JPH0249553Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an airtightness testing device for tubular bodies, particularly long straight pipes, such as cast iron pipes, welded steel pipes, and other non-ferrous or non-metallic material pipes. be.

[Prior art]

Each tubular body has its own defects depending on its manufacturing method and material.

In centrifugal cast iron pipes, defects unique to the casting may occur, and in steel pipes, defects unique to the welds may occur.

When using these tubular bodies as fuel gas pipes such as LPG, stricter checks are required regardless of the type of pipe, as an explosion could occur if a gas leak were to occur.

With conventional magnetic flaw detectors and ultrasonic flaw detectors, it has been difficult to detect pinholes that have small surface lengths and extend deep.

It is well known to those skilled in the art that in order to solve this problem, conducting a leakage test using a gas as a detection medium enables a more severe check.

However, in normal air pressure testing, air leaks are detected visually by workers, so there is a possibility that they may be overlooked, and considering the differences in worker skill and work efficiency, it is not perfect for inspecting mass-produced products.

The technology of applying a special gas other than air as a detection gas to leak tests is not necessarily new, and there have been proposals for pressure test methods and devices using two or three types of gases.

In selecting the type of gas, several points need to be considered, and the first important considerations are that it is safe, has good fluidity, and can be easily diffused into minute defects.

Helium gas is a gas that satisfies this requirement, and has traditionally been used to inspect sealed parts of refrigerator refrigerant (fluorocarbon gas) containers, piping, compressors, etc.
Used for airtight inspection of automobile radiators.

Furthermore, since the pairs to be tested are small, both are batch methods that are carried out on a rotary table, and are considered not to require any new construction.

However, in order to perform a leak test on a long tube body using helium gas, a special configuration is desirable because the gas is expensive and it is desirable to improve productivity in assembly line operations.

An example of this is "Device for testing helium tightness of tubular bodies" (Figure 3 of Japanese Patent Publication No. 53-2595).
There are also such things.

The present invention will be summarized based on FIG. 3 showing an embodiment. Both ends of a test tube T are closed, the inside of the tube is evacuated by a vacuum device 4a, and a helium injection assembly consisting of an annular sleeve coaxially surrounds the outer periphery of the tube. It consists of a drive device to which a solid body 25 is attached and which suspends this assembly and slides it on the outer periphery of the tube parallel to the tube axis.

[Problem that the invention attempts to solve]

The conventional technology listed above performs a pressure resistance test using helium gas as a sample by assembling the unique requirements for testing tubular bodies, but it requires very large-scale factory equipment and is difficult to judge whether a single tubular body is good or bad. Problems in implementation may include poor testing productivity.

Furthermore, from the examples, rubber as the sealing element,
The test tube and helium injection assembly are made airtight using a seal made of butyl, etc., but it is unclear whether a high level of adhesion can be maintained while sliding around the outer circumference of the tube, which is expected to have minute irregularities, and whether the seal is worn out. The question remains whether the decrease in adhesion cannot be ignored.

Furthermore, although tubular bodies are mass-produced products and are standardized in terms of dimensions, there are several types of tubular bodies with different diameters, and it is common for inspection work to consist of a mixture of several types, so it is important to In this example, the testing equipment (gas ejector) must be rehanged each time the type of pipe changes.

In order to solve the above-mentioned problems, the present invention aims to provide a highly versatile airtightness testing device for tubular bodies that has a simple structure, high efficiency, and can respond to changes in the tubular body.

[Means for solving problems]

The straight pipe airtightness test device according to the present invention includes an openable and closable hood 2 that encloses a long straight pipe test specimen 1;
Inside this hood, a gas blowing nozzle 3 for detection is installed in which a large number of openings are made by equally dividing a constriction pipe 13 which is horizontally suspended parallel to the tube axis of the test specimen and has almost the same length, and a gas blow-off nozzle 3 for detection is opened in large numbers along both sides of the test specimen. It consists of buff-full plates 24 that are placed in parallel over almost the entire length in a freely curvature manner, a means 4 for evacuating the inside of the tube of the test specimen, and a means 5 for detecting the detection gas leaking into the evacuated tube. This solved the above problem.

