KROHNE H250 M40 Series Wiring diagram

Equipment category II 2 G / II 2D , EPL Gb / Db
in equipment protection by flameproof enclosures Ex-d and
in equipment dust ignition protection by enclosure Ex-t
H250 M40
H250 M40H250 M40
H250 M40 Supplementary Instructions
Supplementary InstructionsSupplementary Instructions
Supplementary Instructions
© KROHNE 04/2016 - 4002069603 - AD H250-M40-ExII2GD-R03 en

CONTENTS
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H250 M40
1 Safety instructions 3
1.1 General notes ................................................................................................................... 3
1.2 EU conformity ................................................................................................................... 3
1.3 Approval according to the IECEx scheme ........................................................................ 3
1.4 Safety instructions............................................................................................................ 3
2 Device description 4
2.1 Description of device ........................................................................................................ 4
2.2 Description code............................................................................................................... 4
2.3 Marking............................................................................................................................. 5
2.4 Flammable products ........................................................................................................ 6
2.5 Device category ................................................................................................................ 6
2.6 Protection types................................................................................................................ 7
2.7 Ambient temperature / temperature classes.................................................................. 8
2.8 Surface temperature for equipment category II 2 D...................................................... 11
2.9 Electrical data................................................................................................................. 11
3 Installation 12
3.1 Installation...................................................................................................................... 12
3.2 Special conditions........................................................................................................... 13
4 Electrical connections 14
4.1 General notes ................................................................................................................. 14
4.2 Power supply .................................................................................................................. 15
4.3 Inputs/outputs ................................................................................................................ 15
4.4 Grounding and equipotential bonding............................................................................ 16
5 Operation 17
5.1 Start-up........................................................................................................................... 17
5.2 Operation ........................................................................................................................ 17
5.3 Electrostatic charge .......................................................................................................17
6 Service 18
6.1 Maintenance ................................................................................................................... 18
6.2 Dismantling .................................................................................................................... 18

SAFETY INSTRUCTIONS 1
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1.1 General notes
These additional instructions apply to explosion-protected versions of variable area flowmeters
with electrical built-ins and the marking II 2 G or II 2 D. They complete the standard manual for
the non-explosion protected versions.
The information given in this instruction contains only the data relevant to explosion protection
of category 2. The technical details given in the standard manual for the non-explosion protected
versions apply unchanged unless excluded or superseded by these supplementary instructions.
1.2 EU conformity
The manufacturer declares with the EU declaration of conformity on his own responsibility
conformity with the protection goals of directive 2014/34/EU for use in hazardous areas.
The EU declaration of conformity is based on the EC type examination certificate of the
Physikalisch Technische Bundesanstalt (PTB):
1.3 Approval according to the IECEx scheme
Conformity with IECEx standards was tested in accordance with the IECEx Certification Scheme
for Explosive Atmospheres acc. to IEC 60079-0, IEC 60079-1 and IEC 60079-31. The number of
the IEC certificate is:
1.4 Safety instructions
If these instructions are not followed, there is a risk of explosion.
Assembly, installation, start-up and maintenance may only be performed by personnel trained in
explosion protection!
PTB 12 ATEX 1025
PTB 12 ATEX 1025PTB 12 ATEX 1025
PTB 12 ATEX 1025
IECEx PTB 12.0034
IECEx PTB 12.0034IECEx PTB 12.0034
IECEx PTB 12.0034
CAUTION!
The operator or his agent is responsible for observing any additional standards, directives or
laws if required due to operating conditions or place of installation. This applies in particular to
the use of easily detachable process connections when measuring flammable media.

