RU2180738C2 - Method testing articles for leak and device for its realization - Google Patents

Abstract

FIELD: testing equipment. SUBSTANCE: in accordance with proposed method standard article is connected to tested space to adjust and test tightness, leak detector is connected to this space at phase of test of additional space with controllable volume which makes it possible to change pressure in tested space and to simulate effect of leak with high accuracy with the help of simple and accessible tools. This approach allows accuracy of quality inspection of articles by degree of lack of tightness to be raised as it presents possibility to adjust and test devices testing tightness with high accuracy and to set threshold for quality inspection in process of their usage. Device for realization of method can employ injector if article is tested under low test pressure both in chamber and out of it and barrel from bellows mechanically deformed in process of chamber-free test if testing pressure is high. EFFECT: increased accuracy of quality inspection of articles according to degree of leaking. 4 cl, 2 dwg

Description

 The invention relates to testing equipment, namely to control the tightness of products, mainly by air.

 A known method of testing products for leaks, implemented in the device according to US patent 3331237, class. 73-40, 1967, which consists in the fact that the test gas pressure from the preparation unit through the test line is fed into one of the chambers of the differential pressure gauge, and along the discharge line into the other chamber of the differential pressure gauge and into the product under test. The device is configured according to the graphs of the relationships between the volume of the test product and the leakage of the test gas, depending on the pressure drop.

 A disadvantage of the known test method is the difficulty of setting up the device for its implementation.

 For the prototype adopted the method of testing products for leaks, implemented in the device by and.with. 761867, cl. G 01 M 3/26, 1980, which consists in the fact that a pressure drop in the gas is created on the walls of the test or reference product or part thereof, a leak detector is connected to the cavity being monitored, when testing the reference product in the control phase, an acceptable gas leakage flow is established, at the same time, the steady-state indication of the leak detector during the monitoring phase is taken as the rejection threshold.

 The disadvantage of this method of testing products for leaks is the lack of accuracy of adjustment and verification, since the measurement of microflows is a problem in itself and is performed with a large error. There are no classical flow meters (differential pressure across the diaphragm or rotameters) for measuring microflows. As a rule, indirect methods of measuring microflows, for example, heat flow meters, are used for this. In addition, in the known device for implementing the method, the device for performing tuning and calibration is difficult in hardware terms - these are three complex independent devices: a flow meter, a pneumatic throttle with a conductivity setting and an electro-pneumatic valve. And it’s expensive to equip each device for testing products for leaks with such a calibration device. The weight and dimensions of the device are also large. It must also be said that in the known method is not provided and impossible to control the tightness of the cavity of the measuring system, which also reduces the accuracy and reliability of the control. All of the above applies to both tubeless and chamber methods for testing products for leaks, when the controlled product is placed in the chamber and the cavity of the chamber becomes the controlled cavity.

 The objective of the invention is the improvement of the method and device for monitoring products for tightness.

 The technical result is an increase in the quality of products due to the greater accuracy of tuning and calibration of instruments for tightness control.

где Q - допустимый поток утечки газа;
t - время фазы контроля;

Для достижения указанного выше технического результата также предлагается при испытании эталонного изделия измененный объем контролируемой полости удерживать не меньше времени фазы контроля и по уменьшению показаний детектора утечки судить о негерметичности полости измерительной системы.To achieve the named technical result in the known method of testing products for leaks, which consists in the fact that on the walls of the controlled or reference product or part of them create a gas pressure drop, a leak detector is connected to the controlled cavity and, when testing the reference product in the control phase, set the rejection threshold by changes in the volume of the controlled cavity by:

where Q is the allowable gas leakage flow;
t is the control phase time;

To achieve the above technical result, it is also proposed that when testing the reference product, the changed volume of the controlled cavity should be held at least for the time of the control phase and judging the leakage of the measurement system cavity by decreasing the leak detector readings.

где Q - допустимый поток утечки газа;
t - время фазы контроля;

Дополнительно предлагается при реализации способа дополнительную полость выполнить в виде шприца, подпоршневая полость которого подключена к контролируемой полости.In the known device for monitoring products for leaks, containing a node for creating a differential pressure of gas on the walls of the controlled or reference products or parts of them, a gas leak detector connected to the controlled cavity and a device for setting and checking the device, connected in the control phase to the controlled cavity during testing the reference product, the named technical result is achieved by the fact that the device for tuning and calibration is made in the form of an additional cavity with the possibility of changing the volume and by the amount of:

where Q is the allowable gas leakage flow;
t is the control phase time;

Additionally, when implementing the method, it is proposed that the additional cavity be made in the form of a syringe, the piston cavity of which is connected to the controlled cavity.

