KROHNE VA 40 ATEX II2G Ex i EN - Manual (Page 12)

5
OPERATION
12
VA40
www.krohne.com 06/2013 - 4002262402 - MA VA40-Ex-II2G-AD R02 en
Operation
5.1 Start-up
Make the following checks before starting up the device:
• Suitability of the materials used for the measuring unit and for the gaskets for adequate
resistance to corrosion from the process product.
• Correct connection of the built-in electrical components.
• Correct setting of the limit switches.
• Electrostatic grounding of the instrument.
5.2 Operation
Setting of the limit switches may be carried out during operation. For this unscrew the mounting
equipment. After setting the limit switch unit to the switchpoint fix it with the fastening screw.
Additionally the switching behavior of the limit switch TG21 is to adjust in its terminal box. The
switching function of the MS14 is determined by the fitting position of the reed contact. A
changing of the position during operation is permitted. Close the unit immediately.
5.3 Electrostatic charge
In variable area flowmeters, it is possible under field conditions for charge separation to occur in
the measuring tube due to the transport of non-conductive fluids and/or when the flow comes
into contact with non-conductive built-ins.
In glass devices, it is basically possible for the electrostatic field generated inside the measuring
tube to "punch through" to the outside of the device. For that reason, variable area flowmeters
need to be permanently grounded by the operator by way of the process connections in order to
allow discharge of electrostatic build-up.
The operator is also responsible for extending the ground continuity of the process pipeline.
If grounding cannot be made via the process connections, e.g. top and bottom connection blocks
are made of plastic, the flowmeter should be connected to the local ground potential via the
connection to ground described in the section entitled "Grounding and equipotential bonding".
This connection only ensures electrostatic grounding of the device and does not meet the
requirements for equipotential bonding.
When dust-free gases or liquids are measured, the flow rate should not exceed 5 times the
nominal flow rate. The max. allowable working pressure PS printed on the type nameplate is to
be noted. The conductivity of the medium must be min. 1000pS/m.
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