Siemens SITRANS LG250 User manual

Operating Instructions • 03/2014
Guided Wave Radar
SITRANS LG250
4 … 20 mA/HART - two-wire
Rod and cable probe
With SIL qualication

2PBD-51041388SITRANS LG250 - Operating Instructions
46201-EN-150424

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PBD-51041388 SITRANS LG250 - Operating Instructions
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Contents
1 About this document
1.1 Function ........................................................................................................................... 5
1.2 Target group ..................................................................................................................... 5
1.3 Symbols used................................................................................................................... 5
2 For your safety
2.1 Authorised personnel ....................................................................................................... 6
2.2 Appropriate use................................................................................................................ 6
2.3 Warning about incorrect use............................................................................................. 6
2.4 General safety instructions............................................................................................... 6
2.5 CE conformity................................................................................................................... 6
2.6 SILqualicationaccordingtoIEC61508.......................................................................... 7
2.7 FulllmentofNAMURrecommendations ......................................................................... 7
2.8 Environmental instructions ............................................................................................... 7
3 Product description
3.1 Conguration.................................................................................................................... 8
3.2 Principle of operation........................................................................................................ 9
3.3 Packaging, transport and storage................................................................................... 11
3.4 Accessories and replacement parts ............................................................................... 11
4 Mounting
4.1 General instructions ....................................................................................................... 13
4.2 Mountinginstructions ..................................................................................................... 13
5 Connecting to power supply
5.1 Preparing the connection ............................................................................................... 21
5.2 Connection..................................................................................................................... 22
5.3 Wiring plan, single chamber housing.............................................................................. 23
5.4 Wiring plan, double chamber housing ............................................................................ 23
5.5 Double chamber housing with DIS-ADAPT .................................................................... 24
5.6 Wiring plan, Ex-d-ia double chamber housing................................................................ 25
5.7 Supplementary electronics............................................................................................. 26
5.8 Switch-on phase............................................................................................................. 26
6 Functional safety (SIL)
6.1 Objective........................................................................................................................ 28
6.2 SILqualication.............................................................................................................. 28
6.3 Application area ............................................................................................................. 28
6.4 Safety concept of the parameterization .......................................................................... 29
6.5 Setup process ................................................................................................................ 30
7 Set up with the display and adjustment module
7.1 Insert display and adjustment module............................................................................ 33
7.2 Adjustment system......................................................................................................... 33
7.3 Parameter adjustment .................................................................................................... 35
7.4 Saving the parameter adjustment data........................................................................... 56
8 Setup with PACTware
8.1 Connect the PC.............................................................................................................. 57
8.2 Parameter adjustment with PACTware............................................................................ 58
8.3 Saving the parameter adjustment data........................................................................... 59

4PBD-51041388SITRANS LG250 - Operating Instructions
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9 Set up with other systems
9.1 DD adjustment programs ............................................................................................... 60
9.2 Communicator 375, 475................................................................................................. 60
10 Diagnostics and servicing
10.1 Maintenance .................................................................................................................. 61
10.2 Diagnosis memory ......................................................................................................... 61
10.3 Status messages............................................................................................................ 62
10.4 Rectify faults................................................................................................................... 66
10.5 Exchanging the electronics module................................................................................ 68
10.6 Exchanging the cable/rod............................................................................................... 69
10.7 Software update ............................................................................................................. 71
10.8 How to proceed if a repair is necessary.......................................................................... 71
11 Dismount
11.1 Dismounting steps.......................................................................................................... 72
11.2 Disposal ......................................................................................................................... 72
12 Supplement
12.1 Technical data ................................................................................................................ 73
12.2 Dimensions .................................................................................................................... 84
Safety instructions for Ex areas
PleasenotetheEx-specicsafetyinformationforinstallationandop-
eration in Ex areas. These safety instructions are part of the operating
instructions manual and come with the Ex-approved instruments.
Editing status: 2014-03-17

