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Chapter 3 Starting and Stopping this Device
3-10-2 Sealed Tank (Wet Leg or Remote Seal) Setting Range
(1) Calculation Example Using the JTD Model
Calculation of the setting range is described below.
In this calculation, density and distance are represented by the following symbols. In addition,
density is assumed to be constant during liquid level measurement.
ρ: Specific gravity of liquid in tank
ρ
0
: Specific gravity of sealing liquid
l: Distance between the 100% liquid level and the 0% liquid level (measurement range)
h: Distance between the 0% liquid level and the transmitter
d: Distance between the high pressure side output port and the transmitter
High Pressure
Side Outlet
High Pressure SideLow Pressure Side
Low Pressure
Side Outlet
100% Liquid Level
0% Liquid Level
Sealed Tank
Sealed Tank
(for Wet Leg)
Figure 3-18. Sealed Tank (Wet Leg)
0% liquid level differential pressure
LRV = d×ρ
0
- h×ρ
100% liquid level differential pressure
URV = d×ρ
0
- l×ρ+h×ρ
= d×ρ
0
- (l+h)×ρ
Accordingly,
Low limit (LRV): dρ
0
- hρ
High limit (URV): dρ
0
- (l+h)ρ
is the range to set.
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