KROHNE VFM 3100 EN - Manual (Page 43)

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5. Determining Special Measuring Units
There may be a need to use flow units that are not listed in the units
menu. To enter custom units, select “special” from the flow and/or
total units menu.
The following four entries are required to configure the transmitter for
special flow and total units.
• Total name, maximum six characters,
is required for displaying total.
• Flow name, maximum six characters,
is required for displaying the flow rate.
• Total conversion factor for computing total.
• Flow conversion factor for computing flow.
The conversion factors must be related to the internal software and
the manner in which the VFM 3100 computes flow. The conversion
factor for total is a direct conversion from ft
3 to the desired units. The
conversion factor for flow is a direct conversion from ft 3 /sec to the
desired flow units. Any table of conversion factors may be used.
Example: Barrels per hour
To measure total in barrels and flow in barrels per hour.
Total Name: bbl
Flow Name: bbl/h
Total Conversion Factor: 0.1781 bbl/ft 3
Flow Conversion Factor: 0.1781 x 3600 = 641.2 bbl/h
where:
3600 = sec/hr
Example: BTU per minute
The conversion factor for total must be in BTU/ft 3 . If the BTU factor is
known in mass units, then it must be converted to volume units by
multiplying by density. The flow factor is a direct conversion from
ft
3 /sec to the desired units.
Total Name: BTU
Flow Name: BTU/m
Total Conversion Factor: (BTU/lb) x density
Flow Conversion Factor: (BTU/lb) x density x 60
where:
60 = sec/min
Example: Calories per hour
The conversion factor for total must be in calories/ft 3 . If the calories
factor is known in cal/kg, it must be converted to cal/ft 3 by multiplying
by the density and volume conversion factors (m 3 to ft 3 ). The flow fac-
tor must be related to ft 3 /sec.
Total Name: cal
Flow Name: cal/h
Total Conversion Factor: (cal/kg) x density x 0.028317
where:
0.028317 = m 3 /ft 3
Flow Conversion Factor: (cal/kg) x density x 0.028317 x 3600
6. Isolation Valves
Isolation valving is available in single and dual measurement versions
for standard and extended range sensors. The following procedure
applies to all versions. Replacing the sensor in this type of unit is
essentially the same as replacing a sensor in units without isolation
valving. However, particular care must be taken since the process
does not need to be shut down.
WARNING: The isolation valve must be in the closed position prior
to replacing the sensor. It must be gradually depressurized so that
process fluid does not leak. Personal injury could result from such a
leak. Follow normal lockout procedures. Remove power from the
VFM 3100.
6.1. Replacing the Sensor
• Close the valve. This is a dual port, single ball 1/4-turn valve.
Use a wrench on the flat on the valve stem to turn clockwise
one quarter turn. See Figure 38.
NOTE: The right angle position indicator attached to the stem is not
a valve handle. Use a wrench on the valve stem flats.
• Allow the unit to cool down as required.
• Remove power from the VFM 3100 and disconnect input wiring
and conduit connections.
• Gradually loosen the four top bolts that connect the mechanical
connector to top surface of the valve body. Do not loosen the
bottom bolts.
• Allow trapped process fluid within valve body to depressurize.
• Remove the four connector bolts and lift off electrical housing,
mechanical connector, and Sensor as a unit.
NOTE: If electronic housing cover cannot be removed by hand, it
may be necessary to insert a flat bar in slot to remove.
• Proceed to remove the electronic module per instructions
starting on page 30 and replace the sensor per instructions
starting on page 38. Be sure the O-ring is installed on the
sensor and use a new flow dam and gasket.
• When the new sensor has been installed, mount the sensor and
mechanical connector to the valve body and tighten the bolts
per instructions starting on page 38.
• Since it is not possible to leak test the valve-to-connector joint,
it must be assembled carefully.
• Open the valve counterclockwise. Use care and check for leaks.
• Reinstall the electronic module and, when required, the pream-
plifier, using instructions starting on page 35.
• Reconnect the conduit and external wiring.
Refer to instructions starting on page 13.
• Replace the covers and resume operation. There should be no
need to recalibrate the electronic module.