JUMO 902930 Wtrans Transmitter RTD Temperature Probe with Ex approval Operating Manual - Manual (Page 13)

13
1 Introduction
1.7 Heat input through protection tube / protection tube fitting
The medium temperature causes a heat input through the protection tube in the case of the
transmitter for basic types 902930/15 and 902930/17.
A minimum distance of 70 mm between process medium and case connection is to be main-
tained. This minimum distance is to be considered for transmitters with and without process
connection. The following table shows the heat input at a distance of 70 mm or 120 mm.
The admissible ambient temperature is calculated from the difference between the maximum
ambient temperature specified in technical data and the calculated heat input.
Calculation example for medium temperatures deviating from 260 °C:
A medium temperature of 180 °C conforms to 95 K over the maximum ambient temperature of
85 °C for an extension tube length of 70 mm.
Result: The maximum ambient temperature for this calculation example is
85 °C - 8.17 K = 76.83 °C.
1.8 Heating of the protection tube in case of error
In case of error caused by a drop in performance on the Pt1000 temperature sensing element,
the resulting heat increase on the protection tube amounts to max. 5 K.
Extension tube
length or distance
process medium and
case Maximum heat input
at 260 °C medium
temperature Heat input per 10 K medium temperature over the maxi-
mum ambient temperature
70 mm 15 K 0.86 K
120 mm 10 K 0.57 K
95 K
0.86 K
10 K
----------------- × 8.17 K =
DANGER!
The user has to consider the calculated heat input at the maximum admissible ambient tem-
perature.
If a protection tube is used without process connection and the required distance between
process medium and case cannot be kept then the medium temperature must be limited to
the maximum ambient temperature.
The influence of radiant heat and convection must be considered by the user.
DANGER!
The user must make sure that the temperature increase of 5 K does not cause the limits of
the defined temperature classes to be exceeded.