Document 4e5GKXzEr2XEr68wy21eypkQ

The small single-stage turbine is a production type of machine designed to give reliable service where it is not economical to use a more efficient tvpe of machine. In larger horse powers, 200 and above, single-stage turbines are still the most common n-pe used; however, there are indiF cations that as fuel costs increase the more efficient multistage turbines will justify their higher initial in vestment. The multistage machine, such as is illustrated at the left, retains many of the essential features of the singlestage turbine, including the lower half steam admission alid the single governor-controlled inlet valve to gether with a couple of hand valves. At the same time it improves the economy by the addition of several Rateau stages in the casing. In some instances this multistage turbine, which can be built in sizes up to a few thousand horsepower, is equip ped with the same type of oil governor as is found in single-stage machines, or it may be equipped with a vertical relay governor such as the one illustrated at the left. The next step up the line is the multistage turbine equipped with an integral steam chest and multiple in let valves to get improved economy at part load and also to obtain the improved governing that goes with multiple valves. This type ofmachine, depending upon construction details and number of stages, reaches up to the largest horsepowers. It finds con siderable application in the 2000- to 5000-hp range for compressor drives. A large portion of the mechanical-Thrive turbine field is for compressor .^Wve,.both reciprocating and centrif The photograph above shows two Elliott blast Jurnaee compressors, rated 100,000 inlet e/m each, driven by H,00G-hp turbines, steam conditions 250 psig, 7Ot) F. The sectional rierr slum s a blast furnace compressor drive for steam conditions of (h and 000 E. ugal types. These compressors arc installed in refineries and other proc ess industries such as steel mills, coke ovens, gas works, refrigeration plants, and the like, and these applications hold promise ofan expanding market. For example, a modern refinery ad dition may require six or eight com pressors each requiring a 4000- to 5000-hp turbine drive. The speed of these compressors, normally running from 5000 to 7000 rpm, has recentlybeen stepped up to 10,000 and 12,000 rpm. With the advent of the gas tur bine, compressor design has received considerable attention, and rotative as well as tip speeds are being in creased. It is now common to have compressors designed with a tip speed of 900 fps, and indications point to higher speeds in the future. The driving turbines for these compressors thus become high-speed machines. This subject will be discussed in a future article dealing with turbines designed for 10,000 and 12,000 rpm. ivm KHKA.V WINTKM Iv.Vl PAGE 5