RU1837184C - Method for testing articles for tightness - Google Patents

Abstract

The invention relates to test equipment, in particular to leak tests using a test gas. SUBSTANCE: product is placed in a vacuum. a camera that communicates with the leak detector. The leak detector is evacuated through a vacuum chamber until it reaches its operating pressure. Separate the vacuum chamber and the detector. A control gas is supplied to the chamber, the flow of which is chosen equal to the maximum allowable leak rate of the product. The value of the maximum increment of the leak detector readings is recorded. Fill the product with test gas and record the maximum increment of the leak detector readings. The leakage is judged by the difference in the measured increments. 2 ill.

Description

FIELD OF THE INVENTION The invention relates to testing equipment, in particular, to leak tests of space technology products.

The aim of the invention is to expand the range of leaks detected by making it possible to detect leaks in a product that is smaller than the sensitivity of the leak.

The method is illustrated in Fig. 1 and implemented as follows.

The product 1 is placed in a vacuum chamber 2 and the latter is evacuated to a pressure by means of vacuum means 3. The vacuum chamber 2 is communicated with a helium leak detector 8, opening valve 5. After the vacuum chamber communicates with the leak detector, the latter is evacuated through a vacuum chamber, for which they turn off their own vacuum means of the leak detector (for example, for the leak detector PTI-10; close the valve Throttle pumping). In the leak detector and the vacuum chamber, a pressure equal to the operating pressure of the mass spectrometer chamber of the leak detector (determined by the passport of the leak detector) is set. The operating pressure can be established, for example, by supplying a process gas (nitrogen) stream to the vacuum chamber throughout the entire test cycle. Separate the vacuum chamber 2 and the leak detector 8, closing the valve 5 and feed into the vacuum chamber the flow of the control gas (gel or its mixture) from the control leak 4, opening the valve 6, which is equal to the maximum permissible value of the leakage of the product. VacuSO reported

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a camera 2 with a geo-detector 8, opening the ventil 5, and record the maximum increase in the readings of the leak-detector. After the vacuum chamber is connected to the leak detector, the concentration of the control element in the vacuum chamber and the mass spectrometer chamber of the leak detector are diffusely equalized. The time for complete concentration equalization depends on the length of the line connecting the vacuum chamber and the leak detector, and on the pressure in the vacuum chamber, but does not depend on the concentration of the control gas in the vacuum chamber. This time can be determined from the ratio g L2 / (2D), where L is the length of the trunk; D is the coefficient of molecular diffusion (I Vacuum, 1980, v. 30, No. 8/9, p. 333). Concentrations are equalized in a fairly short time, the same for any leakage rates supplied to the vacuum chamber. This means that the amount of leakage supplied to the vacuum chamber can be judged by the acceleration of the increase in the readings of the leak detector after its communication with the vacuum chamber. The secondary leak detector (TLV) has an inertia, which means that, depending on the acceleration of the growth of the readings, its arrow deviates by a different maximum value, then returns to a steady level corresponding to the concentration of the control gas in the leak detector mass spectrometer chamber. Figure 2 shows the case when the increase in the concentration of the control gas in the mass spectrometer chamber of the leak detector is less than its sensitivity, i.e. having established the value of the leak detector readings, it is indistinguishably small in comparison with the initial concentration. Inertia of leak detectors - the value is not normalized. This means that the maximum flows of the control gas supplied to the vacuum chamber, which differ in size by a factor of two, do not cause a maximum increase in the readings on the portable instrument of the leak detector (VPU), which also differ by a factor of two, but for the same flows the maximum increase will be the same. for a larger flow - more, for less - less. That is why, in order to determine the reaction of the leak detector, a flow of control gas is introduced into the vacuum chamber equal to the maximum permissible leak rate of the product. Talking about increasing sensitivity in this case is not possible. The sensitivity of the measuring device is the ratio of the change in the signal at the output of the measuring device I to vkpyr. its changing measure e0

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nost is the quality of the measuring instrument, reflecting the immutability of its metrological properties i.e. the known values of the sensitivity and changes in the output signal of the measuring device uniquely determine the measured value. In our case, the known change in the output signal of the leak detector does not give a quantitative increase in the concentration of the control gas, but only allows us to quantitatively judge whether this increment is smaller or larger which is being compared.

Separate the vacuum chamber 2 and the leak detector 8, closing the valve 5, as well as the valve 6. Fill the product 1 with the test gas from the source 9 of the control gas pressure, opening the valve 7, to the working pressure, after which the vacuum chamber 2 is informed with the leak detector 8, opening the valve 5, and record the maximum increment in the readings of the leak detectors. If the maximum growth rate of the leak detector is greater than the registered one, this means that the leakage of the product is greater than the permissible value. This method does not allow a quantitative determination of the amount of leakage of the product (since it is less than the sensitivity of the leak detector), but it makes it possible to qualitatively determine whether it is larger than the permissible value of leakage of the product.

P r and. me r Tightness tests were carried out on one of the systems in the descent vehicle (CA) in a vacuum chamber. The value of the maximum increment of the leak detector readings from the calibrated control gas flow

Up to & ax, equal to the maximum allowable amount of leakage of the product, amounted to 0.3 V from the initial value. The value of the maximum increment of the leak detector readings from the product

The DOmax charged with the test gas to the operating pressure was 0.42 V from the initial value. These results made it possible to identify the experimental stage; processing, that the actual leakage of the system under test is greater than the allowable value of the leakage of the system.

The method is quite simple to operate and does not require additional development or refinement of existing equipment manufactured by domestic industry.

Claims (1)

SUMMARY OF THE INVENTION A method for monitoring the tightness of products, which consists in placing the product in a vacuum chamber, communicating it with a leak detector, supplying a test gas stream to it, recording the readings of the leak detector, filling the product with test gas and recording a change in the readings of the leak detector, characterized in that that, in order to expand the range of leaks detected by detecting leakage of the product, the value of which is less than the sensitivity of the leak detector, after the vacuum chamber communicates with the leak detector, the last vacuum through the vacuum chamber until 5 After measuring the working pressure in it, disconnect the vacuum chamber and the leak detector, select the test gas flow. Equal to the maximum allowable leakage rate of the product, re-inform the vacuum chamber with the leak detector, record the maximum increment of the leak detector readings, disconnect the vacuum chamber with the leak detector, after filling the product with control gas report the vacuum chamber with the leak detector and record the maximum increment of the leak detector readings. and the presence of leaks exceeding the maximum permissible value is judged by the difference in the measured increments. o (g ah about pi / & f