JP2006084263A - Gas leak inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas leak inspection device for finding a gas leak in an object under inspection by a simple means during gas tightness inspection. <P>SOLUTION: This gas leak inspection device comprises the object under inspection made up of piping, a gas tight container, etc., a gas quantitative feeder 50 for feeding a definite amount of gas to the object, a gas pressure controller 7 for controlling gas pressure in the object, and a flow meter 8 for measuring the amount of gas discharged from the object. The amount of gas flowing through the flow meter 8 is measured with respect to a certain gas pressure in the object while measuring the amount of gas flowing through the flow meter with respect to another gas pressure in the object. This device is characterized in that the amount of gas leak in the object during gas tightness inspection is found from the ratio of a difference in the measured gas pressures to a difference in the gas flow meter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leak inspection apparatus for quantitatively inspecting whether or not there is a leak in a completed pipe (including all accessories) and an airtight container at the time of completion inspection such as piping work.

  When performing normal gas piping, airtight inspection of the piping is performed at the time of delivery at the time of completion. After confirming that there are no leaks in the entire pipe, submit an airtight inspection report. However, this inspection report is of such a level that there is no leakage at the specified inspection pressure, and it is quantitatively performed as having a hermetic performance of several cc / min (or g / sec, etc.) at the specified inspection pressure. is not.

  Usually, when performing an air tightness check, it is confirmed that there are no bubbles by applying soapy water, etc., and there is no leakage. In addition, gas is sealed in piping at a specified inspection pressure, and after a certain amount of time (several hours to several tens of hours) is sealed, it is inspected after confirming that the pressure does not drop. However, in the former case, if the piping is long distance, it is a very difficult work, which may result in an inspection failure. In the latter case, even if pressure is applied and sealed, if there is a difference in temperature between morning and evening in the day, or a change in temperature in a short time, the volume change of the gas due to temperature will be extremely high. Therefore, the pressure is not always the same as the initial value at the time of sealing, and may be increased in some cases.

When testing with soapy water as in the past, piping is not always in a position that is easy to inspect. In this case, the test must be performed over the entire circumference, which may be difficult to implement. And if it has to be tested over its entire length, it is a very difficult task.
In particular, when a leak causes danger, an expensive apparatus such as a helium leak detector using helium gas is also commercially available as a more sensitive leak test apparatus. In this case, a helium gas not in the atmosphere is used for pressurization and a leak test is performed. If there is a leak, the leaked helium is present in that portion, so that the detector reacts. This also detects helium gas with a detector instead of seeing soapy water bubbles. In other words, it is a method for examining whether or not there is gas coming out from the leaking portion, and in principle it is the same method as soapy water. Therefore, as described above, the entire inspection section must be inspected thoroughly, and inspection requires a great deal of work.

  In view of the above-described problems, an object of the present invention is to provide a gas leak inspection apparatus capable of obtaining a gas leak of an object to be inspected at an airtight inspection by a simple means.

The present invention employs the following means in order to solve the above problems.
The first means controls an object to be inspected consisting of a pipe, an airtight container, etc., a gas fixed amount supply device for supplying a certain amount of gas to the object to be inspected, and a gas pressure in the object to be inspected. A gas pressure control device; and a flow meter that measures the amount of gas discharged from the object to be inspected, and measures the gas flow rate in the flow meter with respect to a certain gas pressure in the object to be inspected. The gas flow rate in the flow meter with respect to some other gas pressure in the inspection object is measured, and from the ratio of the difference in the gas flow meter with respect to the difference in the measured gas pressure, the inspection object at the time of the airtight inspection A gas leak inspection apparatus characterized by obtaining a gas leak amount.

