Journal . ical device that would stand up against practicalusage. Relative Thermal Efficiencies. This being calculated for a 1,000 K\V. turbine, and assumingthat the whole of the steam passes to the heating system, thenwhatever heat is lost under these conditions, 92-25% of it isconverted into mechanical work. This is the reason of theextraction turbines efficiency. The efficiency in the use ofthe steam which passed to the condenser is no better ; in fact,it is worse than if it had passed through a high-pressure turbine,but the amount which goes to the condenser must be arrangedto be the small
Journal . ical device that would stand up against practicalusage. Relative Thermal Efficiencies. This being calculated for a 1,000 K\V. turbine, and assumingthat the whole of the steam passes to the heating system, thenwhatever heat is lost under these conditions, 92-25% of it isconverted into mechanical work. This is the reason of theextraction turbines efficiency. The efficiency in the use ofthe steam which passed to the condenser is no better ; in fact,it is worse than if it had passed through a high-pressure turbine,but the amount which goes to the condenser must be arrangedto be the smaller amount. A similar 1,000 KW. high-pressureturbine compares as follows :—The total heat is 1,278 ,and the thermal efficiency is 20%. It is, therefore, worthinstalling an extraction turbine where conditions permit, andthe quantity of heating steam is sufficient to warrant its beingadopted. 218 EXTRACTION TURBTNES. HIGH PRESSURE CONTROLLING VALVES LOW PRESSURE CONTROLLING VALVES LOW PRESSURF STAGCS. OUTLET FDR HEATING STEAM EXHAUST TO CONDENSER Fig. 3. Extraction Turbine Duty. To make the extraction turbine a useful device, it should bepossible to vary the power required from the turbine withoutit affecting the quantity of heating steam. A second conditionnecessary is to give a supply of heating steam at constant pres-sure, and any volume up to the full output designed ; it must bepossible to meet a variation in the quantity of heating steamif necessary, because the quantity of heating steam dependsupon the demands from the factory, and the turbine must fulfilthese conditions. If it is not possible to supply more steamthan the maximum load will allow to pass, and if the load isnot available, steam cannot be passed through. An additionalquantity of heating steam can be obtained, however, by makinguse of a by-pass reducing valve. A by-pass pipe is takenfrom the main inlet to the heating steam pipe, and containsan ordinary reducing valve, so that should the demand forheati
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