SU847113A1 - Method and device for testing article air-tightness - Google Patents

Description

(54) METHOD FOR CONTROLLING THE TIGHTNESS OF THE PRODUCT AND DEVICE FOR IT. IMPLEMENTATION

one

The invention relates to mechanical engineering, in particular to leak detection technology.

A known method of detecting leaks with the help of gases containing halogen, which consists in filling the test object with pressure and containing a halogen-containing gas, and scanning it with a detector sensitive to halogen along its surface to determine its outflow. A device for implementing this method contains a sensor, valves, a pump and a measuring unit 1.

The disadvantage of this method is its instability, as well as the effect on the results of tests of atmospheric impurities, and the disadvantage of the device is the small lifetime of the sensitive element of the sensor and the need to replace it or regenerate it.

There is a known method for detecting a gas leak with an ultrasonic leak detector, which means that the leak points are recorded with the help of a narrow-beam acoustic sensing element 2.

The disadvantage of this method is its low sensitivity, and the disadvantage

acoustic leak detector - its poor immunity from industrial shumov.

The closest to the technical essence of the invention is a method for monitoring the leaktightness of products, which consists in filling the product with gas under pressure, scanning the surface of the product with a sensing element of the sensor, and places of leakage are determined by changing the readings of the recording device. A device for implementing this method contains a thermoelectric sensor and a measurement system f3.

The disadvantage of this method is low reliability of control due to random changes in humidity in ambient air, as well as its inapplicability for testing products that do not allow contact with moisture-containing gas, and the lack of a device for implementing this method is instability of readings and reduced sensitivity during prolonged operation.

Claims (3)

The purpose of the invention is to increase the reliability of the control. The goal is achieved by moistening the sensing element of the sensor, and tightness is judged by the change in its conductivity. A device for implementing a method for monitoring the leaktightness of products is provided with a humidifier installed under the sensor's sensing element and includes a heating element, a vessel with an alcohol-water mixture and a wick, one end of which is placed in the vessel and the other is connected to the heating element. FIG. 1 shows the structure of the sensing element; in fig. 2 - schematic diagram of the device. The design of the sensing element contains a guide 1 for a stream of dry air, a guide 2 for humid air, a protective grid 3, an opening 4 for moist and dry air, p-p transitions 5 of the transistor, housing 6, the leads of electrodes 7. The device contains a humidifier 8 consisting from a vessel 9 filled with a mixture of 10 water and alcohol, a wick 11 and a heating element 12, a thermoelectric sensor 13 in the form of a T1 transistor with a pnp conductivity, made of germanium by a alloy or alloy-diffusive method, for example, MP 42, bias resistance R and limiting resistance Kg, the outputs of which are connected to the base and collector circuits of the transistor T 1, the recording unit 14, which includes a resistor Rj - voltage divider, resistors I4 - Rg, which together with the T2 transistor form a bridge circuit, a microammeter 15 included in the diagonal of the bridge circuit. The emitter terminal of the transistor T1 and the second terminal of the resistor Ri are connected to the + power supply 16, and the second terminal of the resistor Ri is connected to the silicon transistor base. T2 of the recording unit 14. Re-distributing unit 14 is also connected to the power supply 16. The method is carried out as follows. Before the measurement, the device is switched on and the resistor R is balanced against the bridge of the microammeter 15 by balancing the bridge circuit of the recording unit 14 (Fig. 2). Then, the vessel 9 is filled with a mixture 10 of water and alcohol and the heating element 12 of the humidifier 8 is turned on. At the same time, through the alcohol-water wick 11, the mixture enters the heating element 12, where it evaporates, humidifies through the guide 2 moist air and hole 4 npp transition 5 of the transistor T1 (Fig. 1 and Fig. 2). The impact on the pn junction of the transistor T1 of moisture causes an increase in the conductivity of the base-collector of the transistor T1, the transistor opens. The differential resistance of the emitter-collector transitions of the T1 transistor decreases, the current flowing through the emitter-collector transition of the T1 transistor and the resistors Ra, Ra of the measurement circuit of the unit 14 increases, causing a change in the collector-emitter resistance of the T2 transistor. As a result, the balancing of the bridge measurement circuit is violated, and through the diagonal of the bridge resistor Re microammeter 15, collector-emitter of transistor T2, resistor R; A current flows which the microammeter 15 deflects to the maximum position. To determine the leakage location, the sensitive element facing the dry air guide B to the plane of the object to be monitored (not shown) is scanned along its surface. In the case of leakage in a controlled object, a stream of air under pressure flows out of the defect and enters through the guide 1, the hole 4 on the pn junction 5 of the transistor T1 of the scanned sensing element (Fig. 1 and Fig. 2), bringing its numbered junction to wet which causes a change in its conductivity and an imbalance of the bridge circuit, which is recorded by the microammeter 15. The use of a humidifier in the circuit of the device increases the reliability of the leak location. Claim 1. A method for monitoring the leaktightness of products, which consists in filling the product with gas under pressure, scans the surface of the product with a sensitive element of the sensor, and by changing the readings of the recording device, the place of leakage is determined, in order to increase the reliability of control, The sensing element of the sensor is moistened, and the tightness is judged by the change in its conductivity. 2. A device for implementing the method according to claim 1, comprising a thermoelectric sensor and a measuring system, characterized in that it is equipped with a humidifier installed under the sensitive element of the sensor and includes a heating element, a vessel with a mixture) and a wick, one end which is placed in a vessel, and the second is connected to the heating element. Sources of information taken into account in the examination 1.Lanis $. A., Levin, L. E. Vacuum Testing Technique. M., Gosenergoizdat, 1963, p. 150, 186. 2. USSR author's certificate number 442414, cl. G 01 M 3/02, 1972. 3. US patent number 3703356, cl. G 01 N 31/12, 1971 (prototype). g c ////