Environmental Science & Engineering - www.esemag.com - November 2003
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Measuring and maintaining tank levels
Fluid tank operators can utilize a
float and gauge combination, or
a transmitter to obtain a continuous
reading of open storage
tank levels. While a
simple gauge may be
less costly and good for
providing a local reading,
a much more
expensive transmitter is
often necessary in
order to monitor levels
from a remote location
such as a plant’s automated
control room. In
addition, a separate
control is required to
signal when the fluid level is nearempty
or near-full.
Combining the local and remote
readout functions of a gauge and a
transmitter, with the capacity of a
switch in a single control can yield significant
cost reductions for multiple
open storage tank operators.
United Electric Controls’ One
Series gauge pressure switch measures
and maintains levels in open storage
tanks and vented reactor
vessels. The pressure
generated by the
“head” or height of
fluid above the instrument
is converted to a
digital readout displayed
on the electronic
device. For
maximum accuracy,
the instrument is
located as closely as
possible to the bottom
of the tank, as any height of fluid
between the instrument and the bottom
of the tank cannot be measured.
The measurement readout can be
expressed in psi or water column
measurement units. In addition to the
local indicator, the One Series’ 4-
20mA output also provides constant
remote tank level readings when linked
to a PLC or DCS.
Alarm and shutdown functions are
also performed to signal nearempty/
near-full conditions using the
integral switches. The dual control
provides two set points for signaling
both high and low tank levels. In the
absence of a PLC or DCS, the switch
acts as a stand-alone level controller by
cycling a filling pump and/or opening
a drain valve to maintain a certain level
in the tank.
Ultimately, the One Series performs
multiple tasks that would normally
require a variety of mechanical and/or
electronic devices. By using this control
tank, operators obtain the alarm
and shutdown functions of a traditional
pressure switch, the local measurement
indication of a gauge, and the
remote monitoring capacity of a transmitter,
all in one easy-to-use electronic
device. The main advantage, however,
is that the cost of this control is half the
price of a basic transmitter.
For more information contact:
wbernadin@ueonline.com.
See our home page on how to order your subscription. We regret we can
only accept orders from Canada and the United States.
