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1
GENERAL INFORMATION
1.1
INTRODUCTION
Rheotherm
precision flow controllers are designed to provide accurate control of fluid flow rate.
Rheotherm
instruments are manufactured exclusively by Intek, Inc. and employ a patented thermal
technique used by industry since 1978. The unique sensor designs have protected sensors, are easy
to install and require little or no maintenance. The Model 210 is a
smart instrument; its unique
features and performance characteristics are described in SECTIONS 3, 4, and 6.
The Flow Controller is an add-on to a standard Rheotherm Flow Meter that uses PID control to
adjust an integrated valve to a customer selectable setpoint. The PID variables are dependent on
fluid type, flow rate, and sensor size. As such they are programmed at the factory and are not
user adjustable. The Flow Controller is typically available in any mass flow or volumetric flow
units with a 10:1 turndown but can be calibrated to 100:1 with decreased setpoint precision. The
Flow Controller displays the current flow rate (PV) and the setpoint (SV) on the display.
Each
Rheotherm
flow controller consists of three elements
,
a sensor, a transmitter unit, and an
adjustable valve. Design selection is based on application constraints or customer preference.
Key features of
Rheotherm
instruments are:
•
Nonintrusive flow measurement: For pipe sizes from 1/16 to 1/4 inch, flow sensing can be
done from outside the flow tube.
•
Chemical compatibility: The wetted surface(s) can be any of a number of corrosion
resistant metals, alloys and seals.
•
Flexibility:
Rheotherm
meters can be ordered calibrated for mass or volumetric units or in
average velocity. Flow rate displays or output signals are available, as well as rangeability
up to 100:1.
•
Fluid pressure options up to 500 psi (check sensor tag for rating on your unit).
•
Withstands over-ranging
:
No damage or change in calibration will occur due to excessive
flow rates many times higher than calibration range.
1.2
DESCRIPTION OF OPERATION
Rheotherm
flow controllers are available with various nonintrusive sensor designs, but they all use
the same, patented, thermal sensing technique. Two temperature sensors are used
,
one is in thermal
equilibrium with the fluid and provides a fluid temperature reference, while the second temperature
sensor is located near a heater so that its temperature is slightly above that of the fluid. In a TU or
TUL sensor, the temperature sensors and heater are attached to the outside of the flow tube. The rate
at which heat is removed from the heated sensor by the stream is related to fluid velocity. Hence, the
measured temperature differential between the reference sensor and heated sensor is a function of
flow rate. Intek, Inc. is licensed to use this patented and trademarked flow measurement method.