2 DEVICE DESCRIPTION
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2.1 Description of device
Variable area flowmeters measure and display the volume flow of flammable and non-
flammable gases and liquids. Depending on the device version, electrical limit switch contacts
with counter module, reed contacts, a 4...20 mA signal output with HART
®
communication, a
Foundation Fieldbus interface or a Profibus PA interface can be installed in the indication unit.
2.2 Description code
The safety description code * consists of the following elements:
* positions which are not needed are omitted (no blank positions)
1 Type series measuring unit H250
H250 - standard version, vertical upwards
H250H - horizontal orientation
H250U - vertical downwards
2 Measuring unit materials / versions
RR - Stainless steel
C - PTFE or PTFE/ceramics
HC - Hastelloy C
Ti - Titanium
F - Food
3 Heating jacket version
blanc - without heating jacket
B - with heating jacket
4 Signal converter version
M40 - Aluminium housing, painted (standard)
M40S - Aluminium housing with increased corrosion protection
M40R - Stainless steel housing
5 High temperature version
blanc - without HT extension
HT - with HT extension
6 Electrical signal output
blanc - without transmitter
ESK - Electrical signal output 4...20mA (ESK4)
. . . - optionally available with counter, I/O module and display (ESK4-T) or
. . . - Foundation Fieldbus (ESK4-FF) or
. . . - Profibus PA (ESK4-PA)
7 Limit switches
blanc - without limit switches
K1 - One limit switch
K2 - Two limit switches
R1 - 1 reed switch
R2 - 2 reed switches
8 Version
Ex - Explosion-protected version
9 SIL Version
SE - SIL compliant electronic signal output
SK - SIL compliant limit switch

DEVICE DESCRIPTION 2
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2.3 Marking
The marking of the entire device is on the indication unit, where the following identification plate
can be found (see also designation code).
Additional markings on the housing cover:
•SN - serial number
•SO - sales order / item
•PA - order
•Vxxx / Sxxx - product configurator code
•AC - article code
Additional plate
The association of the housing cover to the device is confirmed by an additional plate with the
serial number on the interior of the indicator part.
Figure 2-1: Example of a nameplate
1 Device type
2 Manufacturer
3 Identification number of the notified body ATEX & PED
4 Rating data: temperature & pressure rating
5 PED data
6 Ex data
7 Electrical connection data
8 Note to observe the documentation
9 Internet site of the manufacturer

2 DEVICE DESCRIPTION
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2.4 Flammable products
Atmospheric conditions:
Atmospheric conditions:Atmospheric conditions:
Atmospheric conditions:
The ATEX directive does not stipulate values for atmospheric conditions. However, for
determining the explosion characteristic parameters of temperature and pressure range, the
following is assumed as a basis:
T
atm
= -20...+60°C / -4...+140°F and P
atm
= 0.8...1.1 bar / 11.6...15.9 psi
Outside of these ranges, for most mixtures no key figures are available for the ignition
behaviour.
Operating conditions:
Operating conditions:Operating conditions:
Operating conditions:
Variable area flowmeters operate outside of atmospheric conditions, which means that
explosion protection according to the ATEX directive, regardless of the zone assignment, is
fundamentally not applicable due to the lack of key safety data for the interior of the measuring
unit.
2.5 Device category
Variable area flowmeters are designed in accordance with EN 60079-0, EN 60079-1 and
EN 60079-31 in category II 2 G / II 2 D or EPL Gb and EPL Db for use in zone 1 or zone 21. The
inside of the measuring unit is also approved for zone 1.
WARNING!
Operation with flammable products is only permitted as long as no explosive fuel/air mixture
builds up on the inside of the flowmeter under operating conditions. The operator is responsible
to ensure that the flowmeter is operated safely in terms of the temperature and pressure of the
products used. In case of operation with flammable products the measuring units must be
included in the periodic pressure tests of the system. When using the device version H250/C...
(PTFE version, non-conductive) the minimum conductivity of the media must be 10
-8
S/m, in
order to avoid danger from electrostatic charge.
INFORMATION!
Definition of zone 1 acc. to EN 1127-1, Appendix B:
An area in which an explosive atmosphere may occasionally occur as a result of the mixture of
flammable substances in the form of gas, steam or mist with air under normal operation.
Definition of zone 21 acc. to EN 1127-1, Appendix B:
An area in which an explosive atmosphere may occasionally occur in the form of a cloud of
flammable dust in the air under normal operation.

