JPH0643938B2 - Pinhole position detection method for hollow elongated body - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a pinhole position detection method for a hollow elongated body. TECHNICAL FIELD The present invention relates to a pinhole position detection method suitable for efficiently detecting the position of a pinhole formed on a peripheral wall of a hollow elongated body having a small diameter and sometimes made of a flexible material such as a hollow fiber.

BACKGROUND OF THE INVENTION Separation hollow fibers having a separation layer on a plastic peripheral wall are used for the purpose of separating a specific gas component from a gas mixture, dialysis of blood, and the like. In this separation hollow fiber, a gas or a liquid containing a plurality of components such as a gas mixture and blood is introduced or passed through either the hollow portion or the outside of the hollow fiber, and necessary or unnecessary components are introduced from the gas or liquid. , Is used for the operation of separating through a separation layer. Therefore, it is desirable that the separation layer of the hollow fiber has a structure that is controlled as strictly as possible, and such adjustment is made in actual production.

However, hollow fibers made in this manner have the potential to occasionally include through holes (ie, pinholes) with unusually large diameters. In addition, pinholes are likely to form even with slight changes in manufacturing conditions. When a hollow fiber with pinholes is used for the above-mentioned separation operation, a large amount of liquid or gas leaks through the pinholes, so that the separation efficiency is significantly lowered and the desired separation becomes difficult.

It is possible to detect pinholes generated in the peripheral wall of the hollow fiber by continuously observing and inspecting the peripheral wall of the hollow fiber with a microscope, but the efficiency of the inspection is very low and detection omission easily occurs. Therefore, it is not a practically advantageous method.

A steel pipe is known as another example of an elongated body having a hollow shape such as the above hollow fiber (referred to as a hollow elongated body in the present specification). As a method of detecting defects such as scratches and holes on the surface of the steel pipe, there is a method of hitting the steel pipe with a hammer to detect an acoustic abnormality, and particularly for detecting holes generated on the peripheral wall of the steel pipe. A common method is to radiate ultrasonic waves or light into the hollow portion to detect leakage to the outer surface. These detection methods can be used when the subject is 10m to 2m long.
It is effective when it is a hollow metal body up to about 0 m, but it has a small diameter (for example, an inner diameter of 10 mm or less) and a long length (for example, a length of 100 m or more) like the above hollow fibers. ) It cannot be applied to detect pinholes generated in plastic hollow elongated bodies.

Further, a method is also known in which pressurized air is introduced into the hollow elongated body, and the hollow elongated body is placed in a liquid such as water in that state to observe the generation of bubbles. It is not suitable for the detection of small pinholes, and because the hollow fiber may come into contact with liquid, a cleaning process may be necessary after that, and humans should always observe it during the inspection process. There are drawbacks, and this is also not a practically satisfactory method.

[Object of the Invention] The present invention efficiently detects pinholes (positions of pinholes) generated on the peripheral wall of a hollow elongated body, particularly a hollow elongated body having a small diameter and made of a flexible material such as hollow fiber. An object of the present invention is to provide a pinhole detection method suitable for

SUMMARY OF THE INVENTION The present invention provides a hollow elongated body having a hollow portion having a diameter of 10 mm or less and containing the gas A in the hollow portion.
Gas B different from the gas set to a pressure lower than
The gas A flowing in the (seal gas) atmosphere and flowing out from the pinhole of the peripheral wall of the hollow elongated body is detected by utilizing the difference in thermal conductivity between the gas B and the mixture of the gas A and the gas B. However, there is a method of detecting the position of the pinhole of the hollow elongated body from the detection time and the moving speed of the hollow elongated body.

[Advantageous Effects of the Invention] The method for detecting the position of a pinhole in a hollow elongated body according to the present invention is a very industrially advantageous detection method because it does not require any human observation and inspection in the pinhole position detection operation step. is there.

Further, according to the pinhole position detection method of the present invention, there is no limitation on the size of the inner diameter of the hollow elongated body of the subject, and the length is not limited at all, and the pinhole position can be continuously detected at high speed. You can also determine the approximate size of the pinhole.

The hollow elongated body to which the method for detecting the pinhole position of the present invention is applied is not particularly limited, but the method for detecting the pondhole position of the present invention has a small diameter such as a hollow fiber (for example,
Inner diameter 10 mm or less, and long length (for example, length 1
It can be applied particularly advantageously for the continuous detection of the position of pinholes formed on the peripheral wall of a hollow elongated body made of a flexible plastic (00 m or more, particularly 500 m to 100,000 m). That is, a practical pinhole position detection method for a hollow elongated body such as a hollow fiber has not been known so far.

The hollow fiber used for gas or liquid separation is usually used as a separation module prepared by cutting a unit cut into an appropriate length and bundling a large number of the cut fibers. Therefore, if the position of the pinhole of the hollow fiber can be determined by a simple method, the other part can be efficiently used by removing only the detected pinhole part of the hollow fiber. It will be very advantageous. Further, by incorporating the pinhole position detecting method of the present invention as a monitor in a production process, process control can be made reliable and efficient.

