JPH03210449A - Method for testing liquid leak - Google Patents

Abstract

PURPOSE:To enhance the reliability of a judgement result by setting the minute rising quantity of the pressure in an inspection system circuit generated corresponding to the volume of the air remaining in the inspection system circuit when the volume in the inspection system circuit is minutely reduced to a judging standard. CONSTITUTION:A supply system circuit is provided on the upstream side of a valve 4 and an inspection system circuit is provided on the downstream side thereof and the pressure in the inspection system is detected by a pressure sensor 7. After the pressure is raised to test pressure, the judging standard of the hermetic sealing property in a liquid leak test set on the basis of the hermetic sealing degree required in an object 5 to be inspected is set with respect to the volume in the inspection system circuit and the volume in the inspection system circuit is minutely reduced by the volume corresponding to the tolerant leak amount when a test liquid leaks from the object 5 to be inspected during an inspection time to minutely raise the pressure in the inspection system circuit and, thereafter, the inspection system circuit is allowed to stand in this state for a definite detection time and the hermetic sealing property of the object 5 to be inspected is judged on the basis of the falling degree of the pressure in the inspection system circuit during the detection time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid leak test method performed to determine whether or not the airtightness of a container or the like is good or bad.

[Prior Art] Generally, in the case of containers etc. that require airtightness, it is checked during quality control during the manufacturing process or after the product is completed whether or not the container etc. has the desired airtightness. A leak test will be performed to confirm. Leak tests include methods that use gas and methods that use liquid, and one of them is selected and adopted as appropriate depending on the usage conditions of the test object (the container, etc.).

Among these, a leak test using a liquid (hereinafter referred to as a liquid leak test) is conventionally performed as follows.

A test liquid such as water is filled into the test circuit to which the container to be tested is connected via the supply circuit, and the pressure inside the test circuit is increased to a predetermined test pressure.

Next, the test system circuit is cut off from the supply system circuit and left for a certain detection time. Then, depending on whether or not a pressure drop occurs in the test system circuit during this detection time, and if there is a pressure drop, whether or not the amount of pressure drop within the detection time is within the allowable range, the test target is determined. The quality of the seal is determined.

[Problems to be Solved by the Invention] By the way, ideally speaking of a liquid leak test, when the test system circuit is filled with a test liquid, a layer of compressible fluid such as air should not be formed in the test system circuit. is desirable.

However, in reality, although it is possible to design the test system circuit to have a structure that makes it difficult for air to remain, it is impossible to completely eliminate air.

On the other hand, considering the fact that it is inevitable that a residual air layer will be formed in the test circuit, if a liquid leak test is performed on the same test object using the same method, there will always be a residual air layer in the test circuit. If some volume of air remains, it will not pose a problem in determining whether the airtightness is good or bad. However, even when the same liquid leak test is performed on the same test object, the actual situation is that the volume of residual air differs each time the liquid leak test is performed.

In this way, if the volume of air remaining in the test circuit differs, even when testing objects that originally have exactly the same degree of sealing, the volume of air remaining in the test circuit will vary. This resulted in a difference in the rate of pressure drop, which indicates the state of leakage of the test liquid from the test object, resulting in a lack of accuracy in determining whether the sealing was good or bad. Specifically, when the volume of residual air in the test system circuit is large, the amount of pressure drop during the detection time is small, and when the volume of residual air in the test system circuit is small, even if the detection time is the same, the above case will occur. The pressure drop I becomes larger. Therefore, even when the same test object is tested, depending on the state of residual air in the test system circuit, there are times when the sealing performance is determined to pass and other times when it is determined to be failed.

This invention has been made in view of the problems of the prior art described above, and its purpose is to provide a liquid leak test method that improves reliability when determining whether the sealability of an object to be tested is good or bad. It's there.

[Means for solving the problem] This invention was made to achieve the above object,
The gist is that in the liquid leak test method, the test object is filled with a test liquid and the pressure is increased to a predetermined test pressure, and then the degree of pressure drop is used to judge the sealability of the test object. After increasing the pressure inside the test system circuit to a predetermined test pressure, the test system circuit is closed, and immediately after that, the internal volume of the test system circuit is slightly reduced by the volume corresponding to (a) below, and the test system circuit is closed. A liquid leak test in which the pressure of the test object is slightly increased, and then left for a certain detection time, and the sealing quality of the test object is determined based on the degree of pressure drop in the test system circuit during the detection time. It's in the method.

(B) The acceptable leakage amount in the case where the test liquid leaks from the test object during the above detection time, which is a criterion for determining whether the seal is good or bad in a liquid leak test, which is set according to the degree of seal required for the test object.

[Function] After increasing the pressure in the test system circuit to the test pressure, if the internal volume of the test system circuit is slightly reduced as described above, the pressure in the test system circuit increases slightly, but the magnitude of the pressure increase is are uniquely determined depending on the volume of air remaining in the test system circuit. Then, the determination of whether the airtightness of the object to be inspected is good or bad is performed as follows based on the individual pressure rise amounts that have occurred corresponding to the volume of the residual air.

