US1820940A - gibson - Google Patents

Description

Sept; 1931- G. H. GIBSON 1,820,940 COMBUSTION CONTROL Filed May 9, 1.92s 3 Sheets-Sheet 2 INV NTOR BY 5' mm 3006 600/7 5 W Sept. 1, 1931.

COMBUSTION CONTROL Filed May 9. 1928 3 Sheets-She'et 3 o v v 12 j MX 1- l I 1 1 i&

INVENTQR 6:006:- A4 6/860/V Q5 adgggggf G. H. GIBSON v 1,820,940

ti e Sept, 1, 1931 stares GEQEQE H. GZL'EQGI'CY, 0i? UPI PER MOHTCLAXR, NEW JERSEY oorunnsrron conrnon application filed; Kay 9, 1928. Serial Ho. 2%,278.

My present invention comprises improvements in methods of and apparatus for the automatic control of combustion conditions .in furnaces and particularly in'boiler furnaces, devised with the generalobject of providing a control system for a boiler furnace characterized by its efiectiveness and operative simplicity and by its capacity for the attainment of specific objects hereinafter set forth. p

A more specific object of the invention is to provide a boiler furnace combustion control system of the type in which combustion controlling factors in the difierent boiler furnacesare adjusted in proportion to changes in a primary control force, with improved means for so establishing and adjusting said controlforce as to tend to maintain an approximately constant header steam pressure as the demand for steam varies, notwithstanding the variations in the drop in steam pressure at different rates of steam output between the steam generating boiler or boilers of the system and the steam header due to changes in steam velocity and frictional resistance in the pipe connections through which steam passes from the boiler or boilers to the header.

Another specific object of the invention is to subject the combustion control system to means responsive to certain water conditions i in the boiler or boilers of the system for the furnace .of the maintaimn purpose of reducing the heat supply to each individual boiler when the amount of water in that generator is unduly low, or when the conditions of operation in any boiler are suhas to create excessive foaming and the consequent car ing into the steam main or header of un uly large amounts of entrained water.- 4

A further object of the invention is to pro- .vide improved means for maintaining efii-' cient combustion conditions in each boiler aystem', and in particular .for

flue gases ormed in each boiler furnace The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming a part of this specification. For

esirable CO content in the,

a better understanding of the invention, howi ever, and the advantages possessed by it, reference should be had to the accompanyin drawings and descriptive matter, in which i have illustrated and described a preferred 5.; embodiment of the invention.

Of the drawings V Fig. l is a diagrammatic representation of a preferred embodiment of my invention;

Fig. 2 is a larger scale View of the master so controller employed in Big. 1;' 1 Fig. 3 is a diagrammatic representation of a modified form of the compensating master controller shown in Fig. 2; i

Fig. 4 is a diagram illustrating a control circuit modification; and

Fig. 5 is a diagram illustrating another modification. i

In Fig. 1 of the drawings, 1 have illus-v trated the use of my invention in connection with a control system for regulating combustion' conditions in a plurality of boilers A; (only one of which is shown in Fig. 1) delivering steam to a common header or steam distribution piping system A. The steam generator A shown in Fig. 1 comprises a socalled vertical water tube boiler having upper steam and water drums a connected by banks of water tubes a to a lower water drum a with the usual bailies a for directing the flow of the heating gases from the combustion irhaziberfir' of the generator to the stack out- As shown, the boiler is heated by the combustion of solid fuel on a stoker grate b at a rate dependent upon the speed of the stoker motor B. The air to support combustion is supplied by a blower 0,'the outlet conduit C of which leads directly to the primary air inlet A through which air passes to the underside of the fuel bed, and which also supplies air through. a branch conduit C to a secondary air inlet A? opening directly to the combustion chamber A above the fuel bed. Advantageously, the speed of the blower motor C is controlled by an automatic controller KC as hereinafter described, so as to minimize the power, consumed .b the motor 0 while insuring an adequate air supply at all times. The pressure in the combustion chamlid K and the o eration of the.

her is directly controlled b a damper (1 located in the conduit C. T e division of the totalamount of air supplied between the primary and secondary inlets A and A is reg ulated by a damper'e in the conduit (3*. The volume of draft through the furnace is controlled, in the system shown in Fig. 1, by the adjd stment of a stack damper or stack dampers J The intended operation of the embodiment of the control fiystem Illustrated in Fig. 1, results in the a justment of the speed of the stoker motor B by a controller motor ME by a controller K to adjust the stack dampers f as required to make the rate of fuel supply and the volume of draft, respectively, each normally proportional to the steam load, i. e., the rate at which steam is withdrawn from the header or main A". The proportion may be varied from time to time, however, as a result of individual boiler water conditions,

. sistances R R and R in that circuit. The

-' and in order to restore the header steam pressure to its predetermined value when, as a result of loadchanges and of time lag in the furnaces andin the operation of the control mechanism, the header steam pressure has departed-from its normal value. p

The controller- KB acts through sible motor MB on a stoker controller B. as

hereinafterex plained to control the stoker speed, and the controller KB e fiects adjustments of the dampers f through its action on a reversible relay motor ME. I

In the particular emb diment of the invention shownin hi. 1, the damper d is adjusted as require to maintaina predetermin pressure in A, by a furnace pressure controller "KP which is so associated with the control system as to make'the absolute furnace pressure diminish and increase as the rate'ot combustion increases and diminishes. The controli ler KP actsion the damper at through a reversible relay motor As shown in Fig. 1, also, the dampers-is controlled by a C0 machine H in such manner as to maintain an approximately constant CO ue gas content in thefurnace chamber at the point A at which the sample gas connection H from the UU machine H opens to the combustion chamber, the controller H acting on the damper c through a reversible motor ME.