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PBD-51041388 SITRANS LG250 - Operating Instructions
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1 About this document
1.1 Function
This operating instructions manual provides all the information you
need for mounting, connection and setup as well as important instruc-
tionsformaintenanceandfaultrectication.Pleasereadthisinforma-
tion before putting the instrument into operation and keep this manual
accessible in the immediate vicinity of the device.
1.2 Target group
This operating instructions manual is directed to trained specialist
personnel.The contents of this manual should be made available to
these personnel and put into practice by them.
1.3 Symbols used
Information, tip, note
This symbol indicates helpful additional information.
Caution: If this warning is ignored, faults or malfunctions can result.
Warning: If this warning is ignored, injury to persons and/or serious
damage to the instrument can result.
Danger: If this warning is ignored, serious injury to persons and/or
destruction of the instrument can result.
Ex applications
This symbol indicates special instructions for Ex applications.
• List
The dot set in front indicates a list with no implied sequence.
→ Action
This arrow indicates a single action.
1 Sequence of actions
Numbers set in front indicate successive steps in a procedure.

6PBD-51041388SITRANS LG250 - Operating Instructions
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2 For your safety
2.1 Authorised personnel
All operations described in this operating instructions manual must
be carried out only by trained specialist personnel authorised by the
plant operator.
During work on and with the device the required personal protective
equipment must always be worn.
2.2 Appropriate use
SITRANS LG250 is a sensor for continuous level measurement.
Youcannddetailedinformationabouttheareaofapplicationin
chapter "Product description".
Operational reliability is ensured only if the instrument is properly
usedaccordingtothespecicationsintheoperatinginstructions
manual as well as possible supplementary instructions.
2.3 Warning about incorrect use
Inappropriate or incorrect use of the instrument can give rise to
application-specichazards,e.g.vesseloverllordamagetosystem
components through incorrect mounting or adjustment.
2.4 General safety instructions
This is a state-of-the-art instrument complying with IEC 61508 and
all prevailing regulations and guidelines.The instrument must only be
operatedinatechnicallyawlessandreliablecondition.Theoperator
is responsible for the trouble-free operation of the instrument.
During the entire duration of use, the user is obliged to determine the
compliance of the necessary occupational safety measures with the
current valid rules and regulations and also take note of new regula-
tions.
The safety instructions in this operating instructions manual, the cor-
respondingSafetyManual,thenationalinstallationstandardsaswell
as the valid safety regulations and accident prevention rules must be
observed by the user.
For safety and warranty reasons, any invasive work on the device
beyond that described in the operating instructions manual may be
carried out only by personnel authorised by the manufacturer. Arbi-
traryconversionsormodicationsareexplicitlyforbidden.
The safety approval markings and safety tips on the device must also
be observed.
2.5 CE conformity
ThedevicefulllsthelegalrequirementsoftheapplicableECguide-
lines.ByaxingtheCEmarking,weconrmsuccessfultestingofthe
product.

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PBD-51041388 SITRANS LG250 - Operating Instructions
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YoucanndtheCECerticateofConformityinthedownloadsection
of our homepage.
Electromagnetic compatibility
Instruments in four-wire or Ex-d-ia version are designed for use in an
industrial environment. Nevertheless, electromagnetic interference
from electrical conductors and radiated emissions must be taken into
account, as is usual with class A instruments according to EN 61326-
1.Iftheinstrumentisusedinadierentenvironment,theelectromag-
netic compatibility to other instruments must be ensured by suitable
measures.
2.6 SILqualicationaccordingtoIEC61508
The Safety Integrity Level (SIL) of an electronic system is used to as-
sess the reliability of integrated safety functions.
Fordetailedspecicationofthesafetyrequirements,multipleSIL
levelsarespeciedaccordingtosafetystandardIEC61508.Youcan
nddetailedinformationinchapter"Functional safety (SIL)"
TheinstrumentmeetsthespecicationsofIEC61508:2010(Edi-
tion2).Itisqualiedforsingle-channeloperationuptoSIL2.The
instrument can be used homogeneously redundant up to SIL3 in
multi-channel architecture with HFT 1.
2.7 FulllmentofNAMURrecommendations
ThedevicefulllstherequirementsoftheapplicableNAMURrecom-
mendations.
2.8 Environmental instructions
Protection of the environment is one of our most important duties.
That is why we have introduced an environment management system
with the goal of continuously improving company environmental pro-
tection.Theenvironmentmanagementsystemiscertiedaccording
to DIN EN ISO 14001.
Pleasehelpusfulllthisobligationbyobservingtheenvironmental
instructions in this manual:
• Chapter "Packaging, transport and storage"
• Chapter "Disposal"