DEVICE DESCRIPTION 2
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2.6 Protection types
The variable area flowmeter is designed for equipment protection "flameproof enclosure",
protection level "Gb" acc. to EN 60079-1 and "Equipment - dust ignition protection through
enclosure", protection level "Db" acc. to EN 60079-31.
The marking is:
II 2G Ex d IIC T6...T1 Gb or II 2G Ex d IIB T6...T1 Gb or II 2D Ex t IIIC T70
II 2G Ex d IIC T6...T1 Gb or II 2G Ex d IIB T6...T1 Gb or II 2D Ex t IIIC T70II 2G Ex d IIC T6...T1 Gb or II 2G Ex d IIB T6...T1 Gb or II 2D Ex t IIIC T70
II 2G Ex d IIC T6...T1 Gb or II 2G Ex d IIB T6...T1 Gb or II 2D Ex t IIIC T70 °C Db
C DbC Db
C Db
The marking contains the following information:
The marking contains the following information:The marking contains the following information:
The marking contains the following information:
II
IIII
II Explosion protection, group II
2
22
2Equipment category 2
G
GG
GGas explosion protection
D
DD
DDust ignition protection
Ex d
Ex dEx d
Ex d Protection type flameproof enclosure
Ex t
Ex tEx t
Ex t Protection type "Equipment - dust ignition protection through enclosure"
IIC
IICIIC
IIC Gas group, suitable for gas groups IIC, IIB and IIA
IIB
IIBIIB
IIB Gas group, suitable for gas groups IIB and IIA
IIIC
IIICIIIC
IIIC Dust areas, suitable for Group IIIC, IIIB and IIIA
T6...T1
T6...T1T6...T1
T6...T1 Temperature class, suitable for temperature classes T6...T1
T70
T70T70
T70°C
CC
CMaximum surface temperature of the signal converter housing without dust coating at
ambient temperature 65°C / 149°F and product temperature 65°C / 149°F
Gb
GbGb
Gb EPL, suitable for zone 1
Db
DbDb
Db EPL, suitable for zone 21

2 DEVICE DESCRIPTION
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2.7 Ambient temperature / temperature classes
Due to the influence of the product temperature, variable area flowmeters with built-in electrical
equipment (electric variants) are not assigned to any fixed temperature class.
In fact, the temperature class of a device is a function of the temperature of both the product and
the environment. The classification is outlined in the following tables.
The tables take into account the following parameters:
•Maximum value P
i
•Ambient temperature T
amb
•Product temperature T
m
•Nominal size DN
•Standard or high temperature version (HT)
•Standard or heating jacket version
•Heat resistance of the connecting cable
The permitted ambient temperature range is indicated on the nameplate; depending on the
device version it is T
amb
= -40...+60°C / -40...+140°F or T
amb
= -20...+60°C / -4...+140°F.
The minimum product temperature is -40°C/-40°F.
For certain device versions, lower values apply due to differing boundary conditions (e.g. liner
materials). Here the user should consult the technical data sheet. The maximum values stated in
the handbook for non-explosion protected device versions must also not be exceeded for
explosion-protected versions.
INFORMATION!
The maximum permissible product temperatures listed in the tables are valid under
the following conditions:
• The measuring device is installed and operated in accordance with the manufacturer's
installation instructions.
• It must be ensured that the flowmeter is not heated by the effects of additional heat radiation
(sunshine, neighbouring system components) and thus operated above the permissible
ambient temperature range.
• Insulation must be limited to the piping.
Unobstructed ventilation of the indicator part must be ensured.
For this purpose, the variant with a projecting indicator (HT version) is preferable.
• For device versions with a heating jacket the temperature of the heating medium does not
exceed the maximum permissible product temperature.
INFORMATION!
The following conditions must be met for all versions:
• Standard connecting cable, temperature resistance min. 70 ° C / 158 ° F.
• Heat-resistant connecting cable, temperature resistance min. 90 ° C / 194 ° F.