In the arrangement'shown in Fig. l, the desired relation between the steam load on the one hand, and the rate of fuel supply, the volume of draft, and the gas pressure in the furnace chamber A of each generator A on the other hand, is maintained by subjecting the hereinbefore mentioned controllers KB,

- RF and KP pertainingto each generator A,

to the action of a control force which is adjusted as hereinafter explained in response to changes in the header steam pressure as required'to restore the header steam pressure to articular v the combustion chamber the desired or normal value. In the arrangement shown in Fig. 1, this control force is an controlled by a master controller K responsive to the header steam pressure The controller K produces its control eiiect by varying the portion of a resistance R in the control circuit. As shown, the strength of the current flowing through the control circuit 3 is also dependent on the adjustment of reresistance R is intended to be manually controlled, but the resistances R and R are automatically adjusted in response to variations in water level and degree of foaming in the generator A as hereinafter explained. Resistances similar to the resistances R, R R and R are associated with each of the control circuits 3A, 3B and 3C. The master controller K exerts its controlling ed'ects on the control circuits 3, 3A, 3B and 3G by effecting simultaneous adjustments in the resistances R individual to those circuits.

In the arrangement shown in Fig. 1, the amount of each of the resistance, R included in the corresponding control 3, 3A, 3B and 30 at any one time, depends upon the then relative position's'of a pivoted contact carrying arm K and a rheostat body 1' supporting the resistances R and movable in a direction transverse to the length of the contact arm K and parallel to the plane of movement of that arm. As shown, the rheostat body 1' is guided in its movement by stationary guide-pins r passing through slots r in the resistance body. The resistance body is given its movement by a reversible relay motor MR diagrammatically shown as having a threaded spindle passing through a threaded opening in a lug 1 carried by the resistance body r. The arm K carries a contact shoe K which engages the resistances R and is connected, as shown, to the supply condoctor 2.

the lever K by a link K and connected to the lever K which is fulcrumed at K by a link K. The linkage shown is intended to amplify the movements of the lever K as compared with the movements of the lever K, and the degree of amplification may be varied by adjusting the connections between the link K and the levers K and K lon tudinally of those levers. The thrust of t e 7 MB is provided with two windings which have one common terminal-connected to one terminal of a source of current MR. The opposite terminal of said current source MR is connected to the contact shoe K carried vby the pivoted arm K. The second terminal of one of the two windings of the motor MR isconnected to the contact conductor .Q', and the second terminal-of the other winding is connected to the contact conductor Q When the arm K moves out of a normal intermediate position in the counter-clockwise direction, the shoe K engages the contact conductor Q and thereby energizes one winding of the motor MR which then begins to rotate in one direction. Conversely, when the arm K moves away from its normal intermediate position in the clockwise direction the contact shoe Kl engages the contact conductor Q and thereby energizes the second winding of the motor MR which then begins to rotate in a direction opposite to that 'n which the motor rotates when the contact K engages the contact conductor Q.

If,gf"as indicated in the drawings, the contact conductors Q and Q are so arranged that the resistance in whichever ofthe corresponding motor winding circuits isenergized diminishes as the extent ofpdisplace-j zment of the arm K away from its neutral position increasegthe speed of the motor MR will be greater or less according to the.

extent of said displacement. Advantageously, each winding of themotor MR includesa resistance R which maybe adjusted to vary the speed of the motor MR for any given displacement of the arm K.

When, as a'result of an increase in the header pressure, the lever K is tilted in the counter-clockwise direction, the initial effect is to increase the resistance R in each control circuit, and to bring the contact shoe K carried by the lever K into engagement with the contact condiictor Q. When the shoe tors K engages the conductor Q the motor MR is energized from a current source MB to rotate in the direction to lower the rheostat body 1'. This further increases or tends to increase the amount of each resistance R in the correspondin control circuits 3, 3A, 3B and 3C, and there y decreases the strength of the controlcurrent in eachof the main control circuits, and correspondingly reduces the volume of draft in, and the rate of fuel suppl to the corresponding steam genera- Conversely, on a reduction of the steam pressure in the header A below the normal value the lever K tilts in the clock-- wise direction decreasing the amount of each resistance R in the control circuit and bringing the shoe K into engagement with the contact conductor Q whereupon the motor MB is energized from the source MR to run in the direction required to raise the rheostat body r and. further decrease the amount of each resistance R' then included in the corresponding control circuit, so as to increase the rate of combustion in each boiler furnace;

It will be readily apparent that the lever K will occupy its normal intermediate position in which it does not engage either the contact Q or the contact Q only when the steam pressure in the header A is at the normal value determined by the adjustments of the weight K and that the lever K can remain in this normal position only when the rate of combustion in the various steam generators in service is such as to insure a rate of steam generation without change in boiler steam pressure, which is equal to the demand for steam. Any variation in the ratio between heatsupplied to the boilers supplying steam and the demand for steam results in a change in header steam pressure which sets the master controller into operation to restore the ratio.

draft and the combustion chamber pressure,

respectively, in each boiler furnace, may be of any usual and suitable form. Various instrumentalities suitable for the purpose are well known. As diagrammatically illustrated in Fig. 1, the controllers KB, KF and KP are of types heretofore developed by me and illustrated in, prior patents granted to me.

