- explosion hazard due to the presence of flammable organic powder coating dusts – application of a wide range of different coatings based on polyester resin, acrylic and polyurethane
- lack of tests for the used powders with regard to their flammability and explosiveness
- the need to adapt the analysed systems to the requirements of the ATEX 137 Directive
- collection and analysis of flammability and explosiveness parameters for the used powder coating dusts from the available literature data
- preparation of the Explosion Risk Assessment and the Explosion Protection Document for the aluminium profile powder coating systems under consideration
- preparation of technical and organisational recommendations for the improvement of process safety and protection of dust extraction systems in powder coating areas against possible explosions
Explosion hazard in powder coating installations
The powder coating process carries the inherent risk of fire or explosion, so in order to maintain safety, appropriate conditions should be created in the paint shop. An explosive atmosphere is created in each of the devices that make up the painting system, such as the dust extraction filter, cyclone, extraction cabin, powder tank or vibrating table. For this reason, it is important to bear in mind the good technical and organisational practices to eliminate the causes that favour the formation of explosive atmospheres. Therefore, it is crucial to adequately protect the installations against the occurrence of an explosion and its possible consequences, thus adjusting them to the requirements of Polish and EU law in the field of explosion safety.
Powder coating and explosion safety
One of the manufacturers of aluminium systems, using powder coating processes in their paint shops, asked our ATEX specialists to prepare an Explosion Protection Document, of which the Explosion Risk Assessment is an integral part.
Our customer has three aluminium profile powder coating systems in their plant. These systems differ from each other with different suppliers of painting lines and painting chambers. The systems also differ with regard to dimensions – from 21 m3 to 63 m3 painting chambers volume and painting system (automatic and semi-automatic).
Why the Explosion Protection Document?
The Explosion Protection Document is based on an analysis of the flammability and explosiveness of the powder coating dusts used. Due to the fact that the plant uses a number of different paints manufactured on the basis of polyester resin, acrylic and polyurethane, for which the customer did not carry out appropriate tests in terms of flammability and explosiveness parameters, the analysis was carried out on the basis of the available literature data. Such a solution has its advantages and disadvantages – on the one hand, it eliminates the cost of performing the tests, and on the other hand we have to assume the most unfavourable parameters of explosiveness, which in some cases may lead to selecting an oversized protection system. A great deal of experience is therefore needed to determine the most optimal approach to solving the problem.
First – prevent the formation of an explosive atmosphere
Within the framework of the prepared EPD, the experts pointed out the following recommendations concerning the prevention of the formation of explosive atmospheres, which are extremely important in the context of ensuring an appropriate level of safety in the plant:
- ensuring an adequate level of cleanliness within the installation (periodic removal of dust using ATEX-certified vacuum devices adapted for operation in explosion hazard zones),
- consideration of flammability and explosiveness parameters tests for the dusts of the select powder coatings that have been identified as hazardous,
- observance of procedures for periodic inspections of the technical condition of dust extraction systems and tightness of filter cartridges installed on filters and in the fan chamber (if the cartridges are leaking, an explosive atmosphere may be created both in the clean part of the filters and in the ducts discharging purified air to the hall),
- consideration of the design of ducts discharging purified air from painting chambers’ dust extraction installations outside the production hall (dictated by the risk of creating an explosive atmosphere when discharging air from the filters into the hall – in the event of damage to filter cartridges),
- regular cleaning of the fastening parts of the conveyor system on which deposits of powder coatings may accumulate and lead to a lack of proper grounding,
- recommendations for the storage of highly flammable dusts of select coatings,
- use of non-sparking tools during maintenance and repair work in designated explosion hazard zones (precisely specified per zone),
- use of electrical equipment within the electrical equipment category intended for the specific explosion hazard zone,
- use of specific types of big-bags with grounding.
Second – application of appropriate explosion protection
From the point of view of explosion protection, we can treat the dust filter and cyclone as one or two separate devices – the length of the connecting duct is important here. The decision on how to protect such a system is made on the basis of calculations and engineering experience.
In the analysed example, due to the short length of the pipeline connecting the cyclone and the filter, they were treated as a single system, which further reduced the cost of securing the installation. The use of an explosion suppression system (or alternatively flameless explosion relief) is recommended as a protection system for filters and cyclones. On dusty air ducts, it was recommended to use explosion decoupling to cut off the flame from the cyclone and end filter sides as well as from the painting chamber side (due to the low MIE value, it was recommended to apply the decoupling with HRD cylinders).
Additionally, the necessity of protection at cyclone discharge chutes (HRD type explosion decoupling) in order to eliminate the possibility of the explosion spreading to the hall was pointed out.
What are the benefits of the Explosion Protection Document?
The Explosion Protection Document is the complete set of explosion safety information that an employer must keep in accordance with applicable law. The development of an EPD for our client had the purpose of pointing out the appropriate technical and organisational recommendations to improve process safety and to correctly protect the dust extraction systems of powder coating spaces against possible explosions.