Document Z4ba4j0kgRQdXK0wLKjb6ZLj8

k >' NEW NO. 3 UNIT RATED 15,000 KW, In foreground, con pro* MAIN CONDENSER COOLINC-WATIR CIRCUIT It filled wttJjY. TWO STEAM GENERATORS, Jo. 7 and 8, serve the new con- steam heodor of the superheater, utlng feedwottr for Cooling, duet a moxlmum of 43,750 kw with 850-psig 900*F steam reversing votve for bockwashing unit while carrying gsiwmllonj Jdrrulng and backpressure turbines. Condensers in the soturated control outlet-stoam temperature. Pulverised cool is the fuel High-Pressure Boilers Serve New Condensing and Topping Turbines New highpreiture unit generates enough steam to help develop full load on existing low-pressure units using topping turbine to reduce pressure. Station name was changed to honor operat ing superintendent who has run plant since first constructed By THOMAS Y MULLEN, Sponsor Engineer. Gilbert Aiioe/atei,. Inr. On June 25,1948, the former Middletown Station of the Metropolitan Edison Co in Middletowo, Pa. waa renamed the Crawford Station In honor of Harold J Crawford, plaot superintendent of the station since the first unit waa placed in operation. This station, on the west shore of the Susquehanna River, was the first centra] elation in this country to use all pulverixed-bituminous coalfired boilers. Crawford Station is known for its early experiments in pulverising and burning anthracite coal dredged from the bottom of the river adjacent to the station. The "fishtail" burners and air-cooled refractory walls, which were in the original boilers here, have been largely displaced by turbulent burners and watercooled furnace walls in recent pulverizcd-bituminous-fired boiler in stallations. Burners Hke those included in the original Middletown installations and similar air-cooled refractory walls, or sections of furnace walls, are, how ever, used in some of the most recent anthracite inslallotions to maintain ignition. Haw Unit. Design of the latest Crawford extension started in 1941 when the Metropolitan Edison Co., fore seeing need for added generating capac "64 (670) ity in this orea, contracted with Tbfi'J ?s| (all capocity, which was desirable. Atlantic Utility Service Corp (prede-.i- ^.Consultation with the Foster Wheeler ceaaors of Cilbert Associates, lac) for.j, ifCorp revealed that steam-generator do- engineering and design of a pish*1? tydgn had not proceeded so far that it extension incorporating ooe 35,0W$j tapHcticoble to change their kw turbine-generator and two EOMW**: ripseity. Accordingly, these units were lb-per-hr steam-generating units and'sih'j associated equipment. '* Engineering and design work-pf^^ ceedcd on this basis until 1942 ueresied from 200,000 to 250,000 lb per |Jkr each. In addition to the 35,000-kw |/{43,750-kw maximum) turbine-genera.pr, e 3000-kw (8750-kw maximum) the federal government refusse#^- jjWMBrs-reduclng turbine-generator ex- grant priority for continuation 0 ;--t? W plant's main ateora project. The Edison Co realittdj* ' feeder was purchased. the need for ibis extension would & generators were designed for creased by this delay, and >1* Jl^psig maximum allowable working cancellation charges would be eo > ^Ejeaittre to deliver steam at the super- tered if the project were dropj^. u*4u M a Pressure of 875 pslg Hence, hold orders were Pj." $ iS*10 F 'empwolur.. equipment contracted for, and eng***?^ 7 35,000-kw turbine was designed ing and design suspended until txkr#U"ite0m "* S0 psig end 900 F, itiea could be secured. ,0 eondenser, and with bleed Id June 1945. when Priori""^ S the 7th, 10th, 14th and 18th finally obtained, work was Tae 3000-kw turbine waa do- Alterations lo existing oftfiDOj F > 4 rece{,e ,leom 01 50 psig, had Increased its capacity ,--jijjty'. fo ?3jq 8 l *heu,t at a backpressure 35,000 kw. Bu, .h. P-TS Hd|-xnj!*v' ^`ncc the exhaust from coals, w__h_ic_h__w__e_re__n_o_w being a result of the war, made for the existing boiled sufficient steam to operste u* ifop 0# temperature of about ld, condensate is used l&F*. caMl to a temperoture of t en,erio8 the steam header POWER iSv.it. j. p,*smbor |?48 serving No. 1 and 2 turbines at a pres sure of 325 psig. The small turbine will normally operate at a throttle (low of 100,000 lb per Hr Hut the stage beaters, pumps, de superheating station, piping, etc, have been designed to accommodate flowe up to 150,000 tb per hr during periods when one boiler is out of service in the low-pressure section of the plant, or when peak loads occur. Heat Batonco. Tho heat-balance diagram, page 66, shows the mojor cycle conditions with full capability developed on the large turbine and 150,000-lb-per-hr steam flowing through the small lopping unit on its way to units No. 1 end 2. Condensate leaving the hotwell passes through o low-head condensate pump, inter- end after-condensers of the evactor, the 18th-stage closed heater, end discharges into o tray-type dcoereting heater. The deaerating heater, operat ing at constant pressure of about 2 psig. serves as evaporator condenser for all makeup to tho new extension. Supple mentary steam to maintain constant deoeralor pressure bleeds from tho 14th stage at full lood and from the 10th stage at light loads. A diaphragmoperated valve controls this steam Gow from the -turbine. When evaporetor vapor exceeds that needed for constant deaerator pressure the diaphragm valve closes completely and o bypass valve around the 18th-stage heater automati cally opens to the extent needed to maintain constant deaerator pressure by admitting cooler condensate. Choice of a fixed-pressure deaerator instead of a "Boating" deaerator was based on (1) keeping water flow to tho boiler feed pumps at a constant low temperature (2) preference for a loop seal for the deaerator, thus eliminating possibilty of flooding 14th or 10th stage bleed lines because of overflow valve failure (3) simplifying condensate-re turn system from existing station, which is equipped with constant-pressure de aerators (4) eliminating venting and boiler-feed-pump turbine-shaft sealing probtema that would be encountered when pressure within'a floating-type deaerating heater would bo below atmospheric pressure. The deaerator discharges to three boiler feed pumps, 300,000-lb-per-hr capacity each, connected in parallel. (671) 65