US2612592A - Control system for electric steam generators - Google Patents

Description

Sept. 30, 195 2 w. PAULISON, JR., ET AL 2,612,592

CONTROL SYSTEM FOR ELECTRIC STEAM GENERATORS Filed Oct. s, 1950 5 Sheets-Sheet l INVENTORS AND WILLIAM L. PAULISON JR. HARVEY C. MITTENDORF (WW/{M Sept. 30, 1952 w. L. PAULISON, JR, ET AL 2,612,592

CONTROL SYSTEM FOR ELECTRIC STEAM GENERATORS Filed Oct. 3, 1950 3 Sheets-Sheet 2 HI PLANT Z I DEMAND LO STEAM DEMAND OR A HI HI ExoEss B PLANT EL POWER DEMAND Lo Y INVENTORS FIG, 5 AND WILLIAM L. PAULISON JR.

HARVEY C. MITTENDORF Sept. 30, 1952 w. PAULISON, JR, ET AL 2,612,592

CONTROL SYSTEM FOR ELECTRIC STEAM GENERATORS Filed Oct. 3, 1950 3 Sheets-Sheet 5 ELECTRIC LOAD IN VEN TORS AND HARVEY c. MITTENDORF WILLIAM L. PAULISON JR.

Patented Sept. 30, 1952 nun-13p STATES {ATENT OFFICE icoNrRoL. SYSTEM FOR ELECTRIC STEAM GENERATORS I Application October 3, 1950,5erial No. 188,118 37 Claims. (o1. r al-4t) invention relates to control systems and particularly to method and apparatus adapted to 'control the operation of a power producing apparatus such as an electrically heated vapor generator.

In certain "localities where hydro-power :is abundant, the price of electricity is low enough to n1ake economical its use in vaporizing water intotsteam for processor other purposes. In the operation ofsuch vapor'generators problems of QO ltrOl arise which must'be solved in order that thetemperature ,and pressure of the produced steam will be of optimum value under existing r e'mand conditions and with full safety to life and apparatus.

p The problem with which our .lnethodand app'a atus areconcerned is thesupply or water to the unit, the extraction of water therefrom, the

,Inaintenance .of desired liquid levels, as well as I the conductivity of the liquid within the unit,

all in proper degree so that the vapor which is generated will satisfy the demand while ,maintaining desired conditions of pressure.

,In such a vapor generator, the heat for vaporizing thewateris supplied ,by the passage of electriccurrentthrough the water itself, from one electrodeto .anotheror. to .a neutral plate. Since the voltageof the power supply is constant, the

, ,energy consumed varies directly with the current, while the current varies inversely as the resistance ofthe path ,it travels. The resistance of the path, in turn, depends ,upon the crosssectional areaof the water conductor .(path) and .uponthespecific resistance of the water itself.

inasmuch-as the electrodes are fixed in position, the water area through which the current can pass is .determined by .the depth .of immersion ofjthe electrodes; i. e. the'height of water within the electrode. vchamber. The specific resistance of the water is a,function of the concentration vamount of dissolved solids in the water and also of the temperature of the water.

Ihus, in a'boiler of this type, the amount of steam generated depends upon the amount of electric current passing through the water and this, in turn, depends upon the area of the path through the water and upon the conductivity (or resistivity) of the water to the passage of electric current therethrough. The water area through which the current can pass is determined bythe depth of immersion of the electrodes. "Therefore, if we maintain a constant specific resistance of the water, the .amountpof .steam generated may be controlled by varying the-level of the water in the'electrode chamber.

:"Thus, in order-to maintaina substantially:umform value of :steam pressure, while satisfying thedem-and upon the *boiler for quantity rate of steam generated, we are confronted with the problem of controlling the level of 'liquidwithin the electrode chamber aswell as the specific rewater-supplied is other than condensate. nasmuch as the steam does not carry away any appreciable amount of salts or solids fromthe boiler there is-a continuous tendency to build-up the concentration of solidswithin the boiler-water and thus to continually decre ase the resistivity to current passage through the water :path.

Whenoperatingat rated capacity the boilernlay hourly evaporate many times the water normally contained in it. In generalQitmaybe said t'hat if the conductivity of "the water, is maintained substantially uniform the rate of steamgenera- ,tion will vary with the water level ,or extent'of immersion of the electrodes in the water' pool.

Conversely 'if the water is maintainedsubstantia'lly uniform then therate of steam generation will vary with the concentration of dissolved salts in the boiler Water. In order to keep the concentration of the water from gradually increasing (which would make inaccurate any functional t onshi between wat r level and vapor g neration) it is advisable to continually bleed some part of the highly concentrated water .irom the lower portion of the boiler ,drum in a controlled manner. ,If this is properly accomplished then a control of level within the electrode chamber is a control .of rate .of steam generation.

