10
EB 2043 EN
Design and principle of operation
3 Design and principle of oper-
ation
See Fig. 2.
The safety temperature monitor (STM) oper-
ates according to the liquid expansion prin-
ciple. The temperature sensor (12), capillary
tube (9) and operating element (8) are filled
with an expansion liquid.
The temperature-dependent change in vol-
ume of the liquid in the bulb sensor (12)
causes the piston in the operating element
(8) to move. As a result, the pin of the oper-
ating element (7) moves the plug stem (5)
with the plug (3). The temperature limit can
be adjusted by a key (10). This limit value is
indicated on the dial (11).
The safety temperature monitor closes the
valve when the temperature reaches the ad-
justed temperature limit. The safety tempera-
ture monitor resets itself automatically when
the temperature has fallen to a value of ap-
prox. 5 K below the adjusted limit.
Fail-safe position
The spring mechanism in the operating ele-
ment is released when the capillary tube
breaks or when there is a leak in the sensor.
It moves the plug stem (5) with the plug (3)
over the pin (7) and closes and locks the
valve.
The adjusted limit temperature must have a
minimum temperature difference of 15 K to
the set point of the temperature regulator.
Note
2.1 Material number
Specifying the configuration ID, you can con
-
tact us to find out which material is used. The
configuration ID is specified on the name
-
plate (2 and 3; configuration ID and device
index). For more details on the nameplate,
see Fig. 1.