After slightly increasing the pressure in the test system circuit, the test system circuit is closed and left for the detection time 1. If the amount of pressure drop in the test system circuit is within the above pressure rise on each side, it is determined that the degree of sealing of the test object is within the allowable range and the test is passed, and the pressure in the test system circuit is If the amount of drop exceeds the amount of pressure rise between the sides, the degree of sealing of the object to be inspected is out of the permissible range, and it is determined to be a failure.

Since it becomes possible to make a pass/fail judgment regarding the airtightness as described above, a correct judgment can always be made even if the volume of air remaining in the test system circuit is not constant.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings from FIG. 1 to FIG. 6.

FIG. 1 is a schematic flowchart of a liquid leak test. A test liquid l such as water is pressurized by a pump 2, reduced to a predetermined test pressure Pli by a pressure reducing valve 3, and then supplied to a test object 5 through a valve 4. still,
In the case of this embodiment, the upstream side of the valve 4 becomes the supply system circuit, and the downstream side becomes the inspection system circuit. The pressure within the inspection system circuit can be detected by a pressure sensor 7. This test system circuit is equipped with a calibrator 6 that reduces the internal volume of the test system circuit. The calibrator 6 is
For example, it is composed of a cylinder and a piston, and the cylinder communicates with the test object via a connecting pipe, etc., and by pushing the piston, a certain amount of test liquid stored in the cylinder is pushed out into the connecting pipe, etc. It can be considered that

However, the configuration of the calibrator 6 is not limited to this, and it goes without saying that the calibrator 6 may have other configurations as long as it has the above-mentioned functions. Note that when installing the calibrator 6, care must be taken so that air pockets do not form in the calibrator 6 when the test system circuit is filled with the test liquid.

Change in internal volume of the test system circuit due to the calibrator 6 ffi
V c is determined from the liquid leak test conditions and sealability criteria before starting the actual leak test. For example, a certain test object is tested with water at a pressure P t = 2 k
g/cm'', and assuming the average value of the volume of air remaining in the inspection system circuit, the passing criteria for the liquid leak test under these conditions is ``inspection system circuit''. Test pressure inside Pt = 2 kg/c
After increasing the pressure to +e', the test system circuit is cut off from the supply system circuit, and when it is left as is for a certain detection time 1o = lo seconds, the leakage of the test liquid from the test object is the allowable leakage j
lVI2-1cc or less. ”. Then, the change in internal volume of the test system circuit due to the calibrator 6 ffi
V c is the same volume as the above allowable leakage amount v (i.e., V
c-VQ-1cc).

It should be noted that whether air vent valves or drain valves are appropriately installed in the above-mentioned inspection system circuit is omitted from illustration.

Next, an actual liquid leak test method will be explained.

First, the test object 5 is filled with the test liquid 1 as described above, and the pressure in the test system circuit is set to the test pressure Pt = 2 kg.
/cm'. It goes without saying that at this time, the calibrator 6 is also filled with the test liquid, and the pressure inside it also becomes the test pressure pt.

Next, the valve 4 is closed to cut off the inspection system circuit from the supply system circuit.

Immediately thereafter, the calibrator 6 is activated to reduce the internal volume of the test system circuit by the capacity of the VC. Then,
The pressure inside the test circuit increases slightly. The pressure increase fidP at this time is uniquely determined according to Hoyle's law in accordance with the volume of air remaining in the test system circuit before the calibrator 6 is activated. FIGS. 2 to 5 are graphs in which the vertical axis represents this minute pressure increase amount dP, and the horizontal axis represents time. If the pressure in the test system circuit increases by c (7) due to the operation of the calibrator 6 when the volume of air remaining in the test system circuit is actually the expected average value assumed in advance, then When the volume is less than the expected average value above, the pressure increase amount is j larger than yP above.
When the volume of residual air is larger than the expected average value, the amount of pressure increase appears as dP, which is smaller than dP.

Note that this pressure increase amount dP is about 1 to 2 mml, O, which is extremely small compared to the test pressure P t = 2 kg/cffi2, and is on the order of being almost negligible. Therefore, the test pressure can be considered to be approximately equal in either case.

After activating the calibrator 6, the test system circuit is left as it is for a detection time t0. If there is no leakage of the test liquid 1 from the test object 5, there will be no fluctuation in the pressure in the test system circuit even while the test object 5 is left standing, and the amount of pressure increase based on the operation of the calibrator 6 will be dP+, tiP, , jPs. In either case, FPt+dPJ is maintained. (See Figure 2) By the way, the following phenomenon has been confirmed through experiments. As mentioned above, the amount of pressure increase etP due to the operation of the calibrator 6 differs depending on the volume of air remaining in the test system circuit, but the degree of sealing of the object to be tested is on the pass line of the above-mentioned criteria. If it is, the detection time [. If the test circuit is left for a while, the pressure in the test system circuit will drop by an amount corresponding to the above-mentioned pressure increase amount dP in each case. The curves shown by solid lines in FIGS. 3 to 5 represent this.

