Intek RheoVac SENTRY User Manual

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At the heart of the RheoVac probe is the Rheotherm flow transducer, which uses the same patented
thermal sensing technique employed in all precision flow instruments manufactured by Intek. Two
temperature sensors are used; one sensor is in thermal equilibrium with the flow medium and provides
a temperature and flow signal reference, while the second sensor is located near a constant power heater
so that its temperature is always above that of the fluid. The temperature of the heated sensor will vary
with the stream velocity of the fluid. Hence, the measured temperature differential between the reference
sensor and heated sensor is a function of flow rate, which is approximately proportional to the logarithm
of mass flow rate (USPN 4,255,968).

The Rheotherm flow sensor is calibrated to measure the total mass flow of the water vapor/air mixture.
From the other three measurements, the RheoVac SENTRY electronics converts the total mass flow
signal from the probe into two components, air mass flow rate and water vapor mass flow rate. This
unique measurement method is disclosed in two separate patents (USPN 5,485,754 & 5,752,411). The
RheoVac probe is fully calibrated at the factory under dynamic fluid conditions identical to those within
the power plant vacuum line. No field adjustments are required.

In the RheoVac SENTRY System, multiple RheoVac probes are installed at pre-determined condenser
vacuum line locations to provide the most appropriate measurement data for the condenser system.
Depending on the plant configuration, sometimes a single SENTRY System can be configured to monitor
more than one generating unit. The probes are connected to the SENTRY CPU, which processes the
measured data and provides the system output data. The SENTRY System, in addition to data processing,
display and graphing, also communicates the data, through 10Base-T Ethernet, to the plant control room,
engineer’s office, and/or Intek via modem or internet.


Primary Calibration Accuracy:

±1% of reading


±0.5% of reading

Operating Temperature:

Electronics: 32 to 100°F
Probe: 40 to 160°F
Never subject probe to
temperatures above 210°F

Operating Pressure:

0 to 10 inches Hg absolute

Process Connection:

Hot tap assembly
(1½” thread-o-let must be welded to
pipe for hot tap installation)

Wetted Surface:

300 Series SS and engineering plastic
NEVER allow RheoVac probe heads to
be immersed in liquid water or be
exposed to live steam

Local Display:

touch screen display of all parameters
from each probe, with graphing capability

Input Power:

115 Vac, 50/60 Hz (+10%/



Signal Output:

Ethernet (10Base T) RJ45
4-20mA (optional)

Storage Temperature:


20 to 120°F

Storage Pressure:

15 psig (maximum)

Maximum number of probes/SENTRY CPU: 12