∑ stood-offthe wallor frameby a minimum distanceof 30 mm to enablethe
spacebetween the frameand box to be cleanedproperly.
RemoteI/O blocksand/orvalve islandsshouldbe installedin cabinetsor field
boxes.Thisis because the surfaces of valveislandsand remoteI/O blocksare
not easyto clean.
On/offvalvesand control valvesfrequentlyrequireone or more instrument
air connections,the air beingsupplied throughinstrumentair tubes. In principle,
the installation requirementsfor theseair tubesare similarin natureas thosefor
electricalor control cabling. Valvesshould be procured suchthat onlya single
instrumentair connection is requiredand other air distribution is integralto the
valve.
15.4.9 Lighting
Lightsources mustnot be placed aboveopenprocesses,sinceshould theybe
damaged,broken fragments will fall into openprocess equipment. Whensucha
lightsourcecannotbe avoided,e.g. abovea monitoringpoint,non-glass tubes or
shatter-proofglass shouldbe used.Lighting fixturesand their support are
designedto avoidaccumulationof dust,especially wherecross-contamination
riskscouldarise.Horizontalsurfacesneedto be minimised.
Light(bulbsor tubes) sourcesare coveredwitha protective filmor covered
by polycarbonateto prevent glassshatteringon breakage.Theselightsshould be
changed regularlyas protective films becomebrittlein time. Lightsources must
havewatertightenclosures.
Lighting unitscan be unpluggedand removedfromthe processingareaso
that bulbscan be changed out of processingarea.This facilitateseaseof bulb
changing.
15.5 Installation requirements for high-hygiene areas
A significant part of boththe electrical and controlinstallationsis located within
the hygienicproductionarea, e.g. power cabling supplyingmotorsor packaged
plant/machinery,and control cablesconnecting sensors via fieldboxes/cabinets
to the plant control system(Fig.15.5).These cables should be routed,and
connections made, in such a manner as to create hygienically acceptable
installations.
15.5.1 Generalrequirementsfor wiringinstallations
In hygienic production areas, the electricaland controlinstallationsshould be
limited to that absolutelynecessary for the safe and correctoperation of the plant.
Therefore,the majority of cablingshouldbe routedoutside the production area
where no hygiene classificationis required, e.g. mounted on cable traysinstalled
in the servicearea located abovethe ceiling of the hygienicproductionarea.
250 Handbookof hygiene controlin the foodindustry