The stoker controller KB as shown includes a pressure chamber P, one wall of which is formed by a diaphragm P exposed at its outer side to the pressure of the atmosphere.

Associated with the pressure chamber-P are means for maintaining in that chamber a pressure which is less than that of the atmosphere by an amount proportional, to the square of the stokerlspeed. As shown, those meanscomprise a tachometer fan 'or blower B which is driven by the stoker motor at a i speed roportional to the speed of the latter,

and w ich has its outlet open to the atmosphere and has its inlet connected by a pipe P to the pressure chamber P. The diapghragm P acts on a lever K fulcrumed at The lever K carries at one end the floating coil K of an electro-dynamometer of the Kelvin balance type comprisin stationary coils K" located at opposite si es of the coil K". The coils K and K are connected in series in the control circuit 3 and interact to exert a torque on the lever K which is proportional to'the square of the control current flowing through the circuit 3and which 0 poses the differential pressure effect on t e diaphragm P'- of the atmosphere and the tachometer tan suction.

- In consequence of the arrangement described, the lever K of the balance KB will occupy a normal intermediate position only when the speed of the stoker is in redetermined proportion to the strength 0 the current flowing in the control circuit 3. On an increase or decrease in strength of the control current relative to the stoker speed, the

resultant clockwise or counter-clockwise movement of the lever K effects a' correspondin adjustment of the stoker speed controller g2 serving to respectively increase or decrease the stoker speed and thus restore the balance. As. dia rammatically illustrated, the adjustment 0 the speed controller B is efi'ectedby means'of a reversible relay motor MB. The motor MB may be exactly like the motor MR and be controlled in the same way as the latter. As shown, however, the

controllin provisions for the motor MB arenot inten ed to provide such a graduated speed'control of that motor as is obtained with the motor MR, and in lieu of the specially arranged contact conductors Q and Q1 associated with the motor MR, a sim le contact arrangement comprising contacts as and Q, is employed to closeone or the other of the two energizing circuits of the motor MB when the lever K of the controller KB tilts in the counter-clockwise or clockwise directions, res ectively.

As shown, the stack damper controller KF is in substance exactly like the stoker controller'KB, the damper operating motor MP being controlled by the balance lever K of the controller KF. As shown, the lever of the controller KF is pivotally supported by a flexible suspension K while the lever of the controller KB has a knife-edge fulcrum hearing. The pressure chamber P of the controller KF is connected by pipe P to the stack gas 'outlet A of the boiler A at the inlet side of the stack dampers f. In consequence, the controller KF adjusts the dampers f as required to maintain a. pressure at the stack gas outlet of the boiler which is less than that of the atmosphere by an amount proportional to the square of the strength of rea eeo the control current in the circuit 3. This serves, as hereinafter explained, to maintain a volume of draft through the furnace A which is proportional to t e strength of the control current in the circuit 3.

The furnacegpressure controller KP, as

shown, is also similar in construction and arrangement with the controllers KB and KF. The troller KP is connected by a pipe P to the combustion chamber A of the steam generator A. The motor MD is controlled by the lever K of the balance KP exactl motors MB and MF are controlle b. the levers K" of the balances KB and. K respectively. The controller KP .thus serves to adjust the damper d as required to mainressure chamber P of the con- 7 as the tain a combustion chamber pressure less than that of the atmosphere'by an amount proportional to the square of the control current flowin in the circuit 3.

Wit the minus pressures (pressures less than that of the atmosphere) maintained in the combustion chamber and at the stack gas outlet of the generator A thus maintained b v the respective controllers KP and KF, each proportional to the square of the control current, the difierence between those pressures will also be proportional to the control current. The volume of raft is proportional to the wars root of the draft loss between the com ustion chamber and the stack outlet since the intervenin portion of the boiler serves in efi'ect as a red orifice. Hence, the volume of draft is maintained proportional to the control current in the sguare of the control circuit 3. Furthermore, it the furnace 'pressurecontroller KP is replaced, as it may be in some cases, by a so-call'ed halanced draft controller serving to maintain the combustion chamber pressure equal to that'of the atmosphere, the difierence between the combustion chamber pressure and the pressure in the furnace gas stack outlet A which measures the volume of draft will still be proportional to the stren h of the control current seeing-through t e coils of the controller 'i l" as will be readily apparent to those skilled in the art.

