RU1837170C - Method for testing articles for tightness - Google Patents

Description

WITH

1) 4500563/28.

2) 10.24.88

6) 08/30/93. Bull. Number 32

1) The head design bureau of the Scientific and Production Association of Energy named after S.P. Koroleva

(12) L.V. Lipn kLE.V. Shcherbakov and N.G. Panov (56) Lanis V.A., Levina L.E. Vacuum test technique. M.-L.: Gosenergoizdat, 11363, p. 242-244.

(5

4) METHOD FOR TIGHTNING THE PRODUCT

ABOUT

7) The invention relates to testing equipment and can be used to control bulky products with increased requirements for tightness. SUBSTANCE: method for controlling tightness of products consists in

that the product is placed in a vacuum chamber with a leak detector, the chamber is evacuated to the minimum steady-state pressure, the initial concentration of control gas is measured in the chamber, the vacuum is resumed to the minimum steady-state pressure, a calibrated control gas tray is fed into the chamber, the evacuation is stopped, and the control concentration is measured from the calibrated stream, stop its supply and again vacuum to the minimum steady-state pressure, fill the product with control gas, stop the vacuum tion and the measured concentration of the control gas from the article, but the leak is judged to change the test gas concentration in the vacuum chamber 1-yl,

The invention relates to test equipment and can be used to control large items with increased requirements for hermetically |

I The closest in technical essence to the proposed method is the method, which consists in placing the product in a vacuum chamber with a leak detector connected to it, vacuuming the vacuum chamber to the minimum steady-state pressure, stop vacuuming the vacuum chamber, and record the pressure change Pi in vacuum chamber during Ati and measure the initial horse

centralization of the control gas in the vacuum chamber a at time ti, the vacuum chamber is evacuated to a minimum steady state pressure, the product is filled with control gas, the vacuum chamber is stopped evacuating and the concentration of control gas from the product ag is measured at time t, and the tightness of the product Odis is judged by the change in the concentration of the control gas in the vacuum chamber from the ratio

00

Cs

VI

i

Q

ed;

5-1 ()

-b APiV Lee

f ai-a. (D)

(1)

where V is the free volume of the vacuum chamber. Along with the advantage of this method, due to the accumulation of the control gas in the vacuum chamber, the sensitivity of the control can be significantly increased, its main disadvantage is its low accuracy. This circumstance is explained by the following reasons. Coefficient 5 10 in relation (1) is determined based on the fact that 1/200000 part of the air in the lower layers of the atmosphere is the control gas helium, and the reaction of the leak detector n must be a reaction to this particular concentration. The actual concentration of the control gas in the vacuum chamber differs from that taken due to either its presence in the gas evolution products from the outer surfaces of the controlled product or its ingress through leakages of the vacuum chamber from the surrounding room with a high gel content. Thus, the reaction of the leak detector and in most cases does not correspond to that accepted for the initial reaction to the concentration. When the minimum steady-state pressure is reached in the vacuum chamber. The process of accumulating the control gas, which occurs after the vacuum chamber ceases to be evacuated, characterized by a change in the pressure of the DR over time At, is stabilized, i.e. at a stabilized initial pressure in the vacuum chamber, the final pressure, measured after the accumulation time At, differs insignificantly and the differences in the absolute values of AP and At affect insignificantly the leakage value of Oec. However, taking into account the nonlinear characteristic of the dependence of the sensitivity of the leak detector S on the pressure in the chamber of the mass spectrometer R (see the drawing), even slight deviations in the final pressure in the vacuum chamber and, accordingly, in the chamber of the mass spectrometer lead to significant changes in the sensitivity of the leak detector S and, accordingly, deviations in the readings of the leak detector, which in turn affects the accuracy of the estimation of the leakage value.

The aim of the invention is to increase the accuracy of the tightness control of products.

The goal is achieved. that according to the method by which the product is placed in a vacuum chamber with a leak detector connected to it. vacuum. a vacuum chamber to a minimum steady-state pressure,

stop the vacuum chamber evacuation and measure the initial concentration of the control gas in the vacuum chamber, resume vacuuming the vacuum chamber to the minimum steady state pressure, fill the product with control gas, stop vacuuming the vacuum chamber and measure the concentration of control gas from the product, and the tightness of the product is judged to change the concentration of the control gas in the vacuum chamber, before refueling the product, a calibrated control gas is fed into the vacuum chamber, stop zooming the vacuum chamber and measure the concentration of the control gas in the vacuum chamber from the calibrated flow, stop the flow of the calibrated flow and again vacuum the vacuum chamber to

minimum steady-state pressure

moreover, the measurement of the concentration of the control gas after the cessation of vacuum in the process of increasing pressure in

the vacuum chamber and the chamber of the leak detector mass spectrometer are carried out at the moment when the pressure of the leak detector in the mass spectrometer chamber reaches the optimum sensitivity, and the tightness of the article is estimated taking into account the change

concentration of the control gas in the vacuum chamber from the calibrated flow.