8PBD-51041388SITRANS LG250 - Operating Instructions
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3 Product description
3.1 Conguration
Thetypelabelcontainsthemostimportantdataforidenticationand
use of the instrument:
2
1
5
3
6
4
7
8
11
12
13
14
10
9
1
Fig. 1: Layout of the type label (example)
1 Instrument type
2 Product code
3 Approvals
4 Power supply and signal output, electronics
5 Protection rating
6 Probe length
7 Process and ambient temperature, process pressure
8 Material, wetted parts
9 Hardware and software version
10 Order number
11 Serial number of the instrument
12 Symbol of the device protection class
13 ID numbers, instrument documentation
14 Reminder to observe the instrument documentation
15 NotiedauthorityforCEmarking
16 Approval directives
17 Marking of the safety function in SIS
This operating instructions manual applies to the following instrument
versions:
• Hardware from 1.0.0
• Software from 1.0.0
• DTMfromversion1.67.2
The instrument and the electronics version can be determined via the
product code on the type label as well as on the electronics.
• Standard electronics:Type FX80H.-SIL
The scope of delivery encompasses:
• Sensor
• Documentation
– This operating instructions manual
Type label
Scope of this operating
instructions manual
Versions
Scope of delivery

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PBD-51041388 SITRANS LG250 - Operating Instructions
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– SafetyManual(SIL)
– Testcerticatemeasuringaccuracy(optional)
– Operating instructions manual "Display and adjustment mod-
ule" (optional)
– Supplementary instructions manual "Plug connector for con-
tinuously measuring sensors" (optional)
– Ex-specic"Safety instructions" (with Ex versions)
– ifnecessary,furthercerticates
3.2 Principle of operation
The SITRANS LG250 is a level sensor with cable or rod probe for
continuous level or interface measurement, suitable for applications
in liquids.
DuetothequalicationuptoSIL2orhomogeneousredundantup
to SIL3 (IEC 61508) the SITRANS LG250 is suitable for the use in
safety-instrumented systems (SIS).
The safety function (SIF) can be a monitoring of the max. or min. level
or a combination of both.
High frequency microwave pulses are guided along a steel cable or
arod.Uponreachingtheproductsurface,themicrowavepulsesare
reected.Therunningtimeisevaluatedbytheinstrumentandoutput-
ted as level.
d
h
1
Fig. 2: Level measurement
1 Sensorreferenceplane(sealsurfaceoftheprocesstting)
d Distance to the interface (HART value 1)
h Height - Level
High frequency microwave impulses are guided along a steel cable or
rod.Uponreachingtheproductsurface,apartofthemicrowaveim-
pulsesisreected.Theotherpartpassesthroughtheupperproduct
andisreectedbytheinterface.Therunningtimestothetwoproduct
layers are processed by the instrument.
Application area
Functional principle -
level measurement
Functional principle - in-
terface measurement

10 PBD-51041388SITRANS LG250 - Operating Instructions
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TS
d1
h1
h2
d2
1
L2
L1
L3
Fig. 3: Interface measurement
1 Sensorreferenceplane(sealsurfaceoftheprocesstting)
d1 Distance to the interface (HART value 1)
d2 Distance to the level (HART value 3)
TS Thickness of the upper medium (d1 - d2)
h1 Height - Interface
h2 Height - Level
L1 Lower medium
L2 Upper medium
L3 Gas phase
Uppermedium(L2)
• The upper medium must not be conductive
• The dielectric constant of the upper medium or the actual distance
totheinterfacemustbeknown(inputrequired).Min.dielectriccon-
stant:1.6.Youcanndalistofdielectricconstantsonourhome
page: www.siemens.com/sitranslg.
• The composition of the upper medium must be stable, no varying
products or mixtures
• Theuppermediummustbehomogeneous,nostratications
within the medium
• Min.thicknessoftheuppermedium50mm(1.97in)
• Clear separation from the lower medium, emulsion phase or detri-
tus layer max. 50 mm (1.97 in)
• If possible, no foam on the surface
Lower medium (L1)
• The dielectric constant must be 10 higher than the dielectric
constant of the upper medium, preferably electrically conductive.
Example: upper medium dielectric constant 2, lower medium at
least dielectric constant 12.
Gas phase (L3)
• Air or gas mixture
• Gas phase - dependent on the application, gas pahse does not
always exist (d2 = 0)
Prerequisites for inter-
face measurement

