2808B DP Transmitters / 1B-13
A liquid-filled line is one way to isolate the Transmitter from a steam process. As an al-
ernate method, a steam trap may be installed in the connecting line. Several manufacturers
offer traps for this application.
Liquid Level Application. DP Transmitters can be used to measure the head pressure of
a column of liquid in an open tank. Typical tank configurations are shown in Figures 1B-12
to 1B-15.
Open Tank. For the application of Figure 1B-13, the Transmitter is operated as a
gauge pressure device. The HI side connects to the bottom of the tank while the LO
side is vented to the atmosphere. The span of the Transmitter is calibrated to
correspond with maximum (100%) and minimum (0%) tank levels.
Closed Tank. In the closed tank application, the HI side of the Transmitter connects
to the bottom of the tank while the LO side connects to the top as shown in Figure 1B-
15. The Transmitter measures the differential pressure between maximum and
minimum tank levels. The wet leg in the upper connection provides a liquid head for all
measurements below the maximum tank level.
Closed Tank w/ Purge Line. If the process medium contained in a closed tank is a
substance that reacts with the Transmitter's construction materials, a purge line may
be installed as shown in Figure 1B-14. This line consists of a pipe or dip tube that
extends from the bottom of the tank to the HI side of the Transmitter. The LO side pipe
connection is at the very top of the closed tank and is several inches above the
maximum (100%) measurement line.
Figure 1B-13 - Open Tank Measurement Figure 1B-14 - Closed Tank
Measurement
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