Emerson Rosemount 2051 Reference Manual page 61

Reference Manual
00809-0100-4107
Zero range suppression is required if the transmitter lies below the zero point of the
desired level range.
3.6.2 Closed vessels
Pressure above a liquid affects the pressure measured at the bottom of a closed vessel.
The liquid specific gravity multiplied by the liquid height plus the vessel pressure equals
the pressure at the bottom of the vessel.
To measure true level, the vessel pressure must be subtracted from the vessel bottom
pressure. To do this, make a pressure tap at the top of the vessel and connect this to the
low side of the transmitter. Vessel pressure is then equally applied to both the high and
low sides of the transmitter. The resulting differential pressure is proportional to liquid
height multiplied by the liquid specific gravity.
Dry leg condition
Low-side transmitter piping will remain empty if gas above the liquid does not condense.
This is a dry leg condition. Range determination calculations are the same as those
described for bottom-mounted transmitters in open vessels, as shown in
Figure 3-12: Liquid level measurement example
Reference Manual
Figure 3-12 shows a liquid level measurement example.
Hardware Installation
September 2020
Figure 3-12.
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