 In the proposed method of testing the products for leaks and in the device for its implementation, the technical result achieved is achieved by the fact that the threshold for sorting the products according to the degree of leakage is set by connecting an additional cavity of a completely defined volume to the reference phase during testing of the standard (suitable) product, which causes the same change in detector readings as in the prototype, when installed using a choke with adjustable conductivity and a flow meter permissible, from the point of view of the customer or consumer, gas leakage flow and during the monitoring time, a rejection threshold is set on the differential pressure gauge. But in the proposed technical solution, this is done with greater accuracy, since the change in the volume of the volume connected to the controlled cavity is measured, in contrast to the measurement of the microflow in the prototype, with higher accuracy. This is done faster with a simple and inexpensive tool or measuring tool. Therefore, verification can be done according to the regulations more often or in cases where doubts arise during the testing or when the manufacturing technology of products is being developed.

т. е. при камерных испытаниях в камере, образованной вокруг изделия или части его, абсолютное давление равно атмосферному.For chamber tests, the above formula will take the form:

i.e., during chamber tests in the chamber formed around the product or part of it, the absolute pressure is equal to atmospheric.

где Р_исп - испытательное давление газа, подаваемого в полость изделия.For tubeless tests, the above formula will take the form:

where P _isp - test gas pressure supplied into the cavity of the article.

 In FIG. 1 shows a device for implementing the method for chamber tests of the product for tightness, figure 2 - for tubeless tests.

 The device contains a leak detector 1 connected to the controlled cavity 2, an additional cavity 3, configured to change the volume and connect to the controlled cavity 2. As the tested product 4, the brake wheel cylinder assembly without rubber antisplash caps from the ends is used. As an additional cavity 3, there is a piston cavity of the syringe 5, the volume of which is changed using the piston 6. The rejection threshold is set according to the indications of the scale of the indicating device 7 with a movable contact pair 8, which turns on the relay 9 of the control circuit when the arrow reaches the rejection threshold. In chamber tests, the controlled cavity 2 is formed by the cavities between the ends of the product 4 and the sealing gaskets 10 mounted on the ends of the clamp 11, mechanically connected to the drive (not shown in the drawing), the cavities of the measuring system tubes and the submembrane cavity of the detector sensor 1. In tubeless tests, the controlled cavity 2, where the leak detector 1 is connected, the cavity of the test product 4, the cavity of the connecting tubes of the measuring system, and the submembrane cavity of the detector 1 sensor serve.

 The method is as follows.

After assembly and installation of the device, installation or test bench for testing the product for leaks, it is necessary to configure and verify these devices. To do this, using any method of tightness control, find the reference product 4. In the syringe 5, by moving the piston 6, the required volume of the additional cavity 3 is established using the above formula. For chamber tests, the change in the volume of the additional cavity 3 is equal to:
ΔV = Q • t.

 A cavity 3 with a fixed volume is connected to a controlled cavity 2. And then the whole test technology is performed sequentially. After sealing the reference product 4, a test pressure of gas or air is fed into its cavity, and upon completion of pressure stabilization and transient processes, the piston 6 of the syringe 5 is moved into the cavity of the product 4 until the volume of the cavity 3 changes to zero. This increases the pressure in the controlled cavity 2, simulating an increase in pressure from leakage, and the arrow of the device 7 moves to a certain value on the scale of the device. At this value, the movable contact 8 is established and it is taken as the rejection threshold.

Установившееся значение по шкале прибора 7 принимают за порог разбраковки и на этом значении устанавливают подвижный контакт 8.In tubeless tests, after attaching an additional cavity 3 to the controlled cavity of the product 4, the volume of the cavity 3 is set equal to zero, and after the test gas or air is supplied to the product 4 and the end of transient processes in it, the cavity volume is increased by the value determined by the formula:

The steady-state value on the scale of the device 7 is taken as the rejection threshold and a movable contact 8 is established at this value.

 Examples of the method.

The following instruments were used in the experiments:
- as a detector sensor 1 during chamber tests, a low-limit sensor for measuring pressure "Metran - 45 - DI" model 5110 with an upper limit of measurement of 10 mm of water. Art. and output signal 0 ÷ 5 mA;
- a recording device 7 of type M - 286 K with a scale limit of 0 ÷ 5 mA;
- relay 9 type RES - 22;
- as an additional cavity 3 - piston cavity of the syringe with a volume of 1 cm ³ ;
- as a sensor of detector 1 during tubeless tests - a differential sensor "Metran - 44 DD", model 2410 with an upper limit of measurement of 10 mm of water. Art. and output signal 0 ÷ 5 mA;
- as products 4, wheel brake cylinders assembled without rubber dirt caps installed from the ends of the cylinders were used.

