WIKA TR12-M - Handbuch (Seite 24)

GB
8. Safety-related instructions ... / 9. Calculation examples ...
11419904.02 09/2013 GB/D
WIKA operating instructions models TR12, TC12 (Ex d) 24
8.3 Variant 3:
ATEX/IECEx Ex d certified temperature transmitters.
The evaluation is carried out over a current (4 … 20 mA), voltage (0 … 10 V) or field bus
signal, which is generated by an ATEX/IECEx Ex d certified temperature transmitter.
Use in zone 1, marking II 2G Ex d IIC Gb
The flameproof housing or the connection head is in zone 1 (or zone 2). The sensor is in
zone 1. In the case of a separation of Ex-zones, a thermowell (from corrosion-resistant
steel, min. wall thickness 1 mm) must be used.
The main markings for models TR12-B and TC12-B are found on the certified connection
housing or Ex d field transmitter.
The TR12-M and TC12-M modules are marked through a foil plate on the neck tube.
For a possible use at the partition to zone 0 with a thermowell, the approvals and conditions
of the relevant Ex d field transmitters must be followed.
Temperature class classification, ambient temperatures
For the measuring insert with neck tube, the following ambient temperature range applies:
(-50) 1) -40 … +85 °C
1) The value in brackets applies only for specific low-temperature designs
The permissible ambient temperatures of the certified Ex d field transmitters must be taken
from the respective operating instructions or data sheets. Through deviations in temperature
ranges, limitations can occur.
8.4 Use in methane atmospheres
As a result of the higher Minimum Experimental Safe Gap (MESG) and Minimum Ignition
Current (MIC) of methane, the instrument can also be used in hazardous gas atmospheres
caused by this.
9. Calculation examples for self-heating at the thermowell tip
The self-heating at the thermowell tip depends upon the sensor type (TC/RTD), the
measuring insert diameter and the thermowell design. The table below shows the possible
combinations. The heating at the sensor tip of the bare measuring insert is clearly higher;
the representation of these values was omitted on the grounds of the required assembly
with a thermowell. The table shows that when a failure occurs, thermocouples produce
much less self-heating than resistance thermometers.