SU1668929A1 - Method of quality control of cryogenic vacuum vessel heat insulation - Google Patents

Abstract

The invention relates to non-destructive testing of products and can be used to control the quality of cryogenic vacuum vessels. The purpose of the invention is to improve the accuracy and performance of the control. The quality control of vacuum heat insulation is performed by reducing the sound pressure or the power of acoustic radiation passing through the insulation normally to the surface of a cryogenic vessel. In this case, the emitter and the receiver of acoustic radiation are located on opposite sides of the insulating layer of the vessel. In order to increase the sensitivity of the method, the acoustic radiation propagating along the walls of the vessel is removed with the help of a damping material. 1 hp ff, 2 ill.

Description

The invention relates to non-destructive testing of products and can be used to control the quality of cryogenic vacuum vessels.

The purpose of the invention is to improve the accuracy and performance of the control.

FIG. 1 shows a diagram of the device that implements the proposed method, with a single microphone; in fig. 2 - the same, with two microphones.

The device (Fig. 1) contains a sound source emitter in the form of a loudspeaker 1. a generator 2 connected to it, installed inside a controlled vessel 3 receiving sound waves in the form of a microphone 4. and a sound meter 5 connected to the latter 5. An emitter controlled by a vessel is placed in the soundproofing chamber 6 and a receiver of sound vibrations.

The device (figure 2) contains a loudspeaker 7, placed inside a controlled vessel 8, microphones 9 and 10,

installed respectively inside and outside the controlled vessel 8 and connected to the comparison unit 11 to which the sound level meter 12 is connected. The loudspeaker 7 is connected to the generator 13. The sound insulation material 14 is placed around the perimeter of the vessel 8. In addition, the cover 15 is made of sound insulation material.

The method of quality control of thermal insulation of cryogenic vacuum vessels using the device (Fig. 1) is carried out as follows.

The loudspeaker 1 together with the generator 2 emit acoustic signals directed along the normal to the wall of the inspected vessel 3. Pass the vessel's interstitial space, acoustic radiation significantly reduces its power Microphone 4 installed inside the vessel captures the power of the radiation passing through the evacuated interstitial space. Signal strength is captured.

fe

oh oh

00

Yu

N) o

sound level meter 5 and corresponds to a certain value of residual pressure in between the wall space of the vessel.

According to the previously obtained calibration dependence, the power of the transmitted sound oscillations — the residual pressure in the interstitial space of the vessel — determines the degree of vacuuming of the interfacial space of the heat insulating layer of the cryogenic vessel.

The device (Fig 2) that implements the proposed method works as follows.

The loudspeaker 7 is placed inside the inspected vessel 8. The loudspeaker 7 emits acoustic signals directed normally to the bottom of the vessel 8. Inside the tested vessel 8 is also placed a microphone 9, which measures the power of the generated acoustic radiation.

From the outside of the vessel, i.e. On the other side of the heat insulating layer, opposite the loudspeaker 7, a microphone 10 is placed, which measures the power of the acoustic radiation transmitted through the heat insulating layer. The signals from microphones 9 and 10 are fed through a comparison unit 11 and a sound meter 12. Such a measurement scheme avoids the need to maintain a stable sound signal generated by the generator 13.

Sound vibrations propagating along the walls of the vessel 8 are extinguished using a special sound insulating material 14, such as a rubber band, tightly pressed to the wall of the vessel 8. A sound insulating material cover 15 is installed on the throat of the vessel 8, preventing sound waves from entering the air microphone 9. This reduces the level of interference affecting the measurement accuracy.

Acoustic radiation parameters - acoustic pressure or acoustic

power passing through the insulating layer is reduced. The drop in radiation power is recorded by sound oscillation receivers by microphones 9 and 10.

In this case, the magnitude of the fall in radiation power is proportional to the residual pressure in the space between the walls of the vessel 8.

Pre-calibration of the type of vessels being tested makes it possible to determine the degree of vacuuming of the interstitial space of the layer (residual pressure in the interstitial space of the vessel) and, consequently, the quality of the thermal insulation of the cryogenic vessel by the magnitude of the decrease in acoustic radiation power.

Claims (2)

1. A method of quality control of the thermal insulation of cryogenic vacuum vessels, based on the determination of the degree of vacuuming of the interstitial space of the thermal insulating layer of a cryogenic vessel, characterized in that to increase the accuracy and performance of control, on different sides of the insulating layer of the vessel, they install the emitter and receiver of sound vibrations, emit sound vibrations along the normal to the surface of the heat insulating layer using the radiator, receive sound vibrations transmitted through the layer by means of the receiver, measure the parameters of the sound that passed fluctuations in magnitude changes which, taking into account the previously obtained calibration dependence, determine the degree of evacuation of the interstitial space of the heat insulating layer of a cryogenic vessel. 2. The method according to claim 1, characterized in that, in order to increase the noise immunity by suppressing sound vibrations propagating along the walls of the vessel, sound insulation material is placed along its perimeter. xxxxxxx x ooooob: -: xy b 14 .xg x / r v v v;  .v- Phie