DETAILED DESCRIPTION OF THE INVENTION The pinhole position detecting method of the present invention will be described below with reference to the pinhole position detecting device shown in FIG. 1 of the accompanying drawings.

FIG. 1 is a diagram showing a detection device particularly suitable for carrying out a method of continuously inspecting the peripheral wall of a hollow fiber to detect the position of a pinhole generated in the peripheral wall.

In FIG. 1, the detection device is composed of a tubular main body 11, and two openings 13 and 14 functioning as an inlet and an outlet of the hollow fiber 12 at both ends thereof (these are not necessarily both ends, (Which may be in the vicinity), and the thermal conductivity for detecting the fluctuation of the gas composition in the gas atmosphere and the gas introduction portions 15a and 15b for keeping the space between the openings 13 and 14 in the selected gas atmosphere. A detector (thermal conductivity detector) 16 is provided.

The pinhole position detecting device is preferably provided with traveling devices 17a and 17b for traveling a hollow elongated body such as the hollow fiber 12 in the cylindrical body 11 at a substantially constant speed. The hollow fiber traveling device in FIG. 1 includes a hollow fiber feeding bobbin 17a and a winding bobbin 17b.
And the rotating rollers 18a, 1 for assisting the traveling of the hollow fibers
8b.

The pinhole position detection system in FIG. 1 shows a mode in which the detection device is fixed and the hollow elongated body that is the subject is run, but the subject is made of a rigid material and the lengths are compared. In the case of a relatively short object such as a steel pipe or a plastic hollow pipe, the hollow elongated body may be fixed and the detection device may be moved.

The operation of detecting the pinhole position on the peripheral wall of the hollow fiber 12 using the detection device of FIG. 1 is performed as follows.

First, the gas B functioning as a seal gas is introduced into the cylindrical main body 11 from the gas introduction parts 15a and 15b. Gas B
As the gas, a gas different from the gas A existing inside the hollow fiber 12 is selected. Since the gas A existing in the hollow portion of a normal hollow fiber is air, the gas B is selected from gases other than air, nitrogen, and oxygen. The gas B is preferably a rare gas such as helium gas or argon gas. However, when the air in the hollow portion of the hollow fiber is replaced with another gas, for example, the above-mentioned rare gas or the like, for detection, the gas B is naturally a gas other than the rare gas.

As the gas A in the hollow portion, a fluorinated gas such as tetrafluoromethane or difluoromonochloromonohydromethane, or a hydrocarbon gas such as propane or butane can be used. In that case, as the gas B, for example, nitrogen, air, Helium, argon, etc. are used. Gases A and B used
May each be a mixture.

The gas B such as helium introduced into the cylindrical main body 11 from the gas introduction parts 15a and 15b is discharged from the gas discharge port 19 provided near the center of the main body. It is preferable to discharge the gas B by connecting a vacuum system to the gas discharge port 19 and utilizing the suction force of the vacuum system. The thermal conductivity detector 16 is inserted between the gas outlet 19 and the vacuum system.

That is, normally, the pressure of the gas A in the hollow portion of the hollow fiber is set to normal pressure, and the pressure of the gas B that acts to seal the periphery of the hollow fiber inside the tubular body 11 is slightly reduced from normal pressure. The conditions to be set are set. However, when the hollow elongated body is made of a rigid material, the pressurized gas A may be filled in the hollow elongated body and the seal gas (gas B) may be at normal pressure.

As described above, the gas B is continuously flown into the cylindrical main body 11,
All or part of the discharged gas B is sent to the detector 16 at a constant speed and continuously inspected. Under such conditions, the hollow fiber 12 is run at a substantially constant speed so as to pass through the tubular body 11. If there is a pinhole on the peripheral wall of the hollow fiber 12, the pinhole portion is located at the cylindrical main body 1.
When entering the inside of No. 1, the gas A (usually air) in the hollow fiber leaks from the pinhole to the outside of the hollow fiber. The leaked gas A is discharged together with the gas B, and is inspected by the thermal conductivity detector 16 at a substantially constant flow rate, so that it is easily confirmed that the pinhole portion has passed through the tubular body.

The position of the pinhole can be easily determined based on the detection timing of the gas flowing out from the pinhole on the peripheral wall of the hollow fiber and the moving speed of the hollow fiber. For example, if the running speed of the hollow fiber and the recording system of the thermal conductivity detector are synchronized, the position of the pinhole can be easily known based on those records after the inspection for a certain period of time is completed.

As the thermal conductivity detector of gas, various thermal conductivity detectors (generally TC
Abbreviated as D), and any one is used. In the present invention, when the gas A flowing out from the pinhole is mixed with the gas B which is the seal gas, a partial change in the thermal conductivity of the seal gas occurs, and the occurrence of the change in the thermal conductivity is caused by the heat transfer. By instantly reading with a degree detector,
It is possible to instantly and easily detect the time point when the portion where the pinhole is formed passes through the cylindrical body. As described above, the measurement of the thermal conductivity of the gas by the thermal conductivity detector can be performed at high speed and with high accuracy. Therefore, in order to industrially detect the variation of the thermal conductivity of the gas according to the present invention, the thermal conductivity of The use of detectors is particularly advantageous.

