Dust explosion protection was overshadowed by gas explosion protection even into the 1990s in industrial applications, although there have always been more dust than gas explosions. This balance changed in the 1990s with the Atex directive. However, it still cannot be assumed that all employees will have a universal awareness of the dangers of dust explosions – even if personnel should be sensitised to such risks as required under Atex operator guidelines.
In such cases, one useful risk-reduction measure is to extract the explosive dust directly at the site of production. In addition, the production area must be kept clean so that the dust that is stirred up does not cause an explosion.
This requires industrial vacuum cleaners with a dust explosion protected construction. These industrial vacuum cleaners must be specifically designed for this task, since they will always be collecting dust and therefore will represent a potential fire hazard.
In reality, fires and explosions with industrial vacuums and dedusters have not been uncommon. Because of this, many years ago trade associations defined industrial vacuums in type 1 (Bauart 1 – B1) that are suitable for collecting flammable dusts. The technical requirements for these vacuums were later integrated into
DIN EN 60335-2-69 (“Industrial vacuums for hazardous dusts and flammable dusts”). This standard was later adapted to the requirements of Atex directive 94/9/EG or currently 2014/34/EU.
Annex CC of EN 60335-2-69 describes the special requirements for collecting flammable dusts and for use in zone 22 explosion hazard areas. Manufacturers of dust explosion protected industrial vacuums and testing institutions have managed very well with the current standards. In particular, a greater focus on dust explosion protecion was deemed correct and appropriate, and instruments such as zone classifications (dust ex zones 20, 21 and 22) and uniform explosion protection labels have proven to be practical.
The standards are currently changing. From Annex CC of EN 60335-2-69 has come a new standard project numbered 62784, primarily developed by the German national working group DKE 511.14 and the internationally responsible working group SC61J; this replaces Annex CC. This standard has now been published with the support of the international working groups SC61J and TC31 on the IEC level as IEC and EN 62784; it has been valid since 2017 and should be harmonised under the Atex directive. The boards that developed this standard felt it was necessary to uncouple the contents of “their” standard from DIN EN 60335-2-69. The reason is the standard framework, or relationships between the individual standards. DIN EN 60335-2-69 is a product standard harmonised under the Machinery Directive. IEC/EN 62784, in contrast, does not belong under the Machinery Directive, but is instead classified under the Atex directive 2014/34/EU, even if many basic requirements were adopted from Annex CC to DIN EN 60335-2-69. Therefore, this standard clarifies circumstances in this area.
New standardisation project
Another standard project will also create clarity: a revision of DIN EN 60335-2-69 which explicitly applies to regulations for B1 industrial vacuums – i.e. industrial vacuums that can extract flammable dusts, but are not suitable for use in explosion hazard areas. This type of vacuum is designated as an “appliance for combustible dust” (ACD) in the revised draft standard.
The standard is also going to be expanded in this respect, so that it provides technical standards for wet/dry vacuums. This project is extremely useful, because wet separators are often used to render explosive or flammable suctioned material harmless.
Competition in standardisation
In addition, there is another current standards project applicable to industrial explosive materials vacuums. European CEN working group “CEN/TC 305 WG2” is currently developing a product standard (C standard) numbered 17348 for industrial vacuums in gas and explosion hazard areas.
It has different focal points than working group SC61J, which is developing C standard IEC/ EN 62784 as described above. This working group is developing a product standard based on the electrical explosion protection with a separate ignition type, while working group CEN/TC 305 WG2 focuses on non-electrical explosion protection.
That means: according to EN 17348, in the future industrial vacuums will be considered as an Ex-assembly. Manufacturers of industrial vacuums and dedusters will then assess the non-electric components with respect to non-electrical explosion protection. The electrical components would need to deliver a type examination certificate in accordance with Atex directive 2014/34/EU if they belong to device category 1 or 2. In this case, no additional prototyping procedure must be carried out for the electrical components in accordance with the Atex directive in order to assess the machine as a whole, if these are used within their prescribed application and there is no new resulting source of ignition.
An ongoing process
The standardisation work described here is currently still an ongoing process consisting of the work and coordination between the respective national work groups. The result – a new or revised standard – will be reviewed thoroughly by the European Commission. Only then will the standards be harmonised under an EU directive and go into force.
Ruwac has been working on these standards for decades, and has been involved in the national and international working groups for the aforementioned standards – to integrate manufacturer expertise and be as prepared as possible for new standardised requirements.
Ruwac Industriesauger GmbH, Melle