According to the first aspect of the present invention, there is an advantage that all lines that are the objects to be inspected can be measured from one place at a time, and since the measurement data is also a flow rate value (mass flow rate conversion), it is quantitative. It becomes an expression.
In addition, since the measurement is simple and the whole can be inspected at once, it can also be used for periodic maintenance of the line as the object to be inspected, so that abnormalities can be detected early, and the line can be divided into several places in advance. If the pipes are separated by attaching, the check can be made for each part, and the abnormal part can be found quickly.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration of a gas leak inspection apparatus according to the invention of this embodiment. FIG. 2 is a diagram illustrating an example of a configuration of an inspection target applied to the gas leak inspection apparatus.
In these drawings, an inlet gas fixed amount supply device 50 includes a gas cylinder 1, a pressure reducing valve 2, a mass flow rate type flow rate control device 3, a pressure gauge 5, and a gas supply port 11. An outlet gas flow rate measuring device 51 is a gas introduction port. 12, a pressure gauge 6, a pressurization control device 7, a mass flow type flow meter 8, and an exhaust line 10. Further, the inspection object 54 includes an inspection object main body, a valve 61, a pressure gauge 62, and the like.
As shown in these drawings, the gas supply connection port 11 of the inlet gas quantitative supply device 50 of the gas leak inspection apparatus shown in FIG. 1 is connected to the measurement target line gas inlet 25 which is the inspection target 54 shown in FIG. Then, the gas to be measured is supplied, and the line gas outlet 26 of the object 54 to be inspected is connected to the flow measuring device connection port 12 shown in FIG. 1, and the mass flow type flow meter 8 of the outlet gas flow measuring device 51 is connected. Gas leak is measured by measuring the amount of gas passed.
Here, the inlet gas fixed amount supply device 50 only stably supplies a constant value of gas during measurement to the inspection object 54 shown in FIG. 2, and the pressurization device 7 provided in the outlet gas flow rate measuring device 51 is provided. In use, the internal pressure of the inspection target line (inspected piping) that is the inspection target 54 is changed, and the gas flow rate of the mass flow rate flow meter 8 at that time with respect to the applied pressure value (pressure gauge 6) is measured.

As described above, in the gas leak inspection apparatus according to the present embodiment, attention is paid to the phenomenon that the amount of gas leak from the inspection object 54 increases in proportion to the applied gas pressure, and is added to the outlet gas flow rate measurement apparatus 51 side. A pressure control device 7 for pressure is provided, and thereby the pressure is changed by two or more points. When there is a gas leak, a change occurs in the gas flow rate value of the mass flow type flow meter 8 on the outlet side. In this way, it is possible to inspect the gas leak by measuring only the change in the flow rate on the outlet side while keeping the flow rate on the inlet side constant. Apply this principle to measure the change in flow rate value with respect to pressure with only one mass flow meter on the outlet side, and quantitatively determine the gas that leaks stably and with high accuracy from the slope of the change. Can do.
In this case, since the measurement can be performed within the range of the relative accuracy (± 0.2%) as the accuracy of the catalog value of the mass flow type flow meter 8, a very high accuracy measurement is possible. It is possible to achieve 10 times the accuracy when measuring using absolute accuracy (± 2%).

FIG. 3 is a diagram showing a measurement example in the case where there is no leak in the inspection object 54. The horizontal axis is the pressure value measured by the pressure gauge 6 of the outlet gas flow rate measuring device 51 shown in FIG. It is the gas flow rate value measured by the mass flow type flow meter 8 of the outlet gas flow rate measuring device 51 shown in FIG.
As shown in the figure, when there is no leak in the inspected object 54, the mass flow type flow meter 8 does not decrease even when pressurized using the pressurization control device 7, so that the gas pressure is not affected. Indicates that the measured value of the flow rate is constant.

  FIG. 4 is a diagram showing a measurement example in the case where there is a slight leak in the inspection object 54. When the pressure of the pressurization control device 7 of the outlet gas flow rate measuring device 51 is increased, the mass flow rate flow meter 8 is shown. The measured value of the flow rate decreases. As can be seen from this example, whether or not there is a leak can be detected by detecting whether or not the flow rate value is decreased by increasing the pressure. When performing a higher airtightness inspection, if the flowmeter has a smaller range, it can be used up to the detection limit (reproducibility range) of the device.

  As described above, the gas leak inspection apparatus of the present invention is configured so that the gas flow rate measured by the mass flow type flow meter 8 with respect to a certain gas pressure measured by the pressure gauge 6 of the gas inspection target 54 and the inspection target 54 The gas flow rate measured by the mass flow type flow meter 8 with respect to some other gas pressure measured by the pressure gauge 6 is obtained, and the ratio (gradient) of the difference between the two gas flow rates with respect to the detected difference between the two gas pressures. ) And the amount of gas leakage of the object to be inspected is quantitatively determined from this ratio (gradient).

