Page 467 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

444 Major Process Equipment Maintenance and Repair

address the basic parameters for that design. For a jet engine these are to
minimize frontal area through the use of long blades and a small hub di-
ameter, minimize combustor length and diameter to minimize drag and
overall engine length, and to ensure dimensional symmetry upon rapid
heat up and cool down. A jet utilizes turbine metallurgy and advand
cooling techniques to withstand the relatively short periods of time (take-
offs) during which the engine is fired hard. It must be recognized that an
aircraft engine typically spends 98 percent of its life operating in a clean,
cool atmosphere, burning a good clean fuel, and at a fraction of its rated
firing temperature. These factors all contribute to the high reliability we
have come to expect from jet engines.
The design priorities of an industrial-type turbine are quite different
from the jet. Weight is not one of the most significant factors, although
industrial turbines such as those manufactured by Solar (Figure 9-3) in-
corporate many of the lightweight features of the jets. Larger rotor hub
diameters along with thicker and shorter blades characterize the indus-
trial turbines (Figure 9-4). Long, uninterrupted runs at rated firing tem-

Figure 9-3. Solar Saturn gas turbine (courtesy Solar).