Document 5xRZGgZmVYjXMv9wZMxKM2JR

FANS AND PUMPS IN HOT AND DAMP loeotion* con be lately and efficiently driven by mechanical-drive steam turbines Steam Turbines for Mechanical Drive into* account for using turbine drive: Tj'adiptability to variable-speed needs (j)-ifor direct high-speed applications (3J1 installation in hot or damp locilieu (4) safety in explosive locations. Seldom would one of iheso secondory idysniages be of such importance that turbine would be selected on ouch a Ijuis only. They are, however, deterjmnbig factors if study of primary benetarytelds e borderline decision. freest* Steom. When low-pressure fteim, S to 100 psig, serves process 4*?tnds such os healing, drying, cook"t building heating, feedwater heat- etc. remarkable savings can be made by using turbines as "reducing tlm" between boiler and working Pt*urea. Turbines'"skim ofF1 about 10..lo 20% of the heol in the steam tj^ing the bslsnce available for other Though extra heat must be sup 'll the boilers, the amount is smalt ind (be over-all power cycle becomes efficient. For this reason, turbines be applied economically up to the lai|t established by the low-pressure requirement. Sometimes steam and power demands Sty to such an extent that "doubled-up" Shipment becomes economical to in- These may be either duplicate Spvw, some turbine and some motor, or dual drives, driven equipment with tur bine on one end and motor on the other. Up to their capacity limits such ar rangements provide maximum operating economy as the steam passing through conventional reducing valves slays at a .minimum. Where frequent variations in steam demand occur llio dual-drive ar rangement U preferable. These units automatically follow the steom demand, giving them their name of "steam-bal ance" sets. Inexpensive power from process steam is particularly important in indus trial applications where process steam demands are heavy. In large power plants heating-steam needs are gener ally met by extraction from main tur bine-generator units. Rut. where power plant expansions increase tho demand for low-pressure steam this requirement can be met conveniently by exhaust steam from turbines driving boiler auxiliaries. Powov Failure. Service continuity must enter into every decision concerning selection of equipment. For vital ap paratus normally driven by motors, good practice often drives the spares with turbines because of their reliabil ity and their operation depending only on steam supply. Spare equip* menl such as boiler auxiliaries, fire pumps, exciter sets, house generators and lighting seta (all into this category. Sometimes continuous operation may be so vital that time cannot He allowed for manual starting of the spare equip ment. Under such circumstances auto matic quick-starling control or dual drive turbines can be used. The latter represents the ultimate in protection as the turbines can take over with hardly a change in speed. Waste-Heel Application*. Lumber mills burning their sawdust, plants burning refuse, end reduction, cracking or cstelytic process giving off best typify industries having waste heat available. Conversion of waste heat into electrical or mechanical power often proves to be economical. When this heal fires a steam boiler, conventional steam turbines can be used. When the waste heat appears in a process gas under pressure conventional steam turbines can be modified for gas operation. Steom Availability. In many cases, when steam is the only source of energy available, as in marine work, dredges, steam locomotives end the like, turbines may bo the only type of drive to use. There are some land applications where existing main electrical circuits cannot handle added load because 0! [Continued on page 144) June 1949 i9) ?J