It is consideredgoodinstallationpractice to routeinstrument air tubesand
electricalcables in separate trunkingsor conduits. Cable glands shouldhavea
minimumindex of protection of IP 55.
15.5.7 Connectionsto cabinets and fieldboxes
To enable manualcleaningand visual inspectionof enclosuresurface areas on
whichsoil can accumulate, it is necessary to keeptheseareasas smoothas
possible and preferably limitthe numberof connectionsto themto a minimum.
All connections(e.g.trunking, conduit, cable, air tubes)to cabinetsor field
boxesshould be madevia the bottomside of the cabinetor fieldbox.The best
wayto make the connection between the cabinetor fieldbox and:
∑ trunking must use a proprietary flare/flangetrunking fitting;
∑ conduitmust use a flange(or standard)typecoupling and malebush;
∑ cable must use a cable gland, complete withearthing tag (if required,
mountedinsidethe enclosure), locknutand shroud.
For eachof the aboveconnection methods, foodstandard flexiblesiliconepaste
(Permabondadhesives) shouldbe appropriately applied between the fitting,
coupling or gland and the enclosure to provide both a hygienically and
watertight acceptable connection.Anyboltsor set screwsusedshould be of the
captivetype.
15.5.8 Cabinets
In general,cabinets shouldbe located outsidethe hygienicproduction area. For
cabinets locatedin hygienicproduction areasthe requirementsdetailedbelow
apply.Wherepracticableand material availabilityallows, as a general principle
it is recommended for hygienic installationsthat the installer shouldstandardise
on 304 stainlesssteelcabinets. However,coatedmildsteel or plastic maybe
acceptable provided its exterior has a smoothfinishthat is easyto clean.A
cabinetshouldhavea minimumindexof protectionof IP 55, allowing dust to be
removedfromthe enclosure's exterior by watercleaning.
The distancebetween the cabinet baseand the floorshouldbe no less than
100 mm. Where cabinetsare wallmounted, the wholeof its outer perimeter
shouldbe sealedto the wallwitha foodstandardsilicon sealantto prevent
creatinga soil trap at the rear of the field box.
Temperature controlin cabinets requirespecialattention. Withinhygienic
productionareasit is not advisableto vent the enclosure or to createan
additional airflowsincethesecan leadto microorganismsbeingtransported
fromone point to anotherin the area where they can infect the equipment. Also,
an uncontrolled airflowfroma non-hygienicenvironment(cabinet internals)
into a hygienicarea should be avoided. For these reasonsthe use of ventilatorsin
cabinets should be avoided,especiallywhere the cabinetis locatedin close
proximity (within2 m) of the product.
Improvingthe hygienicdesignof electricalequipment 255