DEVICE DESCRIPTION 2
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Maximum permissible temperatures when using a heat resistant connecting cable
Maximum permissible temperatures when using a standard connecting cable
Maximum permissible product temperature T
m
[°C]
Heating jacket TK T6 T5 T4 T3 T2, T1
without with HT
version
T
amb
[°C] 
≤60 ≤65 ≤65 ≤60 ≤65 ≤60 ≤65
DN15
DN25
DN50
DN15
DN25 85 100 135 200 175 200 175
x85 100 135 200 200 300 300
DN80
DN100 DN50 DN80 85 100 130 185 165 185 165
x85 100 135 200 200 300 300
Maximum permissible product temperature T
m
[°F]
Heating jacket TK T6 T5 T4 T3 T2, T1
without with HT
version
T
amb
[°F] 
≤140 ≤149 ≤149 ≤140 ≤149 ≤140 ≤149
DN15
DN25
DN50
DN15
DN25 185 212 275 392 347 392 347
x185 212 275 392 392 572 572
DN80
DN100 DN50 DN80 185 212 275 365 329 365 329
x185 212 275 392 392 572 572
Maximum permissible product temperature T
m
[°C]
Heating jacket TK T6 T5 T4 T3 T2, T1
without with HT
version
T
amb
[°C] 
≤60 ≤60 ≤65 ≤60 ≤65 ≤60 ≤65 ≤60 ≤65
DN15
DN25
DN50
DN15
DN25 85 100 75 105 75 105 75 105 75
x85 100 95 135 95 175 95 175 95
DN80
DN100 DN50 DN80 85 90 75 90 75 90 75 90 75
x85 100 90 135 90 155 90 155 90
Maximum permissible product temperature T
m
[°F]
Heating jacket TK T6 T5 T4 T3 T2, T1
without with HT
version
T
amb
[°F] 
≤140 ≤140 ≤149 ≤140 ≤149 ≤140 ≤149 ≤140 ≤149
DN15
DN25
DN50
DN15
DN25 185 212 167 221 167 221 167 221 167
x185 212 203 275 203 347 203 347 203
DN80
DN100 DN50 DN80 185 194 167 194 167 194 167 194 167
x185 212 194 275 194 311 194 311 194

2 DEVICE DESCRIPTION
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Reference point observation
Reference point observationReference point observation
Reference point observation
The permissible product and ambient temperatures may be exceeded or undershot as long as
the permissible temperature range of the reference point of the display is not exceeded. The
following table contains the permissible maximum values at the reference point. Note:
•Reference point is the connection of the equipotential bonding conductor of the M40 indicator.
•The temperatures at the reference point are to be determined in the most unfavourable
operating situation.
•The required measuring uncertainty is max. 2 K.
•Measuring conditions and results are to be permanently recorded in a suitable format.
•The measuring unit should be insulated properly.
Maximum permissible temperatures at reference point
The permissible ambient temperature range is indicated on the nameplate; depending on the
device version it is T
amb
= -40...+60°C / -40...+140°F or T
amb
= -20...+60°C / -4...+140°F.
Maximum permissible temperature at the reference
point T
Ref
[°C]
Heating jacket TK T6...T1 T6 T5...T1
without with T
Connecting cable
[°C] standard (70°C) heat-resistant (90°C)
DN15
DN25
DN50
DN80
DN100
DN15
DN25
DN50
DN80
64 74 84
Maximum permissible temperature at the reference
point T
Ref
[°F]
Heating jacket TK T6...T1 T6 T5...T1
without with T
Connecting cable
[°F] standard (158°F) heat-resistant (194°F)
DN15
DN25
DN50
DN80
DN100
DN15
DN25
DN50
DN80
147 165 183
WARNING!
The permissible lowest temperature at the reference point must not fall below the lowest limit
value of the ambient temperature.

