∑ Pipediameters should not varytoo much(to realisesufficient flowduring
cleaning in all partsof the pipingsystem).
∑ The pipesystem should be drainable,^1 witha pitchof 1 in 100 and supported
to prevent sagging.
Although a pipingsystemdesignedaccording to the principles as described
aboveshould be easyto clean,this could be hampered by complexity.Whenthe
piping system contains many branchesone has to be very careful when
designingthe CIP system as usuallysequential and repeatedswitching of CIP
valves is needed. Options^4 for the design of piping systemsare given in
Baumbachand Hoogland.^517.3 Materials of construction
The default choicefor pipingsystems is stainlesssteel(AISI304 or AISI316);
however, alternativematerials shouldbe considered.The use of plasticpiping
systems for low-pressureapplications couldhavethe followingbenefits:
∑ the weldingproceduresare mainly automatic, requiring a low levelof skill;
∑ theyare ableto handle highlycorrosive products;
∑ plastic has superior insulating properties ± avoid condensation when
transporting cold products or reducingheat losseswhen used for heat
treatments(e.g.holdingtube);
∑ the possibility of making lightweightsystems in casethe plantneedsto be
mobile.
Next to thesebenefits thereare a number of uncertaintiesaboutthe use of
plastic pipework:
∑ plastic is moresensitiveto wear;
∑ welding requires special equipment;
∑ cleanability of plastic pipingneedsto be verified;
∑ limited availabilityof hygienic valvesand couplings.
Dependingon the localsituation,plastic pipingmightbe a goodalternativeto
stainlesssteel.
Trends such as late customisation',customisation on demand' and
`distributedmanufacturing'oftenrequire intermediate products to be stored,
transported and coupled to a second processlater.A simple way for doingthis is
the use of containersthat can be connected to the processes by flexibletubing.
This kindof systemis available froma number of suppliers. Selectionof a
system should be basedon the required level of hygiene and the cost of
operation.The currenttrend of healthy/fortifiedfoodsmightlead to the needfor
aseptic coupling of containers to processes,for example post-dosingof flavours
and micro-nutrientsto ultra-heat treated (UHT)sterilisedproducts.
274 Handbookof hygiene controlin the foodindustry