The interrelation ,of the effects of the operating variables may, however, .oause disturbances in th primarycontrol of levelor of conductivity. For example, the conductivity of the waterisnot only a funciiqnof the amount ,of ,dissolvedsolids ther in bu is a so a function of t e te perature of the water (increasing with temperature).

By way of example; if there is an increase in demand upon the vapor generator the steam pressure will tend to fall. Assuming, ,.fo r.".the moment, a uniform conductivity of the water, 'thenthe increase in steam demand indicates a desirability of raising the level of water within the boiler and thus increasing the path for electric current, thereby increasing the rate of current dissipation and consequently the rate of steam generation. However, a rapid increase in the rate of supply of water will tend to dilute the water within the boiler, thus lowering its conductivity, and at the same time will tend to cool the water within the boiler which also effects a lowering of its conductivity. Both of these adverse effects are opposite in nature to a desired increase in vapor generation as would be expected through increasing the level and thus the area of the conductor path. It is, therefore, apparent that a proper control must be judicious in regard to varying the level of water and must definitely take into account such adverse effects as have been mentioned.

It is known to provide a generating unit of this type with a storage or surge tank to which water may be transferred from the boiler, or from which water may be fed to the boiler. In the past the storage or surge chamber has been entirely separate from the main shell of the generating unit and usually has been located at an elevation somewhat above the electrode chamber. The water stored within the generator proper includes both the water within the cloverleaf neu tral plate and also that water between the cloverleaf plate and the shell of the generator. The

latter water unnecessarily adds to the volume of water to be stored in the external surge tank because the load regulation only requires a variation of water within the cloverleaf and surrounding electrodes.

' It has been proposed that the space between the cloverleaf and the outer shell be closed at the top and thus have such space comprise a surge or storage chamber in U-tube connection around the bottom of the cloverleaf plate with the electrode chamber proper. It is to a unit of this general construction that our present inven tion is applied.

7 It is an object of our invention to provide both method and apparatus control for an electrically heated vapor generator.

We have as a further object the provision of a completely automatic control system for such a vapor generator.

.Still another object is to provide a method and apparatus of control of an electric-vapor generator having a vaporizing chamber and storage chamber concentrically arranged within the pressure shell of the unit.

Still another object is to provide method and apparatus for controlling such a vapor generator to keep the total amount of water in the two chambers substantially constant during different rates of operation and for various levels within the two chambers.

Other objects will become evident upon a study :of the specification, drawings and claims.

steam space of the storage chamber.

plied includes a vertically mounted drum or pressure vessel I supported in customary manner (not shown). Insulated through the upper head 5 of the drum I and suspended therefrom are three equally spaced electrodes 2 (two only being shown in Fig. 1) which may be of cast iron or other suitable material. The three electrodes are enclosed by a cloverleaf neutral plate 3 properly spaced from the electrodes and from the inner surface of the pressure drum I. The terminals 4 of the electrodes are connected through the necessary electrical apparatus to a source of electrical power (usually S-phase); the arrangement forming no part of the present invention. Fig. 2 is a somewhat diagrammatic sectional view taken through the assembly of Fig. 1 and shows the general arrangement of the drum 1, the electrodes 2, and the neutral plate 8.

The cloverleaf shaped neutral plate 3 is joined to the shell I, near the upper head 5, by a. plate 6, thus dividing the unit into two chambers. The electrode chamber is enclosed by the cloverleaf 3 and the drum head 5 as well as the top of plate 5. The storage chamber is formed between the inner wall of the shell I and the outer wall of the cloverleaf 3 as well as the bottom of plate 8. Communication of the electrode chamber with the storage chamber is had around the open lower end of the cloverleaf 3. When the unit is not operating and all parts are at atmospheric pressure any water within the unit will find a common level within the two chambers. During operation the level within the storage chamber may be the same as that within the electrode chamber or may differ therefrom as will be pointed out hereinafter.

The uppermost steam space of the storage chamber is joined to the steam space of the electrode chamber by a pipe 1 having therein a control valve 8 of the spring loaded pneumatically actuated type. A steam outflow pipe 9 joins the Steam which is generated within the electrode chamber passes through the pipe 1 and valve 8 into the steam space of the. storage chamber from which steam passes through the pipe 9 to a point of usage. Such outgoing steam passes an orifice I0 across which is connected a steam fiow (SF) meter I I arranged to continually position an arm I2 representative .of rate of steam outflow through the pipe 9.

Connected to the pipe 9 is a Bourdon tube II arranged to position the movable element of a. pilot valve I6 for continually establishing in a pipe I! a fluid loading pressure representative of static pressure of the steam in the outgoing conduit 9. p

. Water is supplied to the unit through a pipe I8 which enters the shell I at a considerable elevation above the bottom of the electrodes. In the pipe i8 is an orifice I9 across which is connected a water flow (WF) meter 20. Meter 20 is arranged to position an arm 2| continually representative of rate of supply of feed water to the unit.