Those skilled in the art will understand, of

course, that the desired pro ortion maintained between the square of t e control current and the pressure in the pressure chamber provide an adjustable resistance shunt R about the coils K and K of each of the different balances KB, ICE and KP. The resistance shunt R about the coils of the bal ance KF would require adjustment, for ex-- ample, to compensate for such a change in operating condltions as would be involved 1n the replacement of the balance KP by a controller maintaining a constant pressure in the combustion chamber, while the shunt R about the coils of the balance KB may be adjusted to compensate for a change from a fuel of one heating value to a fuel of a different heating value.

ably it is separated from the latter to protect the float S therein against some of the surges and ebullition effects occurring in the mam steam and water drum. The float S is pivotally supported at S and is connected to a valve member S which is moved by the float S as the water level risesand falls through its normal range to more or less completely close the feedwater inlet S. The float S" and valve S thus limit the maximum height of water level in the boiler regardless of the tendency of the boiler feed system to continue the supply of water at that time.

The boiler feed system shown in Fig. 1

includes a feed waterboiler pump T which deliverswater to the feed water inlet Set arrangement is one tending to maintain a delivery pressure in each pipe T which 15111- excess of theboller steam pressure whenthe theboiler through the feed pi e T'.. There may be an individual boiler eed pump T for each boiler, or all'of the boilers may be supgflied by a single feedpump. The boiler system contemplated in the particular inlet S is throttled. The full excess pressure thus created may be of a constant value, or it may increase and decrease with the boiler load. Various boiler systems of each of the kinds referred to are known and maybe used. If, as will be the case with the preferred form of feed regulation contemplated, the

" pressure in the feed pipe T builds up somewhat above the boiler pressure as the valve S prevents or throttles the discharge of water into the boiler,I advantageously employ this pressure building up to exert a desirable modification in the control currentflowing through the control circuit 3. To this end, I show in Fig. 1 a differential pressure 'device t divided into two chambers t and t by a diaphragm t The chamber t is connected to the feed pipe T, and the chamber t is connected to the steam and water space of the boiler by the pipe t. The die hra t is connected to a rock shaft it so t at t e movement of the diaphragm resulting from a pressure in the chamber t higher than "the pressure in the chamber 13 will oscillate the shaft i in the counter-clockwise direction. The shaft i carries a contact arm engaging the previously mentioned resistance R in the control circuit 3. When the shaft't is turnedin the counterclockwise direction the amount of resistance R in the control circuit 3 is reduced, and when the shaft t is turned in the other direction the-amount of resistance in the control circuit 3 is increased, and preferably the arm 23 separates from the resistance R and opens the control circuit 3, when the water level falls below a predetermined normal safe minimum.

In the contemplated mode of operation of the apparatus shown, the boiler water level will be maintained at such height as to normall cause the valve S to partially throttle the eed inlet S. Preferably, none or only a relatively small portion of the resistance R is then included in the control circuit 3. On a decrease in the boiler water level the amount of resistance R included in the circuit is increased. Security against the possibility of supplying heat to a boiler at a high rate when thewater level is dangerously low or when the feed supply pressure fails, is insured by arranging the arm tand the resistance R so that when'the feed inlet is subject to nothrottling effect whatever by the valve S, the arm t will move into a position in any of the controlled boilerswhen as a result of excessive load or other causes an in which it separates from the resistance R '105 I means for diminishing the rate of combustion unduly large amount of wateris being carried out of the boiler through its steam delivery pipe A. These provisions, as shown inFig. 1, comprise a steam andwater separating chamber U interposed between the steam pipe A and the superheater A through which the steam is passed and from which it is delivered through the pipe A to the header A". The separator chamber U is provided with an outlet U to a steam trap or other means for discharging collected water which is so restricted that'when' the rate at which entrained water collects in the chamber U is relatively large, the water level therein builds up and thereby raises a pivoted float U. The raising of the float-U rotates a supporting shaft U carrying an external rheostat arm U engaging the resistance R and forming a part of the control circuit 3. The effect of diminish the rate of combustion in the particular boiler.

The control circuit resistances R and R adjusted as previously described, are of especial utility in a steam generatingplant comprising a plurality of boilers controlled in the general manner described, for the reason that they tend to so divide the load among the different boilers as to decrease thev portion of the load carried by a boiler or boilers in which operating conditions are relatively unfavorable while at the same time corre spondingly increasing the portions of the load carried by the boilers in which operating conditions are better.

The CO machine H controlling damper a may be of any usual or suitable form. One form suitable for the purpose is shown in my prior Patent No. 1,564,553, granted December 8, 1925, and other suitable forms are known. As shown, the machine H comprises a circuit controller H deflected in one way when the CO content of the gases passing 1 to the machine through the pipe H exceeds a predetermined value, and deflected in the opposite direction when the C0, content is below a predetermined value. The contact H when deflected from its neutral position,

' closes one or the other of two energizing cirits circuits may be like the motors and cuits for the reversible .motor ME employed to adjust the damper e. The motor ME with MF 1' lrand their circuits.

