The new state-of-the-art hospital specialises in neurological and orthopaedic rehabilitation. As many as 227 patients are looked after in single and double rooms. The extension and conversion work that was completed in September 2019 required firefighting tanks. PORR Bau GmbH, the full service general contractor who was commissioned to do the work, decided to install four Graf Carat XXL underground tanks, which can store a total of 224,000 litres of water.
In order to minimise the impact on hospital operations, a carefully synchronised schedule is required for the construction project. Contrary to the original plan of manufacturing the firefighting water tank of using concrete, the decision-makers decided to install four plastic tanks, each with a capacity of 56,000 litres. Rather than the scheduled time of ten working days, it took just three days to dig the excavation, install the tanks and backfill with gravel.
“This was the first time that we had installed a plastic firefighting water tank, and I was surprised how quickly and smoothly it went,” explains Dipl. Ing. Peter Lubej, the PORR site manager. Within a few minutes, the tank had been put onto the pre-installed straps using a mobile crane and were able to be interconnected using the DN 250 pipe sockets which had been welded on in the factory. These connecting pipes were also welded to each other.
The four firefighting water tanks were installed close to the buildings. The sandy geological formation has made it very easy to excavate an area measuring 18 x 14m. A flat surface consisting of non-angular gravel (8/16mm) was all that was needed for the base.
The Carat XXL firefighting water tanks arrived at site with the project specific connections and accessories having been prefitted in the Graf factory. This saved time during installation and made the onsite commissioning easier.
The scope of delivery includes a holder for a warning sign at the water extraction point, a welded in DN 125 plastic intake pipe, a stainless steel strainer with anti-vortex plate, a firefighting water intake connection with rod fitting and a fixed coupling. The tank is ventilated with a fireproof DN 100 stainless steel ventilation chimney with hood and insect-proof screen.
A ladder installed in the dome shaft makes access for maintenance easy. The Graf telescopic dome shaft height is adjustable, and can be tilted by 5 degrees to adapt to the fnished ground.
The Carat XXL underground tank is available in different sizes with capacities ranging from 16,000 up to 52,000 litres. Bigger storage volumes are possible by connecting several tanks as proved in this project. The firefighting water tanks can be filled with mains water or rainwater.
The ribbed construction of the tank makes it extremely stable. With an earth covering of just 1.00m, the Carat XXL can be driven over by a vehicle weighing up to 40 tonnes. The sturdy tank can also be installed in groundwater up to its midway point. As a mark of its high quality, Graf offers a 15-year warranty on the XXL tank.