DEVICE DESCRIPTION 2
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2.8 Surface temperature for equipment category II 2 D
For use in areas with flammable dust it should be noted that the indicated maximum surface
temperature of T70°C at an ambient temperature of 65°C / 149°F and a product temperature of
65°C / 149°F is valid without a dust coating. For higher product temperatures the maximum
surface temperature is defined by the product.
2.9 Electrical data
Electrical equipment Rated voltage Nominal current
Limit switches K1 / K2 OC output 10...30 VDC ≤100 mA
Limit switches K1 / K2 NAMUR output 5...25 VDC ≤1 / ≥3mA
Reed contacts R1 / R2 0...32 VDC ≤100 mA
Signal output ESK4 14...32 VDC 4...20 mA with HART
®
communication
Switching output ESK4-T OC output 8...32 VDC 1...100 mA
Switching output ESK4-T NAMUR output 8VDC ≤1 / ≥3mA
Signal input ESK4-T input 8...32 VDC ≤2mA
ESK4-FF Foundation Fieldbus transmitter 1 9...32 VDC 16 mA
ESK4-PA Profibus transmitter 2 9...32 VDC 16 mA
1Further information and instructions for operation of the ESK4-FF transmitter are provided in separate supplementary
instructions.
2Further information and instructions for operation of the ESK4-PA Profibus transmitter are provided in separate sup-
plementary instructions.

3 INSTALLATION
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3.1 Installation
Installation and setup must be carried out according to the applicable installation standards (e.g.
EN 60079-14) by qualified personnel trained in explosion protection. The information given in the
standard manual and the supplementary instructions must always be observed.
Variable area flowmeters must be installed in such a way that
•There are no external forces affecting the indicator part.
•The device is accessible for any visual inspections that are necessary, and can be viewed from
all sides.
•The nameplate is clearly visible.
•It can be operated from a location with secure footing.
Take special note of the installation position for the H250/H/... with horizontal flow
direction:
In order to comply with thermal parameters and measuring accuracy, flowmeters for horizontal
installation are to be installed in the pipeline so that the display is located on the side of the
measuring tube. The maximum product and ambient temperatures indicated as well as the
measuring accuracy are based on lateral installation of the display.
CAUTION!
The manufacturer is not liable for any damage resulting from improper use or use other than the
intended purpose. This applies in particular to hazards due to insufficient corrosion resistance
and suitability of the materials in contact with product.

INSTALLATION 3
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3.2 Special conditions
Equipotential bonding
Variable area flowmeters must be included in the equipotential bonding of the hazardous area.
Electronics compartment lock
Lock the dustproof and/or flameproof electronics compartment of the variable area flowmeter
during operation. First tighten the cover by hand. Then tighten the cover again by about 90°. The
cover for the electronics compartment is secured by means of a lock. Use an WS3 Allen key to
turn the screw.
No waiting period is necessary prior to opening the electronics compartment.
Flameproof joints in the housing
The flameproof threads between the cover and electronics compartment must be inspected
visually after opening. The housing must be replaced if there is any damage to the joint area. The
flameproof joints are not intended for repair.

