Rosemount 1199, Справочное руководство

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Reference Manual
00809-0100-4002, Rev BB
November 2012
Rosemount 1199
2-2
Figure 2-2. FFW Exploded View
UNDERSTANDING SEAL
SYSTEM
PERFORMANCE
Seal Temperature Effects
(Process Temperature
Error)
Fill fluids expand or contract with temperature changes, creating a volume
change that is absorbed by the diaphragm seal and is seen as back pressure at
the transmitter. This back pressure creates a shift in the transmitter reading. For
symmetrical or balanced systems, this error is usually minimal due to the back
pressure being equal on both sides. However, head temperature effect is still
present.
NOTE
Other factors that affect seal temperature effect include diaphragm thickness,
seal type and size, capillary length and inner diameter.
Figure 2-3 on page 2-3 shows how diaphragm size can affect the measurement
reading at the transmitter. For smaller seal sizes, such as the 1
1 /
2
-in. size, the
amount of back pressure on the transmitter causes an additional 12.1 inH
2
O
error. Moving to the 2-in. size gives 1.7 inH
2
O and the largest 3-in. size shown
only has 0.5 inH
2
O error. Using a larger diaphragm can drastically improve
performance and provides a more stable reading.
NOTE
Calculations done in Toolkit with Silicone 200 fill fluid with 3051 Transmitter.
Process Flange
Diaphragm
Flushing Connection
Gasket
Clamp