failure. The drainopeningshallbe at a pointlow enoughso that leakingproduct
cannotcollect withinthe valvehousing.16.3.4 Draining
Mostvalvedesigns have addressedthe ability of the valveto be self-draining
when properlyinstalled. However,caremustbe exercised prior to installation,
as some manufacturers still requireattention to drainability of theirdesigns.
Uponinstallationof any multi-port valve,care mustbe takenby the installerto
assure that deadpockets are not createdin the product flowwhena portis
closed. Somevalve designs,suchas mostdiaphragmvalves, are inherently non-
self-draining. In these cases, the valve should have a clearly identified
orientationmarkon the valvebodyto indicateproper installationangles.
Self-drainingis not a majorconsiderationin dry productprocesses. These
systems are designedto go for extendedperiodsof timewithonlydry cleaning.
In thoserareinstanceswhere wet cleaning is necessary because of a con-
taminationor a majormaintenance project,the entiresystem, including any
valves, must be disassembledto cleanand thoroughly dry the wettedsurfaces.16.3.5 Eliminationof cracks, crevices and niches
Some valvedesigns,evenwithautomaticactuators, are inherentlynot suitable
for CIPor mechanical cleaningmethods. Thesedesigns tendto havelarge
sliding seal areas as in plug,ball,iris, inflatableseal duct, and diverter type
valves. The sliding seal will containa filmof product throughoutproduction.
The tolerancesof the sliding seals prohibit the transport of the sufficient
cleaningand sanitizing fluidsto achievecleaningand decontamination.
A valve'sdesignmust takeintoconsiderationthe properattachmentand
compression of elastomeric components.The compression of the elastomeric
componentsmust be controlled so that the materials cannotbe over-compressed,
causing themto extrudeinto the product flow.Additionally,the compression
must be sufficient to assurea tightseal acrossthe full temperature rangeof
processing,cleaningand sterilization.
Theattachmentof elastomericcomponents to metalliccomponents shall
assure that the intended flexingof the elastomericcomponents does not create
crevices or cracksto openbetween the componentsas theyare cycled.Lip seal
valves can be used onlyunder specialconditionswhere cleaning and sanitation
havebeenvalidatedand documented.16.3.6 Internalangles and corners
Sharp or decreasinginternalangles and cornerswithina valvemustbe avoided
to assure that hardto cleanareasare not created in the design.This is especially
importanton valves thatare subjectedto manual cleaningprocedures.The
internal radiimust be sufficiently largeto allowfor the cleaning implementsto
270 Handbookof hygiene controlin the foodindustry