As previously explained, the forced draft fan motor C is advantageously so controlled as to insure an adequate supply of air at all times while mininiizingthe power consumption of the motor. In the form of my invention shown in Fig. l, the power consumption of the motor is minimized by the controller KC, which increases and decreases the speed of the motor C as the need for air increases i and decreases. The controller 19C comprises means responsive to the pressure diderential at the opposite sides of the damper d and I serves to speed up the tan a when the diderphragm's with alever C havinga fulcrum caring at C". The lever and diaphragrns are so arranged that the lever will assume a neutral position only when; the pressure in the chamber C exceeds that in the chamber C by a predetermined amount, which may C engages either contact C or be varied by shifting the fulcrum 0 and/or through the lever fulcrum C. Conversely,

when the differential between the pressures transmitted to the chambers C and G exceeds a predetermined amount, the lever C is deflected in the clockwise direction and closes a control circuit includin the contact C conductor 6, solenoid winding C conductor-7, current source 8, interrupter C, contact 9, and lever G The interrupter C may advantageously be of the bimetallic thermostatic type, arranged to be heated in a brief period by the control current flowing, whene erthe le'er and which when so heated, deflects and separates from the contact 9. After cooling ofi for a brief period the thermostatic interrupter C defiects back into engagement with the contact 9. The thermostatic interrupter C thus servesto alternatel open and close the control circuit at suita 1e inte vals of a few seconds or a minute, or so, uring any period of operation in which the lever C is in engagement with either contact G or C The solenoid coils C and C in the arrangement shown, are co-axial and spaced apart, and serve when either is energized to attract a solenoid core C carried by a rod (G co-axialwith the coils and lengthwise movable in the direction of its length in guides C The core (3 is normally held in a position intermediate of the coils C and C by springs C? acting on a projection C from the rod C The movement of the core (1 in either direction from its intermediate position serves to give a corresponding adjustment to a brush C engaging a l cam surface (3 which engages a stationary pin (1 and thereby causes the member C to tilt in one direction or the other when the rod C is moved in one direction or the otherfrom its intermediate position.- The cam surface C is so shaped that when the core C is moved toward the coil C by the v energization of the latter,.the pawl member "C is tilted by the pin G into the position the core C is de-energized and returns to its intermediate position the pawl member C is returned to its normal intermediate position without effecting any retrograde movement of the bar C. Successive energizetions of the coil C gives additional movements in the same direction as before to the rack bar G \Vhenever the coil C is energized, however, the resultant movement of the coreC causes the pawl C of the pawl member C to engage a tooth C of the rack bar C and moves the brush C in a direction opposite to that in'which itis moved by the energization of the coil C. a

As shown, the portion of the resistance R in the motor circuit is increased or decreased by the controller KO when the pressure drop past the damper d in the duct A falls below or exceeds predetermined limits and thus serves to increase or decreasethe'speed of the motor C. To this end the resistance R I may well be included in the field circuit of the motor C. The operation of the controller KG is thus to effect a step I? step adjustment of the speed of the blower an motor 0 as re,-

.quired to insure an output of the fan 0 at all times ample for the control effected by the damper d and its controller KP, without the waste of power which would be involved if the fan a were operated at all times at the speed necessary to furnish the air required under maximum load conditions, while at the same time the control of the motor 0 is not of the character tending to make the speed of the motor fluctuate or hunt. The described step by step adjustment mechanism insures a full stroke, at each operation,

and avoids the possibility of having the motor controller stop between rheostat points. In the practical use of a control system of the type described, any quickl effected which steam is withdrawn, it is, in general,

desirable, that any change in header steam pressure should result in a change in the rate of combustion approximately proportional to the change in steam load producing the change in header pressure. In other words,

on a-change in header steam pressure it is in general desirable that the strength of the control current flowing in each of the circuits 3, 3A, 3B and 3C should be varied in definite relation to the change in the steam flow rate through the header A which produced the change in header steam pressure.

When all of the boilers supplying steam to the header A are subject to the automatic controlsystem and have their rates of combustion varied simultaneously and proportionally, the control currents flowing in the circuits 3, 3A etc. should normally vary in linear proportion to the header steam flow rate as the latter changes with the demand for steam.- In such case, the change in the 1 header steam pressure occuring on an increase in the rate at which steam is withdrawn will be expressed by the equation:

wherein A is a constant, P equals the standard or normal header pressure, and P is equal to the new value of the header steam pressure produced after a given steam load has been increased by an amount 0!. The quantities L and cl may be expressed in pounds or cubic foot of steam flowing per unit of time or in units of linear velocity of steam flow'through the header A. On a load decrease (d) the same equation applies, but in such case it is to be-noted that d and (P,,P are each negative.

From the equation given above it will be apparent that a given change, i (II;- P,), in header steam pressure corresponds to a greater steam load difference, i (d), when the previous steam load (L) is small than when the latter is larger. In general, therefore, the change in the amount of resistance R in any control circuit 3, 3A, etc. produced by a given change in the header steam pressure should be smaller when the steam load is relatively large than when the steam load is relatively small. This result may be sea cured by arranging the resistance conductors R, asindicated, so that the resistance per unit of length measured parallel to the general direction of the resistance progressively increases from the bottom to the top of the resistance.

Those skilled in the art will understand that with all of the boilers supplying steam to the main A, subject to the control system shown in Fig. 1, the control force in each control circuit will vary with the load if the corresponding resistance R is so proportioned that the total resistance in the control circuit varies in inverse proportion with the steam flow through the header.

