Emerson Rosemount 3051 Reference Manual page 47

Reference Manual
00809-0100-4001, Rev JA
Figure 2-26. Wet leg example.
Installation
Let X equal the vertical distance between the minimum and maximum
measurable levels (500 in.).
Let Y equal the vertical distance between the transmitter datum line and the
minimum measurable level (50 in.).
Let z equal the vertical distance between the top of the liquid in the wet leg and
the transmitter datum line (600 in.).
Let SG equal the specific gravity of the fluid (1.0).
1
Let SG equal the specific gravity of the fluid in the wet leg (1.1).
2
Let h equal the maximum head pressure to be measured in inches of water.
Let e equal the head pressure produced by Y expressed in inches of water.
Let s equal head pressure produced by z expressed in inches of water.
Let Range equal e – s to h + e – s.
Then h = (X)(SG )
1
= 500 x 1.0
= 500 in H O
2
e = (Y)(SG )
1
= 50 x 1.0
= 50 inH O
2
s = (z)(SG )
2
= 600 x 1.1
= 660 inH 0
2
Range = e – s to h + e – s.
= 50 – 660 to 500 + 50 – 660
= –610 to –110 inH 0
2
ZERO ELEVATION
-610
X
Z
Y
LT
H L
20
mA dc
-110 0
inH O
2
Section 2: Installation
November 2012
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