By entering the raw feed water to the storage chamber at an elevated location, the raw water, of lower temperature and reduced conductivity, is diffused through the water of the storage chamber and heated thereby before it turns the lower end of the partition 3 to enter the electrode chamber. A pneumatic control valve 37 is shown in pipe I 8 for regulating the rate of supply of feed water.

As previously mentioned, the vaporization of water within the 'imit'i-l aves or tentrained salts or solidsjihsthelwater rIDQQlfiljld us nhambers would continually :buildzup sirablea-value :It is advi able .toihav. :lableibleednftheimosthi hlv colleen, aandrzto thisend weiprovide'a pipe-23 which ente the lowersportioniofqtheshell land pa esupward within the electrode schamb eribeing tacks-Welded to fithe inner wall tor 2th? icl verleai p t1: on 13- :As:indicated att:24 this ma e; ,v ,7 that bleed water passing ioutward'; hroughthe pip :samnles-v rtti al yzthe water111001 surroimdineth ielectrodes', this .being -;the :water' which is further? est away from the incoming diluting raw iced water andzait triesametimeheinethe nater whi 'i'sicontinually increasing iii-concentrationthrough evaporation; v I

In the pipe :2-3 w :show a pneumatically acts.- ated ,contr'ol valve 25 positioned responsive to -a loading pressure .(in a pipe -26) which is continu Tally established by gthermeter 211 which isa con, ductivity imeter :(GC) having an activeclement Z & located within the electrode; chamber.

intiilssvve show' an -elect-rodechamber level ICECL) measuring device having pressure pipe connections thereto 1-30 and 3 l "The-pipe 3 [passes t-hrough'the outer shell l and opens through the partition -:3 near :the lowest expected level of liquid withintherelectrode chamber. A pipe-3 I joins the steam space of the electrodechamber by0pening through the head :5. The meter ECIi) is arranged to continually position an arm -Z'9A continually representative of: the level of liquid within :the electrode "ch-amber.

" i-n similar manner "device :33' determines storage chamber level (S611) and continually positions an arm 3'5 representative of :liquid level -within the storage chamber." The device 33 is connected-by apipei 34 opening through the outer electrodes zit-are fullyeimm rsed to approximately slevel 1A; rAs rtheisteam. demandgdecreases the. disphargediow-ratethrough offtake v9 drops ,andithe trodes 2 remaining aimmersed generate only sui- "shell 'intothestorage-ch-amber-at an elevation which preferably may be "the same as the connection elevation 130. K The pipe 35 :opensthrough the-:shell l in 'the steam space of the storage chamber above thehighe'st expected liquid level therein.

It will thusbe seen that in Fig. l 'weprovide certain 'ins'trumentalities "which are sensitive to variables-"in the operation of the unit and also provide control or regulating valves "In Fig. 1 -we have shown the pipe I'I joining the diaphragm-chamber of the steam throttle valve 8. "Thusthe-Bou-r'don tube 15, sensitiveto pressure of steam in the outflowpipe 9, adjusts the throttle. opening of control valve 8 regulating communication between the steam spaces of the two -ch-ambers.

In operation, the unit isflrs-t filled=with water tothe level Aanddue to-initial lack of pressure ,in steam oiitake 9 the diaphragm-motor valve 8 is held -i-n wide 'open position. Upon delivering electric current 'to theimrnersed electrodes 2 steam ;will be generated within the --'electrode themseland collect in the steam space above liquid level A. 'When full effect" of steam is through pipe the electrode chamberlevel A is about'at the level A of the storag'e'cha'm-ber surroundin theelectrode chamber. The-throttle valve-1i "is'now-wide open and ofiers substantially n0-resistance-tothe steam fi owfrom the-electrode chamber through -thef pipe *1 1 to ;the s team space of th 'storage chamber to" the oif'take pipe 9. Under this:condition both chambers are; under aboutfthefsame-steani prssur 1 steam'de'ma'nd-onthe unit the Withfull load aicientesteam :to maintain -'-the =slightly1increased vpressure ingthe -ofitake I. 9 and a balance is estabilished 1- l. i l p The depressed water level svit-hin rthe electrode chamber displaces water therefrom into the stor 5agerohamberland causes arise in the outer chamiberiv-ater level. The head-representing -adiffer! ence in water levels between the two chambers is a measure of the steam flowresista-nce intro- :duced by ':-the:throttle valve 45. --With"minimum :steamload on the generator the maximum (lee -pression of the waterin the electrode chamber is-exemplifiedby low-level B and the corresponding level in the storage i chamber might be high level B.

