Fluid Components International MT91 Manual General Information - Manual (Page 2)

FLUID COMPONENTS INTL CHAPTER 1 - GENERAL INFORMATION
Model MT91 Multipoint Flowmeter 1 - 2 Doc. No. 003185 Rev. B
Theory of Operation
The flow element has multiple sensing points that consists of two pairs of thermowells of the same size, shape and
mass. One pair contains a platinum RTD and a heater element. The other pair contains one RTD. The RTD located
next to the heater element is called the active sensor. The other RTD is referred to as the reference sensor. Since the
active sensor is adjacent to the heater, the temperature at the walls of the thermowell are always above the
temperature of the process media. The temperature at the reference sensor is the temperature of the process media.
When the process media is flowing past the active sensor a quantity of heat is carried off into the flow stream. The
amount of heat taken from the active sensor is a function of the process media mass flow rate. A
D T exists between
the two pairs of thermowells and a proportional D R exists between the active and the reference sensors. The D R is
measured by the flow transmitter. The relationship of D T to the mass flow rate is calculated by the flow transmitter
and is converted into a signal and is sent to the flow transmitter's display.
Specifications
Process Connection
2 inch male NPT or 3 inch 150 lb. raised-face carbon steel
flange. Other flange connection sizes and materials
available.
Insertion Length
Variable
Material of Construction
All wetted surfaces are 316 Stainless Steel with nickel
brazed joints per process specification AMS 4777.
Hastelloy C-276 and other materials and electroless nickel
plating also available.
Enclosure
Flow element: NEMA 4. NEMA 7 optional.
Flow transmitter Assembly: NEMA 4 or 19 inch
Rackmount in accordance with DIN 41494 part 1, ANSI/
EIA-RS-310C. NEMA 7 optional.
Temperature Range for Flow Element
Low -50° to 350°F (-45° to 178°C)
High 350° to 850°F (178° to 458°C)
Temperature Range for Flow Transmitter
0° to 140°F (-18° to 60°C)*
* The LCD display will not function in temperatures below
32°F (0°C).
Operating Pressure
Up to 50 psig (3.5 barg)
Power Requirements
85 to 265 Vac, 47 to 63 Hz, 3.5 Amp fused 20 to 32 Vdc 24
Vdc nominal
Electrical Connection
1 inch female NPT
Relay Rating
2 relays per relay output board. Relays are DPDT, 0.3A at
125 Vac, 0.3A at 110 Vdc, 1.0A at 30 Vdc.