Depending on the thermal conductivity detector, in addition to detecting leak gas from the pinhole of the subject, even moisture adhering to the subject surface may not be detected, and high-precision detection may not be possible. In such a case, a means for trapping and removing substances other than the gas A and the gas B from the gas sent to the thermal conductivity detector may be provided between the cylindrical body and the thermal conductivity detector.

In addition, it is possible to return the gas used for the detection by the thermal conductivity detector to the gas introduction part and to circulate and use the gas.

It is also possible to use a thermal conductivity detector equipped with a detection probe and insert the probe into the cylindrical body to detect the thermal conductivity of gas.

Next, examples of the present invention will be described.

Example 1 A polypropylene hollow fiber wound with a bobbin (outer diameter 1 mm,
An inner diameter of 0.5 mm and a length of 1000 m) was set in the running system as shown in FIG. 1, and the inside of the cylindrical main body 11 (tunnel) was run at a yarn speed of 10 m / min and was rewound to another bobbin. Air exists in the hollow portion of the hollow fiber.

The cylindrical body contains helium as a seal gas on both sides.
Flow at a constant flow rate of 0 cc / min and 2 to the thermal conductivity detector.
Suction was introduced at a constant flow rate of 50 cc / min. Helium was used as a reference gas for the thermal conductivity detector. After the rewinding operation was completed, inspection of the chart of the recorder connected to the thermal conductivity detector revealed peaks of air leaking from the pinholes at positions 450 m and 910 m from the start position.

After the above operation, when the same yarn was inspected again by the same operation, a peak of the same size was detected at the same position as the first time.

Next, when the portion of the yarn showing the existence of pinholes on the chart of the recorder connected to the thermal conductivity detector was sampled and observed under a microscope, it was thought that this portion was pin-formed that occurred during the yarn-making process. The hall was discovered.

[Example 2] A bobbin wound polyimide hollow fiber for gas separation (outer diameter 0.3 mm, inner diameter 0.1 mm, length 5000 m) was used in the same manner as in Example 1 at a yarn speed of 30 m / min. I changed it to a bobbin. Since air exists in the hollow part of the hollow fiber, helium was used as the seal gas.

After rewinding, check the chart of the recorder connected to the thermal conductivity detector, 4726 m from the start position.
One peak of leaked gas (air) was observed at the position.
When this portion was sampled and observed under a microscope, one scratch that was considered to be due to a mechanical cause was found.

[Example 3] In the same manner as in Example 2, a trap cooled with dry ice / methanol was used between the tubular body and the thermal conductivity detector.

Surface defect 1 in the inspection of 3000m winding pyrimido hollow fiber membrane
I found an individual.

Example 4 A vinyl chloride tube (outer diameter 5 mm, inner diameter 3 mm, length 5)
00m) was inspected in the same manner as in Example 1. As a result of the inspection, no defective portion was detected.

Next, after making a pinhole by inserting a needle at a position 30 m from one end of the above tube, this tube was inspected by the method of Example 1. As a result of the inspection, one peak of leaked gas (air) was observed in the recorder connected to the thermal conductivity detector. The position of the defect calculated from the chart coincided with the position where the needle was previously placed.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a detection device suitable for carrying out the method of the present invention for continuously inspecting the peripheral wall of a hollow fiber to detect the position of a pinhole formed in the peripheral wall. . 11: Cylindrical main body (tunnel) 12: Hollow fiber 13, 14: Openings functioning as inlet and outlet of the hollow fiber 12 15a, 15b: Gas introduction section 16: Thermal conductivity detector 17a, 17b, 18a, 18b: Running system 19: Gas outlet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masao Kikuchi, 8-1 Goi Minamikaigan, Ichihara-shi, Chiba Ube Industries, Ltd. Chiba Research Institute (56) References JP-A-58-129230 (JP, A) Kai 56-22922 (JP, A) JP 53-130086 (JP, A) JP 50-147787 (JP, A) JP 53-46053 (JP, Y2)

Claims (3)

[Claims] 1. A gas different from the gas in which a hollow elongated body having a hollow portion having a diameter of 10 mm or less and containing the gas A in the hollow portion is set to a condition lower than the pressure of the gas A in the hollow portion. The gas A flowing in the atmosphere of B and flowing out from the pinhole of the peripheral wall of the hollow elongated body is detected by utilizing the difference in thermal conductivity between the gas B and the mixture of the gas A and the gas B. A method for detecting the position of a pinhole in a hollow elongated body from the detection time and the moving speed of the hollow elongated body. 2. The method for detecting the position of a pinhole in a hollow elongated body according to claim 1, wherein the hollow elongated body is a hollow fiber. 3. The gas A is air, nitrogen or oxygen, and the gas B is
The method for detecting a pinhole position in a hollow elongated body according to claim 1, wherein is helium.