Honeywell STR94G User Manual

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34-ST-03-57 
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Description of Diaphragm Seals 
Diaphragm seals are traditionally used when a standard pressure transmitter should not be exposed to the 
process pressure directly.  Diaphragm seals typically protect the pressure transmitter from one or more 
damaging aspects of the process media.  Consideration for using a diaphragm seal should be made in the 
following circumstances. 
 
•  High Process Temperature 
•  Process Media is Viscous or Contains Suspended Solids 
•  Process Media is Subject to Solidifying 
•  Process Media is Corrosive 
• Process 
Application 
Requires Sanitary Connections 
•  Process Application Subjects the Measuring Instrument to Hydrogen Permeation 
•  Tank Level Applications with Maintenance Intensive Wet Legs 
•  Tank Application with Density or Interface Measurements 
•  Measuring Instrument Requires Remote Mounting 
 
The following diaphragm seals are standard from Honeywell (please call your local salesperson if you do not see 
the product you need for your application):
 
Figure 2 -
 Flush Flange Seals can be used with 
differential, gauge and absolute pressure transmitters 
and are available with 3” ANSI Class 150, ANSI Class 
300 and DIN DN80-PN40 process connections.  Flush 
flange seals can also be provided with Lowers.  
Lowers are essentially calibration rings, which allow 
flushing connections if needed – see Figure 31. 
 
 
 
Figure 2 
Figure 3 - Flange Seal with Extended Diaphragm
 
can be used with differential, gauge and absolute 
pressure transmitters and are available with 3” and 4” 
ANSI Class 150, ANSI Class 300, DIN DN80-PN40 
and DIN DN100-PN40 process connections.  2”, 4” and 
6” extension lengths are available.  
 
 
 
Figure 3 
Figure 4 - Pancake Seals
 can be used with 
differential, gauge and absolute pressure transmitters 
and are available with 3” ANSI Class 150, 300 and 600 
process connections.  
 
 
  
Figure 4 
Figure 5 -
 Chemical Tee “Taylor” Wedge seals can 
be used with differential pressure transmitters and are 
available with Taylor Wedge 5” O.D. process 
connection.  
 
 
 
Figure 5