. If with the arrangement'shown in Fig. 1, all. or substantially all, of the drop in steam pressure between each boiler and the point in theheader at which the pipe K is con- 9 to be recalibrated or subjected to any significant adjustment when the number of boilers in service is increased or diminished. In

*such case, when a boiler is. cut into or out ofservicaall that is required, so far as the control system is concerned, is the closing or opening of the corres ondin switch 30. Except for the purpose provi ing for the operation of more boilers at one time than at another, it is not necessary with the regulation apparatus shown in Fig. '1 to employ more than a sin le resistance It. With a single resistance the various controllers KB, KF and KP for the difierent boilers may have their coils K and K connected in serice with one another, and with the resistance R, or the coils of the difierent controllers for each boiler may be connected in 'an individual circuit portion 300, 300A, 3 or 300C as shown in Fig. 4, these individual circuits being in parallel with one another and each in series with the sin le resistance R.

Those skilled in t e art will understand that the ideal condition obtainable with the control system shown in Fig. 1, when all of the boilers are sub'ected to the control systern so that each oiler carries a constant portion'of the total load atall times, is not always obtainable,and for other reasons is not alwaysdesirable in practice. For :ample, it is frequently desirable in some plants to maintain approximatelg constant rates of combustion in some of t e boilers, then commonly referred to as steady load boilers, while taking care of the uctuations in the total steam load with other boillers commonly referred to as variable load boilers. in such case, the variable load boilers Enly are subject to the control system of .With the control s stem shown in Fig. 31, if one or more of the oilers delivering steam to the main A? are subject to the control systern, and one or moreother boilers are operated as steady load boilers, the ultimate .change in header efiect-ofthecohtrol system on the boilers subject to its control is that desired, but the immediate control efiect on the controlled boilers in. res onse to a sudden and appreciable change in load cannot be in the same proportion to the load cha under all conditions at least, if the stea y load boilers have ap reciable heat storage capacity. A ressure occuring on a change-in load requires a-change in the'boiler steam pre'ss'ureof each of the stead load boilers. When, as is the case with a ordinary boilers,"v the steady load boilers havesignificant heat stora e capacity, some time is required for the c sings in boiler steam pressure of the steadyload boilers, which results from a change in the header pressure.

,With the arrangement siown in During the period in which their pressures are changing, the steady load boilers will deliver steam at a rate which is higher or lower than the normal rate, accordingly as the header steam pressure change resulting from the load change is a decrease or increase.

In installations in which all, or the major portion of, the steam pressure drop is in the eader, as distinguished from the pipe connections between the header and the individual boilers, it is in general desirable that the boilers subject to the control system have the coils of their balances KB, KF and KP connected in series with a single resistance R, for example, as in the arrangement shown in Fig. 4. With such a series arran ement, when a boiler is put under steady loa operation, it is desirable to substitute for the windings K" and K of the controllers pertaining to the boiler cut out, and for any portion of the control circuit peculiar to that boiler, an equivalent resistance R, as shown in Fig. 4. In such case, as with the modification of the system shown in Fig. 1 involving the operation of steady load boilers described above, the immediate response of the master con troller cannot edect the ideally required adjustment of the resistances R under all conditions of operation. In all of'the cases referred to, however, better results are obtainable by an arrangement of the resistance or resistances R employed, such as is illustrated in thedrawings hereof, which serves to make the change in the portion of each resistance R in use, greater when the swam load chan ed is relatively small than when the steam load changed is relatively lar e.

In Fig. 5 l have illustrated another orm of the invention especially adapted for use in a plant comprising a; battery of boilers, and in which all, or the major portion of the significant steam pressure drop between the boil.-.

ers and the'point in the main at which the master controller is connected, is due to resistance in the main rather than in the individual connections to the main from the boilers, as might be the case, for example, if all the boilers ass steam to the main through a common in ependentl fired su rheater. ig. 5,'one or more of the boilers may be operating under stead load conditions, one or more others may 0 rating under variable load conditions, an one or more may be out of service at any one time, and at all times the control apparatus tends to make the rate of combustion' in the boilers operatin under variable -load that required to enab e them to carry their loads.

In the arrangement shown in Fig. 5 the master controller KB might be identical with lllltl that shown in Fig. 1, but as shown difiers therefrom in that the main lever K of the controller KB carries the resistance engaging members K and K which are carried by the lever K in Fig. 1. The controller KB operates to maintain a current flow in a circuit 301 which is a function of the pressure in the steam main A receiving steam from so many of the boilers of the plant as are in service. The circuit 301 includes a single regulating resistance R carried by the resistance body 1', and also includes the coil X of a current balance X of known type shown, for example, in my prior Patent No. 1,166,! 58.

