Tracing every smallest leakage

How the energy experts at thyssenkrupp Dynamic Components use digital sound cameras to track down energy loss in compressed air processes.

Compressed air is an expensive commodity in thyssenkrupp's automotive plants. It is produced in compressors at great expense of energy and is used in many machining processes. Compressed air is mainly used to dry components as they are exposed to oil and lubricants during grinding and milling. Compressed air is also used to control many robots in production. "Almost every piece of equipment in our plants has compressed air connections and is connected to our compressed air network. The production and use of compressed air accounts for a good ten percent of annual energy consumption at each of our sites," reports Uli Beyer, energy manager at thyssenkrupp Dynamic Components in Ilsenburg.

Efficient use of compressed air is therefore an absolute must for reasons of sustainability and costefficiency. The natural enemy in the complex compressed air system of an automotive plant are the smallest leaks, through which the compressed air can escape unnoticed. These leaks cannot be seen with the naked eye. Even with the ear, the escape of air is not perceptible during ongoing production.

"In the past, very elaborate directional microphones were used to locate the hissing of the compressed air. Since last year, we have been using digital sound cameras for this purpose. They consist of many highly sensitive microphones and can be precisely adjusted to the frequency range of escaping compressed air. This means that they can be used even when production is running with all the background noise," explains Beyer.

These sound cameras record leakages like acoustic thermal images. The handling of the device is so simple and intuitive that the trainees at Dynamic Components take on the task of "sound detectives". The sound images can be processed easily and provide precise information about the size of the leak and the amount of escaping air. Appropriate countermeasures can be initiated immediately.

Most leaks are caused by wear. Often, the hose connections simply become loose due to the constant movements of the robots. The repair effort are small. It is usually sufficient to retighten a clamp or replace a seal. However, the effect is enormous.

"During the first tours of our Ilsenburg plants, we discovered around 280 leaks. If we had not found them, this would have resulted in additional costs of around 25,000 euros per year. Since then, we have been using these sonic cameras regularly at all our sites worldwide," confirms Beyer. To keep the acquisition costs for these special cameras as low as possible, they are exchanged between the plants. Currently, Dynamic Components uses three of these devices, which are deployed according to a fixed schedule at the various sites in North America, Europe and China.