WIKA TR25 - Handbuch (Seite 18)

14073045.01 10/2013 GB/D
18 WIKA operating instructions model TR25 (Ex i)
GB
The values in brackets apply to special designs. These sensors are manufactured using special
sealing compounds. Moreover, they are equipped with connection heads made of stainless steel
and cable glands for the low-temperature range.
These thermometers are suitable for temperature classes T6...T3 in accordance with the
approval certificate. This applies to instruments without built-in transmitters and/or digital
displays. Thermometers equipped with transmitters and/or digital displays are for use in
temperature classes T6...T4 and are marked accordingly. Using equipment for applications which
require a lower temperature class (e.g. T2) than the marked one is permissible. In doing so, it
must be ensured that the maximum ambient temperature for safe operation of the instrument is
not exceeded.
7.3 Temperature carry-over from the process
A heat backflow from the process that exceeds the operating temperature of the transmitter
(digital display) or housing is not permissible and must be prevented by installing suitable heat
insulation or a neck tube of suitable length.
Increasing the separation of the connection components and hot surfaces
The neck distance (N) is defined as the distance between the lower edge of the connection head
(or the housing) to the heat-emitting surface. The temperature to be expected at the lower edge
of the connection head or housing is, at most, 100 °C. The conditions for built-in transmitters or
displays must be observed. If required, the neck length must be increased accordingly.
To help select the minimum neck length, the following standard values have been determined.
Maximum temperature of the
medium
Recommendation for
dimension N
Recommendation for
dimension X
100 °C - -
135 °C 20 mm 20 mm
200 °C 50 mm 50 mm
> 200 °C ≤ 450 °C 100 mm 100 mm
WARNING!
For reasons of work safety and saving of resources, hot surfaces should be protected
against accidental touch and energy loss by means of insulation.
7. Information on mounting and operation in hazardous areas