FIG. 5 is a diagram showing a configuration of an inlet gas quantitative supply device 50 different from the inlet gas quantitative supply device 50 of the gas leak inspection apparatus shown in FIG. 1, and a switching valve 20 is provided in series with the mass flow rate type flow rate control device 3. In both cases, a series body of the auxiliary circuit pressure reducing valve 21 and the switching valve 20 is connected in parallel with the series body of the mass flow rate type flow rate control device 3 and the switching valve 20, and the auxiliary circuit pressure reducing valve 21 is used. Thus, the gas is supplied from a separate circuit to the vicinity of the measurement pressure, the waiting time is shortened, and the efficiency is improved.
By configuring in this way, when the pipe capacity is large, if you want to measure in the range of minute leak amount, increase the supply flow rate, shorten the time to reach steady state, and shorten the measurement time be able to.

  FIG. 6 is a diagram showing the configuration of an inlet gas fixed amount supply device 50 and an outlet gas flow rate measuring device 51 different from the inlet gas fixed amount supply device 50 and the outlet gas flow rate measuring device 51 of the gas leak inspection apparatus shown in FIG. In the gas fixed amount supply device 50, a switching valve 20 is provided in series with the mass flow rate type flow rate control device 3, and the mass flow rate type flow rate control device 4 is provided in parallel with the series body of the mass flow rate type flow rate control device 3 and the switching valve 20. A series body of the switching valve 20 is connected, and the outlet gas flow rate measuring device 51 is provided with a mass flow type flow meter 8 in series with the switching valve 20, and further in parallel with the series body of the switching valve 20 and the mass flow type flow meter 8. A series body of the switching valve 20 and the mass flow type flow meter 9 is connected to the above.

By configuring in this way, it becomes possible to easily measure a large to small flow rate, and a plurality of flow meters (two or more) can be used to cope with various situations from a large leak amount to a small leak amount. Easy to use structure.
In the first stage, a large leak is also expected. In such a case, the measurement is performed using a large flow meter, and the structure is such that a small flow rate range can be measured later and a small amount of inspection can be carried out step by step. By arranging different ranges and making them smaller, it is possible to handle a wide range with a single device, and at the same time, it can be used more easily.

It is a figure showing the composition of the gas leak inspection device concerning the invention of this embodiment. It is a figure which shows an example of a structure of the to-be-inspected target applied to a gas leak inspection apparatus. It is a figure which shows the example of a measurement when the to-be-inspected target object 54 has no leak. It is a figure which shows the example of a measurement in case the to-be-inspected target object 54 has some leaks. It is a figure which shows the structure of the inlet gas fixed quantity supply apparatus 50 different from the inlet gas fixed quantity supply apparatus 50 of the gas leak test | inspection apparatus shown in FIG. It is a figure which shows the structure of the inlet gas fixed supply device 50 and the outlet gas flow measuring device 51 which are different from the inlet gas fixed supply device 50 and the outlet gas flow measuring device 51 of the gas leak inspection apparatus shown in FIG.

Explanation of symbols

1 Gas cylinder
2 Reducing valve 3, 4 Mass flow type flow control device
5,6 Pressure gauge
7 Pressure controller
8,9 Mass flow type flow meter
10 exhaust
11 Gas supply connection port
12 Flowmeter connection port
20 Switching valve 21 Auxiliary circuit pressure reducing valve 25 Measurement target line gas inlet 26 Measurement target line gas outlet 50 Inlet gas fixed supply device 51 Outlet gas flow rate measurement device 54 Inspected object (passing type)
61 Valve 62 Pressure gauge

Claims (1)

An object to be inspected consisting of piping, an airtight container, etc., a gas metering supply device for supplying a certain amount of gas to the object to be inspected, a gas pressure control device for controlling the gas pressure in the object to be inspected, A flow meter for measuring the amount of gas discharged from the object to be inspected, and measuring a gas flow rate in the flow meter for a certain gas pressure in the object to be inspected, and other in the object to be inspected Measuring a gas flow rate in the flow meter for a certain gas pressure, and obtaining a gas leak amount of an object to be inspected during an airtight inspection from a ratio of the difference in the gas flow meter to a difference in the measured gas pressure Characteristic gas leak inspection device.

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