13.5 Types of equipmentin dry material handlingareas
Typicalequipment in the dry material handlingareaincludes,e.g.,powder
blenders,grinders,rotaryvalves,powder dischargesystems,fluid bed dryersand
spray dryers.In principleall the design criteria as mentionedearliershallbe
implementedin theseequipment. However, typicalhazards in all partsof the
totalprocess line are considered as well. For example:
∑ In thespraydriers and fluidbed systemspecialattention shouldbe paid to the
air inletsystem.The dryingair in fluid bed systems and spray dryersshould
be filtered to avoida directproduct contamination.EHEDG recommenda-
tionsare that the filtersshould be at leastof classEU-7for hot dryingair. In
the downstreampart of the spraydryerthe powder has to be transported with
coldair and this shallbe filteredwithan EU-10filter. The air outletsystem
can also be a critical area.Dustis collected in thesefiltersand frequently
pulsed backintothe product.Bag filtersin the fluidbed systemcan be
especiallycontaminatedwhen the cleaningproceduresare not carried out
accordingto strictprocedures.
∑ The dust extraction systemin thepowderchargecabinetsshouldbe designed
in sucha way that lumpsin the exhaustline cannotfall backinto the powder
(see Fig. 13.3).
∑ Rotaryvalvescannotbe cleanedin placeand therefore specialattention has
beenpaidin orderto design retractablerotor devices in orderto enhance the
cleaning procedures.
Fig. 13.3Powderchargecabinet(CIP= cleaning-in-place).226 Handbookof hygiene controlin the foodindustry