Collecting meaningful samples from cohesive and adhesive bulk solids in a downpipe
The compact screw sampler is particularly well suited for dry, powdery products that have restricted flowability on account of adhesive or cohesive properties. Here, the extraction of a meaningful analysis sample – under usually inhomogeneous transport conditions in the downpipe – requires the collection of a highly representative cross-section in the process line.
With an installation height of just 30 mm, the compact sampling screw can be effortlessly integrated in the product-carrying downpipe via a DN25 weld-on stud and a clamp connection. The immersion depth of the screw is adjusted between 200 mm and 300 mm depending on the cross-section of the production line to be sampled. Thanks to the openings in the sample collection tube, in which the screw runs, a representative cross-sectional sample of the free-falling particles is obtained. Prior to sampling, the screw runs in reverse gear for self-cleaning and empties the product that was collected between two measurements back into the product stream. The rotational speed and the runtime of the screw are adapted to the product and to the process conditions in order to obtain the optimum sample amount. In downpipes with typical throughputs ranging from 1 kg/h to over 1,000 kg/h, just a few seconds are enough to collect a representative analysis sample of approx. 2 g to 5 g. In order to optimise the sample extraction – e.g. for powders with poor flowing properties – it is also possible to assist the particle transport with aspirated secondary air or with optionally supplied compressed air. As an alternative to oxygen-rich air, inert gases can be used for fluidisation of products that are at risk of oxidation. In order to adjust the SCREWSAMPLER even further to the product, feeding screws made of polyamide and stainless steel are optionally available.
The rotational speed and run time of the screw are software-controlled and follow the optical concentration defined for the sensor in order to branch off an optimal sub-amount of the product from the process stream. The feed of the extracted sample amount to a downstream laser diffraction or image analysis system takes place in a tube line and is ensured via the vacuum of the integrated RODOS dry dispersion in the MYTOS and PICTOS systems.
- Compact screw sampling in the downpipe | Installation height 30 mm
- For extraction of a representative cross-section from the product mass flow
- For cohesive and adhesive powders and granules ranging from 0.25 µm to 1,750 µm
- For downpipes with mass flow rates from 1 kg/h to 1,000 kg/h
- Downpipe diameters from 200 to 300 mm | Special lengths on request
- Product temperatures from -20°C to 80°C
- Operable at ambient temperatures from -20°C to 40°C
- Self-cleaning via change of rotation direction
