US2298700A - Superheater and reheat control - Google Patents

Description

Oct. 13, 1942- R. D. JUNQKINS ETAL ,2 3,

sursnammn AND REHEAT CONTROL Filed July 18, 1940 s sh ts-sheet 1 3nbentors RAYMOND D JUNKINS AND THOMAS C.TOOMEY 'CHARLES SPSMITH w -"Mt R. D. JuNKlfis ETAL 2,298,700

SUPERHEATER AND REHEAT CONTROL Filed July is, 1940 5 Sheets-Sheet 2 -5/61 I00 77 Zmnentorx RAYMOND D. JUNKlNS i THOMAS C. TOOMEY CHARLES" 8. SMITH 1942- R. D. JUNKINS ET'AL 2,293,700 I SUPERHEATER AND REHEAT CONTRQL 5 Sheefs Sheet F115;! ul 18, 1940- FIG. 4

Juventorx' RAYMOND D. JUNKINS AND THOMAS C. TOOMEY I 7 CHARLES 5. SMITH avf Z ATTORNEY LITA Oct. '13, 1942. R. D. Jl JNKIN-S ETAL 2,293,700

surnnmmsn AND REHEAT common Filed July 18, 1940 5 Sheets-Sheet 5 Zinuentor: RAYMOND D. JUNKINS THOMAS C. TOOMEY CHARLES S. SMlTH AND Patented Oct. 13, 1942 SUPERHEATER AND REHEAT CONTROL I Raymond D. Junkins, Cleveland Heights, Ohio, Thomas C. Toomey, West New Brighton, N. Y.,

and Charles S. Junkins assignor Jersey Smith, Westileld, N. 1.; said to Bailey Meter Company; a

corporation of Delaware, Smith assignors to Th Company, Newark, N.

and said Toomey and e Babcock & Wilcox 1., a corporation of New Application July 18, 1940, Serial No. 346,120

Claims.

This invention relates to control systems and particularly to temperature control systems.

In steam power installations it is usual to superheat the steam above the temperature cor- I responding to its pressure. superheated steam is used in practically all steam turbines, but in many turbine installations the steam is reheated between some of the expansion stages 50 that a reheater is employed as well as a superheater. This is particularly the case where high pressure turbines are used for it has not proven practi cal or economical to use high enough initial temperature to prevent excessive wetness of steam at the lower pressure end.

It is frequently desirable to have a unitary installation in which the steam generated and superheated by a single boiler furnace supplies a single turbine, and'in which case the steam extracted from a preferred stage of the turbine may be reheated in a fluid path heated by the same furnace or by a separate furnace. For economic and operating reasons a single setting is most desirable.- The arrangement in which our invention is particularly advantageous is one wherein the steam to be reheated is returned to the same furnace assembly, and in this case the control of the temperature of the superheat and of the reheat must be separately and collectively accurate and speedy. A particular feature of our invention resides in the control of a vapor generating unit wherein three primary results are attained: namely,

steam is generated, steam is superheated to desired degree, and steam is reheated todesired degree.

The rate of generation of steam, the temperature to which the steam is superheated, and the temperature .to which steam is reheated in such a unit may be regulated or controlled manually under the guidance and by the aid of measuring instruments, or by automatic means positioned by measuring means; in either case by mechanisms operating dampers controlling the flow' of hot gases'over heat exchange surfaces. Automatic means are of course desirable in the interest of constant vigilance, promptnessof action, etc. Naturally thearrangements disclosed and perature, and that the temperature standard (usually superheat) of the flows may be the same or be difierent. Furthermore, that the temperature standard for either or both flows may be constant or variable with rating. These possibilities exist and are herein disclosed for either hand or automatic regulation.

-While the particular embodiment illustrated and described herein is shown as having two steam heating gas passes and an idle pass, it is contemplated that any number of active and idle passes may be in combination, and that the passes may be horizontal or vertical. Furthermore, the fluid flow paths located in the gas passes need not contain steam or vapor. For example, one active pass may have a steam superheater, while another active pass may have an economizer section of either steaming or nonpaths.

steaming type therein. Such an arrangement has particular advantage where the water entering the boiler drum should be near the saturation temperature at the drum to prevent leakage at the tube seats in the'drum.