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PBD-51041388 SITRANS LG250 - Operating Instructions
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The instrument is always preset to the application "Level measure-
ment".
For the interface measurement, you can select the requested output
signal with the setup.
3.3 Packaging, transport and storage
Your instrument was protected by packaging during transport. Its
capacity to handle normal loads during transport is assured by a test
according to DIN EN 24180.
The packaging of standard instruments consists of environment-
friendly, recyclable cardboard. For special versions, PE foam or PE
foil is also used. Dispose of the packaging material via specialised
recycling companies.
Transport must be carried out in due consideration of the notes on the
transport packaging. Nonobservance of these instructions can cause
damage to the device.
The delivery must be checked for completeness and possible transit
damage immediately at receipt. Ascertained transit damage or con-
cealed defects must be appropriately dealt with.
Uptothetimeofinstallation,thepackagesmustbeleftclosedand
stored according to the orientation and storage markings on the
outside.
Unlessotherwiseindicated,thepackagesmustbestoredonlyunder
the following conditions:
• Not in the open
• Dry and dust free
• Not exposed to corrosive media
• Protected against solar radiation
• Avoiding mechanical shock and vibration
• Storage and transport temperature see chapter "Supplement -
Technical data - Ambient conditions"
• Relative humidity 20 … 85 %
3.4 Accessories and replacement parts
The display and adjustment module LG Local Display Interface is
used for measured value indication, adjustment and diagnosis. It can
be inserted into the sensor and removed at any time.
Youcanndadditionalinformationintheoperatinginstructions
manual "LG Local Display Interface" (Document-ID 43838).
The LG Remote Interface is an external display and adjustment unit
for sensors with single chamber housing and Ex-d double chamber
housing.
It is suitable for measured value indication and adjustment of sensors
and is connected to the sensor with a four-wire standard cable up to
50 m (164 ft) long.
Output signal
Packaging
Transport
Transport inspection
Storage
Storage and transport
temperature
Display and adjustment
module
External display and
adjustment unit

12 PBD-51041388SITRANS LG250 - Operating Instructions
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Youcanndadditionalinformationintheoperatinginstructions
manual "LG Remote Interface".
The LG Remote Interface is suitable for measured value indication
and adjustment of sensors with HART protocol. It is looped into the
4 … 20 mA/HART signal cable.
Youcanndadditionalinformationintheoperatinginstructions
manual "LG Remote Interface".
The adapter "DISADAPT" is an accessory part for sensors with dou-
ble chamber housings. It enables the connection of the exterbal dis-
playandadjustmentunittothesensorhousingviaanM12x1plug.
Youcanndfurtherinformationinthesupplementaryinstructions
"Adapter DISADAPT".
The electronics module SITRANS series LG is a replacement part for
TDRsensorsofSITRANSseriesLG.Thereisadierentversionavail-
able for each type of signal output.
Youcanndfurtherinformationintheoperatinginstructionsmanual
"ElectronicsmoduleSITRANSseriesLG".
If you are using an instrument with rod version, you can extend the
rod probe individually with curved segments and rod extensions of
dierentlengths.
All extensions used must not exceed a total length of 6 m (19.7 ft).
The extensions are available in the following lengths:
Rodø12mm(0.47in)
• Basic segments: 20 … 5900 mm (0.79 … 232 in)
• Rod segments: 20 … 5900 mm (0.79 … 232 in)
• Curved segments: 100 x 100 mm (3.94 … 3.94 in)
Youcanndfurtherinformationintheoperatinginstructionsmanual
"Rod extension SITRANS series LG".
If you mount the SITRANS LG250 in a bypass tube or standpipe, you
have to avoid contact to the bypass tube by using a spacer at the
probe end.
Youcanndadditionalinformationintheoperatinginstructions
manual "Centering".
External display and ad-
justmentunitwithHART
protocol
DISADAPT
Electronics module
Rodextension
Spacer

