DE102008010619A1 - Leakage locating method for vacuum insulation panel, involves loading surface of evacuation system to be tested, with fluid, and measuring surface temperature, and detecting evaporative loss of fluid - Google Patents

Abstract

The method involves loading a surface of an evacuation system to be tested, with a fluid, and measuring a surface temperature. Evaporative loss of the fluid is detected, where the evacuation system comprises a porous core. Adsorption heat of the heat is detected, and an interior side of an envelope of the evacuation system or an additional inner envelope, film, laminate or fibrous web are thermally reacted with the fluid. Thermal radiation of the system is measured by an infrared camera.

Description

The The present invention relates to a method for quick and easy Locating leaks in evacuated systems, in particular with a porous filling core and finite envelope thickness by means of the detection of temperature differences, which by a previously placed on the system liquid be caused. The detection and location is done, for example with a thermal camera, and may, among other things, for non-destructive Quality control in the production of vacuum insulation panels be used.

[Problem]

evacuated Systems are becoming more and more popular among others in building and transport area.

Vacuum insulation panels (VIP), see z. B. DE 4133611 A1 . DE 29906028 U1 . DE 102004003603 A1 ], have about five to ten times lower thermal conductivity than conventional insulation materials. However, this good insulating effect is only given as long as the residual gas pressure in the panel is sufficiently low. VIPs often consist of a porous, evacuable core material and a thin wrapping film or laminate. If the (usually) sensitive envelope of the vacuum insulation panels is damaged and thereby the gas pressure in the panel increases, the thermal insulation effect of the vacuum insulation panels deteriorates drastically. Typically, the leaks in a vacuum insulation panel are so small that they are invisible to the naked eye.

One big problem, for example, is the quality control after or during the production of vacuum insulation panels represents.

To determine the internal pressure of vacuum insulation panels, there are some measurement options, for example, can be determined by lifting the flexible film surface by suction cup, the internal pressure. In addition, in [ DE 10164004 B4 ] describes a method for measuring the gas pressure in vacuum insulation panels, in which the dependence of the gas thermal conductivity on the pore size of the filling material is utilized. A test specimen with larger pores is embedded in the microporous filling core. As the gas pressure increases, the increase in gas thermal conductivity within the specimen is shifted to lower gas pressures. The gas thermal conductivity in the specimen is detected from the outside by applying a thermal signal.

Either for manufacturers as well as users of VIPs It is often of interest, at which point a leak occurred at a VIP. Reasons are On the one hand, the optimization of production technology, here are systematic Leaks are avoided and the rejects reduced. on the other hand is the leak detection for the optimization of the fastening technology in the later application important to from the position of leaks inappropriate fastening measures to be able to and / or even in case of warranty To clarify liability issues.

[State of the art]

So far, the following methods have been used to detect leaks in vacuum insulation panels:
In the panel a slight overpressure is generated with a test gas (eg air). Subsequently, an attempt is made to locate the leak under water by visible blistering. Typically, however, the leaks in VIPs are so small that bubble formation is barely noticeable. To overcome this problem, the overpressure in the VIP is then increased, which not infrequently leads to the bursting of the VIP or at least produces further damage in the enveloping foil or the sealed seam. The location of leaks in this method is also possible by the application of foam-forming liquids.

A Another method of leak detection is a test gas detector to fling to the VIP and then locally the test gas (eg helium, forming gas) on the VIP. Will then be from the test gas detector detects an increased test gas concentration in the VIP, can be closed to a leak at the point in question.

• • Falls das Leck zu groß ist, wird der benötigte Enddruck für den Prüfgasdetektor nicht erreicht;
• • Durch etwaige langen Totzeiten des Prüfgasdetektors zwischen zwei lokalen Messungen (typischerweise einige Minuten) ergeben sich insgesamt sehr lange Messzeiten für ein einziges Paneel;
• • Da zur Lecksuche das Paneel in einem Raster mit vielen lokalen Einzelmessungen abgesucht werden muss dauert die Untersuchung eines VIPs typischerweise mehrere Tage.
• • Um das Prüfgas nur lokal aufzubringen sind aufwändige Absaug- oder Abdichtmaßnahmen erforderlich.

