POWER July 2011 - 58

MATERIALS
Titanium Tubing Still Going Strong
After 40 Years
Since 1972, titanium-tubed power plant surface condensers have been providing
corrosion-free service. Recent process advances are making the material
suitable for even more applications.
By Dennis J. Schumerth, Valtimet Inc.
T
itanium was discovered by British scientist
William Gregor in 1791 and named
by Austrian chemist Martin Klaproth
after the Titans, the first sons of the earth in
Greek mythology. This " reddish brown calx "
remained largely a curiosity until William
Kroll of Luxembourg, recognized as the father
of the titanium industry, perfected his
manufacturing process, which, even today,
remains largely responsible for 80% of the
world's production of titanium.
Titanium exhibits dramatic and highly
useful characteristics as a reactive metal that
make it useful for many applications. Its superior
strength-to-weight ratio makes it valuable
for use in military and commercial avionics;
alloy advancements have led to its use in the
field of biomedical engineering; it's extensively
used as " the " white-base pigment; and
its high desirability index has led to extensive
use in power generation, chemical and industrial
processing industries, and other applications
where both strength and corrosion
resistance are desirable, if not mandatory.
Given the material's unusual qualities, power
plant owners in the early 1970s took the unprecedented
risk of installing Grade 2 (Gr. 2) titanium
in their surface condensers. The first two
utilities that retubed a condenser were located on
the Northeast and California coasts. The utilities
prefer to remain anonymous. These were arguably
the first complete power plant surface condensers
ever retubed using Grade 2 titanium.
Both utilities performed several years of
independent in-situ testing of titanium against
competing tubing materials-including yellow
metals, stainless alloys, and titanium Gr.
2-for use in their once-through cooling systems,
using either brackish water, seawater,
or a combination of both for condenser cooling.
Both tests found titanium was the only
material that remained completely unaffected
in these hostile environments.
Since those first two projects, many plants
along both U.S. east and west coasts have
chosen Gr. 2 titanium as the material of
choice to mitigate the problem of condenser
and associated boiler tube failures. In fact,
more than 600 million feet of welded tita58
1.
Fast gun. Typical semi-automatic tube-to-tubesheet fusion welding is under way using
ASTM B-338 Gr. 2 titanium tubing and ASTM B265 solid titanium plate. Courtesy: Valtimet Inc.
nium tubing (Figure 1) have been installed
without one reported corrosion event. That's
an unparalleled track record.
For reasons detailed below, titanium has
proven an indispensible material, especially
given today's demanding power markets.
Though the metal has proven its staying
power in power plants for four decades, new
applications are still being discovered. Some
were not possible just a few years ago.
The Offense
The presence of water contaminants and their
omnipresent corrosion activities pose enormous
challenges for power generators. (For
example, see " Biofouling Control Options
for Cooling Systems in the Sept. 2007 issue
of POWER, available in the archives at www
.powermag.com.) A much larger challenge
for thermal power plants that use local water
in a once-through cooling process presents
itself during the building, operation, and
maintenance of those plants. The deposition,
corrosion, biofouling, and mitigation that are
often associated with water from lakes, rivers,
and oceans affect not only these once-through
cooling systems but also other cooling water
systems as well as tower circuits.
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The Defense
Insidious attack from any number of aggressive
organisms raised plant owners' awareness
of the problem, but they were perplexed about
what material to choose for their surface condensers
when traditionally used tube materials
were failing at an alarming rate. In many
cases, originally installed tubes made from
materials such as aluminum bronze (C60800)
and copper nickel alloy (90/10 CuNi/C70600
and 70/30 CuNi/C71500) failed prematurely
due to high chloride and elevated levels of pollution
in the circulating water system.
Ti Then and Now
In 1972, titanium material options were limited
principally to the commercially pure
(cp) family. Today, 38 grades of titanium tubing
are identified just within ASTM B-338/
ASME B-338 Standards.
The most common grade used for power
plant surface condenser tube applications is cp
Gr. 2 (Table 1). Its properties of high strengthto-weight
ratio, workability, near corrosion
immunity to aggressive water systems, and
relatively stable pricing structure versus stainless
alloys and yellow metals make it a highly
attractive long-term investment.
POWER | July 2011

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POWER July 2011

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