. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . s of greater volume than satu-rated steam. The increase in volume is nearly pro-portional to the absolute temperature460 degs. F. Highly superheated steam behaves likea gas, and can work by expansion with-out condensation. The greater volume of superheatedsteam makes it possible to use less weightof it to fill a like volume as comparedwith saturated steam. The total heat per cu. ft. is less thanthat of saturated steam per cu. ft. atsame pressure in spite of the fact thatthe specific heat incr
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . s of greater volume than satu-rated steam. The increase in volume is nearly pro-portional to the absolute temperature460 degs. F. Highly superheated steam behaves likea gas, and can work by expansion with-out condensation. The greater volume of superheatedsteam makes it possible to use less weightof it to fill a like volume as comparedwith saturated steam. The total heat per cu. ft. is less thanthat of saturated steam per cu. ft. atsame pressure in spite of the fact thatthe specific heat increases. The higher the superheat the greateris the advantage to be gained, 570 practical limit of temperature at valvechest. Steam of low or high pressure can besuperheated to same temperature. It is practically possible to use a muchlower pressure to advantage with super-heated steam than is to be attained bysaturated steam, and in fact it is hard torealize a like advantage. Superheated steam is practically a non-conductor of heat acting as an insulator. Superheated steam at 13 atmospheres. TIN BAND IN PLACE IN AIR PUMPSTRAINER. or lbs. absolute and 200 degs. , there is an increase in per cent., but this does not neces- 168 RAILWAY AND LOCOMOTIVE ENGINEERING. May, 1914. sarily call an increased boiler capacityto that amount. The actual case in prac-tice is that a cooling effect of the cyl-inders decreases this volume. Anotherpoint the expansion of superheated steamis more rapid than that of saturatedsteam; therefore, a longer cut off shouldbe used than that used for saturatedsteam locomotives for the same powerwhen the cylinders are of like dimen-sions (increased size of cylinders is bet-ter practice). Even considering that less steamingcapacity is made by applying the super-heater, this is made up by the saving insteam through the increased volume attime for admittance of steam to the cyl-inder, and in practice from IS to 30 percent, saving
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