JP3701394B2 - Leak test method for thin specimens with helium leak detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak test method for thin objects that may be deformed by a pressure change of a drum can or a food package bag.
[0002]
[Prior art]
Conventionally, a submergence method and a soapy water application method are known as a leakage test method for this type of thin object. Also, as a method of testing for minute leaks, either inside or around the specimen is set to a helium gas atmosphere and the other is evacuated to a vacuum atmosphere. A method of detecting the presence or absence of mixed helium gas with a helium leak detector is also known. The helium leak detector ionizes gas molecules in a vacuum, selects only helium ions with a mass spectrometer tube and enters them into an ion collector, and can quantitatively detect helium gas leaking into the vacuum as an ion current.
[0003]
[Problems to be solved by the invention]
The above submerging method is based on testing a leak amount of about 8.8 × 10 ⁻⁴ Pa · m ³ / s, and the submerged specimen is left for 1 minute, for example. If it does not come out, it is a test method to make it a non-defective product.However, when the specimen is submerged, the surface of the water sways and it is difficult to visually observe the water, and the water bubbles adhering to the specimen rise when submerged. A distinction from water bubbles caused by leakage cannot be made, and this submersion method is actually limited to a leak amount test of about 10 ⁻² Pa · m ³ / s. The soapy water application method is not suitable for testing a large number of specimens because the specimen is soiled and the soap water is applied in anticipation of leaking points.
[0004]
In addition, the helium leak detector can perform a highly sensitive leak test because helium gas molecules are small and pass through a small gap, but this device requires that the test specimen be evacuated and the specimen is thin. Deforms due to its exhaust and is not suitable for product inspection. A leak inspection method called sniffer method is also known, in which the inside of a thin specimen is pressurized with helium gas and helium gas leaking to the outside is detected by a helium leak detector. It is not suitable for leakage inspection of food packaging containers or the like that must be sequentially filled with contents according to the manufacturing tact time.
[0005]
An object of the present invention is to provide a leakage test method that can be performed efficiently and with high sensitivity without causing deformation of a thin specimen.
[0006]
[Means for Solving the Problems]
In the present invention, the inside of the thin specimen is set to a normal pressure helium atmosphere, and then the outer circumference of the thin specimen is set to a micro vacuum pressure so that the thin specimen is not deformed by a vacuum pump. The above object was achieved by guiding the detector to a detector and testing the leakage of the thin specimen. In order to make the outer periphery of the thin test specimen have a fine vacuum pressure, the thin test specimen is placed in an airtight chamber provided with a gas introduction pipe provided with a flow rate adjusting valve and an exhaust pipe connected to a vacuum pump. While adjusting the amount of gas flowing in from the gas introduction pipe with the flow rate adjusting valve to such an extent that the test body does not deform, the exhaust pipe exhausts it to the atmosphere , and a part of the gas flowing through the exhaust pipe is led to the helium leak detector. This test is for leakage of the specimen.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an airtight chamber provided with a gas introduction pipe 2 and an exhaust pipe 3, and the gas introduction pipe 2 includes the chamber from the atmosphere. 1 is provided with a flow rate adjusting valve 4 for adjusting the amount of gas introduced into the exhaust pipe 3, and a differential of a dry pump that does not generate oil mist or the like for exhausting the gas in the chamber 1 in the exhaust pipe 3 An exhaust vacuum pump 6 was connected. The flow rate adjusting valve 4 is controlled by a pressure gauge 7 provided in the chamber 1 so that the inside of the chamber 1 has a constant set pressure. A gas inlet 9 of the helium leak detector 8 is connected between the test valve 5 of the exhaust pipe 3 and the vacuum pump 6. The helium leak detector 8 is a known one, and a small amount of gas introduced from the gas inlet 9 through a variable inlet valve 10 is ionized and led to a mass spectrometer tube, and predetermined ions such as helium ions are selected. The amount of leakage of various specimens is detected by detecting the ion current that flows into the ion collector and flows through the ion collector. Inside the chamber 1 is a thin specimen 11 such as a drum can or a food package bag, which is the subject of a leak test according to the present invention, and a gas mixed with helium gas at an appropriate concentration is sealed at normal pressure. A thin specimen 11 is received. When testing pharmaceutical and food packaging, a dry pump that does not use oil is optimal as the vacuum pump 6.
[0008]