' As the :unit steam -fiow again increases the immersion adjusting-operation by steam pressure control of valve 8 :takes -place in--reverse; Wi'bh increased steam -demand the pressure the steam offtake fl falls, the valve =8 opens'andwater "level in the storagechamber falls. The-resulting greater immersion of the electrodes 2 generates more steamuntil the balance again occurs-"where the rate of steam generation by the electrodes is just sufficient to maintai-n :the slightly decreased pressure inofftaket. inordertofullyutilize the storage "spaceefiec tivelyat all-ratings and particularly sit-maximum -ber: -water and of the storage chamber water possibiy being differential: di-iferenteleva-tions and different the one from the otherfitis not usually possibleto-measure the level of -one' chamber or the other as representative of .bOth. Preferably we provide instrumentalities continually adding the two levels asrepresentativeof the -total amount of water in the-unit. When the level is lthe same in botli chambers thetwo meters and SCL WiIl readthe same; Aswater =level decreases in one chamber it increases i-n' the other but' not necessarily in'the same proportion. *The meters maybe calibrated to take into account the areas of the two chambers -at difierent levels. tIFhe continuo'us totalizing of the values from the meters EGL and SCL gives a representation of "total" watersincithe unit andc-ofsanyldeparture -from =predetermineddesirable amount,

Reference will now bev had to Figs. 3, 4 and'5 which illustrate preferded arrangements or the instruments and control valves for controlling the operation of the unit.

The arrangement of Fig. 3 shows the meters ECL'and SCL interconnected by mechanical linkage 40 for positioning the movable element of a pneumatic pilot valve 4| to continuously establish in the pipe 42 a loading pressure representative of total liquid within the unit.

We show the steam flow meter SF and the water flow meter WF in Fig. 3 as interconnected by mechanical linkage 43 continually comparing the rate of inflow of feed water with the rate of steam outflow through the pipe 9. When the feed water rate is equal to or in desired proportion -to the steam flow rate a predetermined loading pressure is established within a pipe 44. The linkage 43 is preferably adjusted to continually compensate for the bleed rate which is under control of the meter CC and preferably is substantially constant and-equals a very small'percentage of the total rate of water supplied. The system provides a three-element control of feed water to match steam flow against water flow, readjusted by water level 'or total amount in the unit.

The pneumatic loading pressure established in the pipe is efiective within the A chamber of a standardizing relay such as is disclosed and claimed in the Dickey Patent 2,098,913. To the B chamber of the relay is applied the loading pressure in the pipe 42.

After the various elements of the control system are adjusted, in connection with the actual operating unit, the loading pressure within the pipe 44 will have a predetermined value at all times when the water flow rate and the steam flow-rate are in desired proportions. Such proportion would be one .of equality between the two flow rates were it not for the continuous bleed of water from the pool. Inasmuch as the bleed constitutes such a relatively small portion of the total inflow rate, and variations in the bleed flow are correspondingly of a relatively minute proportion of the inflow rate, the bleed flow may be considered as a constant rate and the linkage 43 biased; by that amount. Thus the desired relation between water inflow and steam outflow would -be one of equalityslightly biased; to take .into account the predetermined uniform rate of bleed. -Atany time when this optimum relation exists between the inflow water rate and the steam outflow rate the linkage 43-will establish in the pipe a predetedmined air loading pressure. I .7

Under optimum operating conditions the total amount of water in the unit, namely, the sum of the water-in the electrode chamber and that in 42 a predetermined air loading presspring of the relay will be in equilibrium. Should the water inflow rate or steam outflow rate depart from desired proportionality the loading pressure effective within the A chamber will be greater or less than the optimum value and the relay 50 will varythe loading pressure, within the pipe 5| effective upon the motor of ,thevalve 31 for adjusting the latterto vary-therate of water inflow through the pipe Idinproperdirectionto through the pipe 9.

return the water flow rate and steam flow rate to'optimum proportionality. f

If; on the other hand, the total amount of water in the unit varies from optimum value then the pneumatic loading pressure within the pipe 42 will be increased or decreased from its optimum value and the equilibrium of the relay 50 will be disturbed whereby the valve 31 will adjust the rate of water inflow to return the total amount of liquid within the unit to the desired value.

Located in the pipe 5! is a manual-automatic selector valve 52 providing the possibility of removing the feed water control from automatic and remotely positioning the valve 31 by manual dictates.

It will be appreciated that the system being described includes three separate portions simultaneously operating to control the unit as a whole These are the steam outflow pressure control of the throttling valve 8, the just described threeelement control of feed water inflow, and the conductivity control of the bleed valve 25. The three portions cooperate and are simultaneously eflective to regulate the unit as a whole.

