appealingand easysolution it actually creates serious soil traps and can
compromise electricalintegrity.
Conduitsshould be suitably sealedat bothends.Thisshould be achievedby
using a removable rubberplugat an openend wherea cable doesnot pass
throughor by a proprietary cablegland/sealing glandwherea cabledoespass
through.In ordernot to compromisethe sealing integrity of the conduit system
where cables enterand exit,cableglandsshould be dedicatedto a single cable
only.The index of protectionfor the conduit system should be no less thanIP
- In orderto maintain its integrity, it is important that all conduitentries, boxes
and couplings are adequately sealed.
It is permittedto run morethen one cable througha singleconduit. Whentwo
or morecables partlysharea commonroute, but go to differenttermination
points, the creation of unsealableopenings allowingthe cable(s) to enteror exit
the conduitshouldbe avoided.For long,verticalwiring routes,trunking should
be usedinstead of conduitto prevent the conductor or cablesufferingdamage by
its ownweight.
If cablesare installed in rigidconduit,thenfinal connectionsto equipment
that is subjectto vibration (e.g.motors) shouldbe madevia flexible conduit
(having a smoothouter surface) or by someothersuitable means. For example, a
suitable conduit box could be usedto connect the flexibleconduit to the ridged
conduit system.Sinceflexible conduitshouldnot be relieduponto provide
adequate earthcontinuity,it is necessaryto install a separate protective con-
ductor withinthe flexible conduitbetween the conduit box and the equipment.
This typeof installationis particularly suitedto the types of cable that require
additionalmechanical protection,e.g. PVCinsulatedsingle-corecables.
Where practicable,the practice of glandinga cabledirectly into a conduit
coupling shouldbe avoided. Conduitsystemsshouldprovideadequate meansof
access for drawing in cables.Thebendingradiusof every bendin a wiring
system shouldbe suchthat conductors and cablesdo not suffer damage.
15.5.5 Use of cableladderand cabletray
Owing to theiropen structure, cableladdersand cabletraysrequiresignificantly
more cleaningeffortthanthat required for trunking and conduit. Consequently,
the use of cableladdersand cabletrays withinthe hygienicproduction area is to
be avoided.
15.5.6 Cablesand flexible instrument air tubes
Cablesand flexibleinstrumentair tubesshouldhavea smooth outer PVCor
polypropylenesheath,as applicable,suchthat theyare easyto cleanwherenot
protectedby trunking or conduit. Whentwo single cables or tubes are routed
together in parallel they shouldnot be tied to eachother.Instead, they should be
separated by a distance of no less than 25 mm to prevent the build-up of soil and
to easecleaning.Stainless steel instrumentair tubeis easierto routeand givesa
much betterinstallationand so is preferredoverflexible PVC.
254 Handbookof hygiene controlin the foodindustry