Inasmuch as a steam reheater may be considered as a form of. superheater, the invention may broadly be considered as relating to the heating of a plurality of superheating surfaces in a single boiler setting, preferably where such superheating surfaces are not connected for series flow, but are independent parallel superheater In the drawings:

Fig. 1 illustrates in somewhat diagrammatic fashion a sectional elevation of a vapor generating unit to which the invention has been applied.

Figs. 2, 3, .4 and 5 diagrammatically illustrate I diiferent arrangements of electrical apparatus which may be substituted for the electrical arrangement of Fig. 1.

Figs. 6 and '7 illustrate in diagrammatic manner arrangements which may be applied to the ,1 boiler of Fig. 1 illustrating control of the heating claimed herein are useful with vapor generators f conjointiy from a measure of temperature and of flow.

Fig. 8 diagrammatically illustrates how the invention may be carriedout by means of hydraulic or pneumatic control arrangements.

Referring now particularly to Fig. '1, a watercooled furnace l is fired by burners 2 and the unit is arranged for vertical upward gas flow. A slag screen 3 is positioned across the furnace outlet and is backed by a bank of convection tubes 4. The gases in passing upward from the furnace I, pass successively through the slag screen I and convection bank I, where after they a are divided into three parallel gas flows confined by the closely fitted water walls I, 6 forming three parallel passes I, U, 9 to the economizer II and air heater H. In pass I is located the superheater H, in pass I the reheater l3, while pass I is an idle pass.

In the three gas passes are arranged independent dampers, so that the division or gas fiow over the two difierent superheatirg surfaces l2, I3 may be adjusted in accordance with the operating demands. This permits of the following combination of operating conditions:

(1) All gas up the idle pass, no superheating, and no reheating. This would probably be a starting condition with the economizer coolin the gases and thus protecting the damper.

(2) No gas up the idle pass, the whole gas fiow being divided between superheatingand reheating in any desired ratio as adjusted by the dampers of these two gas passes, from zero superheating and all reheating, to zero reheating and all superheating. 1

(3) Part oi the gas up the idle pass with the rest divided between the other two passes, in any ratio as may. be necessary to give the proper final steam temperatures, but with less total heat to be divided between the heaters in proportion as gas is by-passed through the idle pass.

Conditions 2 and 3 represent operating conditions to control. both superheat and reheat through control 01' the quantity of gas for both and its division between them. Condition 1 represents a starting condition, or perhaps a condition after a sudden loss of a heavy load when there is little or no steam flow and before the unit is cooled off.

In Fig. 1 and throughout the description we refer to the damper or dampers at the outlet of the superheaterpass I by the number it; the damper or dampers at the outlet of the reheater pass 9 by the numeral l6; and the damper or dampers at the outlet of the idle pass 8 by the numeral l5. The number and type oi dampers used at the various locations ll; IE, i6 is imma terial to the broad concept of our invention.

A preferred embodiment of the invention utilizes reversing electric motors forpositioning the dampers, and to that end the motors are diagrammatically represented at l1, l8, l9 respectively, each shown with double windings representative of the possibility of rotation in either direction according as to which winding is energized. The motors are, of course, provided with the necessary gear reduction, linkage, etc. for connection to the respective dampers and for positioning the dampers at a speed relatively low compared to the speed of the motors. In order to readily follow the description in connection with the drawings, we have designate the windings of the motors l'l, I8 and is by M and L, indicative of more and less," by which we mean the winding of the motor which would be energized to rotate the motor in proper direction to position the related damper or dampers to allow the passage of more" or less gas flow therethrough. It will be observed that in the M and L wires to each of the motors we have shown a springclosed limit switch 28 provided to limit the travel 01 the motor in either direction to thus protect the motor and gearing, as well as the damper, from travel beyond predetermined limits.. I

It will be apparent from an examination of Fig. 1 that through the control of motors ll,

i8 and E9, and consequently o! dampers l4. IS and it, we may proportion the flow of the hot gases through the passes I, 8 and 9 in any desired manner, such as to attain the desiredtemperature of the steam leaving the superheater i2 and/or of the steam leaving the reheater II.

