material and metalductsurface. In smaller diameterdevices,ductendsare
connected withrubberor plasticsleeves.
Ringclampsfor mountingflexible connectionsshouldbe placedclose to or
rightat the ductend to minimise deadareasfor dry material build-up as
demonstratedin Fig. 13.2.The plastic sleevemustallowsmallaxial and radial
movements withoutgeneratingaxialforces. The flexible material shouldhavea
smoothsurfacethat minimisessurface build-up of dry material.
Largerdiameter ductendsare oftenconnected withrubbertypeprofiles
mounted withflanges.Thesedevicesare most probablyneverremovedand
cleanability is difficult.As suchtheseare criticalareasin the processline.This
is one of the areas where improvementsare neededand present a challenge for
the currentengineers.
Fig. 13.1Examplesof staticflangesealsfor dry products:(a) hygienicallydesignedseal
usablefor wet cleaning,(b) seal creatinga gap and misalignment,(c) metal-to-metal
flangejoint(onlyfor dry cleaning).
Fig. 13.2Examplesof flexibleconnectionductends(right).One ring clampcloseto the
pipeend usedfor smallerdiameters;crevicenot totallyavoidable(left).Applicationof
two clamps,one of whichis mounteddirectlyat the pipeend to avoidany crevice
(middle).
Improving the hygienic designof equipmentin handling dry materials 225