Therefore, as shown by the two-dot chain lines in FIGS. 3 to 5, the detection time t. Even after the lapse of time, the test system circuit still has the pressure increase amount ciP in each case.
If there is no pressure drop corresponding to 3, JP, , dP, the degree of sealing of this inspection object 5 is within the permissible range, and a pass is determined. On the other hand, as shown by broken lines in FIGS. 3 to 5, the detection time t. If the pressure drop in the test system circuit reaches the pressure rise ↑dPs, tiPt, dP in each case before , the degree of sealing of this test object 5 is out of the permissible range. , a judgment of failure is made.

In this way, according to this liquid leak test method, even if the volume of air remaining in the test system circuit differs for each leak test, it is possible to determine whether the airtightness of the test target is good or not. This eliminates the possibility of erroneous judgments, and the reliability of pass/fail judgments in liquid leak tests is significantly improved compared to conventional methods.

The above-mentioned embodiment is a liquid leak test method in which the pressure inside the test object 5 is detected based on atmospheric pressure, and the degree of drop in this pressure is used to determine whether the test object is airtight. In the leak test method, a reference object called a master, which is known to have no or almost no leakage, is used to measure the pressure drop due to leakage of test liquid from the test object 5 between the master and the test object. There is also a method in which the above judgment is made based on the detection based on fluctuations in the differential pressure that occurs between the two.

FIG. 6 shows a schematic flowchart when the present invention is implemented in the liquid leak test method using the differential pressure check method described above. Hereinafter, the same reference numerals will be given to the same parts as in the flowchart of the first embodiment, and the explanation will be omitted, and only the different parts will be explained. Test liquid 1 is supplied through valve 4 to both test object 5 and master 8 at the same time. The inspection object 5 and the master 8 can be communicated with and shut off by another valve 9. Further, the pressure sensor 10 can measure the differential pressure generated between the inspection object 5 and the master 8. In the case of this embodiment, the upstream side of the valve 9 serves as the supply system circuit, and the downstream side thereof serves as the inspection system circuit.

In the case of this second embodiment, both the test object 5 and the master 8 are first filled with the test liquid 1, and the internal pressures of both are increased to the test pressure pt.

Next, valves 4 and 9 are closed. The test system circuit is cut off from the supply system circuit by the valve 9, but at this point, the pressure inside the test object 5 and the master 8 is the same, so the pressure sensor 1
No differential pressure appears at 0.

Immediately after closing the valves 4 and 9, the calibrator 6 is activated to reduce the internal volume of the test system circuit by the volume Vc set based on the same concept as in the first embodiment. Then, as in the case of the first embodiment, the pressure inside the test system circuit increases slightly corresponding to the volume of air remaining in the test system circuit, and this pressure increase of 11 dP is due to the difference between the master 8 and the test system circuit. A positive value appears on the pressure sensor 10 as a differential pressure. After this, the test circuit is left alone for a detection time t0. In the case of this liquid leak test method, the pressure drop in the test system circuit due to the leak of the test liquid appears as a decrease in the differential pressure. The determination of whether the airtightness is good or bad is made at the detection time t. If the differential pressure is a positive value after the elapsed time, the test is passed, and if it is a negative value, the test is rejected.

This invention is not limited to the above-described embodiments, and various embodiments can be adopted.

For example, the calibrator may be connected directly to the test object.

In the case of the above-mentioned embodiment, the decrease i1 Vc in the internal volume of the test system circuit is defined as ice, but this decrease amount is set depending on the degree of sealing required for the test object, and rVc = It is not limited to 1 cal.

[Effects of the Invention] As explained above, according to the present invention, when the internal volume of the test circuit is slightly reduced in determining whether the airtightness of the test object is good or bad, the air remaining in the test circuit is Since the judgment criterion is the amount of minute increase in pressure in the test circuit that occurs in response to the volume of This has the excellent effect of greatly improving the reliability of the determination results.

[Brief explanation of drawings]

The drawings from Fig. 1 to Fig. 6 show an embodiment of the present invention, Fig. 1 is a schematic flowchart of the liquid leak test method in the first embodiment, and Fig. 2 to Fig. 5 respectively show an inspection system. A graph showing the change in pressure in the circuit over time,
FIG. 6 is a schematic flowchart of a liquid leak test method in the second embodiment. l...Test liquid, 5...Test object, 6...Calibrator.

Claims (1)

[Scope of Claims] In a liquid leak test method in which a test object is filled with a test liquid, the pressure is increased to a predetermined test pressure, and the sealing quality of the test object is determined based on the degree of the subsequent pressure drop, the test object is connected. After increasing the pressure in the test system circuit to a predetermined test pressure, the test system circuit is closed, and immediately after that, the internal volume of the test system circuit is slightly reduced by the volume corresponding to (a) below, and the test system is closed. A liquid that slightly increases the pressure in the circuit, then leaves it for a certain detection time, and determines whether the sealing quality of the test target is good or bad based on the degree of pressure drop in the test circuit during the detection time. Leak test method. (B) The acceptable leakage amount in the case where the test liquid leaks from the test object during the above detection time, which is a criterion for determining whether the seal is good or bad in a liquid leak test, which is set according to the degree of seal required for the test object.