The balance X comprises a second coil X,

i and a lever X so fulcrumed that the electromagnetic interactions between the two coils and their movable cores X? and X respecti vely, which are pivotally suspended from the lever, oppose one another.' The coil X has one terminal connected by a conductor 10 to the current supply main 1 and has its other terminal connected by a. conductor 11 to a steady load bus bar 12, and by a conductor 13 to a variable load bus bar 14. Included in series with the conductor 13 is a rheostat comprising a resistance R and a rheostat arm Z adjusted by a reversible relay motor When the current flow through the coil X exerts a pull on the magnet core- X which exactly balances the opposing action on the lever X of the pull due .to the current flow in the coil X on the core X, the lever X assumes a neutral position and the motor MX is then de-energized. When, as on an increase in load, the current flow through the coil X increases relatively to the current flow through the coil X the lever X tilts and closes contacts Y thereby energizing one of the circuits of the motor MX. The latter thenrotates the rheostat arm Z in a counterclockwise direction and thus reduces the amount of resistance R -in circuit with the conductor 13, until the current flow through the coil X is increased as required to restore the balance and return the lever X torts neutral position.- one. decrease in load and resultant decrease in the current flow through the coil X, the lever X tilts to close the contacts Y and thus energize the motor MX in the direction 're uired to turn the rheostat arm Z in the cloc wise direction and thereby increases the portion of the resistance. R in circuit with the conductor 13 until the resultant decrease in current flow through the coil.

-X restores the balance lever X to its neutral position.

In Fig. 5A A A and A represent the control mechanisms for corresponding boilers. One terminal of each control mechanism is connected to a bus bar 15 connected in turn to the supply conductor 2 by a conductor 16. The other terminal of the control mechanism. for each boiler is connected through a manually adjustable resistance R to a switch blade 31. The latter may be ad-. justed into one position in which it is connected to the variable load bus bar 14, into a second position in which it is connected to the steady load bus bar 13, or into an off position in which it is not connected to either bus bar,

coil X which is proportional to the load.

The balance X operates through the motor MX to maintain a current flow in the coil X which is proportional to the current flow through the coil X, and hence is also proportional to the load. The boiler control mechanism or mechanisms, (A as illustrated), for the boiler orboilers operating under steady load take whatever portion of the current flow through the coil X corresponds to the load to .be carried by the boiler, or boilers, operating under steady load and having their control mechanisms connected to the steady load bus bar 12. The remainder of the current flow through the coil X passes to the variable load bus bar 14 and thence through the control mechanism or mechanisms of the boiler or boilers operating under variable load. With this arrangement a boiler may be cut into or 'out of service, or

transferred from operation under steady load' to operation under variable load,without requiring any change of the control apparatus other than the adjustment of the correspondingswitch 31, and at all times the control system tends to maintain a rate of combustion in each boiler connectedto either bus bar 12 or 14, which is that required-to enable the boiler to carry its proper load.

The master controller employed may depart widely from the form illustrated diagrammatically in' Figs. 1 and 2 without impairment of its capacity for performing some or all of the regulating functions previously described. For example, the master controller in some cases may advantageously be of the type illustrated in Fig. 3. The master.-

controller KA, shownin Fig. 3, differs from the controller K principally in the manner. in which the motor MR shifting the rheostat body is controlled, and in the fact that the pressure responsive device of the controller KA does not directly engage and adjust the resistance R.

In the master controller KA, a contact arm 7 K, which is movable independently of the.

controller arm K, performs the control circuit resistance engaging function performed in the controller K by the contact, K 9 engaging the resistances R, which in this form are stationary. The arm K is carried by a frame K? which is mounted and adjusted by the motor MR as is the rheostat body 1' of the controller K. In the master controller KA the energization of the motor MB is di- 5 rectly controlled by the engagement of a con-' .1 is effected by a motor m1- mounted on the 1'5 frame K and shown as having a threaded spindle passing through a threaded opening in the member r. The energization of the motor mr is controlled by theengagement of a contaet'K carried by the lever K of 20- the balance KA with one or the other of elongated contacts Q 9 or Q.

On a decrease in the header stream pressure and the'consequent clockwise deflectionof the lever K of the master controller KA,

25 the motor MB is energized to move the frame K in the direction to diminish the amounts of the resistances R included in the various control circuits 3, 3A, 3B and At the same time, the motor m1 is energized 1n the mi direction to move the member r relative to the frame K in a direction opposite to the .absolute movement 'ofthe latter, The ad- 'ustments thus initiated continue until the eader pressure is restored to its normal value at which time both of the motors MR and war will be de-energized. Conversely, upon an increase in the header steam pressure the motors MR and mr are actuated in the opposite directions and the amounts of resistances R in the various control cireuits are thereby increased until the header pressure is restored to its normal value and the lever K is returned to its normal neutral position.

Since with the form of the master controller KA shown in Fig. 3, the pressure responsive deviceis not employed to directly 1 adjust the resistances R, that device may be made lighter and more sensitive than is neces 'fi sary with the form of controller shown in.

. Fig. 1 and Fig. 2. With the form of master controller shown in Fig. 3, the motor MR may be arranged to rapidly efi'ect wide ad justments when required in the portions of -the resistances R includedin the ,control circuit without any appreciable tendency of the control system to hunt, provided that the motor m1" is made sufliciently slow acting to prevent its action from approaching too close synchronism with the responses of the controlled boilers to the changes in the rates of combustion produced by the adjustment in the resistances 'R'.

While in accordance with the provisions of the statutes, I have illustrated and de- I claim as new and desire to secure by Letters Patent, is

1. The combination with steam generating apparatusand piping receiving steam generated thereby, of a combustion control system including a master controller including an element moving in response to-changes in steam pressure at. a point in said piping at which the steam pressure varies in response to changes in steam load and .in response to changes in boiler steam pressure, means for establishing an electrical combustion controlling force including a rheostat element cooperating with the first mentioned element to vary said force as the first mentioned pressure changes, by amountswhich are'greater or less, accordingly as the steam load prior to said change was relatively light ,or relatively heavy.