However, the following problems arise:

• • If the leak is too large, the required end pressure for the test gas detector is not reached;
• • Any long dead times of the test gas detector between two local measurements (typically a few minutes) result in very long measurement times for a single panel;
• • Since the panel must be searched in a grid with many local individual measurements for leak detection, the examination of a VIP typically takes several days.
• • Applying the test gas only locally requires complex extraction or sealing measures.

OBJECT OF THE INVENTION

The object of the invention is to quickly, easily and precisely locate leaks in an evacuated system. For this purpose, the system to be examined is moistened with a liquid, applied, sprayed or immersed in a liquid. Due to the pressure difference, the liquid is sucked into the system through the leak, evaporates there and evaporative cold occurs. By observing the surface temperatures of the envelope, for example with a thermal camera, leaks can be detected and located immediately. However, the envelope of the evacuated system should not exceed a maximum thickness, since otherwise the temperature differences on the inside of the envelope and / or the filling core on the outer surface can no longer be observed or observed in finite time. The evaporation cold spot on the thermal image is clearly distinguishable from other spots (eg residues of the liquid on the surface). The evaporative cold spot has a characteristic circular shape in thermally isotropic surface materials.

is The system already vented, will be a pump, with the well Vapors of volatile liquids (vapor pressure at room temperature over 20 mbar) can be pumped (eg a water jet pump), flanged to the system, again evacuated and examined according to the above procedure.

is the evacuated system additionally with a porous Nuclear material equipped, in addition to the characteristic circular shape of the evaporation cold spot a heat front by adsorption heat of the liquid in the porous Nuclear material on. About the propagation speed the cold spot or its heat front leave Draw conclusions about the size of the leak.

To This allows several leaks to be detected simultaneously and theirs determine relative size to each other easily.

The Procedure is also for quality control during production of evacuated systems (eg VIPs) as the system is direct after manufacturing without a flange moistened and moistened can be examined. Leaks of sufficient size Although they are immediately detectable with a thermal camera, minor leaks but would go unnoticed by the quality control to run. This procedure becomes the system under test not destroyed. After unsuccessful leak detection, the system can continue be used.

The The leak detection method according to the invention is not only suitable for VIPs but also for other objects, where the evaporation cold through the outer Serving is recognizable by.

When Modification of this method may be different for VIPs Prüfflüssigkeiten- or gases are applied, with the protective fleece (which in many VIPs between support core and wrapping film), the (modified) inside the cladding film or the support core thermally react.

[Embodiment 1]

A vacuum insulation panel is evacuated with a water jet pump, then it is sprayed with water and the surface temperature is measured with a thermal camera. In 1 is very good to see the circular temperature sink (dark spot) by the occurring evaporative coldness of the water. Likewise, the leading Adsorptionswärmefront (light ring) of the water can be seen in the porous Füllkernmaterial. The right dark stripe is no longer part of the VIP, this is the cooler background. In 1 It is also easy to see that other temperature sinks, such as drops or impurities on the VIP surface, can be well distinguished from cold spots caused by leaks with their typical circular shape.

The Size and speed of the adsorption heat front to draw conclusions about the size of the Draw leaks.

1

Evaporative cooling spot

2

Adsorptionswärmefront

3

edge of the vacuum panel

4

Lower temperature

5

flange

6

acetone

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4133611 A1 [0003]
• - DE 29906028 U1 [0003]
• DE 102004003603 A1 [0003]
• - DE 10164004 B4 [0005]

Claims (6)

Method for locating leaks in an evacuated system, in particular in an evacuated system with a porous core such as a vacuum insulation panel, characterized in that a liquid is applied to the surface of the system to be tested and the surface temperature is measured. Method according to claim 1, characterized that the evaporation coldness of the liquid is detected becomes. Method according to claim 1, characterized the evacuated system has a porous core and detects the heat of adsorption of the liquid becomes. Method according to claim 1, characterized that's the inside of the shell of the evacuated system or an additional inner shell, foil, laminate or nonwoven thermally react with the liquid. Method according to one of claims 1 to 4 characterized in that the heat radiation detected becomes. Method according to one of claims 1 to 5, characterized in that the heat radiation of the system is measured by a thermal camera.