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Process Engineering Equipment Handbook 2009 Part 2

Tham khảo tài liệu 'process engineering equipment handbook 2009 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A-62 Air Filtration Air Inlet Filtration for Gas Turbines FIG. A-49 Drain valve. Source Altair Filters International Limited. It is almost universally agreed that stainless steel is the most cost-effective longterm solution for construction of the air-inlet system. The premium between stainless steel over painted carbon steel can now be as low as 20 whereas there are no further painting costs and the life is infinitely longer. The grade of stainless steel is also important. It is recognized that the lower grades such as American Iron and Steel Institute AISI 304 and AISI 321 do not have sufficient corrosion protection particularly if the material is work hardened. AISI 316 is the most popular choice since it has up to 18.5 chromium a metal whose presence helps to build up a passive protective film of oxide and prevents corrosion. Together with 10 to 14 nickel content the steel has an austenitic structure that is very ductile and easily welded. It also can have a low carbon content below 0.03 as well as a molybdenum content of between 2.0 and 3 which increases its resistance against pitting. Indeed one operator has paid a significant premium in both cost and delivery time by insisting that the molybdenum content be no lower than 2.5 . Not only are the filter housings now constructed in AISI 316 but also almost all of the items such as vane separators door locks hinges and instrumentation are supplied in this same material. These inlet systems will give a long life and they look good as well. A typical system is shown in Figs. A-64 and A-65. Air Filtration Air Inlet Filtration for Gas Turbines A-63 FIG. A-50 Salt penetration through filters. Source Altair Filters International Limited. The attention to detail is now evident. Figure A-65 clearly shows the elaborate drain systems that are now installed. In addition the stainless-steel housings are carefully segregated in the manufacturing shop to prevent any cross-contamination from any other ferrous materials which .