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6/08 ST 3000 Release 300 and SFC Model STS103 User’s Manual 243
B.1 Possible Solutions/Methods, Continued
Electric heating,
continued
Although systems are available with hollow bolts replacing the normal
transmitter body bolts and containing electrical heating elements and
thermostats, certain precautions are required with such arrangements.
Some transmitter meter body bolts are too small to accept the available
thermostats. Also thermostat settings should not approach the body
temperature limit because the heat gradient across the meter body can be
such that limits are exceeded adjacent to the heating elements even when
the thermostat setting is lower.
Electrical heating systems are available in explosionproof ratings for
Class I, Group D, Division I and II installations.
The possibility of electric supply failure must be considered. For this
reason, we recommend using alarm devices with manual acknowledgment
and reset.
See Figures B-6 and B-7 for typical piping installations.
Figure B-6 Piping Installation for Differential Pressure Transmitter and
Impulse Piping with Electric Heating and Control.
Electric heating cable
1/2" , 3-valve manifold
(standard type )
Differential pressure
transmitter
Temperature
controller
(thermostat)
Temperature
sensor
Insulated enclosure
Continued on next page