Figure 2-2: FFW Seal and Components
A
B
C
D
A. Process flange
B. Diaphragm
C. Gasket
D. Flushing ring (optional)
2.3
Seal system performance
2.3.1
Volume temperature effects (process temperature
effects)
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.
shows how diaphragm size can affect the measurement reading at the
transmitter. For smaller seal sizes, such as the 1
½
-in. size, the amount of back pressure on
the transmitter causes an additional 12.1 inH
2
O (307 mmH
2
O)error. Moving to the 2-in.
size gives 1.7 inH
2
O (43 mmH
2
O)and the largest 3-in. size shown only has 0.5 inH
2
O (13
mmH
2
O)error. Using a larger diaphragm can drastically improve performance and
provides a more stable reading.
Remote Seal Systems
Reference Manual
May 2020
00809-0100-4002
10
Rosemount DP Level
Summary of Contents for Rosemount 1199
Page 4: ...4 ...
Page 8: ...Introduction Reference Manual May 2020 00809 0100 4002 8 Rosemount DP Level ...
Page 22: ...Remote Seal Systems Reference Manual May 2020 00809 0100 4002 22 Rosemount DP Level ...
Page 74: ...Installation Reference Manual May 2020 00809 0100 4002 74 Rosemount DP Level ...
Page 92: ...Fill Fluids Reference Manual May 2020 00809 0100 4002 92 Rosemount DP Level ...