In Fig. 3 wemay additionally introduceinto our control system an element of load uponithe unit as represented by steam flow rate- The steam flow meter H is arranged to also position the movable element of a pilot valve 53 to continually establish in the pipe 54 a pneumatic loading pressure representative of steam outflow rate. The pipe 54 is'connected to the B chamber of a standardizing relay 55 to the A chamber of which is connected the pipe [1. Thus the relai 55 receives a pressure representative of steam pressure in the outflowpipe 9 and also a loading pressure representative of rate of steam flow The throttling valve 8 is thus positioned in general in consonance with steam outflow rate and with readjustment de pending upon deviations Of steam outflow pressure from optimum value.

In Fig. 4 we show another pneumatic control system arrangement incorporating certain of the features of the system of Fig. 3 and'in addition further features of our invention. Like parts carry like reference numerals. The conductivity control of the bleed as well as the three-element control of the feed water inflow rate remain the same as described in connection with Fig. 3.

However, here the control of the throttle valve 8 includes, in addition to steam pressure efl'ect, certain advantageous effects from other variables of thesystem.

We illustrate in Fig. 4 the electrode chamber level-device 29 arranged to position themovable element of a pilot valve continuously establishing in a pipe 5| 9. loading pressure representative of liquid level within the electrode chamber." The pipe BI joins the B chamberof a relay 62, to the A chamber of which is connected the pipe H. The output of the relay G2 is effective ina pipe 63 which joins the A chamber of a relay 64. The relays 62 and 64 may be termed limiting relays and are of a type disclosed andclaimed in the Gorrie Reissue Patent Re. 21,804.

At 65 we'indicatean electric load determining controller'arranged to position the movable eleplant to which the present steam generator suppliessteam.- In; the particular embodiment being described the electric load to which thecontroller ;6 5 is sensitive-includes not only the electric'curstratus a rent 1 dissipated thelunit lbutalso thaeleetric demand ofthe re'st ofrthe-plant or factory It'is appreciated that for certain: installations and 1 6 the electrie'igenerator load drops; to tolflbmial' point the electrode! level 1 controller: 2e:- will'i'acti as a limiting deviceiupon theivalve 83.4.1; There is alsma; possibility that at certain. loadiconditionsK there vv-illibev more; electric cursirentl available than. the steam demand; inithe plantil andt. itwouldtend to: build up; the. steam pressure above. the desired total; We have? therefore introduced: a steam. pressure. controls le'r tdwhichmill, through therelay B2 actlupon i the relay 6:tI.-.to.:tend1to close offthesteam out? v putbyclosinglthei valve-.8; There may-be timesi mand rate schedule. While'the demand schedule may allowdeviations from a base demand rate er a mien-my: ShOrt' timei ntervaI; it ieeesiieu to-hol'd the total power t'o the plant at a substantiany constant rate This tetaidemand rare Xi-as previously mentioned is-madeun not only of eleetrical demand of'th'ei present: vapor genera-tor: but alsoof: the-other: electrical. dem'amds throughout the plant; Inasmuch'ias the plantdemandhas preiierence' it: will be. appreciatedithat the vapor: generating unit must be; so; controlled. as to utilize only the-remaining portionCi of-Jthe totaI'ieIectricaI. demandrA at. any: given time. Thusgither COIItTOLOf the st'eamjtthrottling valve: 8

isziprimarilw under 'the control o'flthei.electric.loa'd;v

controller'fifi with readjustmentiactors efiective: from: the steam: pressure: pilotxltx and from. the electrode'chamberlevekpilot'.61!.

The-steam throttlevalverfii isoi" a springclosina typeflg When this valve .closes; the differential pressure lowers the watenintheelectrode chain ber,,while raising, the water. in the storage chainwhen. the; steam load-:isnot sufiicientito support.

' therenergy available. trom the: electric load sconet'rollen. Stir At: such'rtimes: other: boilers wii'll lnofi besused'iandiall of thet steamwill'i be ge'neratcdi from the: electric.- generators' 'l At thati-timel wei propose: throwingf the three-way: valve: H7 to alternate. dotted position solthatz the ist'eami presi-i here and thereforejesssteamgis produced. Whe ntheivalvejopensqthe. level of water in the electrode chamber tendsto equalize: withthe level: of. Water in the storage chamber thus permitting-i more e enin theael e r de.ch mb nd ne a i mor steam. wT eio he r e Of eam sens eration- -Willbe determined: by; the. electric loadcontroller 65 inorder to hold a constant electrical.

qemarciqaine n i ei l t see nire duced in .accordancawith .the. available electrical. power andi-t will be necessaryt'o useoth er. boilers. fuel fired tor maintaining a oonstant s team-pressure on. theiplant system thatisdesired. The: use? of such fuel. fired vapor generators. and pos sihl, tieinof. sa'rne with the plant formsno part ofthe pre's ent'invention.

