(Reprint of an Elektror technical article from the magazine New Business, issue 05/23)
Extraction, blowing off, lifting, blowing in, heating, filtering, cooling, drying – so much industrial machinery relies on air. Ventilation technology thus plays an important role in many production processes in many industries – as it needs to have a specific effect at a particular point within a production system.
To produce crispy French fries, the potatoes must be dried after washing, and the greasy air used during baking needs to be filtered. To pack the French fries in an automated line, the plastic packaging needs to be blown open. Composting processes can be optimised with the right supply air management, such as by extracting air so that no odour can escape. In the metal-processing industry, pieces of metal are held in place by air for processing. These are just a few examples of the kinds of application for which Elektror airsystems GmbH offers plug-and-play systems for plants and production processes.
There are a few key parameters that need to be clarified before you can opt for a radial fan, axial fan or side-channel compressor. Christian Reischauer, Head of Sales for Austria at Elektror airsystems GmbH, understands what needs to be considered when selecting and designing the system: ‘Industrial fans are a permanent component of many production machines and systems. Without air with the appropriate volumetric flow and pressure at the right location, many production systems will come to a standstill. In many cases, it’s the smaller fans that cause a problem and prevent much larger systems from running. That’s why selecting and correctly designing ventilation systems is so important.’
Accurate description needed first
‘Depending on the application, there are typical secondary applications or sticking points that need to be considered when designing a system. With our experience, we already know what they are,’ says Reischauer. When air is blown into something or extracted, there’s always the question of whether that air needs to be filtered as well. ‘One customer project involved blowing air into the production hall used by a sensor manufacturer. As the sensors are very sensitive to dust, the air needed to be filtered before being blown in. A filter generates high air resistance, which is something that needs to be taken into consideration when designing the fan,’ explains the expert. Elektror also has considerable experience when it comes to blowing water from drinks bottles, including the air knives that are needed, plus the piping suitable for the model of fan and the blow-off power required. The distance between the blow-out opening and the point of action also plays an important role. ‘We can offer customers advice on the complete process,’ explains the Head of Sales.
Accompanying processes
The accompanying processes within a system are also relevant to ensuring seamless operation, as these can modify the parameters for the optimal operating point of the air. In the textiles industry, lengths of material are fixed to the cutting tables under negative pressure. During cutting, the resistance of the material changes, and to maintain the same level of fixing, the air pressure needs to be adjusted. This requires a frequency converter to be installed in addition to the fan so that the speed of the fan, and in turn the air pressure, can be controlled.
System geometry
What is the pipe diameter for the air supply? How long is the path of the air from the fan to the point of action of the air? What are the air resistances and pressure losses within the system? Christian Reischauer recommends that users find answers to these questions. Space also plays a major role in systems, and that costs money. With this in mind, compact fans are very important. At the same time, this has an effect on pipe diameters. ‘The smaller they are, the less space they occupy. But, if the planned pipe diameters are too small for the volumetric flow needed, the pipes will need to be enlarged. This can be a challenge if the space in the system is limited. We can support system engineers in finding the right design,’ says Reischauer.
Positioning of the fan
The place at which the fan will be used needs to be taken into consideration in the planning. ‘If the system is installed more than 1000 metres above sea level, normal air pressure changes so significantly that the design needs to be adjusted accordingly,’ explains the Elektror specialist. The distance between the fan and the point of action of the air also plays a role – the greater the distance, the higher the air resistance in the pipes through which the air needs to flow. To design a system that is as efficient as possible, the fan needs to be as close to the point of action as possible. With high-pressure fans, this can be problematic because higher pressures require faster fan speeds. This means noise – often too much for the ergonomic requirements in places of work. In that case, additional noise protection needs to be incorporated into the design. There are various solutions for this, such as the Elektror BOX, which is a multi-function noise insulation cover.
Medium temperature
The temperature of the air passing through the fan is another important parameter. If the temperature of the medium is above 80°C, for example, there needs to be a spacer between the impeller wheel and the motor to prevent the motor or ball bearing from overheating. If the temperature of the medium increases to more than 180°C to 200°C, it will impact the strength of the impeller wheel, so additional temperature-resistant materials will be required.
Abrasive substances and hygiene
Abrasive and corrosive substances have a similar impact to high temperatures. ‘In that case, fans with an aluminium housing quickly reach their limits, and so we have to consider impeller wheels made from standard steel for stainless steel fans,’ explains Christian Reischauer. Stainless steel is also the best material if there are strict hygiene requirements. Fans used in the food-processing industry must satisfy high hygiene requirements, like those used to dry vegetables after washing and before packing. Only stainless steel fans can do that. If pollutants are transported in the air, additional seals or filtration are important to prevent those pollutants from escaping into the ambient air.