20 min as a minimum.Duringsteamsterilisation, all product contactsurfaces
shallreachthe requiredtemperatures. The dynamic sealsshould be double seal
arrangements to allowfor a secondarybarrierof steam or sterile liquids. The
staticsealsmaycomprisea singleseal arrangement, providedthat it doesnot
allow any external contamination under any operational conditions. If
satisfactory operationcannotbe assuredwitha singleseal,thena doubleseal
arrangement witha continuous sterilebarrier must be provided.Depending on
the application,in particularon the length of the productionperiod,the sterile
barrier mayconsist of a sterile fluid or an antimicrobial fluid(e.g.steam, hot
wateror chemical solution).
18.4 Materials and motordesign
All productcontactedpartsgenerally consistof stainlesssteel(e.g.1.4301(X5
CrNi18-10),1.4306(X2 CrNi 19-11), 1.4541(X6 CrNiTi18-10), 1.4401(X5
CrNiMo17-12-2),1.4404(X2 CrNiMo 17-12(13)-2),1.4571(X6 CrNiMoTi17-
12-2),1.4435(X2 CrNiMo18-14-3),1.4581(GX5CrNiMoNb 19-11-2), 1.4462
(X2 CrNiMoN 22-5-3), 1.4460(X3 CrNiMoN 27-5-2),1.4405(GX4CrNiMo
16-5-1),1.3974(X2CrNiMnMoNNb23-17-6-3),1.4542(X5 CrNiCuNb19-16-
1)). Suitablenon-metallic materials are carbon,siliconcarbide, tungstencarbide,
ebonite, nitrile rubbers,ethylene(polyethylenes), propylenes,fluoro rubbers
(Viton= DuPont registeredtrademark),siliconerubbers, urethanerubbers,
natural rubbers, PTFE (poly(tetrafluoroethene)), ETFE (ethylenetetrafluoro-
ethene), polyamide, perfluoroelastorners (Kalrez/Chemraz), ceramics and
aramides.Products in contact with elastomers should be Food and Drug
Administration(FDA),Codeof Federal Regulations(CFR) or Bundesinstitutfu»r
Risikobewertung(BfR) approved.
Standardthree-phase asynchronous motorsare preferable to motorswith
specialshafts(blocktype)because theycan be easily replacedthroughoutthe
world.Eachpumpmanufacturersees to it that the modular designof the pump
ensuresa maximumuse of standardisedpartsfor cost reasons and for adapting
the pumpcapacity to any hydraulic requirements.
18.5 Summary
To produce foodproducts in hygienicallyand microbiologicallyperfectcondi-
tion,highstandards are givento foodpumps withregardto hygienicdesignand
cleaning technological requirements. The main aspects in this respect are
hydraulic efficiency, flowcharacteristics,pocket-free designand low-cost manu-
facture. Thischapter has described the special requirementsof the foodindustry
on components, seals,cleanability, material compositionand surface quality.
Improving the hygienic designof pumps 285