2. The combination with steam generating means and piping receiving the steam generated, of a combustion control system regulat-' ing the supply of heat to lsaid means, comprising means for mainta ning a regulable' electrical control force inc uding a rheostat and a master controller, the latter including 1 a member moving in response to changes in steam pressure in said piping at a point at which the steam pressure changes in response to changes in the rate of steam delivery as well as in response to changes in the pres sure at which the steam is generated, means controlled by the movement of said member away from a neutral position in either direetion to effect an initial adjustment of said rheostat, and means set in operation by the movement of said movable member efi'ecting a subsequent further adjustment of said rheostat at a rate increasing with the magnitude of. the departure of said steam pressure from a predetermined value.

3. The combination with steam generating means and piping receiving the steam generated, of a combustion control system regulating the supply of heat to said means comprising means for maintaining a regulable electrieal control force including a rheostat and a master controller, the latter including member movingin response to changes in steam pressure in said piping at a point at which the. steam pressure changes in response to changes in the rate of steam delivery as well as in response to changes in the pressure at which the steam is generated,

means controlled by the movement'o f said member away from a neutral position in either direction to effect an initial adjustment of said rheostat, and means set in operation by the movement of said movable'member for efi'ecting a subsequent further adjustment of said rheostat, said rheostat including provisions whereby the effect on the control force of a given change in the pressure impressed on the master controller is greater when the previous steam load has been relatively light than when it has been relatively heavy.

4. The combination with a steam enerator and its steam outlet, of mechanism or regulating the supply of heat to the generator including means tending primarly to vary the supply of heat in roportion to the steam outflow through said outlet, and means responsive to the amount of water passing with the steam out of the generator through said outlet for adjusting said mechan1sm todiminish the ratio of heat supplied to the steam outflow as the amount of water carried out of the boiler increases.

5. The combination with a'steam generator.

and its steam outlet, of combustion control provisions therefor includin a control cirflow in said circuit increasing and decreasing as the steam output increases and decreases, and means automatically responsive to the amount of water carried out of the boiler through said outlet for decreasing the current flowing in said control circuit as said amount increases.

- 6. The combination with a steam generator sive to the steam load carried by said bollers for regulating the combustion in the difierent boilers, of means associated with the individual boilers and responsive to the amount of water carried out of the different boilers with the steam delivered thereby for so modifyin the action of said control system as to diminish the rate of combustion in each such boiler in which the amount of water discharged with the steam exceeds a predetermined height.

8. The combination with a steam generator, of means including a feed pipe for supplying feed water to said generator,

means responsive to the height of water level in the generator for throttling said feed pipe minimum value. cult and means tending to ma ntaln a current lets,

' sponsive to the height of the water level in individual boilers for so modifying the action of said control system as to diminish the rate of combustion in each such boiler when the Water level therein diminishesbelow a predetermined height.

10. The combination with a steam generator and an automatic control system for regulating the rate of combustion therein and tending to maintain said rate proportional to the steam output of the generator, of means responsive to the height of water level in said generator for adjusting said system to diminish thecombustion rate when said height of water level falls to a predetermined 11. The combination with a furnace having separate primary and secondary air'inlets, of means for supplying air under pressure in regulated aggregate amounts to said inlets,and means responsive to the CO contentof the gases of combustion for variably throttling the supply of air to the secondary air'inlet so as to maintain said CO content approximately constant.

12. The combination with a furnace having separate primary and secondary air in- '0 means for supplying air in regulated aggregate amounts to said inlets, and means responsive to the CO content of the ases of combustion for variably throttling t e supply of air to the secondary-airinlet so as to maintain said CO content approximately constant.

13. In a combustion control system, the combination with a draft creating motor, a speed controller for said motor, a draft regulating damper, and means responsive to the draft pressure drop ast said damper for effecting one or more efinite' step adjustments of said controller when said pressure differential approaches either of predetermined deslrableminimum and major values.

14. The combination with a steam generator-having water storage capacity and a normal water level and an automatic control system for regulating the rate of combustion when said excess falls below a predetermined minimum.

15. The combination with a battery of steam generating boilers and 'iping receiving steam generated thereby, o? a combustion control system including a master controller including an eleinent responsive to changes in steam pressure at a point in said piping at which the steam pressure varies in response to changes in the steam load and in response to changes in boiler steam pressure, means for establishing an electrical battery combustion controlling force, said means including a rheostat element, cooperating with the first-mentioned'element to vary said force as the first-mentioned pressure changes, means for maintaining boiler electrical combustion controlling forces corresponding to the rates of combustion in the several boilers of the battery, and means for automatically adjusting one or more of the last mentioned forces while holding the. other or others at a 2 constant value as required to maintain the aggregate value of said boiler forces proportional to said battery force.

Signed at Philadelphia, in the county of Philadel hia and State of Pennsylvania, this seventh ay of May, A. D. 1928.

' GEORGE H. GIBSON.

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