Heinrichs Messtechnik GmbH
Operating Manual K09
Page 17 of 28
11
Use in hazardous areas
Only devices with Ex-markings may be operated within areas with potentially explosive
atmospheres.
Ambient temp.
Process-Temp.
Marking
Zone Description
-20 °C ...+70 °C
-25 °C ...+70 °C
II 2G Ex h IIC T6 Gb
II 2D Ex h IIIC T85°C Db
1
With built-in switch,
observe the type
certificate of the contact
manufacturer!
-20 °C ...+100 °C -40 °C ...+100 °C
II 2G Ex h IIC T6...T5 Gb
II 2D Ex h IIIC
T85°C…T100°C Db
1
As a purely mechanical
device
11.1
Atmospheric Conditions
According to EN 1127-1, a “potentially explosive atmosphere“ is defined as a mixture of air and combustible
gases, vapour, mist or dust under atmospheric conditions. These conditions are defined in DIN EN ISO 80079-
36, para. 1, with values Tatm = -20 °C to +60 °C and Patm = 0.8 to 1.1 bar. Outside of this range, safety
parameters for most ignition sources are not available.
The operating conditions inside the measuring tubes of variable-area flow meters generally lie outside the
atmospheric conditions of 0.8 to 1.1 bar. Therefore, due to the lack of safety parameters, the explosion
protection does not apply to the process conditions inside of the measuring tube, irrespective of the zone
classification.
Operation with combustible products is therefore only permissible if a potentially explosive air mixture is not
formed inside the flow meter. Where this condition is not met, the operator is required to assess the ignition
hazard in each individual case giving due consideration to existing parameters (e.g. pressure, temperature,
process product, materials)
11.2
Electrostatic charge of non-conductive parts
In hazardous areas the risk of electrostatic charge in dangerous quantities must be considered
during cleaning of the measuring tubes synthetic cover.
Devices where explosive electrostatic charges are to be expected are marked with an adhesive
label. Use a damp cloth for cleaning of the synthetic materials.
Caution! Danger of electrostatic charge! Do not rub!
11.2.1
Grounding
In variable-area flow meters, under operating conditions it is possible for charge separation to
occur in the measuring tube due to the transport of non-conductive fluids.
For this reason, variable-area flow meters must be permanently grounded by the operator by way
of the process connections (flanges) to ensure the discharge of electrostatic build-up.
