Visible benefit from zoo's conditioning system
A fully automatic water conditioning system recently installed at the polar bear enclosure at Nuremburg Zoo in Germany has improved visibility for visitors, and safety for staff. Thilo Sporbert of German technology group Siemens' Automation and Drives division, explains how this complex system is likely to be extended.Large windows and a high performance water conditioning system mean that visitors to Nuremberg Zoo can now see the polar bears frolicking in and under the water. The complex water conditioning system, a waterfall and a geyser use a single set of pumps.
A closed-loop speed control precisely adapts the pumping characteristics to the particular application. The planners placed a great deal of influence on open and seamless drive and automation technology because the zoo has some quite ambitious plans. In the new, 1700m2 polar bear compound at Nuremberg Zoo there is a good 600m2 area of water so that the polar bears can cool down and frolic around. 1200m3 of water must be moved every day in the pool.
An extremely wide variety of substances is introduced to the pool daily: polar bear faeces, beverage cans, plastic bags, leaves, small branches and even pollen. A scoop net and a manually controlled suction device can be used to keep a normal swimming pool clean, however, in the polar bears pool this must be done without any personnel because even for trained staff, a short stay in the compound can be hazardous.
There are several conditioning circuits to remove floating, suspended and sinking substances from the pool:
- the surface debris withdrawal system
- a mechanical rake
- a system that flushes the base of the pool segment-by-segment
- a complete series of conditioning steps to filter and regenerate the water in the pool.
Automatic valves connect the individual pumps to the pipe system for the particular conditioning step. One of the five pumps is always as back-up in case a pump fails. This high degree of flexibility results in an extremely high operational reliability but at the same time with relatively low investment and operating costs.
The water conditioning system is controlled by a Simatic S7 programmable logic controller and is fully automated. The individual process steps are set-up differently depending on the season, as every season has its own special challenges for the system.
Herr Sixt of Shp Sixt, Heiß & Partner, the German company that designed the process engineering system, explained: "In the autumn, for example, the surface debris withdrawal system and the moving rake must handle lots of leaves floating in the pool. On the other hand in the winter the water must be circulated to keep it reliably free of ice."
The Micromaster 430 drive inverter plays a significant role in achieving the required operational reliability by softly starting the pumps. It prevents pressure surges in the system that could subject the piping and filter equipment to stress and could disturb the animals.
These drive inverters also use energy efficiently and therefore ensure cost-effective operation of the water conditioning system. In addition to the low power losses of the IGBT power semiconductors used, a control technique optimised for the partial load range of pumps, with a square-law load torque, plays its role in saving energy. This partial load range is frequently used in the pool as a result of the changing tasks of the pumps.
The German electronic engineering company Projektgesellschaft für die Kommunale Ver- und Entsorgung (PfK) was responsible for the drive and automation system at the pool. In addition to the five main pumps, there are numerous sensors and actuators, dosing pumps and valves that had to be integrated into the automation system. All of the components are connected to the control through Profibus DP.
Herr Bittner, managing director of PfK, explained the reasons for selecting Micromaster 430, Simatic S7 and Profibus: "The polar bear pool is only part of the aqua park in the zoo and in turn the aqua park is only just one part of the Nuremberg Zoo. A central supervisory system is to be set-up in the zoo; in the long term not only the aqua park with its polar bear pool, the delfinarium and also the planned dolphin lagoon are to be integrated into this supervisory control system, but also the monitoring and control of all of the equipment related to operating the zoo.
He continued, "Open and seamless automation technology is the most important prerequisite - and for many communal large projects we have had excellent experience with the seamlessness and integration capability of Siemens automation systems."