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Helium leak detection of glass coating equipment

Helium leak detection of glass coating equipment

The Spanish truck enters slowly into the Plattling industrial estate. While the low profile loader drives into the Interpane glass company site, we are on the way to the glass coating HIP2 workshop. We are in company of Joachim Limbrunner, the maintenance team leader for the two architectural glass coating plants in Plattling.

The Plattling industrial estate

The Plattling industrial estate

«The truck you saw is driving towards Spain loaded with glass for the new Madrid international airport.» mentioned Mr Limbrunner while welcoming us. «This is, after Nice, the second airport, that we equip with our ipasol low-e and solar control glass.»

«The high reproductibility in production and the layers homogeneity resulting from it are the conditions for the even appearance of the glazing over very large surface areas. This is one of our specialities. We are pround of the success we obtained such as the Millenium Tower in Vienna, the Commerzbank center in Frankfurt, the bank of China in Hong Kong, the Trump international Hotel and Tower in New York or the Volkswagen headquarter in Dresden.

Whenever we notice any deviation in the homogeneity, it is the result of some leaks somewhere on the system and we have to proceed to a leak detection.»

On the screens of light absorbtion instrument inspecting the last 6 meters x 3,21 meters coated glass subtrates, one can see that the differences between the target curve and the result of measurement are very small, however the strict quality control at Interpane does not even allow this small defect.

Downstairs on the coating plant stands Konrad Voelkl, one of the most experienced Interpane layers team leader. The men are concentrated on the remote control display of their helium leak detector and spray the tracer gas on the coater system flanges and seals.

«We do proceed to a leak detection after each maintenance routine and plant shut down. The load lock and transfer chambers pumping systems are so efficient that even large leakage flow are simply evacuated. In the sputtering chamber where the glass is coated, things are completely different. We already noticed that some leaks impact the ultimate pressure during first evacuation. Instead of the 5 · 10-4 mbar necessary for the production, we only achieved a pressure in the 1 · 10-2 mbar. We had then to look for gross leaks. Most of the time, the leaks are located at the chambers covers seals or coating targets. The covers are sealed with a lip seal, that require high care during installation. Leaks are usually due to lack of cleaning or insufficient precision during installation. Our seals cannot be compared to standard vacuum engineering seals. For us a small flange gaskets is rather a micro seal, our seal length is bigger than 7meter per chamber.»

«We trust the ASM 122D leak detector from Alcatel. Since most of the time leaking problems occur at sputtering chambers, we usualy install the leak detector at the common backing line just above the fore vacuum pump that is used for production. Other operational areas are so rare that we can dismantle the leak detector from the fixed installation and take it to the place where needed. Together with the Alcatel team, we developped a pressure reducer feature connected and integrated in the exhaust line. That way we were able to reduce the pressure at this location of the forepump line in order to be compatible with the inlet test pressure of the leak detector, and keep at the same time a short response time.»

A large smile appears on Konrad Voekls face and he raises his thumb upward. Immediately his team starts working. After venting the sputtering chamber, the cover is lifted in order to clean the seal and reinstall it properly. The leakage is eliminated and the production can start again.

«We can find gross leaks easily.» explains Joachim Limbrunner. «The leak detector is operated in parallel mode with the fore pumps, the helium background is then lower than 5 · 10-8 mbar · l/s. The leak that we have just found, produces a leak flow in the 1 · 10-3 mbar · l/s, with such leak we are completely unable to produce functional layers over the glas substrate. Such leaks are quite easy to detect, it becomes much more difficult with small leaks. Within the 1 · 10-7 mbar · l/s range leak many layer system are still operating well.

The modern High Tech layers are not forgiven and small leaks need to be detected and fixed too. With our new leak detector and its high helium pumping speed, we have no more difficulty to do so, as compared to what it used to be. We still have a good signal to background ratio. Each opening of a glass coating system means several hours of dead time for production. An effective leak detection method with an efficient leak detector such as the Alcatel ASM 122D, saves us time and money. Now we have located the leak, our colleagues know what to do.»

«Coating professional training does not exist, but through internal training courses we achieved a high technical and quality knowledge for our coworkers. Within the leak detection technique, Alcatel has been providing us a valuable support. Apart the efficiency and reliability of Alcatel leak detector, the support and training courses given by Alcatel personal have also been a key decision criteria for the purchase of the leak detector.»

Authors:

Interpane Glasgesellschaft GmbH & Co.
Robert-Bosch-Str. 2
D-94447 Plattling
www.interpane.net

Ralf Landgraf

Technischer Leiter Beschichtung
Joachim Limbrunner
Technik Beschichtung

Alcatel Hochvakuum Technik GmbH
Am Kreuzeck 10
D-97877 Wertheim

Dr. Rudolf Konwitschny
Field Sales Engineer
Key Accounts IRIS
Jutta Uecker
Sales Manager Europe North
Industry, R&D Segment



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