In the steam header 2| is located the bulb of a gas filled temperature sensitive system connected through a capillary 22 with a Bourdon tube 21, adapted to position an indicator 24 relative to an index 25 for providing a visual indication of the temperature 01 the steam leaving the superheater it. In the outlet conduit 26 from the reheater i3 is located the bulb of a gas filled temperature sensitive system connected through the capillary 2? with a Bourdon tube 28, adapted to position an indicator 29relative to an index 30. for providing a. visual indication of the temperature of the steam leaving the reheater I 3. In general, the positioning of the dampers H, II! and I6, and correspondingly the proportioning of the gas .fiow through the passes 1, 8 and 8, is accomplished automatically responsive to the positioning of the Bourdon tubes 23, 28 and correspondingly responsive to the value of, and changes in the value of, the temperature of the superheated steam and of the reheated steam.

To this end the Bourdon tube 23 is arranged to angularly position a contact bar 3! around a pivot to cause engagement or disengagement with contacts 32, 33, 36, or 35. In like manner the Bourdon tube 2? is arranged to angularly position a pivoted contact arm 38 to open or close contacts 31, 38, 38, or 40. The contact bars 3! and 36 are connected to one side of a power source all through a normally closed finger of a switch 38 to be mentioned hereinafter. The neutral of the motors I1, I 8 and i! are allconnected to the other side of the power source A; through a normally closed finger oi the switch $5 and an interrupting finger 42 which is'periodically opened and closed through the agency of a cam 43 driven by a continuously running motor 64. Such periodic interruption of rotation, of any or all of the motors I1, I. or I! which may he energized, is to provide movement of the dampers II, I 5 and/or It by periodic increments rather than continuously, and thus precluding any possibility of over-correction or hunting. It will be evident that in one installation the speed or frequency of the opening and closing of the finger 42 may necesarily be diiferent from that in another installation, and to that end the gearing between the motor 44 and the cam Q3 may have to be different on one job from another, and at the same time the shape of the cam 63 may desirably be changed. In fact. on certain installations it may not be necessary to have the interrupter 42, 43, M at all,

In general, the arrangement of Fig. 1 is such that when the boileris started from a cold condition the dampers H and I6 are preferably closed. and the damper I5 is wide open. This may be accomplished through the provision of manually actuated switches 45, 48 and I! and the manually actuated selector switch 48. The latter is indicated on the drawings as having two positions representative of autoatic and hand control. The three switches l5, l6 and 41 are preferably spring urged to the shown position wherein they are not closing any circuits. 'Wben it is desired to actuate the motors l1, 18 or I! manually and entirely independently of the automatic control system, then the selector switch 48 is moved to the hand position (shown in autopassing through the interrupting finger 42.

maticposition in Fig.1), whereinthe power line 4| is connected directly to the neutrals .of the motors II, II and II through the lowermost (shown open) contacts or switch 48 without At the same timethe switch 48 breaks the circuit between the power line 4| and the contact. arms ll, 36 so that the contactors are without power and thus ineffective for the control of the motors; and energizes switches 45, 48, and 41.

After placing the switch 44 in the hand position, and thus connecting-the neutrals of the motors ll, II and is directly to the power source 4|, any or all of the switches 45, 4 6, 41 may be actuated to either a more or :a. less position ,ior moving the dampers l4, "or ii in the more orless"v direction separately or collectively. The moment a switch 45 or or 41 is released by hand, it is spring urged to a neutral position as shown in Fig. 1. The switch 48 must be returned to automatic position before the cntac-' tors II, it become effective to-automatically control the dampers.

