Technical Information Analytical Products
Electric, Gas, & Sanitary Services-SIC 4900
APPLICATION NOTE
ANALYTICAL-SIC4900-04
Introduction
Steam is used throughout the world
as a means of producing energy.
This steam is converted back to
water in condensers and further
cooled in Heat Exchangers.
Wherever there is steam, there is a
process liquid to be cooled. Since
steam is used to produce energy,
corrosion of the heat exchanger is a
constant maintenance problem.
The use of corrosion-resistant
metals and improved methods of
water tr eatment have minimized the
effects of corrosion on the steam
side of the heat exchanger, but
corrosion on the process side
remains a serious problem.
Exchanger Leakage
Corrosion on the process side
causes the heat exchanger tubing to
mechanically fail, allowing process
fluid to leak into the condensate
return line. This can cause serious
damage to the boiler. Therefore, it
is necessary to monitor the
condensate downstream of the heat
exchanger and to dump the
condensate as soon as it shows
signs of contamination.
An excellent indication of
contamination is obtained by
measuring the conductivity of the
condensate. Pure condensate has a
very low conductivity value (1 to
10 S), while the contaminants
(typically salts, acids or alkalis)
that are introduced when leakage
occurs have significantly higher
conductivity values. Any marked
increase in the conductivity of the
condensate indicates that leakage is
present, and the condensate should
be sent to drain.
As shown in the simplified diagram
below, the conductivity instrument
can be utilized to directly control
the dumping of contaminated
condensate. A single point
conductivity analyzer (EXA
SC402) can be located downstream
of the heat exchanger, and utilize a
high alarm relay to actuate the
valve. Another option is to use a
dual input conductivity analyzer
Heat Exchan
g
er Leaka
g
e
STEAM HEADER
USER
TRAP
TO WASTE
STEAM DRUM
MAKE-UP WAT ER
CONDENSATE
RETURN
BOILER
FEEDWATER
CONDENSATE
HOLDING TANK
CONDUCTIVITY SENSOR
CONDUCTIVITY SENSOR
OPTION #1
EXA SC402
OPTION #2
EXA DC402
HEAT EXCHANGER
2
ANALYTICAL-SIC4900-04
(EXA DC402) with one sensor
upstream of the heat exchanger and
one downstream. The built-in
deviation calculation of the
analyzer can be used to alarm, or
actuate a valve, when the
downstream conductivity deviates
significantly from the upstream
conductivity. This method
compensates for any variance in the
condensate conductivity.
Summary
Measurement and control of Heat
Exchanger Leakage can help
prevent costly maintenance, repair
and downtime. The simple,
essentially maintenance-free
measurement of condensate
conductivity will give the operator
information necessary (or provide
automatic control) to prevent
severe damage to the boiler should
a breakthrough of the heat
exchanger occur.
Recommended Products:
Transmitters:
SC202 two-wire Conductivity Transmitter
Converters:
SC402 four-wire Conductivity Converter
DC402 four-wire Dual Channel Conductivity Converter
SC150 four-wire ΒΌ DIN Panel Mount Conductivity Converter
Sensors:
SC42-SP34 Large-Bore Conductivity Sensor (fittings available for
Flow-Thru, Insertion, or Immersion installations)
SC4A Conductivity Sensor (fittings available for Insertion, Sanitary,
or Retractable installations.)