Electro-Chemical Devices (ECD) DCA-23 - Manual (Page 7)

DCA-23 Page 1
1.0 GENERAL DESCRIPTION
The Model DCA-23 is a single purpose analyzer designed to
monitor the chlorination and/or dechlorination of seawater in
the range of 0.00 - 2.00 ppm.
Sea water is used for cooling in power plants, refineries and
SWAC systems (salt water air conditioning). The heat
exchangers on LNG terminals use large quantities of sea
water in the regasification process. Sea water is also
chlorinated and de-chlorinated at desalination plants. The
chlorination of sea water inhibits the growth of marine life on
the various filters, screens and heat exchange surfaces that the sea water passes over. Before the
chlorinated water is returned to the environment it must be dechlorinated to a level acceptable to the
local authorities.
Sea water contains approximately 68 mg/L of bromide. When chlorine is added to sea water, the
bromide ion is oxidized to hypobromous acid (HOBr) and hypobromite (OBr-) by the Free Chlorine (HOCl
and OCl-). This is a very rapid reaction and essentially all of the chlorine is instantaneously converted
into bromine and bromamines. The DCA-23 displays Chlorine ppm in order to conform to existing
conventions. It actually measures the temperature, pH and Total Residual Oxidant (TRO) potential of the
seawater and converts them into an equivalent “ppm chlorine” value. TRO is defined as the total
oxidizing capacity (free and combined) of the sea water that is available after chlorination.
The Model DCA-23 analyzer is supplied as a fully assembled rack mounted system. The ¾” schedule 80
PVC pipe flow through assembly is configured with ¾” slip fittings on both the Input and Drain ends. The
flow through assembly and the T23 Analyzer/Transmitter are mounted on two 1 ⅝” x 1 ⅝” Uni Strut rails
pre-drilled with two 0.38” holes 24” apart and with 6” between the Struts. The Standard Configuration
allows the sample to flow through either the measurement loop or the bypass loop depending on the
valve orientations. The pH sensor and TRO sensor are pre-wired into the analyzer allowing for easy
installation and Start Up of this measurement system. Simply mount the DCA-23 assembly to a wall,
plumb the Input and Drain lines, connect the power and output wiring and the system is up and running.