JUMO 14597 safetyM STB/STW Ex - Safety Temperature Limiter and Safety Temperature Monitor Operating Manual - Manual (Page 82)

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7.4.3 Explanation of probe temperature classes
The listed probes can be used in temperature classes T1 to T6.
Temperature classes
Item 26.5.1.3 in EN 60079-0:2009 stipulates a safety margin for type-tested devices of Group II (potentially explosive gas atmo-
spheres excluding mines susceptible to firedamp) of 10 K for the highest measured surface temperature for T1 and T2, and 5 K
for T3, T4, T5, and T6.
In the case of RTD temperature probes, a measuring current flows through the sensor element, which causes a rise in temper-
ature. In addition, a fault in the JUMO safety
M STB/STW Ex means that the sensor circuit may introduce a maximum output of
61.8 mW to the probe. This also applies to the thermocouple probes.
The maximum rise in temperature was determined through measurements.
The following values represent the worst case scenario and apply for all probes:
The maximum temperature rise of Pt100 probes is
7.5 K.
The maximum temperature rise of thermocouple probes is
0.9 K.
1. The following safety margins must also be observed:
Category 1: Acc. to EN 1127-1:2011 Item 6.4.2 (hot surfaces), the surface temperatures of all devices ... for use in zone 0..., that may come into contact with poten-
tially explosive atmospheres, … must not exceed 80 % of the ignition temperature.
This means the temperature class, minus 20 %.
As described above, in temperature classes T1 and T2, 10 °C must be deducted and in temperature classes T3 to T6, 5 °C must be deducted.
Table 17: Temperature classes
Temperature class Maximum surface temperature of apparatus 1
Ignition temperature of the flammable
materials
T1 450 °C > 450 °C
T2 300 °C > 300 < 450 °C
T3 200 °C > 200 < 300 °C
T4 135 °C > 135 < 200 °C
T5 100 °C > 100 < 135 °C
T6 85 ? > 85 < 100 °C