4 ELECTRICAL CONNECTIONS
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4.1 General notes
Rated values for insulation
•The insulation of the H.../..../M40 - Ex variable area flowmeter is rated in compliance with
IEC 60664-1. The following rating parameters are taken into account:
•Overvoltage category for signal and instrument loops: II
•Pollution degree of the insulation: 2
Terminal compartment
The electrical connection for the power supply and I/O functions is made in the electronics
compartment of the signal converter. The protection type of the electronics compartment is "d"
and/or "t". Unused entries are to be closed in accordance with EN 60079-1 and/or EN 60079-31.
The entry of the cables in the electronics compartment is possible in two different ways.
•Direct entry of the connecting cables by way of approved flameproof cable glands (M20x1.5)
into the flameproof terminal compartment (V ≤2000 cm³). The cable glands require a
separate test certificate in accordance with EN 60079-1. Observe the requirements of the test
certificate for the cable glands.
•Direct entry of the connecting cables by way of conduits into the flameproof enclosed
terminal compartment of the device. Once the conduit has been screwed in, it must form a
flameproof joint with the housing with a minimum thread length of 8 mm. A suitable
mechanical stopping box must be provided in accordance with installation provisions. The
conduit must be installed in compliance with its separate test certificate.
•Direct entry of the connecting cables by way of approved dustproof cable glands (M20x1.5)
into the dustproof terminal compartment (V ≤2000 cm³). The cable glands require a separate
test certificate in accordance with EN 60079-31. Observe the requirements of the test
certificate for the cable glands.
Connecting cables
The connecting cables should be selected according to the applicable installation standards (e.g.
EN 60079-14 / VDE 0165) and the maximum operating temperature.
•The connecting cables must be fixed and laid so they are sufficiently protected against
damage.
•Lay cables so as to ensure that there is sufficient distance between surfaces of the
measuring unit and the connecting cable.
•Supplied blind plugs / cable entries guarantee protection against foreign objects and water
(protection category) IP66/68 according to EN 60529.
•The outer diameter of the connecting cable must be within the sealing range of the cable
entry (7...12 mm / 0.27...0.47").
•Unused cable entries are to be closed in accordance with EN 60079-1 and/or EN 60079-31
(>IP66/68).
Ensure that the seals and cut seals are tight.
CAUTION!
The IP protection category of the signal converter housing is largely determined by the cable
gland used and the installation.

ELECTRICAL CONNECTIONS 4
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4.2 Power supply
The variable area flowmeter does not require a separate power supply. The required supply for
the built-in electronics is provided via the 4...20 mA current output and the bus connection.
4.3 Inputs/outputs
The terminal assignment of the built-in electrical equipment is described in the standard
manual. The signal circuits of the variable area flowmeter may only be connected to downstream
devices or circuits that satisfy the requirements of protective extra-low voltage (PELV).
Connecting power and I/O functions
•Before connecting or disconnecting the electrical connection cables of the device, make sure
that all cables leading to the converter are isolated from the ground of the hazardous area.
This also applies to protective ground (PE) and equipotential bonding conductors (PA).
•All connecting cable conductors and shields that are not securely connected to the
equipotential grounding system of the hazardous area shall be carefully isolated from one
another and from ground (1500 V
rms
test voltage for non-intrinsically safe cables).

4 ELECTRICAL CONNECTIONS
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4.4 Grounding and equipotential bonding
The signal converter shall be connected to the equipotential bonding system of the hazardous
area via the internal or external grounding connection on the signal converter housing. The
measuring unit and the signal converter are electrically connected via an equipotential bonding
connection.
Any existing cable shields should be connected to earth according to applicable installation
regulations (EN 60079-14). A terminal connection in the terminal compartment permits a short
way earthing of the cable shields.
Alternatively, the equipotential bonding of the signal converter can also take place by way of the
measuring tube incorporated into the equipotential bonding of the hazardous area.
The measuring tube can be incorporated into the equipotential bonding system of the hazardous
area using the U-clamp mounted on the flange if present, or suitable conductive connections
(seals, etc.).
1 Grounding connection in the indicator
2 Grounding connection outside