 Example 1

При этом стрелка прибора 7 устанавливалась на значении 2,2 мА, на этом значении устанавливается подвижный контакт 8 и оно принималось за порог разбраковки. Теперь при испытании штатных изделий 4, если поток утечки будет больше, чем 1,2 см³/мин, то такое изделие будет отбраковываться, так как при его испытании произойдет замыкание контакта 8 за установленное время фазы контроля.Must be rejected as shown in FIG. 1 product 4 with leakage Q≥1.2 cm ³ / min, control phase time t = 6 sec. After sealing the reference product 4 in its cavity fed test pressure P _isp = 1 kgf / cm ² and, after 2 seconds, when the pressure in the cavity of the product 4 was stabilized and ended transients to the controlled space 2, which includes a cavity between the ends of product 4 and gaskets 10, the tube cavity of the measuring system and the submembrane cavity of the detector 1 sensor, a syringe 5 was connected and, by moving the piston 6, its volume was changed (decreased) by

In this case, the needle of the device 7 was set at a value of 2.2 mA, a movable contact 8 was established at this value, and it was taken as the rejection threshold. Now, when testing standard products 4, if the leakage flow is greater than 1.2 cm ³ / min, then such a product will be rejected, since when it is tested, contact 8 will close in the set time of the control phase.

 Example 2

.It is necessary to reject the product 4 according to the scheme in figure 2 with leakage Q≥1.2 cm ³ / min, the control phase time t = 6 sec. In the cavity of the reference product 4 was fed a test pressure P _isp = 1 kgf / cm ² and, after 2 seconds, when the pressure in the cavity of the product 4 was stabilized and ended transients volume controlled cavity 2 (cavity articles 4) by moving the piston 6 increased by the value:

.

In this case, the needle of the device 7 was set to a value of 2 mA, with this value, contact 8 was established and it was taken as the threshold for rejection. Now, when testing standard products 4, if the leakage flow in it is greater than 1.2 cm ³ / min, then such a product will be rejected, since when it is tested, contact 8 will close in the set time of the control phase.

 Example 3

In the measuring system (Fig. 1), an incision is made in one of the tubes. After changing the volume of the controlled cavity by 0.12 cm ^{2, the} arrow of the device 7 deviated by 2.2 mA, but after 6 seconds the readings of the device 7 changed (decreased) to 2.12 mA, i.e., the results of this experiment can be said about leaks measuring system.

 Thus, the proposal of the authors allows with greater accuracy than in the prototype, to check the products for leaks, since the adjustment of the manufactured devices to control the tightness and calibration during operation is made with greater accuracy. The verification device is simple, very accessible during operation, inexpensive and not bulky. Also, the authors' proposal allows us to control the tightness of the measuring system, which also increases the accuracy of tuning and calibration of instruments for monitoring the tightness of products.

 And it is precisely the reliability and accuracy of the tightness of the measuring system that can be detected when the rejection threshold is set quickly. Against the background of a slow and long-term change in the output signal during the entire monitoring phase to the rejection threshold value, as in the prototype, the leakage of the measuring system cannot be detected, since changes in the output signal from the leakage of the product and the cavity of the measuring system are directed in different directions.

Claims (2)

1. The method of monitoring products for tightness, namely, that on the walls of the controlled or reference products or parts of them create a gas pressure drop, a leak detector is connected to the controlled cavity and, when testing the reference product in the control phase, a rejection threshold is set, characterized in that the threshold sortings are established by changing the volume of the controlled cavity when testing the reference product by the amount of:

where Q is the allowable gas leakage flow;
t is the control phase time;

2. The method according to p. 1, characterized in that the changed volume of the controlled cavity of the reference suitable product can withstand at least the time of the control phase and to reduce the leak detector readings are judged about the leakage of the cavity of the measuring system. 3. A device for implementing a method for monitoring products for tightness, comprising a unit for creating a gas pressure drop on the walls of a controlled or reference product or parts thereof, a gas leak detector connected to a controlled cavity, and a device for tuning and checking the device connected in a controlled phase to a controlled cavity when testing a reference product, characterized in that the device for tuning and calibration is made in the form of an additional cavity with the possibility of changing the volume by

where Q is the allowable gas leakage flow;
t is the control phase time;

4. The device according to p. 3, characterized in that the additional cavity is made in the form of a syringe, the piston cavity of which is connected to the controlled cavity.

Images