[Effect]

First, the openable hood is opened to accommodate the first tubular test specimen, the hood is closed, the test specimen is placed horizontally in the hood, and the inside of the tube is evacuated using a vacuum means connected from the outside. do.

Here, the means for spraying the detection gas provided in the hood is activated to spray the detection gas onto the outer periphery of the test specimen, and at the same time, the manual detection gas detection device connected from inside and outside of the test specimen tube is activated.

Detection gas is sprayed around the outer circumference of the test specimen, and the inside of the tube is vacuumed, so if there is a defect communicating from the inner surface to the outer surface, the detection gas will be sucked into the tube, and this sucked gas will be transferred to the outside. It is detected by the detection means connected to the gas and immediately emits a signal to notify the existence of a defect causing gas leakage.

〔Example〕

1 and 2 illustrate a preferred embodiment of the present invention.

Reference numeral 1 denotes a tubular test specimen, which is a centrifugal cast iron tube, and is a single tube having both ends of a socket 1A and an insertion port 1B.

There is a face plate 7 at the opening of the socket 1B that can be moved back and forth horizontally, while a fixed face plate 6 is located at the opening of the socket 1A, and the inside of the tube of the test specimen 1 is evacuated at the center of the face plate 6. A suction tube 8 is provided for this purpose, and its tips are connected to a vacuum pump 4 and a helium gas detector 5, respectively.

Sheet packings 9 and 10 are sandwiched between the socket 1A and the face plate 6, and between the socket 1B and the face plate 7 to maintain airtightness inside the tube, and the test specimen 1 can be sealed by horizontal sliding of the face plate 7. shall be.

This sealed test specimen 1 is encased by a hood 2 which is placed on top and a lower partition plate 11 which forms a lower bottom surface.
The hood 2 has a semicircular shape, has an exhaust port in the center in the longitudinal direction, and is connected to an exhaust blower 22 through a flexible duct, and the hood 2 can be opened and closed vertically by a drive device 12. ing.

Both ends of the hood 2 are along the outer periphery of the face plates 6 and 7, and the test specimen 1 is surrounded by the hood 2, the lower partition plate 11, and the face plates 6 and 7, so that the blown helium gas is not dissipated to the outside. Therefore, the hood 2 is filled with helium gas to efficiently perform the detection function and to save gas usage to a minimum.

It has been found through experiments that the leakage detection sensitivity is poor when the defect is near 90° and 270° within the 360° circumference of the tubular body.

This is because helium gas is light, so it easily rises and fills the upper part (around 0.360°), and the lower part (180°) is directly blown, improving detection sensitivity.

As a solution to this problem, we installed a buff-full plate 2 in the longitudinal direction of the tubular body that can be changed by a drive device inside the hood, keeping the gap between the external surface of the tubular body and the buff-full plate constant regardless of the tube diameter, and spraying from the bottom (180°). The helium gas is brought into contact with the outer surface of the tubular body as it rises, thereby improving detection sensitivity around 90° and 180°. In other words, since the supporting metal fitting 25 that suspends the buttful plate 24 above the hood can protrude into the hood by freely moving back and forth by rotating the screw, the buttfull plate whose lower part is fixed is not necessary. Accordingly, the upper part moves back and forth to freely increase or decrease the curvature as a whole, so that even if the outer diameter of the straight pipe changes, it is adjusted to form a constant distance.

This means that the detection sensitivity remains constant regardless of the pipe diameter that changes during operation.

An air supply pipe 13 for supplying helium gas is provided in the longitudinal direction between the test specimen 1 and the lower partition plate 11, and a plurality of blowing nozzles 3 are installed in this air supply pipe 13 upwardly.
has been established.

To explain the operation of this embodiment, first, the hood 2
is lifted open by the drive device 12, the test specimen 1 is carried into the center of the face plates 6 and 7, the face plate 6 is advanced, and both ends of the test specimen 1 are sandwiched between the sheet packings 9 and 1.
The inside of the tube is kept sealed and held in a predetermined position by pressing the tube through the tube.

