YOKOGAWA AXFA14G - Page 8

<3. Installation>
7
IM 01E20A01-01EN
(4) Maintaining Stable Fluid Conductivity
IMPORTANT
Donotinstalltheowmeterwhereuidconductivity
tends to become uneven. If chemicals are fed near
theupstreamsideofamagneticowmeter,theymay
affecttheowrate’sindications.Toavoidthissituation,
it is recommended that the chemical feed ports be
locatedonthedownstreamsideoftheowmeter.If
it is unavoidable that chemicals must be fed on the
upstreamside,provideasufcientlengthofstraight
run (approximately 50D or more) to ensure the proper
mixtureofuids.
(Incorrect)
Upstream side
(Correct)
Downstream side
F0302.ai
Figure 3.1.2 Chemical Injection
(5) Precautions for Use of Liquid Sealing
Compounds
IMPORTANT
Care must be taken in using liquid sealing compounds
onthepiping,asitmayhaveanegativeinuence
ontheowindicationsbyowingoutandcovering
the surfaces of an electrode or grounding ring. In
particular, care must be taken if a liquid sealing
compound is used in the case of vertical piping.
(6) Service Area
Select locations where there is adequate space to service
installing, wiring, overhauling, etc.
(7) Bypass Line
It is recommended to install a bypass line to facilitate
maintenance and zero adjustment.
Bypass valve
Block valve
Block valve
F0303.ai
Figure 3.1.3 Bypass Line
(8) Supporting the Flowmeter
CAUTION
Donotsecuretheowmeterseparatelytopreventthe
vibrations, shocks, and expansion and contraction forces
ofthepipingfromaffectingit.Fixthepipesrst,then
supporttheowmeterwiththepipes.Withextrasmall-
sizedowmeters(sizes2.5to10mm(0.1to0.4in.)),in
particular,xtheowmeterinparallelwiththepipingona
mounting base.
(9) Mounting Positions
 Pipesmustbefullylledwithliquids.
IMPORTANT
Itisessentialthatpipesremainfullylledatalltimes,
otherwiseowrateindicationsmaybeaffectedand
measurement errors may be caused.
Piping shall be designed so as to maintain the interior
oftheowtubelledwithuids.
Vertical mounting is effective in such cases as
whenuidstendtoseparateorsolidmattermaybe
precipitated. When employing vertical mounting, direct
theuidsfromthebottomtothetoptoensurethatthe
pipesremainfullylled.
h
h>0
h>0
h
F0304.ai
(Incorrect)
(Correct)
(Incorrect)
(Correct)
Figure 3.1.4 Mounting Positions
 Avoid air bubbles.
IMPORTANT
Ifairbubblesenterameasurementpipe,owrate
indications may be affected and measurement errors
may be caused.
Incaseswhereuidscontainairbubbles,pipingmust
be designed to prevent them from accumulating in the
measurementpipeofaowtube.
Ifavalveexistsneartheowmeter,trytomountthe
owmeteronthevalve’supstreamsideinorderto
prevent a possible reduction of pressure inside the pipe,
thereby avoiding the possibility of air bubbles.
(Correct)
(Incorrect)
Valve
F0305.ai
(Correct)
(Incorrect)
Figure 3.1.5 Avoiding Air Bubbles
Installation
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