Transmitter for Field Use

Transmitter for Field Use

Georg Fischer Chooses Display Adhesive made by DELO

Electronic equipment for fluid and gas pipes has to be extremely resistant to adverse conditions. Georg Fischer has chosen to use DELO DUALBOND display adhesive for a transmitter with a particularly large display. In addition to meeting all the optical requirements, it also enables an efficient production process.

Many pipelines are exposed to the elements and must face tough environmental conditions, including humidity, temperature variations, heavy frosts in winter, or long hot spells in summer. It goes without saying that the electronic equipment also has to face these same demands. Georg Fischer has first-hand experience of these challenges. This enterprise is offering plastic and metal pipe systems and associated system solutions for the safe transport of gas and water. Its product portfolio for industry, utilities, and building technology comprises fittings, valves, pipes, automation, and connection technologies.
One product from the company's control systems range is the Signet 9900 Transmitter, a device used to measure and monitor fluid and gas media through a single-channel interface for sensors such as flow, pH / ORP, conductivity / resistance, pressure, temperature, filling level, and salinity. It can be integrated into a control cabinet or installed in the field, and is used for many other applications in addition to media filtration, wastewater treatment, and chemical production.
What makes the transmitter stand out is its extremely large display. Thanks to the transmitter display's generous dimensions of 99 mm × 99 mm, information can be read at up to four or five times the distance compared with conventional transmitters, reducing the risk of incorrect readings or misinterpretation of the displayed values.

Display Bonding Considerably Improves Readability

Good readability is not just the result of a backlit display - bonding the display also helps. In this process, a glass cover is bonded onto an LCD module (LCM) using optically clear adhesive. It's refractive index is adapted so that light reflections can be reduced by up to two thirds. At the same time, the shock resistance of the display massively increases, because it is more stable in the event of shocks and falls.
There was no question of Georg Fischer using tape for display bonding, since it has inadequate humidity resistance. Instead, the company initially chose a two-component adhesive that in principle met the optical requirements. However, Georg Fischer were looking to establish a more stable and faster production process. With two-component adhesives, air bubbles frequently form, even if the two components are mixed accurately. These bubbles can be time-consuming to remove, and may even result in the unit being scrapped. The pipe system provider also felt that speed was even more of an issue: The complete bonding process, starting with mixing, took too long and led to excessively high storage costs in relation to the transmitter quantities required.

The 9900 Transmitter for pipe systems from Georg Fischer has a particularly large display

As well as conducting joint tests, good project management should also include working with the customer to define the production process and all its curing parameters, and offering advice on choosing the right equipment."

Light Curing Accelerates Production Process

That is why Georg Fischer contacted DELO, which suggested using 1C optically clear adhesives. They can be dispensed without bubbles and also cure in seconds under high-energy light, so that the displays can be handled immediately. One benefit is that the adhesive also cures in shadowed areas, where light cannot reach, through contact with humidity present in the air. This ensures that no fluid adhesive remains.

Thorough Testing

First it was necessary to check that the material developed for this application, DELO DUALBOND OC4922, met the specified properties. So, Georg Fischer and DELO subjected the bonded sample to three demanding industry-standard tests: A UV test acc. to ASTM G154, a simulation of outdoor weather conditions acc. to ISO 4892-2, and heat / humidity cycling from -15 °C through +70 °C. The adhesive met the optical requirements in all tests. The b value remained at an excellent level for the yellowness, meaning that Georg Fischer could be sure that the adhesive does not become perceptibly yellow.
"It was the extensive reports and research conducted by DELO that instilled confidence in this new option", said Gert Burkhardt, Vice President Operations, Georg Fischer, explaining their product choice.
But for DELO, the project did not end there. "In line with our philosophy, an adhesive manufacturer should do more than just recommend an adhesive, provide samples, and then send an invoice", said Robert Saller, Director of International Sales. "Good project management should also include working with the customer to define the production process, and offering advice on choosing the right equipment."
Georg Fischer opted for the DELOLUX 20 area lamp, which is also produced by DELO and is perfectly suited to the adhesive. The LED lamp has a wavelength of 400 nm and cures the material at a low intensity within 60 seconds. However, the valve of another manufacturer was suitable for dispensing the adhesive, so its use was also recommended.
"It is an exciting time as we look to move forward with the process that will address long-standing issues in our optical bonding", Mr. Burkhardt added.
With the definition of the process completed, Georg Fischer were able to forge ahead with the ramp-up phase, integrate the adhesive into production, and gradually increase the volumes. After such great collaboration and the successful completion of this project for the display, the two companies want to tackle a new application together in the future. But all they will say for now is that it too involves tough requirements for the adhesive to cope with.