Here, the drive device 12 is operated to suspend and close the hood 2.

Next, the vacuum pump 4 is activated, the gate valves 15 and 16 are opened, and the air inside the tube of the test specimen 1 is sucked out to create a vacuum.

A preset degree of vacuum (0.05 TORR) is set in the vacuum gauge 17, and when this value is reached, the gate valve 18 is opened and connected to the helium detector 5.

Next, the gate valve 21 is opened, and helium gas passes through the air supply pipe 13 and is blown to the lower part of the test specimen 1 from the blow-off nozzle 3 to fill the space of the hood 2.

Helium gas used as detection gas is gas cylinder 1
A commercially available product with a concentration of 95% is sufficient in this example.
% or more, the discharge pressure is 1.0 to 1.5 Kg/cm ² and the amount used is about 1.0 to 3.0 liters/test specimen, the gas passes through the suction pipe 8 and the vacuum pump 4, reaches the helium detector 5, and is detected at the terminal, and this effect is transmitted through the signal line 23 and input to the leak rate meter 19 and the alarm device.

When the first atmospheric pressure test is completed, the exhaust blower 22 attached to the top of the hood 2 is operated to exhaust the helium gas filling the hood to the outside, and then the gate valves 15, 16, and 18 are closed. 20 to introduce air.

Furthermore, the drive device 12 is activated to open the hood 2, the face plate 7 is moved back, the seal and restraint of the test specimen 1 is released, and the test specimen 1 is carried out of the hood and replaced with a second specimen.

By measuring the amount of leakage using the recremeter 19, the diameter of defects such as pinholes can be calculated to 0.01.
It is possible to detect defects up to ~0.02mm.

Furthermore, even if the test specimen is sealed and suctioned with a vacuum pump, if a predetermined degree of vacuum is not reached within a predetermined time, the presence of a defect is already indicated without the need for spraying detection gas.

In this example, helium was used as the detection gas, so the blowout nozzle 3 was installed between the test specimen 1 and the lower partition plate. However, if the detection gas is a type with a higher specific gravity than air, such as fluorocarbon gas, the blowout nozzle 3 It is reasonable to provide the above structure on the upper part of the test specimen 1.

[Effect of idea]

As described above, the present invention mainly uses gases (such as helium gas) that have small molecular weights and can easily leak through minute defects, but any gas can be used as a medium as long as it can be combined with a gas detection means. It is possible.

When inspecting pipe types that are prone to serious accidents, such as the inspection of LPG gas pipes, the completeness, efficiency, and versatility of the inspection are more important than the cost of the media.
It is preferable to use helium gas as in the embodiment.

Other types of pipes can be used freely depending on the purpose, taking into consideration the cost of gas media such as argon gas, N ₂ gas, CO ₂ gas, etc.

At the very least, this has the remarkable effect of eliminating the possibility of inspector oversight or individual differences as in conventional barometric pressure tests.

Furthermore, compared to the conventional technique shown in FIG. 3, advantageous effects can be recognized in terms of installation area, installation cost, inspection workability, and versatility in testing multiple pipe types.

However, as mentioned above, when a gas having a higher specific gravity than air is regularly used as a medium, a structure different from that shown in FIG. 1 is preferable.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an embodiment of the present invention, and FIG.
The figure is also a side sectional view, and FIG. 3 is a front sectional view of the prior art. 1...Test object, 2...Hood, 3...Blowout nozzle, 4...Vacuum pump, 5...Gas detector.

Claims (1)

[Scope of utility model registration request] For detection, a hood 2 that can be opened and closed encloses a long straight tube-shaped test specimen 1, and a large number of air supply pipes 13, which are horizontally suspended parallel to the tube axis of the test specimen and of approximately the same length, are equally divided and opened within the hood. a gas blowing nozzle 3, and a buttful plate 24 arranged in parallel with a gap along both sides of the specimen over almost the entire length so as to be able to freely curvature;
An airtightness testing device for a tubular body, comprising a means 4 for evacuating the inside of a tube of a test object, and a means 5 for detecting a detection gas leaking into the evacuated tube.