'I he'. outputof tfe -rel'ay 64,. througliapipe. HI,

passes; througha. three vvay-valve H. to a, pipe nied'eetivenpmi theA cliamber offa'st'andardiz- I 145 18155; Tfiddllllpllflofi th .relay 'lzt'fis effecti vethifough apipeifi tocontrol the steam throte tle valve 8. i p I v We'd o not wish to have-too highalevel -around the. electrodes If; valve: 8 becomes-widesopen we c an onl'y eonalize the two chambers: and if the. three-element. feed .water supply is. correct, .which eccentially maintains arconstant t'otalofthe two levels, it seems impossible to get' a higher level in the electrode chamber than is desired; H'oweven} there is a possibility of getting too lovv'al'evel aroundthe electro'des'a'nd this would" produce an arcingor" burning effect at thebase of the elec trodesdueto'high an electrical energy flow for too-small anarea. This preferablyshould; not-go below 8" minimum submersion; The controller 2 9',-s'ensitive to liquid-1eve1 inthe electrode chambiq -is thereforeequipped-with the pilot 1 60 which, through. the relay. 62; will. readjust the: valve 8:.

sure, controller 16 will serve as -a master and the. electricrloadi controller:lifiwillzbecutsout of servicecompletely: I. 1-,; 1

In: case of. an; exceptionally l'ovir -leveliiwithlm the electrode chamberxonalow electriclp'owezi; We; wish to. shutioifi. thezlunitl entirely and-there foretwei have/incorporated a pressure switch .1 S t andsa' solenoid threei-way.t.valve.. lfi which will cl'oservalve. 8 andiatt-the' same; time's-be arranged electrically tes'trip' the;electrio'poweritoithe i'i-r i'ittv Under normal-roperating .conditionsz the steani flow control; valve 8f will; be. controlled directly 1 7 f-rom- ,.the? load.z-.contro'll'eni '65: inirfresponsw t" changesninetotal: plant electrical load so a ito: controlthe output; of the steam genera-tor and? thus maintain total plant electrical demand alt aconstant value :regardlessioftheplant demands" I for: other services... .The: new Jot feed v'vater' the-boiler: will-be controlled byilproportionin it to ;.the; steam outputyoft the boiler witnireadjnstmerit; of-ther feed.- watennow .fir'om the; was amount of water I in: the min i Blowedow-n; will be? controlled so asxtoimaintain the;- conductivft" of, the: boiler": water: within: the:Idesir-ed limit In theqevent .thatrith'e'waterSleveLiri the elec trode chamberrfallsrbelow az-predeterminedwaliie the limiting controller? 60: will readjust-mire: p0 sition ofi' thei steam. fiow: contrnl valve -li so to preventpthe levelirom-getting toe low; If'the' leVel". contir'iue'sf to" drop b'elowa predetermined? minimumiivalue the;pressure switch li will ep'-- I crate; to trip the: -electricipower on, ma-y soun'd an alarm, and will open the steam valve 8 'wi'dei In orderrto; prevent thesteam in the imain steam header. ll 'fro'm exceeding -a predetrn medrhight limit; steam:- 'pres'sure controller V6 will :r'eadjust the" position. of the sream -vaive so as to lower the water level initl ie electrode chamber and-thus reduce the steam output of the boiler. There may also be times-wl ierithe entire plant steam. load; will be: carried by the electric boiler andtat such. times it will be p'ossible to controlthe steam pressure by"- the p'ressure controller l6 through the manual transfer valve 'il; 'I'heprinci'pal object oil. thie -Fig: 4 system isto maintain a predetermined total ipower f r l'li while the portion C is thatwhich is available for the steam generator I. Normally C is within the availability of the generator and the unit operates .to hold a constant total demand A. Point :I- illustrates a vcondition'where the electric loadrequired by the plant rises to some value suchthat the difference between this and the generator. demand is so small that .it is below thezdesired minimum of the generator. In that casesone of. twoxithings must happen. Either reason a-manual .reset .trip. on the three-way,

value l6;isdesirable.-.-:

;*Point. 2;represents a low plant demand where the plant load drops to such a .low point that.

the.difierentialbetweenithis load and the genchamber and-by-transferring water between pool chamber and the storage chamber,

3. The method'of operating an electric steam generator of the type having two interconnected pressure chambers in one of which electric energy is dissipated in a water pool for vaporizing the water and the other chamber providing water storage, which includes, maintaining de-- sired conductivity of the pool water inwhich the electrodes are immersed .by controllably bleeding water from the pool, regulating extent of electrode immersion and thereby rate ofvapo t generation by transferring water between the chambers, and maintaining the total amount of water in the .two chambers substantially constant.

