BS EN 17199-3:2019 pdf free.Workplace exposure – Measurement of dustiness of bulk materials that contain or release respirable NOAA or other respirable particles.
6.2.3 Drop pipe, with an inner diameter of 15 mm and a length of 400 mm. The drop pipe shall be made from inert and electrically conducting material, e.g. stainless steel. The drop pipe is a thin-walled tube. 6.2.4 Backflow pipe, round with an inner diameter of 150 mm. The backflow pipe shall be manufactured from an inert and electrically conducting material, e.g. stainless steel. Within the backflow pipe a vertical air speed of 0,05 3 m/s, measured below the end of the drop pipe (6.2.3) shall be generated. It is critically important that a constant vertical air speed of 0,053 rn/s is maintained as the sum of the main pump’s flow rate and those of all sampling/measuring devices employed in the tests. For this purpose, a suitable instrument (e.g. a mass-flow controller (6.2.5)) to control the air flow generated by the main pump shall be in place. The backflow pipe needs to be equipped with suitable openings/probes to connect the sampling devices. All openings shall be situated in one measurement plane (i.e. in an identical distance from the metering device 100 mm above the end of the drop pipe. They shall be situated in a symmetrical way around the drop pipe (i.e. for example if two openings arc needed, they shall be opposite one another, if three are needed they shall be situated in a 1200 orientation). Additionally, in the case of different sampling flow rates of the applied devices, they shall be oriented in such a way as to generate as homogenous distributions of sampling flows (out of the backflow pipe) as possible, in order to avoid inhomogeneous air flows in the vicinity of the end of the drop pipe. 6.2.5 Mass-flow controller, or another suitable instrument to control the air flow generated by the main pump.BS EN 17199-3 pdf download.