INSTALLATION
SETUP AND PHYSICAL INSTALLATION
3 - 10
WBPEEUI110505A0
open tank level measurements), connect a pressure tap
from the tank above the maximum level to be measured to
the low pressure connection of the transmitter.
Noncondensing Atmospheres
If the atmosphere above the liquid is noncondensing, the pres-
sure line from the top connection to the low pressure connec-
tion of the cell is a dry leg. The transmitter responds only to
the pressure of the fluid measured at the lower tap of the tank
that connects to the high pressure
(+) connection of the cell
(Fig.
). The calculations are the same as those for an open
tank level measurement.
1. The transmitter design allows for direct connection of the
high pressure (+) connection of the cell to the tank or vessel.
2. Make the connection from the upper tap of the tank to the
low pressure
(–) connection of the transmitter.
3. The output of the transmitter is proportional to the level of
the liquid above the cell multiplied by the specific gravity of the
liquid. If the zero point of the desired level range is above the
cell, the lower range value must be changed to reflect this.
Refer to
and
for more information. Refer to
Figure
for a graphical representation of this application.
Condensing Atmospheres
If the atmosphere (vapor state of the liquid) above the liquid is
condensable (such as steam above boiler water), the pressure
line from the upper tap of the tank to the low pressure
(–) con-
nection of the cell fills with condensate. This creates a wet leg
or reference leg that exerts a pressure at the low pressure con-
nection of the cell that is greater than that exerted by the vari-
able level on the high pressure
(+) connection of the cell.
, if h
3
is the level of the liquid at any
point between minimum and maximum level range values, the
transmitter senses the difference in pressure between the fixed
head at h
2
and the variable head at h
3
. As the level of h
3
increases, the difference between h
2
and h
3
decreases. The
transmitter output decreases with increasing level and
decreasing differential pressure. The effect is that of a negative
differential pressure that decreases in numerical value as the
level rises. This negative differential is simulated for
calibration purposes by a positive pressure, increasing in
value, imposed on the low pressure
(–) connection of the cell.
1. The transmitter design allows for direct connection of the
high pressure
(+) connection of the cell to the tank or vessel.
Содержание Platinum standard Series
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