SU1343257A1 - Method of checking articles for leak-proofness - Google Patents

Abstract

The invention relates to a test technique and permits an increase in accuracy and sensitivity by eliminating the effect of a pressure change in the reference capacitance, which is achieved by compensating for the 1st change in the volume of the cavity of the measuring tube connected to the reference capacitance. The product 4 is placed in a storage tank 3. The test gas is connected to the cavity of the measuring tube 1, which is equipped with a piston 2. The other cavity of the measuring tube is connected to the reference capacity 5 of a variable volume. Test pressure is created in the cumulative and reference containers 3 and 5 and the pressures in them are equalized before starting the measurements. Fill product 4 with test gas. The operation of measuring the speed of the p-displacement of the piston 2 in the measuring tube 1 is performed, which corresponds to the degree of tightness of the product 4. At the same time, the pressure in the reference tank 5 is kept constant by increasing its volume by reducing the volume of the cavity of the measuring tube 1 associated with the reference capacitance 5. The method provides testing for tightness at pressures other than atmospheric. 1 il. (L / "13 so 4; ii with hO SL

Description

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Itobristeyie relates to testing equipment, in particular to methods for monitoring tightness.

The aim of the invention is to improve the accuracy and sensitivity of the tests by eliminating the effect of a change in pressure in the reference capacitance by measuring the variation in the volume of the cavity of the measuring tube connected to the reference capacitance.

The drawing shows a setup diagram for implementing the method.

The installation includes a measuring tube 1 with a piston 2 placed in it, for example, drop mercury. Measuring tube 1 is connected by one cavity with accumulative capacity 3, into which test product 4 is placed, and the other cavity with reference capacity 5, having a variable volume and made for example in the form of a bellows box, the movable bottom of which is connected through a hinge 6 with an arrow 7, and the fixed bottom is connected by means of a slider 8 to a guide 9. The slider 8 is connected via a cylindrical hinge 10 to an arrow 7 and a bolt 11 to fix the slider 8 relative to the guide 9. The reference capacitance 5 is connected to a storage tank 3 awn through the valve 12 and the vacuum pump 13 or a source of test medium (depending on the test conditions) The two containers 5 and 3 are connected via a valve 14.

The method is carried out as follows.

The test article 4 is placed in the accumulation tank 3. The valves 12 and 14 are opened with the help of the vacuum pump 13 and the vacuum tank 13 is created in the accumulation tank 3 and in the reference tank 5, the bellows box of which is compressed.

The storage tank 3 and the reference tank 5 are kept with the valve 12 open until the pressure in them is equalized, then the valve 12 is closed and the vacuum pump 13 is disconnected by closing the valve 14 from the reference tank 5 and the storage tank 3. Test gas is supplied into the product 4. Before the operation of measuring the degree of non-geometricity of the product 4, the arrow 1 is combined with the division on the scale of the measuring tube 1 corresponding to the initial

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the position of the liquid piston 2 by moving along the guide 9 of the slide 8 with the movable bottom of the bellows box of the reference container 5 and the cylindrical hinge 10 of the arrow 7 attached. After reaching the initial value of the pressure gauge 2 in the measuring tube 1, the position of the arrow 7 is fixed by fixing the slide 8 on the direction 9 bolt 11. Turns on the stopwatch, fixes the initial position of pressure 2, which is driven by the pressure of the test gas,

entering the storage capacity

3 through product discontinuities 4.

Tracing the position of the liquid piston 2, the arrow 7 and its associated through the movable bottom of the reference container 5 are moved, which causes an increase in its internal volume by an amount compensating for the decrease in the volume of the cavity of the measuring tube 1 associated with the reference capacity 5 the piston 2 under the effect of an increase in pressure in the storage tank 3 due to the leakage of test gas from the product 4. After a predetermined

time, the distance that the piston 2 has moved is measured, and the degree of leakiness of the product is determined

4 according to the formula

35

 ,R"

Lt

meas

0

Where

tr

q - the degree of leakage

products 4 (m Pa / s); i1 is the distance that the liquid piston 2 moved during the measurement; - area of the internal cross section of the measuring tube - 5ki 1;

Pn is the pressure in the storage tank 3 at which the measurements were made. Maintaining the equality of the pressures 0 before carrying out the measurement operation in the storage tank 3 and the reference tank 5, and thus on the ends of the pressure chamber 2, ensures that its position is kept in the measuring tube 1 non-g depending on the pressure change in the storage tank 3.

The operation of measuring the speed of movement of the piston 2 is carried out at a constant pressure of the reference tank 5,

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made in the form of bellows of variable volume.

The increase in this volume in the measurement process by an amount that compensates for the decrease in the volume of the cavity of the measuring tube 1 associated with the reference capacitance 5 increases the accuracy of measurements.

In addition, a decrease in pressure in the storage tank 3 increases the sensitivity of the measurements, since it causes a larger displacement of the piston 2 in the measuring tube 1 with the same increase in the volume of test gas in the storage tank 3. Increasing the sensitivity of this method reduces the measurement time.

The method of testing products for leaktightness can be implemented both with an overpressure in the accumulative tank 3 and the reference tank 5, and when evacuating these tanks 3 and 5, i.e. The value of the test pressure is chosen from technological considerations, for example, ensuring the minimum labor intensity of the tests in the chain, taking into account the technical characteristics of the test product 4.

It is also possible to carry out the method when creating a test pressure in the internal cavity of the product 4, in this case the measuring cavity

Compiled by S. Malkevich, edited by S. Patrushev Tehred M. Didyk Proofreader S. Cherni

Order 4801/42 Circulation 776 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

7

The tubes are connected to the internal cavity of the product 4. Next, with the product 4, all the operations described above are carried out with storage tank 3.

Claims (1)

Invention Formula A method for testing products for leaktightness, which involves creating appropriate test pressure in the reference container and storage tank and / or in the internal cavity of the product, reports the reference a container with a storage tank or with an internal cavity of the product prior to pressure equalization, disconnecting the reference container and determining the degree of product leakage by the speed of movement of the piston in the measuring tube connected by one cavity with the storage tank or with the cavity of the product, This means that, in order to increase accuracy and sensitivity by eliminating the effect of pressure changes in the reference capacitance, the variation in the volume of the measuring tube is compensated, union of the reference capacitance by equal to it in magnitude variation of the reference volume container.