If the thin specimen 11 is deformed at, for example, 80000 Pa, the effective flow rate of the vacuum pump 6 is 5 L / min (8.3 × 10 ⁻⁵ m ³ / s). If the adjustment valve 4 is adjusted so that an atmospheric flow rate of 6.64 Pa · m ³ / s can be obtained from the gas introduction pipe 2, the inside of the chamber 1 becomes a slight vacuum pressure and the test body 11 is deformed by the pressure. Never do. If there is a leaked part in the test body 11, helium gas leaks from the inside into the chamber 1 and is discharged to the outside together with the gas from the gas introduction pipe 2 through the exhaust pipe 3 and the pump 6. In the middle of the exhaust pipe 3, a part of the exhaust is led to the helium leak detector 8, and helium gas leaking from the test body 11 is detected. The flow rate adjusting valve 4 is controlled by a signal from a pressure gauge 7 so that the pressure in the chamber 1 becomes constant. The conventional pressurized vacuum method and sniffer method take time to exhaust because they are evacuated, but in the case of the present invention, the inside of the chamber 1 is set to a fine vacuum pressure, so only a very short time is required, and the leak test time is greatly reduced. it can.
[0009]
If nitrogen gas is introduced instead of introducing the atmosphere from the gas introduction pipe 2 and the helium leak detector 8 is set so as to detect the nitrogen gas, the background of 5 ppm helium gas contained in the atmosphere can be detected. It is possible to perform detection without being affected, and to perform highly sensitive leak tests. The flow rate of the flow rate adjusting valve 4, the exhaust speed of the vacuum pump 6, and the concentration of helium gas sealed in the test body 11 are appropriately changed depending on the amount of leakage to be detected and the detected concentration. For example, when it is desired to increase the detected concentration, the vacuum pump 6 The concentration of helium gas in the chamber 1 is substantially increased or the concentration of helium gas sealed in the test body 11 is increased by decreasing the exhaust velocity of the gas and reducing the introduction of air from the flow rate adjustment valve 4. . Further, when it is desired to shorten the leakage detection time, the response can be improved by increasing the pumping speed of the pump 6 within a range where the detected concentration is allowed.
[0010]
As shown in FIG. 2, a gas introduction pipe 2 provided with a flow rate adjusting valve 4 and an exhaust pipe 3 connected to a vacuum pump 6 are directly attached to the leak test specimen 11, and the test specimen 11 is attached to a helium atmosphere at normal pressure. If the gas is exhausted from the exhaust pipe 3 while adjusting the amount of gas introduced by the flow rate adjusting valve 4 in the same manner as described above, the leakage test can be performed without deforming the thin specimen 11. In this case, if there is a leakage portion in the test body 11, helium in the hood 12 enters the test body 11 and is detected by the detector 8. Also in this case, if a nitrogen gas is used instead of the helium gas and the leak detector 8 is set to detect a nitrogen gas, a highly sensitive leak test can be performed.
[0011]
【Example】
(Example 1)
In the chamber 1 shown in FIG. 1, a thin specimen 11 deformed at 80000 Pa in which helium gas having an appropriate concentration was sealed was placed. The test valve 5 was opened and differential pumping was performed by the dry pump 6. The effective pumping speed of the dry pump 6 was set to 5 L / min, and the flow rate adjusting valve 4 was set to obtain an atmospheric flow rate of 6.64 Pa · m ³ / s from the gas introduction pipe 2. The inside of the chamber 1 is maintained at a constant micro vacuum pressure of 5 × 10 ⁴ Pa so that the specimen 11 is not deformed, and there is a leak in the specimen 11 3 seconds after the dry pump 6 is operated. This was detected by the helium leak detector 8.
[0012]
(Example 2)
A thin sample test body 11 of a drum can deformed at 10 ³ Pa is provided with a gas introduction pipe 2 equipped with a flow rate adjusting valve 4 and an exhaust pipe 3 connected to a dry pump 6. The sample was placed in a hood 12 made of synthetic resin, the test valve 5 was opened, and differential exhaust was performed by the dry pump 6. The effective pumping speed of the dry pump 6 was set to 5 L / min, and the flow rate adjusting valve 4 was set to obtain an atmospheric flow rate of 6.64 Pa · m ³ / s from the gas introduction pipe 2. The chamber 1 is maintained at a constant micro vacuum pressure of 1328 Pa so that the test body 11 is not deformed, and that there is a leak in the test body 11 3 seconds after the dry pump 6 is operated. Detection was possible with the detector 8.
[0013]
【The invention's effect】
As described above, according to the present invention, after the inside of the thin specimen is set to a normal pressure helium atmosphere, the outer periphery of the thin specimen is set to a micro vacuum pressure that does not deform the thin specimen by a vacuum pump. The leak test is conducted by guiding the ambient atmosphere to the helium leak detector, so that a leak test can be performed without deforming a thin specimen that is easily deformed with a short exhaust time, and a highly sensitive test by changing the type and concentration of gas. There is an effect that can be performed .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of claims 1 and 2 of the present invention. FIG. 2 is an explanatory diagram of an embodiment of claim 3 of the present invention.
1 chamber, 2 gas introduction pipe, 3 exhaust pipe, 4 flow rate adjustment valve, 6 vacuum pump, 8 helium leak detector, 11 thin object specimen, 12 hood,

Claims (1)

Place the thin specimen in an atmospheric helium atmosphere in an airtight chamber with a gas inlet pipe equipped with a flow control valve and an exhaust pipe connected to the vacuum pump so that the thin specimen does not deform. While adjusting the amount of gas flowing in from the gas inlet pipe with the flow rate adjusting valve, the exhaust pipe exhausts it to the atmosphere , and a part of the gas flowing through the exhaust pipe is led to a helium leak detector to test the leakage of the thin specimen. A leak test method for a thin specimen using a helium leak detector.

Images