KROHNE VFM 3100 EN - Manual (Page 37)

37
Apply 500 V ac
or 707 V dc
between
shorted
terminals and
ground for
1 minute
Case ground terminal (earth) Terminal block
Figure 27. Connections for Post-Assembly Dielectric Test Figure 26. Preamplifier – Remote Mounted VFM 3100
4.6. Sensor Replacement with Integral
Electronic Module
The VFM 3100 does not need to be removed from the pipeline for
Sensor replacement. The pipeline must, however, be shut down and
emptied before loosening the connector bolts.
4.6.1. Disassembly
• Disconnect power from the VFM 3100. If the VFM 3100 is wired
with rigid conduit, it may be necessary to remove the field termi-
nal cover and disconnect input wiring and conduit connections.
• Remove electronic module compartment cover.
(For CENELEC Certified Flameproof Extended Range
VFM 3100, remove lock assembly prior to removing the
housing covers.)
NOTE: If cover cannot be removed by hand, it may be necessary
to insert a flat bar in tapered cover slot to remove.
• Remove the electronic module and preamplifier and disconnect
the sensor leads per the instructions starting on page 30 for
meters with integrally mounted electronics housings.
• Remove the mechanical connector bolts and lift off the electrical
housing, mechanical connector, and sensor as a unit.
See Figure 28.
• Slide the sensor out of the mechanical connector.
See Figure 30.
NOTE: The Standard Temperature Range VFM 3100 has a ptfe gas-
ket and flow dam and a silicone rubber O-ring. The Extended Tempe-
rature Range VFM 3100 has a stainless steel gasket and flow dam
and a Graphoil O-ring.
4.5. Post-Assembly Dielectric Test
To ensure there are no faults to ground in any of the internal wiring,
apply 500 V ac or 707 V dc dielectric strength test for 1 minute bet-
ween shorted input terminals (+), (-), (A), (B), and housing ground as
shown in Figure 27.
Sensor switch
Sensor wires
Remote cable
Preamplifier assembly
Brown (+)
Red
Orange
Yellow (-)
Remote Mounted VFM 3100
(CENELEC Certified Flameproof)
• Mount the new preamplifier on the mounting plate using the two
screws. Refer to Figure 23.
• Feed the yellow and brown sensor wires through the strain relief
clamp on the preamplifier board. Tighten the clamp and connect
the sensor leads to the terminal block. The color coding is
important. Check to see that this is correct. See Figure 25.
• Connect (brown-red-orange-yellow) cable from the preamplifier
to one side of the two-sided terminal block on the mounting
plate.
• Before placing assembly into the junction box, connect the four
(brown-red-orange-yellow) wires entering the junction box
through a conduit opening, to the other side of the terminal
block on the mounting plate (following the same sequence as
the ribbon cable from the preamplifier). See Figure 23.
• Place mounting plate with preamplifier in the junction box and
mount it using the two mounting screws.
• Connect ground wire from the preamplifier to the U-shaped
ground strap on the mounting plate.
• Mount metal shield over the preamplifier as shown in Figure 24.
• Replace the junction box cover and add the lock assembly.