11984 Rev 01 Page 3 of 8
1.2 General Description
3. An increase in clean room air pressure (from a door closing, for example) will
increase the downward force on the piston. The downward movement of the
piston closes the valve, causing the pressure in the chamber to increase,
maintaining a constant pressure differential between the chamber and the
clean room.
4. An increase in facility exhaust (i.e., a more negative exhaust pressure) will in-
crease the pull on the piston, closing off the valve. As the valve is closed off,
the pressure differential across the valve is increased, and the upstream side is
maintained at a constant.
Nitrogen Supply
Nitrogen is supplied to the SENTRY 1510 to perform several necessary functions:
1. Purge of the transducer line to prevent HCl damage
2. A nitrogen curtain in the exhaust line to prevent backstreaming of contaminants
from house exhaust into the process tube
3. A nitrogen bearing to “float” the piston
Figure 1-1: A) SENTRY 1510 input; B) output (Note: the unit shown has custom
fittings and is not shown with the standard female 1" NPT input and output.)
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