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Titanium 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 is still largely responsible for 80 percent of the worlds production of titanium.
Titanium exhibits dramatic and highly useful characteristics as a reactive metal in today’s world. Consider its superior strength to weight ratio for use in military and commercial avionics, alloy advancements in the field of biomedical engineering, extensive use as “the” white-base pigment and its high desirability index in the power generation, chemical and industrial processing industries and other applications where both strength and corrosion resistance is desirable if not mandatory.
Notwithstanding today’s recognition of these unique characteristics, utilities in the early 1970s took the unprecedented risk of installing Grade 2 titanium in their surface condensers.
These precedent setting events became arguably the first complete power plant surface condensers ever retubed using Grade 2 titanium.
The bad guys
Understanding the presence of pollutants and its omnipresent corrosion activities poses enormous challenges to electric utilities. A much larger challenge presents itself in the initial build, operation and the continuous-op/maintenance of thermal power plants that use the local water as a direct, once-through cooling process. This inhospitable environment affects not only once-through systems but is contagious among other cooling water systems, including tower circuits, lakes, rivers, etc. Insidious attack from any number of aggressive organisms has raised the awareness bar affecting many and diverse installations. As a result of these aggressive corrosion activities that permeated the cooling water systems, plants along both U.S. East & West coasts have chosen Gr. 2 titanium as the material of choice to mitigate a conundrum of condenser and associated boiler tube failures.
The good guys
As a result of the onset and expansion of aggressive pollutants, many utility engineers were perplexed about what material to choose for their surface condenser when traditionally-used tube materials were failing at an alarming rate. In many cases, these originally installed materials, such as aluminum bronze (C60800) and copper nickel alloy tubes (90/10 CuNi/C70600 & 70/30 CuNi/C71500) failed prematurely due to high chloride and elevated levels of pollution in the circulating water system. After years of in-situ testing, which considered competing materials – including yellow metals, stainless alloys and titanium – Gr. 2, titanium was the only material to remain completely unaffected in these hostile environments. Several condensers were initially retubed, either partially or fully in the early 1970s and continue to provide reliable electric power to the grid. Since that time, more than 6 million feet of welded titanium tubing has been installed without one reported corrosion event – indeed an unparalleled track record where water quality and proper material selection are as important today as it was 40 years ago.
Then and now
In 1972, the titanium material options were limited principally to the cp (commercially pure) family. Today, there are 38 grades of titanium tubing identified just within ASTM B- 338/ASME B-338 Standards. The cp Gr. 2 is the most common grade used for power plant surface condenser tube applications. Its properties of high strength to weight ratio, workability, near corrosion immunity to aggressive water systems and relatively stable pricing structure vs. stainless alloys and yellow metals make it a highly attractive long-term investment in today’s volatile PowerGen markets. Titanium tubing remains arguably one of the most tested of the competing ASTM condenser tube materials requiring full Eddy Current (EC), Ultrasonic (UT) and a final pneumatic proof test.