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PBD-51041388 SITRANS LG250 - Operating Instructions
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4 Mounting
4.1 General instructions
Withinstrumentswiththreadedprocesstting,suitabletoolsmustbe
applied for tightening the hexagon.
Warning:
The housing must not be used to screw the instrument in! Applying
tightening force can damage internal parts of the housing.
Usetherecommendedcables(seechapter"Connectingtopower
supply") and tighten the cable gland.
You can give your instrument additional protection against moisture
penetration by leading the connection cable downward in front of the
cableentry.Rainandcondensationwatercanthusdraino.Thisap-
plies mainly to outdoor mounting as well as installation in areas where
high humidity is expected (e.g. through cleaning processes) or on
cooled or heated vessels.
In the case of instrument housings with self-sealing NPT threads, it is
not possible to have the cable entries screwed in at the factory. The
openings for the cable glands are therefore covered with red protec-
tive caps as transport protection.
Prior to setup you have to replace these protective caps with ap-
proved cable glands or close the openings with suitable blind plugs.
The suitable cable glands and blind plugs come with the instrument.
Makesurethatallpartsoftheinstrumentexposedtotheprocess,in
particular the active measuring component, process seal and process
tting,aresuitablefortheexistingprocessconditions.Theseinclude
above all the process pressure, process temperature as well as the
chemical properties of the medium.
Youcanndthespecicationsinchapter"Technical data" resp. on the
nameplate.
4.2 Mounting instructions
MountSITRANSLG250insuchawaythatthedistancetovessel
installations or to the vessel wall is at least 300 mm (12 in). In non-
metallic vessels, the distance to the vessel wall should be at least
500 mm (19.7 in).
During operation, the probe must not touch any installations or the
vessel wall. If necessary, fasten the probe end.
In vessels with conical bottom it can be advantageous to mount the
sensor in the center of the vessel, as measurement is then possible
nearly down to the lowest point of the bottom. Keep in mind that
measurement all the way down to the tip of the probe may not be pos-
sible.The exact value of the min. distance (lower dead band) is stated
in chapter "Technical data".
Screwing in
Moisture
Cableentries-NPT
thread
Suitability for the process
conditions
Installation position

14 PBD-51041388SITRANS LG250 - Operating Instructions
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Fig. 4: Vessel with conical bottom
Plastic vessel/Glass vessel
The guided microwave principle requires a metallic surface on the
processtting.Therefore,inplasticvessels,etc.,useaninstru-
mentversionwithange(fromDN50)orplaceametalsheet
(ø>200mm/8in)beneaththeprocessttingwhenscrewingitin.
Makesurethattheplatehasdirectcontactwiththeprocesstting.
When installing rod or cable probes in vessels without metal walls,
e.g.inplasticvessels,themeasuredvaluecanbeinuencedby
strongelectromagneticelds(emittedinterferenceaccordingto
EN 61326: class A). In this case, use a probe with coaxial version.
1 2
Fig. 5: Installation in non-metallic vessel
1 Flange
2 Metal sheet
Ifpossible,avoidsockets.Mountthesensorushwiththevesseltop.
If this is not possible, use short sockets with small diameter.
Type of vessel
Socket