OPERATION 5
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5.1 Start-up
Start-up is only permitted when the variable area flowmeter:
•is correctly installed in the system and connected.
•has been checked for the proper state with regard to its installation and connection
requirements.
•and the electronics compartment have been properly closed (pressure-resistant casing or
dustproof housing) and the applicable special lock has been fitted.
The user of the system must have it checked before start-up in compliance with the national
regulations for checks before startup.
If the device needs to be configured due to the existence of an explosive atmosphere, this can be
done using the supplied bar magnets. There is no need to open the housing as it can be done
through the glass window of the electronics compartment or digitally via the signal output
(HART
®
interface).
5.2 Operation
Variable area flowmeters must be operated in such a way that they remain within the maximum
and minimum permissible temperatures and pressures and the electrical limit values.
Variable area flowmeters may only be operated if the equipment parts necessary for safety are
effective in the long run, and are not rendered inoperable during operation.
In case of operation with flammable products the measuring units must be included in the
periodic pressure tests of the system.
Opening the housing of the electronics compartment (equipment protection by flameproof
enclosure or dustproof housing) in hazardous areas is only permitted in a de-energised state.
5.3 Electrostatic charge
In order to avoid ignition hazards due to electrostatic charge, variable area flowmeters
may not be used in areas with:
•processes that generate strong charges,
•mechanical friction and cutting processes,
•spraying of electrons (e.g. in the vicinity of electrostatic painting systems).
WARNING!
Ignition risks caused by pressure surges, impact or friction must particularly be avoided when
titanium measuring units are used.
WARNING!
Electrostatic charging of the housing surface by friction must be avoided.
Variable area flowmeters must not be dry cleaned.

6 SERVICE
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6.1 Maintenance
Maintenance work of a safety-relevant nature within the meaning of explosion protection may
only be carried out by the manufacturer, his authorised representative or under the supervision
of authorised inspectors.
To maintain proper condition, regular inspections are required for systems in hazardous areas.
The following checks are recommended:
•Checking the housing, the cable entries and the feed lines for corrosion and/or damage.
•Checking the measuring unit and the piping connections for leakage.
•Checking the measuring unit and the indicator for dust deposits.
•Including the flowmeter in the regular pressure test of the process line.
6.2 Dismantling
General notes
The dismantling and installation is within the responsibility of the operator.
Due to the modular design of the variable area flowmeters, from a safety perspective the
complete indicators or their components can be replaced with identical spare parts.
After opening the signal converter, grease the ignition-proof cover threads including the cover
seals if necessary. Use the multi-purpose grease NONTRIBOS
®
, type Li EP2.
WARNING!
Only identical indicators or modules from the manufacturer may be used.
If it is absolutely necessary to open the flameproof enclosure or the dustproof electronics
compartment in the presence of a potentially explosive atmosphere, the device must be de-
energised.
Before connecting or disconnecting the electrical connection cables of the device, make sure
that all cables leading to the signal converter are isolated from the ground of the hazardous
area. This also applies to protective earth (PE) or functional earth (FE) and equipotential bonding
conductors (PA).

SERVICE 6
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Replacing the indicator / modules
When exchanging a complete indicator or individual modules, refer to the section "Connecting
power and I/O functions". In both cases, the measuring tube of the variable area flowmeter can
remain in the pipeline. This also applies to line systems carrying product.
Exchanging the entire device
Observe the information above. Also, ensure that all process connections and the pipeline are
depressurised and free of product. Where environmentally critical products are concerned,
carefully decontaminate the wetted parts of the flange system after dismantling.
CAUTION!
There may be a loss of measuring accuracy!
Faulty prisms between the measuring tube and the indicator housing should be replaced.
WARNING!
• Pressurised pipes have to be depressurised before removing the measuring unit.
• In the case of environmentally critical or hazardous products, appropriate safety precautions
must be taken with regard to residual liquids in the measuring unit.
• New gaskets have to be used when re-installing the device in the piping.

KROHNE –Process instrumentation and measurement solutions
• Flow
• Level
• Temperature
• Pressure
• Process Analysis
• Services
Head Office KROHNE Messtechnik GmbH
Ludwig-Krohne-Str. 5
47058 Duisburg (Germany)
Tel.: [phone]
Fax: [phone]
[email protected]
© KROHNE 04/2016 - 4002069603 - AD H250-M40-ExII2GD-R03 en - Subject to change without notice.
The current list of all KROHNE contacts and addresses can be found at:
www.krohne.com