It will be seen that the manual control as well as the automatic control issubiect to the limit switches 20, so that there is no danger of running the motors I I, II or il in one direction or the other past a predetermined extreme of travel;

thus avoiding the possibility. oi damage to the motors or dampers. p

A preferred method of placing the boiler unit in operation from a'cold condition is to so manipulate the switches 4!, 45, 46 and 4'! that the dampers I4 and ii are closed and that the damper i5 is wide open. All of the gases from the furnace I will then pass through the idle pass 8. be cooled by the economizer i0, and pass through the damper ii at a temperature not high enough to damage the damper. The same condition may be encountered after a sudden loss of a heavy load when there is no appreciable steam flow, and before the unit has cooled oil. More will be said about this operating condition hereinaiter.

The arrangement of Fig. lprovides tor the automatic control of the dampers I4, I! and I! versa; in such a case the motor being responsive responsive to temperature 01 the steam passing through the conduit 2i and the temperature of the steam passing through the conduit 2!. Assuming that the switch 48 is as shown in the automaticposition, then the contact bars Ii, 38 will control the position of the dampers l4, l5 and I8 responsive to temperature oi the steam leaving the superheater and 01' the steam leaving the'reheater.

Assume that the temperature of the steam leaving the superheater I 2 decreases below the desired value. The Bourdon tube 23 will tend to contract, moving its free end in a clockwise direction, thus positioning the pointer 24 downward relative to the index 2! to give a visual indication or the change in temperature, and at the.

same time positioning the contact arm II in a counterclockwise direction around its pivot. If the said temperature deviates a predetermined number of degrees below the desired value, then the contacts 34 are close circuited, thus completing the circuit for energizationjct the M coil of the motor i1, whereby the dampers II are moved in an opening direction. The energization of the M coil or themotor il will be, by increments (so long as the contacts 34 are closed) through the agency of the interrupter fingers 42. As the 'increased flow or hot gases through the superheater I1 is accomplished by a further opening of the contacts 49 or the contacts 50. The arrangesteam leaving the superheater -will be eflective to position the Bourdon tube 23 and eventually open the contact l4. If, however, the temperature oi the steam leaving the superheater continues to fall. or falls at a iastrat'e, sothat the counterclockwise rotation of the contactbar 1| causes engagement of the contacts n. "this results .in a positioningoi' the damper I! infarless direction to further cause an increase ingas 'flow past thesuperheater 12. 1

Conversely, should the temperature or the steam leaving the super-heater befhigher than desired, then the Bourdon tube 23 will have positioned the ,contactor :arm. I' l in-a clockwise direction, .flrst closing the contacts 32 to energiz the L coil of the motor l -1, and 101' a continued increase in temperature to nex t'close theoontacts 35 effective to energize the M coil or the motor II. It will be appreciated that when more-gas is by-passed through the idle pass 8 it tends to decrease the amount of gaseflective through the passes l and 9, and vice versa. 7

The Bourdon tube 2| is positioned representa-- tive of the temperature of the reheated steam, leaving, through the conduit 26, and as such temperature falls below a predetermined value,

the contact 39 is first closed, causing an energization of the M coil of the motor is. and it a reheater, and if this does not satisfy the condi tion to then tend to close the damper l5 and decrease the amount of gas by-passed through the idle pass 8. Obviously the motor It must be of a type wherein no damage to the motor windings will occur if the M and L windings are simultaneously energized, the one from the contactcr II and the other from the contactor 38, or vice to the algebraic sum of the contacts. r

.It will be appreciated that in the remaining illustrations of the present application we have avoided duplicating thereon those parts of Fig. 1 which are common to all of the drawings. For example, we have not duplicated the arrangement of boiler, superheater, reheater, etc., but in mostinstances have illustrated only those parts or the control arrangement which difler 1mm that shown in Fig. 1. We intend that withany of the remaining figures of the drawings we may apply the limit switches, as well as the handautomatic arrangement of switches, of Fig. 1, without the necessity of duplicating the showing in each of the other figures of the drawings.