4. The method oioperating-a vapor generator,

, of thetype having ;a plurality of interconnected eraton demand exceeds the; total allowable on thegeneraton. :At this time;all.that can happen =is forthe valve .8 to open wide, the level inside the, electrode chamber to riseto a given maxi-..

mum, the electrical load to go to this given maxi- ...Therefore the. actual demand will drop belowthe. set demand nntilitgets back to some plant load where the diiferential between it and the set demand is again the maximumofthe gen- At that. time therefore the steam eneratonwill, produce its design capacity and 4 ;=.Point 3 illustrates acasewhere the steam re erator or. less.

no, more...

quirementsv inthe plant-.drop so low that the stearnr-pressurebegins to rise above the optimum .value..;At that .timezthe steam pressure ontroller l6 .will out beckon valve 8 producing less steam-and thereforepullingless electrical enersLinto. he steam generators .Here again thenemandrate or actual rate on theplant will mp belowithe demand which is set iorth.

grit will be understood that the electric load coptrollenfiimay bearranged to be sensitive to the electric, demand .A or. B .or 'C. We have chosen, byway of,,,illustration only, 'todescribe the systemioi Fig.5 operating with the electric load controller 65. sensitive .to. thevalue -A which 8...i. .S n ceudesirably to be-.ma,mt 1= f Khile we have. chosen .to. illustrateand describe certain preferred embodiments f our vention, it will, be understood. that -theseare Iorillustration only, and that ;we are:not to be limited thereby.- l

Whatwe claim as newand desire to secure by Letters Patent of the United States, is:

-1., Themethod of operating an. electric'stea generator of the type having .two interconnected pressure chambers in oneof which electric energy is dissipated. in a water pool for vaporiz-- ing the water and the other chamber providing water storage, which includes, continuously determining the amount of water in the two chamhers, continuously comparing the rate of steam outflow from the unit with-the rate of feed supply to the unit, and continuously controlling the rate of feed supply conjointly responsive :to the determining and comparing.

f The method of claim 1 including continuouslycofntrolling the conductivity of the pool water in which the electrodes are immersed by controllablybleeding pool water from the pool pressure chambers in one of which electric en-, ergy is dissipated ina liquid pool for VGPOIi-Z', ing the liquid, which includes, supplying teed liquidunder elevated pressure to one oithe chambers,'regulating extent of electrode immersion and thereby rateof vapor generationgby.

transferring liquid between the; chambers, and

maintaining the total amount of liquid in the chamberssubstantially constant.

5. The method of. operating an electric steam generator: of the type having two interconnected pressure chambers in one of which electric'energy is dissipatedrin a water pool for vaporiz v ing the water andithe'other chamber providing water storage, which includes, supplying reed Water to the unit in'consonance with steam outfiow rate, and maintaining total amount of liq.-: uid in the unit substantially constant. I 6. The method of claim 5 including the stepof regulating rate of vapor generation through transferring liquid from one chamber-tothe other whereby the extent of electrode immersionis varied. y A

7. The method of claim-5'including the step' of regulating the conductivity of electrode poolwaterthr'ough controllably bleeding water-there from .1. 1.1:.

8. The method of operating an electric steam generator of the type having twointerconnected pressure chambers in one of which electric energy isdissipated in a water pool roryaporizing the 'water and the other chamber provid-- ing water storage, which includes, continuously establishing a control effect representative oi. the amount of liquid in the-two 1chambers,fcon-'- tinuously establishing a control 7 effect representative of the instantaneous relation between va por outflow rate and liquid feed rate, and utllizing the two control effects conjointly to control the rate of supply of "liquid feed tothe unit: 9. The method of claim 8 wherein each" 01. the control effects isafluid pressure.

10. The method of claim 8 including "the further step of continuously establishing a control" efiect representative of the specific conductivity of the pool water and utilizing this latter con j trol efiect in controllablyjbleedin'g water from the pool.

11. The method of claim s including' the, step of continuously establishing a control effect repramming: dent- 1: efife ct representative time: p e'r' outflow rate ana amt nny at smetme such las't' twogeeeas" m mas er-mgm le-iro one chamber to another.

-13. The method of O eradng'afi electric steam mg the water and the other provid'iri the i I here th rate. e s am" e rate ferring liquid between the, chambers de ing' an electric demand factorl and'utl Zin the extent 'of electrode immersion and anddirectiori of transfer. v

14.- The method of claim 13' inclu'ding' theste'p of limiting the effect of the demand factor"when vapo-r out'flow pressure reaches a predetermined va'1u the-extentlo f'electro'deimniersion reaches a predetermined value.

16. The method of claim 13 including the step of limiting transfer ofweiter'f'rjom'the pool chamberto the storage chamber when either minimum immersion of the electrodes" in -t'h'eflpool chamber is reached or maximum predetermined vapor pressure is reached.

