Explosion protection of dust collectors
Dedusting systems, inside of which an explosive atmosphere may occur due to the filtration of combustible dusts, have to be equipped with protective devices which are compliant with the ATEX directive.
The heart of a dedusting installation is a dust collector. In our designs of EKO-FILTR central dust collectors we include a whole range of preventing solutions which aim at protecting a dust collector against explosion.
The basic explosion preventing solution is to design a dust collector in a way which eliminates the ignition source inside of it and to combine a dust collector with other devices within the system so the spread of explosion is impossible.
In our EKO-FILTR dust collectors designed for explosive dusts the following solutions are applied:
– filter bags are made of antistatic farbics
– the structure of a dust collector is strengthened and equipped with certified explosion vents (4), which are an independent protection system – in case of explosion, the vents (also called decompression panels) reduce the explosion pressure to the safe level (reduced pressure) so that the structure of the dust collector is not damaged by the explosion. The exact number and size of the decompression panels is always provided in our offer and they can be modified depending on needs of the installed dedusting system.
– the devices being part of the dedusting system are produced in adequate ATEX explosion proof category. As standard, a baghouse dust collector is equipped with devices that work inside of the dust collector and outside of it. The devices (whether electrical or non-electrical) working inside of the dust collector (being an integrated part of), where a potentially explosive atmosphere may be present continuously, long or frequently, have to be produced in accordance with the 2014/34/EU ATEX directive and classified with a category. Such category defines which explosion zone a device is designed for. It is also crucial to make sure all the safety requirements are met and the good housekeeping practices are implemented outside around the dust collector, where other devices are usually installed – these are not included in the ATEX directive and they are not given ATEX category.
In the EKO-FILTR type of dust collectors, the following 2 areas need to be recognized:
The dirty area – the internal part of the dust collector where dirty and dusted air is separated by the filtrating sleeves (5) which stop the dust. Here the highest concentration of dust occurs creating a continuous, long or frequent explosive atmosphere. Therefore, this area of a dust collector is classified as zone 20. Consequently, all moving parts, which can be considered as mechanical devices, such as a screw conveyor (3) or rotary valve (2) which discharge the separated dust, have to be compliant with the ATEX directive 2014/34/EU.
Other devices located on the dirty side of a dust collector, which also need to be compliant with the ATEX directive, are:
– filter bags shaking mechanism (electrical and pneumatic)
– other emptying systems such as chain conveyors, rotary scrapers etc.
The clean area – the internal part of a dust collector, on the clean side of the filter bags. It is unlikely that an explosive atmosphere in the form of combustible dust in the air occurs here in normal operation but, in case when it does occur, it persists for a short time only. This area is classified as zone 22, therfore, both moving and electrical parts such as regenerative systems for filter bags (7) or extraction fans (8) have to be compliant with the ATEX directive.
Other devices located on the clean side of a dust collector, which also have to be compliant with the ATEX directive, are the following:
- mechanical filter bags shaking systems (moving parts, electro-vibrators),
- compressed air systems used for filter bags cleaning,
- other measuring devices, and safety devices.
In order to have easy access to the clean side of the dust collector a ladder (1) with protective door and platform are installed (6).