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Technical Note
00840-0700-4016, Rev AA
February 2009
The remote seal construction also needs to be
evaluated for lower limits on vacuum applications.
Standard Welded-Repairable remote seal
construction on Coplanar modules uses PTFE
o-rings, so it can be used for vacuum pressures
down to 6 psia (0.41 bar). Below 6 psia (0.41 bar),
All-Welded Vacuum construction should be used as it
also includes welded isolator caps to eliminate any
potential for air to be sucked into the seal system
under deep vacuum conditions.
If the minimum process pressure is below the sensor
pressure limit, then the pressure transmitter needs to
be mounted below the bottom process connection
using a short length of capillary. The vertical column
of fill fluid creates a head pressure on the sensor
module to protect the sensor's fill fluid within its
operating limit.
INSTALLATION GUIDELINES
Direct mount remote seal systems need to be
installed properly to ensure they operate within the
operating limits stated above. In particular, the use
and location of insulation will determine if a direct
mount remote seal system will operate to its limits.
The general recommendation is to wrap insulation
around vessel process connections and seal only,
not the direct mount transmitter/flange. The direct
mount systems are designed to balance the heat
dissipation from the remote seal and process
connection, so if the entire unit is wrapped in
insulation, the transmitter electronics could be
overheated. For the example shown to the right, it is
acceptable to insulate around the remote seal and
process pipe, but not the direct mount extension.
Rosemount 1199
Acceptable to
insulate around remote seal
3
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