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DIN EN 1539 refers in particular to a safe process flow because the processing of solvent-based or flammable materials can lead to fatal accidents or explosions if they are handled incorrectly or if the system is incorrectly designed. DIN EN 1539 in the planning and design phase and in the process ensures safe and economical operation of the dryer.
Drying is generally understood to be the removal of liquids from a substance or object – the material to be dried – by evaporation. If the liquid is not only water but also, for example, solvents, the furnace must practically always be designed in accordance with DIN EN 1539. It is important to note that this specification does not only apply to solvents, but also to “dryers in which flammable materials are released”.
DIN EN 1539 defines flammable substances as “mainly volatile organic compounds (VOCs), which can occur as gases, vapours, liquids, solids or mixtures thereof and can enter into an exothermic reaction with air on ignition.”
There are therefore many substances whose manufacturers and data sheets advertise them as “solvent-free”, but which nevertheless contain VOCs and are therefore potentially dangerous during the processing. The only thing that helps here is to take a look at the safety data sheet, which gives clear information about the risk of explosion posed by the substances.
This is often a complex and confusing task, especially in the case of mixtures of substances. Here too, you can rely on our know-how – send us the safety data sheets of the substances that you use and we will check them for VOCs, thus verifying the safety of your existing dryer. We will then revise it or design a new, safe dryer from Airtec for you.
At the same time, you can be confident that we will also design your system correctly in accordance with economic aspects! Do you know the exact batch quantities of VOCs that you feed into the dryer or would you like us to determine this in our technology centre? Then we can adjust the dryer exactly to these quantities. In the most economically favourable case, you even remain below a concentration of 3% in relation to the lower explosion limit in any operating condition and your dryer does not need to have been designed or be designed according to DIN EN 1539. We are also happy to offer to test your existing dryer according to DIN EN 746 or to offer you a new dryer designed according to DIN EN 746.
If your process does not fall under this 3% regulation, your dryer must be designed in accordance with DIN EN 1539 to ensure a safe process. Some basic measures need to be taken:
It must be calculated with how much fresh air your process needs to be supplied so that the solvent concentration in the recirculating air does not exceed the lower explosion limit of the corresponding substance. This fresh air supply must be monitored electrically and in the event of a fault, the heating and other potential ignition sources must be switched off safely.
Before starting the heating process or switching on any potential ignition sources (lamps or similar), a purging process must be carried out with sufficient fresh air to safely remove any solvent pockets that may have formed as a result of cleaning work or evaporation at room temperature. This must also be calculated depending on the size of the dryer.
The volume of recirculating air must be large enough and the mechanical design of the dryer must be such that no solvent pockets can form during the process. This is why the recirculating air must also be monitored safely during the process.
These measures must be safely monitored electrically according to the performance level specified in DIN EN 1539. The functions must be validated and verified before the dryer’s declaration of conformity is signed and the type plate with CE is attached.
In addition, the circulation fans and exhaust air fans required to ensure the purging process before switching on the heating must be designed in such a way that they do not generate sparks in the event of a fault.
One thing is certain: Dryers are in most cases one of the largest energy consumers in companies. That is why it is particularly important to take a close look at this area and to exploit the savings potential!
Especially today, every competitive advantage and every reduction in the burden on the environment is essential – and this can be combined with dryers from Airtec!
Our know-how and our experience can help your company in this area as well. Our exact calculations – in conjunction with your data or our joint tests in our technology centre – can therefore reduce the fresh air volumes and hence the amount of air to be reheated to the required minimum. For this purpose, it is possible to significantly reduce the amount of exhaust air after the end of the main evaporation time of your substance – we are happy to advise you in this respect explicitly adapted to your product. It is also possible to reduce the amount of exhaust air for smaller batches or lower process temperatures – we are happy to provide you with the necessary know-how or calculate it directly as a service.
Even complex temperature curves with different exhaust air volumes at different temperatures and/or process times are no problem for us – including the reliable monitoring of the different process points!
Thanks to our intelligent dryer control system in conjunction with a frequency converter, it is also possible to reduce the recirculating air performance of the dryer when the doors are opened in a hot state (indispensable for many processes), thus protecting the operator from excessive air movement and minimising heat loss.
Another major topic here is heat recovery of the contaminated exhaust air volume. In drying processes, it is not uncommon to lose more than 100 kW of heat output from the process through the exhaust air stack – doubly annoying in today’s world. In such cases, even a larger investment can pay off in a very short time (ROI 2 years). But Airtec is also the right partner for small companies with smaller budgets: By using very low-cost heat exchangers with lower efficiency, every customer can significantly reduce their operating costs and make their contribution to environmental protection. Here too, a short ROI of 2 years is realistic due to the very low costs. We are happy to carry out the corresponding calculations for you – adapted to your manufacturing method (1, 2 or 3 shifts).
Even after delivery, we do not abandon you – our sister company, Meier Anlagenservice GmbH, is happy to carry out the annual expert inspection, whereby the safety functions are also validated annually here. This ensures safe operation of your dryer for decades.
DIN EN 1539 is a harmonised standard published in the Official Journal of the European Union and is therefore not only valid for the whole EU, but also accepted by many other countries. The USA, on the other hand, has its own standard for furnaces, which in some areas deviates from DIN EN 1539. This applies, for example, to the basic design calculation, but also to the specifications of add-on parts, such as gas-powered burners. Of course it is no problem for Airtec to design the dryers according to NFPA 86 and UL and therefore to deliver them to the USA for you.
Airtec Thermoprocess GmbH
Heinrich-Hertz-Str. 2
DE-46414 Rhede
