Windage steam

For Main Air Blower serviee without a steam turbine in the string, the unit shall be started by first applying windage steam and then aeeelerating the train to rated speed using the eleetrie motor. After aehieving stable rated speed, the expander inlet valve will be... 

The 4 hr hot test shall be at the normal point exhaust temperature or 1,000°F, whichever is higher. Tlie temperature may be attained by recirculating the air heated by windage in a closed loop the temperature shall be controlled within 25°F of the desired value by adding steam to the loop. During the hot test, the vibration shall be monitored for conformance to the specified limits. 

First, for Figure 14-22, enter at the top at rpm and move to the first estimating turbine wheel diameter then read down to the TSR (calculated or from tables) at Ib/kw-hr read across to base steam rate in Ib/hp-hr. Note that the base steam rate is per hp-hr, and the TSR is per kwh (or kw-hr). Now correct the base steam rate for the horsepower loss (i.e., the portion of blades of turbine spinning outside the nozzle arc, creating friction and windage). From Figure 14-23, at the top read rpm at the exhaust pressure on curved lines noted cond, read down to the estimated wheel diameter, and read the horsepower loss on the left vertical axis. 

Divide your answer by 2500 Btu/hp. This is the fraction of a horsepower that each pound of steam can produce. However, as turbines are not 100 percent efficient, multiply the calculated horsepower by 0.90 to account for internal turbine inefficiencies called -windage losses. Incidentally, the reciprocal of the calculated horsepower per pound of steam is called the water rate, which is the pounds of motive steam needed to generate 1 horsepower worth of shaft work. 

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