KROHNE GA 24 ATEX II2G Ex i EN - Manual (Page 11)

OPERATION
5
11
GA24
www.krohne.com 06/2013 - 4000836702 - MA G24-Ex-II2G-AD R03 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-on electrical components of the electical option.
• Proper fastening of the mounting elements of the limit switches.
• Electrostatic earthing of the measuring device.
5.2 Operation
Adjusting the limit switch during operation is permitted.
To do this, loosen the fastening screws on the mounting device.
Tighten the fastening screws again immediately after the switching point on the limit switch has
been set.
The switching behaviour for the TG21 limit switch can also be set in the terminal compartment.
Close the terminal compartment immediately after adjustment.
The mounting position of the reed contact cartridge determines the switching function of the
reed contact in the MS14/ limit switch. Changing the switching direction during operation is
permitted. Close the limit switch housing immediately afterwards.
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 measuring dust-free gases or liquids, the flow rate should
not exceed ten times the nominal flow rate. The max. allowable working pressure PS printed on
the type nameplate is to be noted.
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