As recently proved by Hermos AG of Mistelgau near Bayreuth, building automation is benefitting from experiences gained in industrial applications. In a 50-story high-rise building, Frankfurt's new Tower 185, the company has for the first time used failsafe controllers to control pressure ventilation and smoke extraction systems. The experience gained demonstrates that it's not only in high-rise buildings that advanced building automation solutions can reach new heights.
Located in the heart of the European quarter not far from Frankfurt am Main's Trade Fair Tower, the new Tower 185 reaches proudly upwards to a height of around 200m. The horseshoe-shaped plinth building and the tower comprising two multi-story sections enclosing a central glass structure appear imposing and powerful. Tower 185 is centrally located between the Trade Fair, main station and banking district. The office building is due to be completed at the end of 2011. "Alongside the architectural refinements, building automation and safety represent other especially important features of large buildings such as these," explains Dipl.-Ing. Thomas Sturm, Project Manager at Hermos AG in Mistelgau.
The family company with around 350 employees operates at international level and posts annual sales of 45 million euro. It boasts core expertise in many areas of industrial automation and in building automation. "Our industrial expertise means we can also apply sound, efficient and most importantly, proven automation solutions in building management systems", adds Hermos Software Project Manager Matthias Maisel.
This was the basis underlying the managers' decision to use Siemens failsafe controllers - which have been used by the thousands over a period of many years in industry - to control pressure ventilation and smoke extraction systems for the first time in such a building. This type of solution is similarly sustainable and also globally available. In the event of a fire, the controllers activate pressure ventilation and automatic smoke extraction; they also close the ventilation flaps/switch off the ventilation system. Thomas Sturm explains: "Bus-based implementation of the entire safety engineering system enables even the complex systems in a high-rise building to be mapped extremely transparently; at the same time, we create high levels of flexibility, which are of incalculable benefit in a building of this size."
Bus-based failsafe controllers offer high levels of flexibility
A fire alarm panel located on the ground floor of Tower 185 centrally logs all data from the distributed control units within the building. The fire department can, for example, use this panel to ascertain the status of the individual fire sections within the building and the tower and to switch certain sectors manually where necessary. This process is controlled via a Siemens Simatic S7-319F failsafe programmable logic controller.
Communication in the building is via a ring line that is based on Profinet, an Ethernet-based bus system that has long been the state of the art within industrial automation. Communication is based on the Profisafe communication standard and enables failsafe data exchange both between the different failsafe programmable logic controllers, and to their associated distributed I/Os with corresponding failsafe modules. Matthias Maisel emphasizes: "Thanks to their relatively simple installation and programming, failsafe controllers are increasingly being used within large buildings."
Winding its way around the office building, this Profinet ring line is around two kilometers long and connects the distributed control units. Most of these have been designed on an intelligent basis - i.e. with integrated CPU - to process the signals from the central fire alarm system reliably even without bus communication. To this end the Simatic S7-315F failsafe controllers for smoke extraction and Siemens' Simatic ET 200S scalable distributed I/O which are also used have failsafe electronic modules.
Smoke extraction as an efficient and flexible solution
Distributed failsafe intelligence has been used for closing the fire protection flaps as these transfer to safe status when in non-activated state.
The situation is quite different if, for example, the central fire alarm system identifies a fire and initiates corresponding measures. Defined smoke extraction measures are then requested in accordance with the fire matrix.
The heart of the smoke extraction system is provided by the large fans of the smoke pressure system in the basement; these are started by the failsafe controllers in order to build up a defined overpressure in the tower's stairwells and thus keep the staircases smoke free so they can be used as escape routes.
At the same time the distributed control units in the stories must activate corresponding shut-off flaps to ensure the required pressure ratios for smoke extraction throughout the tower's entire height. There are also several pressure relief windows on each story that allow the volume flow of the pressure ventilation fans to escape. At the same time the overflow flaps in the affected buildings are opened so that the overpressure from the stairwells can ensure smoke-free escape routes here, too.
The smoke extraction flaps for supply and return air are assigned to around 40 smoke extraction groups. They are all controlled via failsafe Simatic controllers. "This is an extremely efficient and flexible solution that is ideally suited to the tasks presented here," reports Thomas Sturm. Within the building, ten of them are arranged as close as possible to the corresponding I/O, keeping distances short and further reducing installation costs.
Distributed I/O for standard and failsafe signals
Here, too, communication is via the aforementioned Profinet ring line with Profisafe protocol. For closing the fire protection flaps, the stories have twelve Simatic ET 200S distributed I/Os. In the tower, one such unit covers six stories. Here, failsafe connection to the Profinet ring line is provided via the Simatic ET 200S IM151-3 header module. These units also offer failsafe reading of the signals from the central fire alarm system via input modules.
"A major benefit of these modular-based stations is that standard and failsafe signals can be processed flexibly according to the task in hand," comments Matthias Maisel in justifying the decision. In Tower 185 they were, for example, equipped with failsafe, digital I/O boards and also with the header module with Profinet connection. They were also supplemented with standard boards for additional building automation tasks.
Software simplifies many things
All failsafe controllers are placed in information centers, a number of which are located throughout the building. As Matthias Maisel explains, programming such a distributed integrated solution is very easy: "The additional feature "distributed safety" is simply installed at the Simatic Step7 programming level; safety engineering can therefore be managed in the same way as the main program without switching platform." Thomas Sturm adds: "The flexibility this offers means we can map extremely safe response scenarios and adapt to changes in framework conditions within the building on an individual basis at any time."
Hermos AG provides day-to-day proof of how smoothly everything works: Much of the commissioning and service work is already carried out via remote access. "This is another major benefit of Ethernet-based automation and safety systems," stresses Thomas Sturm. Using password protection, the experts use a DSL modem to dial into the building management system via an encrypted VPN (virtual private network) tunnel. This is connected to the distributed information centers via the Profinet ring. Using visualization, a Hermos expert can use a computer at any time to check/adjust the correct function within the entire building automation system, of which safety engineering accounts for around ten per cent.
A bright future for Ethernet-based safety engineering
For Hermos AG, the building automation for Tower 185 represents its biggest project to date in this field. It has shown that by using the right components, such as failsafe controllers from Siemens combined with Profinet and Profisafe, safe and efficient solutions are indeed possible. Thomas Sturm and Matthias Maisel are convinced: "Industrial and process automation standards are gaining increasing recognition within building management systems, for example for smoke extraction or for fire and personnel protection."
They see this as a huge benefit as the Siemens hardware can process standard and failsafe signals on the same platform. The resulting flexibility and simple programming via Step7 software and the additional feature "distributed safety" is creating the basis for further development of building automation. The two experts therefore agree: "We believe bus-based safety engineering in buildings offers tremendous potential."