The volumeof fluidusedfor the intermediate rinsingstepsshould be keptto
a minimum. Intermediaterinsinghas no real cleaningtask and merely serves as
a separatorbetween the cleaningsteps (e.g.fromcausticsolution to acid),so
sending an appropriately sized water barrier through the pipe system is
sufficient.This barriercan be produced as a definedvolumeusinga volumeter.
Intermediate rinsingphases that fill the entirepipesystemsignificantlyincrease
fresh-water lossesand effluent rates,and this effectis particularlyextreme in
systems of longand/orwidepipes.
The volumeof media usedfor flush-outsduringa phasechange-overshould
be calculatedusing appropriatemeasuringmethods. In this instance, conduc-
tivityand volumemeasurementsare adequate. Controllingby timingis not
recommendedbecause this methodrequires a constantflowrate,whichcannot
be guaranteedbecauseof fluctuatingpressurefromthe watermains.
Cleaningsystempartsshouldnot be arrangedin parallel withthe production
systemto be cleaned.Parallel pipesystems divideflowand leadto undefined
flowin the associatedpartialsystems,theyalso increasetransition zonesduring
flush-out and ultimatelycontributeto detergent losses.
Measuring unitsusedfor next-stepswitching of the cleaning stepsshould be
installed at optimal pointsin the pipesystem.Positioningmeasuring points
carefullyavoidsunnecessary waste of time. For instance,temperaturemeasure-
mentsshould be taken at the outletof the production system, to ensure that the
required temperature has beenreached. Downstream CIP returnsdo not needto
be heated beforenext-stepswitching can takeplace.
CIP supplysystems should be equippedwithshuttlevalves that distribute CIP
mediato the individualCIP circuits. For CIP return,shuttlevalves are usedto
combineCIP mediafromthe individualCIP circuits. The shuttlevalvesprevent
contaminationor mixing of the mediafromdifferentpartsof the system.
27.4.2 Other operationswithinthe CIPsystem
Refillingthe recoverytanks withfreshwater
Thisproceduretakesplace onlywhenthe CIPcircuitsassociated withthe
recoverytankconcernedare not operating,as otherwise the tankwouldover-
flow.The recovery tanksfor detergent,causticand acidmust be refilled auto-
matically withfreshwaterwhen the volumefallsbelowfillinglevel HL,to
lowerthe primary concentration.Duringthe subsequentcirculation,the required
concentrationis re-established in the circuitby in-linedosing. Afterthe contents
of the circuit are flushedout into the recoverytank, the primaryconcentration
increases again,and mayreach the maximumconcentrationfor use.
The recoverytank for returnwaterneedsno additional refilling becausemore
returnwateris produced thanneeded, so this tanktendsto overflow ratherthan
empty.In the unusual eventthat the levelin the recoverytankfor returnwater
dropstoo low,it is possible to switch overto fresh-water supply.Whenthe level
in the returnwaterrecoverytankreachesthe higherlevel,LH,it mustbe
Improving cleaning-in-place (CIP) 441