18.3 Cleanability,surface finishand other requirements
Cleanabilityof all parts in contact withproductin flow(CIP,cleaning-in-place)
without the needof disassemblyis imperative.The product chamber must show
no deadendsand gaps.If the impelleris plugged, the hub of the impeller must
be sealedtowards the pumpshaftand towards the shaftnut. The seal rings must
be clampedin a waythat theyare exposed to and cleanedby the detergent
stream. Centringand guidingmustbe located outside the seals.The NPSHreq
value of the pumpshouldnot exceed 2 m. The reasonis that foodpumpsare
often usedas CIP pumpswithhot CIP mediasupply(up totà95 ÎC). The
chamber of the mechanical sealsmust havefree accessfor cleaning and cooling
the mechanicalseals.For all internal corners withan angle <135Î, the radius
must be >3.0 mm.All edgesmust be deburred.Exposedthreads,keywaysor
splinesshouldbe avoided.The outercontoursof the pumpmustensurefree
drainage of cleaning solutions,condensation waterand similar.
18.3.1 Surfacefinish
The surfacefinishinfluencesthe cleanability of pumpparts.The cleaningtimes
decreasewithimproved surfacefinishes. Typically highrelativevelocitiesand
turbulenceare created by the rotatingelements of pumps during cleaning. Test
results haveshown that the pump type (geometry) and operation(relative
velocities)havea significantinfluence on cleanability and cleaningof hygienic
pumps.
On CIP pumpsthe surface roughness of the partsin contactwiththe product
should not exceedRaà 3 :2 m (see EHEDG, 2004). For customer-specific
(aseptic)applicationsthe pump designmustallowthat the product-contacted
surfacescan be brought to a surfaceroughness (innersurface)ofRaà 0 :8 m
(EHEDGoptional,3A Standard).
18.3.2 Gentleproducthandling
Gentle handling of the product maybe an importantaspect withfoodpumps.
The shearing strainactingon the product mustnot be excessive.Thecore
parameterfor this unit is the flow velocityin the impeller channel. The meridian
absolute flowvelocityshould not exceedthe calculation pointcmà2 m/s. This
is also to the benefit of the NPSHreqvalue of the pump. The flow channels
should all be designedin true alignment and without dead ends.The use of spiral
housings with a logarithmically shaped spiral, if applicable,would be an
advantage.
18.3.3 Additional requirementsfor aseptic equipment
The equipment shall be designed as to be impermeable to external
microorganisms.The design mustallowfor steamsterilisationat 121 ÎC for
284 Handbookof hygiene controlin the foodindustry