SU1649337A1 - Method of testing air-tightness - Google Patents

Abstract

The invention relates to the control of the leaktightness of articles by a manometric method and makes it possible to increase the reliability by eliminating the influence of the capillary effect in the knee of a liquid manometer. The cavity of the product, which is under pressure control, is connected to the measuring knee of a liquid manometer. The knee is filled with fluid by communicating with the source of fluid, moving the source of fluid parallel to the axis of the knee in the direction of possible movement of the liquid column in the knee from the leakage of the product. When the liquid reaches the zero mark, they separate the knee and the source of the fluid, register the position of the liquid column in the knee relative to the reference mark. By this provision, the degree of leakage of the product is judged. 3 il.

Description

The invention relates to instrumentation engineering and allows monitoring the leaktightness of products by a manometric method.

The aim of the invention is to increase the reliability by eliminating the influence of the capillary effect in the knee of a liquid manometer.

FIG. 1 shows a diagram of an apparatus for implementing a method for monitoring a product leaktightness; in fig. 2 - the same, with excessive pressure in the product; in fig. 3 - the same, when evacuating the product.

The device contains a pressure gauge elbow in the form of a capillary 1, a reading ruler 2 fixed on the capillary 1. The source of liquid — compensatory tank 3 — is fixed on the actuator 4 of the reciprocating motion and connected by a flexible pipe 5 through the valve 6 to the cavity of the capillary 1 bellows 7. The latter is located in the cavity of the gas chamber 8,

connectable with cavity of controlled product 9.

The position of the liquid in the capillary 1 and the compensation tank 3 is characterized by the difference in height D h (Figs. 2, 3).

In the initial position of the device, the valve 6 is open. The fluid is installed in some position inside the capillary 1 and the compensation tank 3. S In general, the method is used to measure the leakage either with an increase in pressure in the controlled cavity 9 or with a decrease in pressure in it.

In the case of leakage measurement with an increase in pressure in the controlled product9 (the case is realized if the product is loaded with excessive gas pressure and it flows into the cavity of chamber 8), the position of the compensation tank 3 sets the liquid column in capillary 1 so that its level is below the zero line mark 2. Using the drive

t iff - jWra

And the tank 3 rises, which will cause the liquid level in the capillary 1 to rise. When the level approaches the zero value of the ruler 2 smoothly, the valve 6 closes and the monitoring time begins. In the case of leakage of the product 9, the liquid column in the capillary 1 continues to rise for a predetermined time, and the magnitude of this rise is determined by the amount of leakage.

With this method of measurement, the capillary forces AR determined by the dependence

2 7COS0

DR

R

where is the surface tension;

в- boundary angle of the meniscus fluid;

R is the radius of the capillary 1, are compensated by the action of the elastic forces of the bellows, i.e. the movement of the liquid column does not depend on the action of the capillary forces.

The analysis of the above dependence shows that the larger the microchannel radius, the smaller the capillary forces. And they can be eliminated by increasing the diameter of the microchannel, and not by this method. However, the sensitivity in this case decreases due to the error in determining Ah.

In the case of leakage measurement at a pressure drop in a controlled product, product 9 is evacuated, and leakage occurs through leakage from the cavity of product 9. By positioning the compensation tank 3, the liquid column in the capillary 1 is set so that its level

was above the zero line of the ruler 2. The compensation tank 3 is lowered by the actuator 4, which causes the liquid level in the capillary 1 to decrease. When the zero value is gradually approached, the valve b closes and the control time begins. In this case, the capillary forces are compensated by the elasticity of the bellows and excluded from the process of tightness control.

A positive effect is also the expansion of the range of use of liquids for pressure gauges, which makes it possible to reject

Claims (1)

harmful fluids such as mercury. Claim Method The method for monitoring the leaktightness of a product by connecting the cavity of the product under control pressure with measuring the knee of a liquid manometer, filling the knee with liquid by communicating it with a source of liquid, disconnecting the knee and the source when the liquid reaches the reference point, registering the position of the liquid column in the knee relative to the reference point, judging by the degree of product leakage, characterized in that to increase credibility by eliminating the effect of the capillary effect in the knee, filling the knee with liquid is carried out by moving the liquid source parallel to the axis of the knee in the direction of the possible movement a column of fluid in the knee from the leakage of the product. 2 Editor B, Trubchenko Compiled by L. Vihl ev Techred M. Morgenthal FIG. J Proofreader O. Kravtsov