POWER July 2011 - 60

MATERIALS
Table 2. Holding power. Source: Valtimet
Test project
Utility A, South Carolina
Utility A, South Carolina
Utility A, South Carolina
Utility A, South Carolina
Utility B, Georgia
Utility B, Georgia
Utility B, Georgia
Utility B, Georgia
Ti Gr 2
Ti Gr 2
Ti Gr 2
Ti Gr 2
Ti Gr 2
Ti Gr 2
Ti Gr 2
Tube material Tube OD (inches) Tube wall (AVW, inches) T.S. material Pull-out load range (lb) ID grooves
Ti Gr 2
1.0
1.0
1.0
1.0
0.875
0.875
0.875
0.875
0.028
0.028
0.035
0.035
0.022
0.022
0.035
0.035
Muntz
Muntz
Muntz
Muntz
Muntz
Muntz
Muntz
Muntz
4. Strength and immunity. This chart showing the influence of temperature, sodium
chloride concentration (representing brackish and ocean water), and pH on the crevice corrosion
and pitting corrosion propensity of commercially pure titanium in seawater and sodium chloride
brines shows the material's immunity to corrosion at typical operating temperatures and far
beyond. Source: IMI plc
240
220
200
180
160
140
120
100
80
60
40
20
5
1,750
2,350-2,500
2,050-2,250
3,900-3,950
1,200-1,300
2,700
1,400-1,550
3,400-3,700
No
Yes
No
Yes
No
Yes
No
Yes
Pitting and crevice corrosion probable
pH9
Increasing
Ph
pH3.5
Crevice corrosion
probable
Complete immunity
10
Concentration % NaCL
ing era, pollutants identified within the cooling
water stream included high levels of chlorides,
suspended solids, macro fouling, heavy metal
accumulation, and a host of Environmental
Protection Agency-identified toxins. Notwithstanding
significant efforts on the part of plant
owners to clean up this witches' brew, emerging
and even more insidious contaminants have
been identified both locally and nationally. Significant
among these are surface pollution and
nitrate runoff from agriculture, which increase
the incidence of microbiologically influenced
corrosion (MIC) to alarming levels.
For example, manganese, which can cause
underdeposit pitting even in chlorinated environments,
has been identified as plating out
on equipment, and gray or impaired water
60
has been identified as a result of sewage runoff
or inadequate facility control.
These new, non-traditional corrosion
streams have forced power plants to closely
review their material selection process, taking
into account not only existing levels of
impurities but also expected future trends
that may lead to using cooling water from
untraditional sources.
Plenty of Redundancy
For more than 40 years, titanium condenser
tube materials have demonstrated corrosion
immunity from both traditional and newer
pollutants found in the cooling water stream
of a surface condenser. Depending on the
plant location, many cooling water systems
www.powermag.com
15
20
Quality Is More Important Than Ever
Even though recent U.S. power generation
totals have been down slightly, work continues
at the engineering and plant level to develop
and expand continuous improvement
programs that can enhance the performance
of the fleet. In fact, as some coal-fired units
retire in coming years, low maintenance
and high reliability will become even more
important for the remaining units. Consequently,
power generators around the world
will continue to select titanium tube material
as a long-term solution to a common
problem.
Plant owners who installed the first titanium
tubes four decades ago continue to reap
the long-term rewards of their decision-
both in terms of corrosion resistance and a
positive return on asset investment. Today,
water quality and proper material selection
are as important as they were 40 years ago. ■
-Dennis J. Schumerth (dennis
.schumerth@valtimet.com) is director of
business development for Valtimet Inc.
POWER | July 2011
Typical surface
condenser operating
point (120F/48C)
(including once-through, tower, pond, canal,
and others) can, through cycle concentration
and recirculation, experience increased pollutant
concentration. In particular, chloride
level conductivity concentrations can increase
significantly-anywhere from 1.3 to 2
times normal levels.
Testing completed by IMI plc (formerly
Imperial Metal Industries) in the UK found
that in seawater concentration levels of 3.5%
and beyond (Figure 4), titanium's general
corrosion immunity in sea and brackish water
environments at temperatures at or near
120C/248F (the typical condenser operating
point) was confirmed. It's noteworthy that
this same study confirmed that Gr. 2 titanium
remains completely immune to chloride
attack, even when approaching sodium
chloride concentrations of 6x normal and
temperatures approaching 80C/176F-well
above normal concentrations and well below
the operating metal temperature of a surface
condenser.
Metal temp. (C)
Seawater

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POWER July 2011

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