Siemens SITRANS F Operating Instructions Manual page 13

● Factor for heat input: F = 0.2
● Temperature class: T4
● Te = excess temperature
● Ta = ambient temperature at limiting value transmitter (limit switch SJ 3.5-N)
Example 2
Example of the calculation of the max. process media temperature in relation to the max.
ambient temperature for the installed sensor type at widths for sizes DN 15 and DN 25
● Ta = 70 °C
● Tamb = 60 °C
● F = 0.2
Special conditions for safe use
The maximum surface temperature of the measuring substance is decisive as the equipment
does not exhibit its own energy sources that could lead to a rise in temperature.
Regular cleaning is essential when the equipment is employed in dust-explosive zones in
order to prevent sedimentation exceeding the thickness of 5 mm.
It is required that:
● Electrical connections are in accordance with EN 60079-14 (Installing Electrical Systems
● The protective cover over the power supply is properly installed. For intrinsically safe
● Appropriate cable connectors are used for the output circuits:
● Sensor and transmitter are connected to the potential equalization.
● Sensor insulation thickness is max. 100 mm (only insulated sensors).
SITRANS FVA250
Operating Instructions, 02/2013, A5E03821131-01
Te = Tm − Tamb = 120°C − 40°C = 80°C
Ta = (Te* F) + Tamb = (80°C* 0,2) + 40°C = 56°C
Figure 2-1 Calculation of ambient temperature at limiting value transmitter (limit switch SJ 3.5-N)
( )
Ta – Tamb
Tm =
F
Figure 2-2 Calculation of max. process media temperature
in Explosion Hazardous Areas).
circuits the connection area can be opened.
– Intrinsically safe: blue
– Non-intrinsically safe: black
For intrinsically safe output circuits potential equalization must be maintained along the
entire connection path.
(
70°C – 60°C
+ Tamb =
0.2
2.3 Installation in hazardous area
)
+ 60°C = 110°C
Safety notes
13