JPS6353488B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leak test device for performing a leak test on a device under test having an airtight flow path, such as a flow meter.

In equipment that handles fluids, such as flowmeters, the airtightness of the internal channels must be maintained. This is because if the fluid leaks, measurement errors may occur, and if the fluid is highly flammable, it may lead to accidents such as explosions.

Therefore, leakage tests are essential for devices such as flowmeters. Conventionally, when performing this leakage test, gas is sealed inside the device under test.
Tests were conducted to determine whether there was a leak by measuring pressure changes inside the equipment.

However, in tests that measure pressure changes inside devices, it is well known that when gas is sealed in a container with a constant volume, the pressure within this volume also changes depending on the temperature. Therefore, it also has the inconvenience that temperature correction must be performed when performing high-precision measurements such as leakage tests. Furthermore, the method using pressure changes requires a long test time;
The drawback was poor work efficiency.

This invention has been made with attention to the above points, and an object of the present invention is to provide a leak test device that can reliably determine the presence or absence of leakage.

Furthermore, another object of the present invention is to provide a leakage testing device that can sensitively detect even the slightest leakage from a device under test.

In order to achieve the above object, a leak test apparatus according to the present invention is equipped with a density meter and is configured to detect changes in gas density inside a sealed device under test.

An embodiment of the present invention will be described below with reference to the drawings.

1a, 1b...1n each indicate a plurality of devices under test such as flowmeters, one flow path of each device under test is blocked, and the other flow path has control valves 2a, 2b... A test channel 3 is connected via 2n. Reference numeral 4 denotes a density meter, which is capable of measuring the gas density within the test channel 3.

The density meter 4 is a vibrating density meter, and as shown in FIG. The vibration of the vibrating tube 20, which changes in inverse proportion to the change in density of the fluid to be measured passing inside and outside the vibrating tube 20, is electromagnetically detected by the receiving coil 22, and the vibration can be detected directly. Or it can display the so-called gas leakage amount by counting and displaying the difference from the amount of gas sealed in advance through the calculation unit 23, 5 is a vacuum tank, 6 is a vacuum pump, 7 is a pressure sensor, and 8 is a pressure regulator. , and the vacuum tank 5
The gas inside is sucked by the vacuum pump 6, and the pressure inside the vacuum tank 5 is constantly detected by the pressure sensor 7, and the pressure regulator 8 controls the vacuum pump 6 to maintain the pressure inside the vacuum tank 5 at all times. It is now possible to maintain a constant value, for example 1500mmAg. This vacuum tank 5 is connected to the test channel 3 via a control valve 9. Reference numeral 10 denotes a control section that controls and monitors the entire leak test apparatus, and a specific example of its configuration is shown in FIG.

In the figure, 11 is a timer that generates a signal when a preset time has elapsed after the start of the test, and 12 is a clock circuit that generates a clock pulse at fixed intervals (for example, 1 second) after receiving the signal from the timer 11. , 13 is a period measuring circuit for measuring the period of the signal obtained from the density meter 4, 14a and 14b
represent a first data hold circuit and a second data hold circuit, respectively, where the first data hold circuit 14a holds the first cycle data after the start of the test, and the second data hold circuit 1
4b is designed to always hold the latest cycle data in synchronization with the clock pulse. Further, 15 is a comparison circuit, and each data hold circuit 14a, 1
This is to compare the periodic data held in 4b. Reference numeral 16 indicates a judgment circuit, and the comparison circuit 15
Based on the comparison results of the devices under test 1a, 1b...1
It is designed to determine whether there is any leakage of n. 1
Reference numeral 7 denotes an input terminal for an output signal from the density meter, for example, if the density meter 4 is a vibrating density meter, an input terminal for a pulse signal such as a vibration frequency. 18 is a start button. Also, although not shown, the control unit 10
Also includes control circuits for the control valves 2a, 2b, . . . 2n, 9, etc.

In the above embodiment, the vacuum pump 6 is used to suck fluid, but it may instead be configured to discharge high-pressure fluid into the device under test.

