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Manual
PTB 24 ATEX 1002 X
4.3
Protective measures for adherence to
surface temperature or temperature
class
The surface temperature of the trace heating
system is dependent on the relationship between
various parameters:
–
the heat output;
–
the temperature of the surroundings and the
surfaces to be heated;
–
the heat transfer properties between the
trace heater and the immediate surround-
ings.
4.3.1 Temperature class (Type HTSB)
The temperature class is determined during rou-
tine thermal testing taking the local and opera-
tional conditions into consideration. According to
the specific project, the heaters shall be fitted
with one of the following protective devices:
4.3.2 Safety temperature limiter (TSA++)
If the safety temperature limiter (or limiters) is
activated (according to the number of heating
stages), the trace heating system is directly or
indirectly isolated from the mains immediately.
An automatic re-start of the trace heating system
when the temperature drops is not possible. The
safety temperature limiter shall be independent
of the operation of the temperature control
device. The resetting device of the safety tem-
perature limiter may only be operated if the error
condition for the triggering has been remedied
and, in addition, the specified operation condi-
tions have been regained. The setting of the
safety temperature limiter must be fixed and
must not be changed at a later time during oper-
ation.
Edition May 2024
Copyright
/
PTB 24 ATEX 1003 X
15
thuba Ltd., CH-4002 Basel
Switzerland
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