17. The method of claim 1 3?inc1uding; iii-see of supplying feed watertc the unit in conso'riari-ce with-steam oumcwirate. I I

18". The 'm euied'er operatingaa electric steam generator of the type havifig interconnect} ed pressure chambers in" on .iwhichw elej'ctric energy" is dissipated in a water pool for vapdriz ing the water and the other providing water storage, which includes, continuously controlling the extent of electrode immersion and thereby the rate of steam generation by transferring liquid between the chambers, determining an electric demand factor, utilizing the demand factor'as a guide in regulating the rate and direction of transfer, and maintaining the total amount of liquid in theunit substantially constant. e

19. The method of operating an electric steam generator of .the type having twointerconnected pressure chambers in one of which electric energy is dissipated in a water pool for vaporizing the water and the other providing water storage, which includes, continuously control-' demand factor asaguide inregulating 'the rate' 5. The-method of ast 1'31" mending-ti e step of limiting the efiect'o'f thef'deinand factdr when trans:

ed to regulate transfer or waterib tween n ,rent is dissipated inga waterpo'ol for vapor-12:.

mg-hthe water' and the other providing water: storagd'means sensitive to the total -amount of liqui'd in -th'e two chambers; means'pen'sitive to the reefer steam outflow, meanssensitiv e-to' the] rate of feed water inflow,- compar'is'cn means conjointly acted u on by'the second an thirdmeans, andcontrol means responsive to the? means and the gcomparison means regulatefthe feed water supmyingpl vifsions,

ZSITh combination of c1aiin-"'22=-mc1uc n conduct ity determining means of the waterin; the unit and c ntrol means daptec t bleed water from; the water pool unde tneucmma tionfof s'aid conductivity determining means. i 24;; The combination] cream-Q22 including mea sensitiveto vapor pressure, and control" means" responsive to said pressu e se'nsiti means adapted to regulate transferof waiter between chambers; v

25. The combination of claim :22; i cluding means s'ensitive to vapor outflow rate, a trol meansresponsive to said rate mea be 'SL.

- 26. he eerna aauonyef claim 22 inclufldif g? meanssensitive tova'por pre s re me s mi: tive to vapor outflfw t e,,and' control means; c-onjointly responsive 'to said pressure sensit ve means and to. said'Ifl-ow sensitive means adapted to regulate transfer of water between chambers."

27. The combination with an electric steam generator of the type having two interconnected pressure chambers in one of which electric current is dissipated in a water pool for vaporizing'the water and the other providing water storage, means establishing a control effect continuously representative of the total amount of water in the two chambers, means. establishing a control effect continuously representative of the rateof steam outflow, means establishing a control effect continuously representative of the rate of feed water inflow, comparison means continually comparing said steam outflow effect and said water inflow effect and establishing a control effect representative of the relation between steam outflow rate and water inflow rate.

ling the extent of electrode immersion and mand factor as a guide in regulatingthe rate.

and direction of transfer, supplying feed water to the unit in consonance with steam outflow rate, and maintaining the total amount of liquid in the unit substantially constant.

20. The method of claim 13 including the step of regulating the conductivity of electrode pool water through controllably bleeding water therefrom.

21. The method of operating an electric steam generator of the type having two interconnected pressure chambers in one of which electric energy is dissipated in a water pool for vaporizing the water and the other providing water storage, which includes, continuously determining an electric demand factor, vapor outflow pressure, and electrode immersion; and conjointly representative of vapor pressure, and control means responsive to said pressure representative effect adapted to regulate transfer of water between chambers.

31. The combination of claim 27 including means establishing a control effect continuously representative of vapor pressure, means essteam space of the chambers, a throttling valve in the steam passage, a steam outflow pipeconnecting to the steam space of the storage chamber, means sensitive to a variable condition of the unit operation adapted to control said'valve resulting in a control of electrode immersion by transferof water from one chamber to another, and means-maintaining the total amount of liquldin the two chambers substantially constant.

33. The combination with an electric steam generator of the type having two interconnected pressure chambers in one of which electric current is dissipated in a water pool for vaporizing the water and the other providing water storage, a water passage connecting the lower portions of the chambers, a steam passage connecting the steam space of the chambers, a throttling valve in the steam passage, a steam outflow pipe connecting to the steam space of the storage chamber, and means sensitive to an electric demand factor adapted to control said valve resulting in a control of electrode immersion .by transfer of water from one chamber to another.

, 34. The combination of claim 33 including means sensitive to vapor outflow pressure, and

as. The combination of claim 33' including means sensitive to extent of electrode immersion,

and control means responsive to said last named means arranged to limit the effect of the electric demand ractor when the extent of the else-- trode immersion reaches a predetermined value. '36. The combination of claim 33 including meansisensitive to vapor outflow pressure, means sensitiveto extent of electrode immersion, and control means responsive to both said last named means arranged to limit the eifect of the electric demand factor when either a minimum electrode immersion or a maximum vaporpressure is reached.- a l l 37. The combination of claim 33 including means sensitive to steam outflow rate, and feed water supply control means positioned by said steam outflow sensitive means. WILLIAM L. PAULISON, Js. HARVEY'C. MI'I'I'ENDORF.

Toensfeldt Dec. 26, 1950

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