Calculation Examples For Self-Heating At The Thermowell Tip; Additional Information - Wika Tr31-3 Betriebsanleitung

11. Calculation examples for self-heating at the ...
11. Calculation examples for self-heating at the
thermowell tip
11.1 Example calculation
Use at the partition to zone 0
The maximum possible temperature, T
with transmitter is being sought.
T is obtained by adding the temperature of the medium and the
max
self-heating. The self-heating depends on the supplied power P
as the thermal resistance R
Example
Diameter: 6 mm
Temperature of the medium: T
Temperature class T3 (200 °C) must not be exceeded
Self-heating: 15 K
T = T + self-heating: 150 °C + 15 °C = 165 °C
max M
As safety margin for type-examined instruments (for T6 to T3), an
additional 5 °C must be subtracted from the 200 °C; hence 195 °C would
be permissible. This means that in this case temperature class T3 is not
exceeded.

Additional information:

Temperature class for T3 = 200 °C
Safety factor for type-tested instruments (for T6 to T3)
Safety factor for type-tested instruments (for T2 to T1)
1) EN/IEC 60079-0: 2012 Ch. 26.5.1
WIKA operating instructions models TR31-3, TR31-K (Ex i)
, at the Ø 6 mm thermowell tip
max
and is 15 K.
th
= 150 °C
M
as well
o
= 5 K
1)
= 10 K
1)
41
EN