing the airtightness of a plastic tube end connection in which a short collar tube 8 is connected to the end of a plastic tube 10, a push rod 11 and a pull rod 13 that are fitted together so as to be able to move relative to each other in the axial direction are used. Rod 11,
Reference numeral 13 is formed by making the tip of the pull rod 13 protrude from the tip of the push rod 11, and forming a clamping surface with at least one of the two tips facing each other in the axial direction as an inclined surface that is open to the outside. An annular rubber packing 12 is placed in contact with and clamped between the push rod 11 and pull rod 13, and the push rod 11 and pull rod 13 are inserted into the plastic tube 10 without being tightened between them. By relatively tightening the inserted pull rod 13 and push rod 11 in the axial direction, the annular rubber packing 12 is pressed against the inner surface of the plastic tube 10 to airtightly close the inside of the tube. 1. A method for airtightness testing of a plastic tube end connection, characterized by flowing gas 1 into a tube 1 and detecting leakage of the gas 1.