15
PBD-51041388 SITRANS LG250 - Operating Instructions
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Higher sockets or sockets with a bigger diameter can generally be
used.They can, however, increase the upper blocking distance (dead
band). Check if this is relevant for your measurement.
In such cases, always carry out a false signal suppression after instal-
lation.Youcanndfurtherinformationunder"Setup procedure".
h
d
dh
DN40 ... DN150
> DN150 ... DN200
150
100
_
<
_
<
Fig. 6: Mounting socket
Whenweldingthesocket,makesurethatthesocketisushwiththe
vessel top.
1 2
Fig.7:Socketmustbeinstalledush
1 Unfavourable installation
2 Socketush-optimuminstallation
Before beginning the welding work, remove the electronics module
from the sensor. By doing this, you avoid damage to the electronics
through inductive coupling.
Donotmounttheinstrumentsinorabovethellingstream.Makesure
thatyoudetecttheproductsurface,nottheinowingproduct.
Welding work
Inowingmedium

16 PBD-51041388SITRANS LG250 - Operating Instructions
46201-EN-150424
Fig.8:Mountingofthesensorwithinowingmedium
The reference plane for the measuring range of the sensors is the
sealingsurfaceofthethreadorange.
Keep in mind that a min. distance must be maintained below the refer-
ence plane and possibly also at the end of the probe - measurement
in these areas is not possible (dead band).The length of the cable
can be used all the way to the end only when measuring conductive
products.Theseblockingdistancesfordierentmediumsarelisted
in chapter "Technical data". Keep in mind for the adjustment that the
default setting for the measuring range refers to water.
Theprocessttingmustbesealedifthereisgaugeorlowpressurein
the vessel. Before use, check if the seal material is resistant against
the measured product and the process temperature.
Themax.permissiblepressureisspeciedinchapter"Technical
data" or on the type label of the sensor.
Standpipes or bypass tubes are normally metal tubes with a diameter
of30…200mm(1.18…7.87in).Uptoadiameterof80mm(3.15
in) such a tube corresponds to a coax measuring probe. Lateral inlets
inbypasstubesdonotinuencethemeasurement.
MeasuringprobescanbemountedinbypasstubesuptoDN200.
For bypass tubes, select the probe length such that the blocking
distance (dead band) of the probe is above and below the lower
lateralllingopeningsofthebypasstube.Youcanthusmeasurethe
complete range of the medium in the bypass tube (h). When design-
ing the bypass tube, keep the blocking distance of the probe in mind
andselectthelengthofthebypasstubeabovetheupperlaterallling
opening accordingly.
Microwavescanpenetratemanyplastics.Thisiswhyplastictubesare
problematic for measurement applications. If durability is no problem,
we recommend the use of uncoated metal standpipes.
Measuring range
Pressure
Bypass tubes

17
PBD-51041388 SITRANS LG250 - Operating Instructions
46201-EN-150424
When the SITRANS LG250 is used in bypass tubes, contact with the
tube wall must be avoided. We recommend for this purpose a cable
probe with centering weight.
Caution:
When mounting, make sure that the cable is straight over its entire
length. A kink in the cable can cause measurement errors and contact
with the tube.
With rod probes, a spacer is generally not required. However, if there
is a risk of the rod probe being pressed against the tube wall by in-
owingmedium,youshouldmountaspacerattheprobeendtoavoid
contact with the tube wall. In the case of cable probes, the cable can
be strained.
Keep in mind that buildup can form on the spacers. Strong buildup
caninuencethemeasurement.
1
2 3
h
Fig. 9: Mounting in a bypass tube - Position of the spacer or the centering weight
1 Rodprobewithspacer(PEEK)
2 Cableprobewithcenteringweight
3 Spacer(PEEK)onthegravityweightofacableprobe
h Measurable tube section
Note:
Measurementinastandpipeisnotrecommendedforextremelyadhe-
sive products. In case of slight buildup, you should choose a bypass
tube with bigger diameter.
Instructions for the measurement:
• The 100 % point with bypass tubes should be below the upper
tube connection to the vessel.
• The 0 % point with bypass tubes should be above the lower tube
connection to the vessel.

