The Poly-Slovakia air dome stays erect due to a minimal overpressure inside the dome. The layers of the hall are held up with air blown to the inside by ventilators. The increasing pressure causes lifting of the layers right up to the point when they are stretched and tightened by a net made of steel cables placed above and holding the layers. In a 2-layer dome technology, the shape of the main cover itself provides the boundaries for the inflation of the air dome. The pressure does not affect people and it is insensible. It reaches about 250 Pa - 350 Pa (25-35 kg/m2), which is enough to resist the wind force and the weight of the snow. The pressure is automatically regulated to match the current weather conditions.
The Poly-Slovakia air dome consists of several elements which we shall briefly describe.
The heating and blowing system provides constant, even pressure in the hall, the circulation of the air and a suitable temperature within the object. The ventilator air-flow travels through a heating aggregate, where it is warmed up, and then through a duct into the hall. Approximately 30 % of the air from the dome space is sucked back into the ventilator unit where it is mixed with fresh air. The result is a constant circulation of warm air, ensuring the perfect and uniform heating of the hall. The control of the temperature and the pressure is, within the scope of set parameters, fully automatic.
Further information on this topic can be found in the aggregate section.
In case of any failure, such as power cut, failure of the main ventilator or pressure drop, the system automatically activates an additional independent ventilator powered by backup diesel engine. The system is also equipped with wind and snow automatics, which - depending on the weather conditions - regulates the pressure and temperature inside the air dome.
Anchoring system provides the base for the steel-rope net or the main cover (in a 2-layer dome technology), connecting it to the ground. We offer two different types of anchoring – anchoring by ground wedge anchors or chemical anchoring requiring concrete base around the perimeter of the air dome.
Each airdome is equipped with a set of doors, including four-wing revolving doors and one or several emergency evacuation doors. Additionally, if required, we can equip the airdome with a special service tunnel for placing larger objects inside the hall.
THREE LAYER COVER
The airdome's cover, the most visible part of the air dome, consists of three independent layers, fulfilling distinct functions:
1. Bearing layer
Bearing layer is made of high-quality reinforced polyethylene fabric. This material is translucent, thus reducing the need of artificial lighting, with the exception of a non-transparent stripe used within the tennis air domes, in order to provide a contrasting background allowing the better visibility of the tennis ball.
2. Insulation layer
Insulation layer is a thick foil with closed air cavities. Its function is to minimise heat losses inside the hall. It is placed between the bearing layer and the protective layer.
3. Protective layer
In order to protect the bearing and insulation layer against soil, rain, snow and harmful effect of UV radiation, the protective layer is used. Owing to this layer, the hall does not lose its transparent properties and maintains high aesthetic quality.
TWO LAYER COVER
In a 2-layer technology, there is only one main cover, consisting of 2 joined layers divided by an air cushion. This cover is of much higher density than the one used in three-layer technology (therefore more expensive) as it has to perform all the functions maintained by separate layers and the cable net.
This specially designed net of steel cables is the element that conditions the resulting shape of the air dome, because the layers can only expand as far as this steel net allows. Beside giving the air dome its shape, its most important function is that of stabilisation. The net absorbs the forces resulting from the pressure differences caused by the activity of natural forces such as wind or snow, and transfers them to the ground, through the system of anchors.
Lighting is provided by series of stripe lights, which are fixed directly to the bearing polyethylene layer. The lighting stripes are mounted in way that ensures uniform light conditions above each playing area. Switching on and off is controlled either manually or automatically by a time sensor, according to requirements.