To remain with the example of the beverage industry, the high-performance beverage filling plant is another case in point. This type of machine is capable of filling up to 70,000 bottles per hour. This equates to 20 bottles per second, each of which has to be filled, labeled and transported. The extreme demands made on dynamics, signal processing and coordination of the controls, motors, sensors and so on are not difficult to envisage. Although the individual bottles are practically indistinguishable to the human eye as they flash past, the electronic devices and systems used are required to reliably pick out and register each individual bottle with the utmost accuracy.
The vital importance of high-speed communication is also demonstrated by the example of a hot rolling mill used to process steel for the automotive industry, which demands ever more stable and lighter-weight steel grades. The cooling process following the last roll stand is instrumental in determining the mechanical properties of the steel. Exceeding the specified tolerances in the cooling temperature or the temperature profile even by only a few percent can alter the mechanical properties of the final material so decisively that it may have to be scrapped or its quality is severely compromised.
A change in the speed of the strip will frequently mean varying material properties in different sections of the same strip. To avoid this happening, a programmable logic controller monitors the optimum time for valve opening and closing, adjusts the cooling pattern and cooling zones to the varying strip speeds and controls the phase fractions along the whole cooling section in real time. Deviations from target values are corrected every 200 milliseconds and forwarded to the actuators.
These examples illustrate how much more hangs on the precision and reliability of communication in industrial plants than it does in the average office network. The faulty assignment of parts in a distribution center can result in substantial financial loss; if the motors of a paper machine are not absolutely synchronized, the resulting paper congestion can produce a complete operational shutdown; if the safety sensor of a mine pit cage fails to give off a signal, the coal will remain stuck in the shaft. The individual systems working in these generally enormous networks have to operate without a hitch and to communicate reliably with each other – irrespective of whether the individual components of an installation are supplied by a number of manufacturers each using a different communication variant.
There is another crucial factor which distinguishes the needs of the office network from those of industrial communication: the ambient conditions. Location makes an enormous difference to the installed components: an air conditioned building, an iron rolling mill or a drilling platform in the middle of the Atlantic all have quite distinct requirements. Because salty air is fatal for all electronic components, including of course communication networks, all terminals and connections have to be encapsulated against environmental influences and stowed inside a housing. This is the only way to protect all metallic components and connecting elements against the effects of salt water and corrosion. Approved for a temperature range of -40° to +70°C, the devices and connectors used for industrial communication have to be capable of withstanding even the most intensive sunlight, snow and ice. They also have to work reliably and accurately in potentially explosive atmospheres such as those encountered in mining applications, in compressor stations and painting booths. Depending on requirements, a distinction is drawn between different protection ratings which denote ability to withstand adverse conditions in light and heavy industry, in railway tunnels and on ships. These components offer enhanced immunity to electromagnetic interference, are protected from vibrations, dirt, moisture or damaging substances and are resistant to a variety of media such as oils, lubricants and acids. They are vibration-proof and capable of 35 mm top hat rail mounting.