Why is the design of furnaces according to DIN EN 1539 important?
DIN EN 1539 refers in particular to a safe process flow, because the processing of solvent-containing or flammable substances can lead to fatal accidents or explosions if they are handled incorrectly or if the plant is incorrectly designed. DIN EN 1539 in the planning and design phase and in the process ensures a safe and economical operation of the dryer.
Drying – what is this?
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 oven must practically always be designed in accordance with DIN EN 1539. It is important to know that this specification does not only apply to solvents, but also to “dryers in which flammable substances” 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 which can enter into an exothermic reaction with air on ignition”.
Thus there are many substances whose manufacturers and data sheets advertise them as “solvent-free”, but which nevertheless contain VOC’s and are therefore potentially hazardous during processing. The only thing that helps here is to take a look at the safety data sheet, which gives clear information about the explosion hazard of the substances.
This is often a confusing and confusing task, especially with mixtures of substances. Here too, you can fall back on our know-how – send us the safety data sheets of the substances you use and we will check them for VOC’s for you and thus check the safety of your existing dryer, revise it or design a new, safe dryer from Airtec for you.
At the same time, you can be sure that we will design your plant correctly according to economic aspects! Do you know the exact batch quantities of VOC’s that you introduce 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 will even remain below 3% concentration in relation to the lower explosion limit in any operating condition and your dryer does not have to be or become 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.
Drying – but safe
If your process does not fall under this 3% regulation, your dryer must be designed according to DIN EN 1539 to ensure a safe process. Some basic measures must be taken:
It must be calculated that your process must be supplied with a lot of fresh air so that the solvent concentration in the circulating air does not rise above 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 with sufficient fresh air must be carried out to safely remove any solvent nests 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 circulating air must be large enough and the mechanical design of the dryer must be such that no solvent pockets can form during the process. For this reason, the circulating air must also be reliably monitored 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 declaration of conformity of the dryer is signed and the type plate with CE is attached.
Furthermore, the circulation fans and exhaust 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.
Drying – in an economical and ecological way!
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 relief of the environment is essential – and this can be combined with dryers from Airtec!
Our know-how and our experience will help your company in this area as well. By means of our exact calculations – in connection with your data or our joint tests in our technology centre – the amount of fresh air – and thus the amount of air to be reheated – can be reduced to the required minimum. For this purpose it is possible to reduce the exhaust air volume considerably after the end of the main evaporation time of your material – we will be pleased to advise you on this explicitly adapted to your product. It is also possible to reduce the amount of exhaust air for smaller batches or lower process temperatures – we will be happy to provide you with the necessary know-how or calculate it for you 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!
By means of our intelligent dryer control in connection with a frequency converter it is also possible to reduce the circulating air capacity of the dryer when opening the doors in hot condition (indispensable for many processes), thus both protecting the worker from excessive air movement and minimizing heat loss.
A further major issue here is heat recovery of the polluted exhaust air volume. In drying processes, it is not uncommon to lose more than 100kW 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 inexpensive heat exchangers with lower efficiency, every customer can significantly reduce his operating costs and make his contribution to environmental protection. Also here a short ROI 2 years is realistic due to the very low costs. We will be pleased to carry out the corresponding calculations for you – adapted to your production method (1, 2 or 3 layers).
A permanently safe operation through our service
Even after delivery, we do not leave you alone – our sister company, Meier Anlagenservice GmbH, is happy to carry out the annual expert inspection, whereby the safety functions are also validated annually. This ensures safe operation of your dryer for decades.
NFPA 86 – Handling of flammable materials in the USA
DIN EN 1539 is a Harmonised Standard published in the Official Journal of the European Union and therefore not only valid for the entire EU, but also accepted by many other countries. The USA, on the other hand, has its own standard for stoves, which deviates from DIN EN 1539 in some areas. This applies, for example, to the basic design calculation, but also to specifications for add-on parts, such as the gas-operated burners. Of course it is no problem for Airtec to design the dryers according to NFPA 86 and UL and to deliver them to the USA.