18 PBD-51041388SITRANS LG250 - Operating Instructions
46201-EN-150424
• A false signal suppression with installed sensor is generally rec-
ommended to achieve the best possible accuracy.
Standpipes or surge pipes are normally metal tubes with a diameter
of30…200mm(1.18…7.87in).Uptoadiameterof80mm(3.15
in), such a pipe corresponds to a coax measuring probe. It does not
matter if the standpipe is perforated or slotted for better mixing.
MeasuringprobescanbemountedinstandpipesuptoDN200.
≥ 10 mm
(0.39")
≥ 10 mm
(0.39")
ø 150 - 200 mm
(5.91 - 7.87")
ø 150 - 200 mm
(5.91 - 7.87")
h
1
2
AB
3
Fig. 10: Mounting in a standpipe
1 Holes (for mixing)
2 Standpipe - vertically mounted - max. deviation 10 mm (0.4 in)
3 Ventilation opening
A Rod probe with spacer (steel)
B Cableprobewithcenteringweight
For standpipes, select the probe length such that the upper blocking
distance (dead band) of the probe is above the upper ventilation hole.
This allows you to measure the total level range of the medium in the
standpipe.When designing the standpipe, keep the upper blocking
distance of the probe in mind and plan the length above the upper
lateralllingopeningaccordingly.
Standpipes

19
PBD-51041388 SITRANS LG250 - Operating Instructions
46201-EN-150424
Microwavescanpenetratemanyplastics.Thisiswhyplastictubesare
problematic for measurement applications. If durability is no problem,
we recommend the use of uncoated metal standpipes.
When the SITRANS LG250 is used in standpipes, contact with the
tube wall must be avoided. We recommend for this purpose a cable
probe with centering weight.
Caution:
When mounting, make sure that the cable is straight over its entire
length. A kink in the cable can cause measurement errors and contact
with the tube.
With rod probes, a spacer is generally not required. However, if there
is a risk of the rod probe being pressed against the tube wall by in-
owingmedium,youshouldmountaspacerattheprobeendtoavoid
contact with the tube wall. In the case of cable probes, the cable can
be strained.
Keep in mind that buildup can form on the spacers. Strong buildup
caninuencethemeasurement.
Note:
Measurementinastandpipeisnotrecommendedforextremely
adhesive products. In case of slight buildup, you should choose a
standpipe with bigger diameter.
Instructions for the measurement:
• The 100 % point with standpipes should be below the upper
ventilation hole.
• The 0 % point in standpipes should be above the gravity or center-
ing weight.
• A false signal suppression with installed sensor is generally rec-
ommended to achieve the best possible accuracy.
If there is a risk of the cable probe touching the vessel wall during
operation due to product movements or agitators, etc., the measuring
probeshouldbesecurelyxed.
Thereisaninsidethread(M8)inthegravityweight,e.g.foraneye-
bolt (optional).
Makesurethattheprobecableisnotcompletelytaut.Avoidtensile
loads on the cable.
Avoidundenedvesselconnections,i.e.theconnectionmustbe
eithergroundedreliablyorisolatedreliably.Anyundenedchangeof
this requirement can lead to measurement errors.
If there is a danger of the rod probe touching the vessel wall, then the
probe must be fastened at the bottom end.
Keep in mind that below the fastening, a measurement is not possible.
Fasten

20 PBD-51041388SITRANS LG250 - Operating Instructions
46201-EN-150424
1
2
1
2
Fig. 11: Fasten the probe
1 Measuring probe
2 Retaining sleeve
Incaseofdicultinstallationconditions,theprobecanbealso
mounted laterally. For this purpose, adapt the rod with rod extensions
or bow-shaped segments.
Let the probe length determine automatically by the instrument to
compensate the resulting running time changes.
The determine probe length can deviate from the actual probe length
when using bow-shaped segments.
If installations such as struts, ladders, etc. exist on the vessel wall,
then the probe should have a distance to the vessel wall of at least
300 mm (11.81 in).
Youcanndfurtherinformationinthesupplementaryinstructionsof
the rod extension.
Incaseofdicultinstallationconditions,forexampleinasocket,the
probe can be adapted respectively with a rod extension.
Let the probe length determine automatically by the instrument to
compensate the resulting running time changes.
Youcanndfurtherinformationinthesupplementaryinstructionsof
the rod extension.
Lateral installation
Rodextension