Taking into account that the value of the calibrated control gas flow O ™ obeys relation (1). we have

.

P-s 1P-6 ARTP U (“TP P, Otp-5-10 -. (-}

Att

"1

where A P ™ is the change in pressure in the vacuum chamber 40 during the time A tTn after a calibrated flow is supplied;

"Mp is the concentration of the control gas in the vacuum chamber from the calibrated flow at time trn.

From relations (1) and (2) we have

45

("Tp -" 1)

DR1 Ati

x A tm

And RTg,

(3)

If the gas evolution and leakage flows in the vacuum chamber after stabilization, the vacuum chamber vacuum process is several orders of magnitude greater than the values of the calibrated control gas flow or the control gas flow through the leakage of the product, i.e.

AP ™.

Aim

(4)

o with a sufficient degree of accuracy, you can discount the leakage of the product in the following ratio:

Oizd - QT

("2 -" 1) ("tp -" 1)

about at the same time taking readings

for all measurements of the concentration of the control gas in the vacuum chamber, the same pressure must be carried out in the chamber of the leak detector mass spectrometer, which ensures constant sensitivity of the device.

I Thus, the accuracy of the method is improved by linking the measurements of the leak detector to a specific pressure in the chamber of the leak detector mass spectrometer, {i.e. due to stabilization of sensitivity | of the geo-detector and, ultimately, of the entire test system.

The selection of the optimum pressure in the chamber of the leak detector mass spectrometer is carried out in the process of evaluating the sensitivity of the test system, depending on the required minimum. registered Leaks in controlled products |

; In addition, the accuracy of the proposed method of tightness control is increased by calibrating the leak detector not by the absolute concentration of the control gas in the lower atmosphere, but by the change in concentration formed by the supply of a calibrated jro flow of the control gas to the vacuum chamber .

; The proposed method is carried out as follows. The product is placed in a | vacuum chamber with a detector connected to it, and the vacuum chamber is vacuumized to a minimum steady-state pressure. Stop vacuuming the vacuum chamber and measure the initial concentration of the control gas in the vacuum chamber1 while increasing the pressure IB of the vacuum chamber and the mass spectrometer chamber of the leak detector at the moment the pressure detector reaches the mass spectrometer chamber, the sensitivity of the leak detector which meets the specified requirements - | m control, i.e. pressure sensitivity. Resume vacuuming of the vacuum chamber to the minimum steady-state pressure.

A calibrated Q ™ control gas stream is introduced into the vacuum chamber. Stop the vacuum chamber vacuum and measure the concentration of the control gas in the vacuum chamber from the calibrated flow a ™ in the process of increasing the pressure in the vacuum chamber and the chamber of the leak detector mass spectrometer at the moment the pressure detector in the mass spectrometer chamber is reached

10 optimal sensitivity. Stop the flow of the calibrated flow and again vacuum the vacuum chamber to the minimum steady-state pressure. The product is charged with test gas.

15 Stop the vacuum chamber vacuum and measure the concentration of the control gas from the product during the pressure increase in the vacuum chamber and the chamber of the leak detector mass spectrometer

20 is the moment when the pressure detector reaches its optimum sensitivity in the chamber of the mass spectrometer. The tightness of the Oizd product is judged by the change in the concentration of the control gas in the vacuum chamber taking into account the change in the concentration of the control gas in the vacuum chamber from the calibrated flow from relation (5).

Claims (1)

The claims 30 A method for checking the tightness of products, by which they place the product in a vacuum chamber with a mass spectrometric leak detector connected to it, vacuum the vacuum chamber to the minimum steady-state pressure, stop the evacuation and measure the initial concentration of the control gas in the vacuum chamber, resume vacuum evacuation cameras up 40 minimum steady-state pressures, charge the product with control gas, stop evacuation and measure the concentration of control gas from the product, and the tightness is judged by the change 45 concentration of the control gas in the vacuum chamber, characterized in that, in order to improve accuracy, a calibrated flow of control gas is fed into the vacuum chamber before refueling, 50 stop vacuuming the vacuum chamber, measure and measure the concentration of the control gas in the vacuum chamber from the calibrated flow, stop supplying it and again vacuum the vacuum chamber to the minimum steady-state pressure, all measurements of the concentration of the control gas are carried out at the moment the mass spectrometer is reached in the chamber optimal pressure leak detector sensitivity, and the tightness assessment is made taking into account the change in concentration 50 100 150 200 control gas in the vacuum chamber from the calibrated flow. 250 300 350 400 P (μA-)