Dry vacuum cleaner in gas hazardous areas
According to the guideline, there is a restriction on the use of vacuum cleaners in the GasEx area. When sucking in gas / dust mixtures, a hybrid mixture is created.
In this case, the following must be observed:
All dusts that are insulating in the electrostatic sense and have the limit value * mentioned below must not be vacuumed up. Non-conductive dusts build up charges during transport (suction / conveyance) with one another or in contact with conductive or non-conductive surfaces. These charges are not diverted immediately when they come into contact with a conductive connection to the earth potential; instead, for example, a very high charge potential can initially develop in a container. The charge created by the collapse of the charged dust is not very high, but this energy can be sufficient to generate ignitable brush discharges towards the earthed container wall. Brush discharges can ignite most flammable gases and vapors, as well as hybrid mixtures. It is therefore forbidden to vacuum non-conductive dust in gas Ex areas without additional safety measures. (For more information, ask for our data sheet "Questions about non-conductive dusts".) "
*The limit value for bulk solids is a specific resistance ≤ 1*10^8 Ωm (see also TRBS 727, Chapter 6.3). For bulk materials with a higher specific resistance, the occurrence of ignitable brush discharges cannot be ruled out.
The KRAHNEN models EGS for the gas Ex area of Zone 1/2 as well as the model EGS GD and DGS for the DustEx (Z21) and the GasEx (Z1) area are designed to accommodate dry, flammable, conductive and non-conductive ** Substances with a minimum ignition energy of> 0.3 mJ have been safety-tested and approved.
(** up to the specified limit value)