The operation of the leak test device having the above configuration will be explained. First, as shown in FIG. 1, a desired number of devices under test are installed in parallel. The vacuum pump 6 is operated to bring the pressure inside the vacuum tank 5 to a specified value. When the control unit 10 is operated here, first the control valves 2a,
2b...2n open the control valves 9 while keeping them all closed. Then, the pressure in the test channel 3 containing the density meter 4 is set to a specific value that is balanced with the pressure in the vacuum tank 5. In this state, the control valve 9 closes and the test flow path 3
Since the test channel 3 is sealed, the signal obtained from the density meter 4 will not change over time unless there is any leakage in the test channel 3. In this way, first a leakage test is performed on only the test channel 3, and if it is normal, the test moves on to each device under test. For example, when first testing whether there is a leak in the device under test 1a, the control valves 2a and 9 are opened for a certain period of time, and then the control valve 9 is closed, so that the test channel 3 and the device under test 1a are connected to one closed flow. It will form a road. In this case, the test is first conducted on all meters under test, and if there is no leakage, the test is completed, and only when leakage is detected, the test is carried out one by one as described above to find the leakage meter. Try to shorten it. After the start of the test until the control valve 9 closes, the period measurement of the control unit 10 is regulated by the timer 11, and when a sealed flow path is formed, the period measurement is first performed by the vibrating density meter 4. The periodic data held in the first data hold circuit 14a is held in the first data hold circuit 14a. Subsequently, the periodic data is input to the second data hold circuit 14b at predetermined intervals, and the latest data is held there. Therefore, the first
The data hold circuit 14a always holds data corresponding to the fluid density inside the device under test 1a at the time of forming the sealed flow path, that is, immediately after the start of the test.
Since the data corresponding to the gas density at that time is held in the data hold circuit 14b, if there is no leakage in the device under test 1a, the data contents of both are the same, and the judgment circuit 16 determines that the data is normal. If there is a change, it is determined that there is an abnormality. When one test is completed in this manner, for example, control valve 2b is selected, the next device to be tested (for example, 1b and control valve 2b) is selected, and the same test as described above is automatically repeated.

As described above, the present invention has various advantages because leakage in the flow path is detected by measuring density. That is, compared to the conventional measurement of pressure changes, density measurement has a higher sensitivity, so the test time is extremely short, and there is a great advantage in automation. Furthermore, since the measured value does not change due to temperature, there is no need for temperature correction, making it possible to perform a leakage test extremely easily. Furthermore, if a plurality of devices under test are installed, each device can be tested for leakage in sequence simply by automatically switching the control valves, which improves work efficiency in the case of mass-produced products.

[Brief explanation of the drawing]

FIG. 1 is an overall block diagram showing an embodiment of the leak test device according to the present invention, and FIG. 2 is a control unit 10.
FIG. 2 is a block diagram showing an example of a specific configuration.
FIG. 3 is an explanatory diagram showing an example of a vibrating density meter. 1a, 1b...1n...Equipment under test, 2a, 2b
...2n, 9...control valve, 3...test flow path, 4...
Vibrating density meter, 5... Vacuum tank, 10... Control unit, 11... Timer, 12... Clock circuit,
13... Period measurement circuit, 14a... First data hold circuit, 14b... First data hold circuit, 15... Comparison circuit.

Claims (1)

[Claims] 1. A plurality of control valves branched and connected to a test flow path, a device under test having a connection port at one end connected to the plurality of control valves and a connection port at the other end being closed, and a vibrating density meter connected to the test flow path, one control valve connected to the other end of the vibrating density meter, and a constant pressure device connected to the one control valve;
a control section that applies a valve opening/closing signal to the operating end of each control valve and inputs a signal from the vibrating density meter, and the control section generates a signal when a predetermined time has elapsed in response to a start signal. a timer, a clock circuit that generates clock pulses at regular intervals after receiving a signal from the timer, a period measuring circuit that measures the period of the signal from the vibrating density meter, and an initial period from the period measuring circuit. a first data hold circuit that holds data; a second data hold circuit that always holds the latest periodic data in synchronization with clock pulses from the clock circuit; It consists of a comparison circuit that compares the signals of the hold circuit, and by switching the plurality of control valves, it detects leakage in the sealed flow path formed by the test flow path including the vibrating density meter and the device under test. A leak test device characterized by detecting each device.