KROHNE VA FLOWMETERS EN - Manual (Page 6)

2
SAFETY INSTRUCTIONS
6
VA FLOWMETERS
www.krohne.com 11/2012 - 4000419904 MA VA Mech Ex AD R04 en
2.5 Static electricity
2.5.1 Process dependent charging
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 (e.g. liners, floats).
For all metal devices, the measuring tube and the welded on process connections form a shield
(Faraday cage) from which the electrical field cannot escape.
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 charges.
The operator is also responsible for extending the ground continuity of the process pipeline. If
grounding cannot be made via the process connections (plastic process connections or
undefined connections), the measuring device should be connected to the described ground
potential via the connection to ground. This connection merely ensures electrostatic grounding
of the device and does not meet the requirements for equipotential bonding.
2.5.2 Charging non-conductive external parts by cleaning
Area limits are taken into consideration with respect to the chargeability of non-conductive
external parts under atmospheric conditions. Devices for which it can be expected that
combustible electrostatic charging will occur due to cleaning are to be identified with an
adhesive sign:
A cloth moistened with water should be use to clean surfaces that could be loaded with a charge.
CAUTION!
Use of the equipment is not permitted in areas where the following occur: processes that
generate strong charges, machine grinding and separation processes, electron spraying (e.g.
near electrostatic painting systems) or pneumatically conveyed dust.
CAUTION!
Achtung! Gefahr elektrostatischer Aufladung! Nicht reiben!
Caution! Risk of electrostatic charge! Do not rub!
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