Fig. 2 illustrates a somewhat similar arrange- ;ment of the control to that illustrated in Fig. 1,

except that herein the tree end of the contact bar 3i and that of the contact bar It are pivotally connected to position a floating contact bar it adapted under certain conditions to close the ment is such that it the superheat temperature should decrease, and the reheat temperature should increase, each by a certain amount, the contact member 5| would be relatively moved in one direction or the other, but the center thereof would remain substantially undisplaced and neither the contacts 49 or 50 would be closed. Such a condition would be indicative that the proper total amount of heat, as represented by controls the total heat applied to both the re- 'two interrupting fingers entirely independent of each other, the one in connection with the motor hot gases, was being applied through the passes 1 and 9, but not properly distributed therethrough. It would indicate that no change should be made in the amount of hot gases bypassed through the idle pass 8. If, however, both 5 the superheat temperature and the reheat temperature were to fall and in substantially the same amount, as for example upon a sudden change in load, then the contacts 58 would be closed, energizing the less coil of the motor ID for positioning the damper l5 in a closing direction whereby the flow of hot gases through the idle pass 8 would be decreased and additional gases would be sent over the passes I and 8 to bring both or the temperatures up toward predetermined normal. Conversely, if both temperatures increased in substantially the same amount, then the contact 49 would be closed, calling for an opening of the damper I! to take some of the total heat away from the reheater and superheater. Thus in the arrangement of Fig. 2, the contact arms 3! and I will cause a distribution of heat relatively between the superheater and reheater, while the contact member heater and superheater.

Fig. 3 shows anarrangement somewhat similar to that of Fig. 2, but herein a second Bourdon tube 23 is positioned responsive to temperature of the superheated steam along with the Bourdon tube 23; while a second Bourdon tube 28' is positioned along with the Bourdon tube 28 responsive to temperature of the reheated steam. The diiferential in temperature between that of the superheated steam and that of the reheated steam, as indicated by the position of the contact beam 5|, controls the damper l5 oi the idle pass 8. Fig.3 providesover Fig. 2 many possibilities as to adjustment of the spacing between the contacts and otherwise to arrange for temperature valueor differential to result in a movement of the damper l5, as well as in the sensitivity, and speed of motion of said damper relativeto the dampers I4, I 8. In Fig. 3 we provide 5 i 8 and the other in connection with the motors l1, l9. Thus the motor I8 may be eiiective to open or close the damper l5 at a faster or slower rate than the other dampers and {or longer or shorter increments of time frequency.

' thus energizing the relay 53 and closing the proper circuits to energize the L coil of the motor H, the M coil of the motor l8 and the M coil or the motor l9. Thusto take care of too high a superheat temperature the dampers M will be moved in a closing direction, while the dampers l5and It will be moved in an opening direction. In similar manner the Bourdon tube 28 is adapted to position all three of the motors l1, l8 and I9. The neutral of the motors l1 and i9 is taken through one interrupting finger, while the neutral or the motor [8 is taken through another interruptingfinger, so that by proper arrangement the speed of opening or closing of the damper l5 may be at a different rate than that of the dampers I 5, I6.

It will be seen that'the arrangement at Fig. l"

is one in which a predetermined substantially constant superheat temperature and reheat temperature is the desideratum and where each is controlled relatively independent of eachbther and of load. It may happen, however, the either the superheat temperature or the reheat temperature would tend to stabilize at a value other than the desired value, as for example it the superheat temperature falls enough to cause a closing of contacts 34 but not a closing of contacts 33. The energized M coil of motor I! would cause an intermittent positioning of dampers H in an opening direction, which might continue until the dampers were wide open. Under this condition the only way to further increase the hot gas flow through the pass I would be to close down damper l5, but this is not accomplished because the superheat temperature has not fallen to low enough value to close the contacts 33. If

the temperature of the superheat and reheat are below the desired standard and dampers l4 and I8 are wide open, then the superheat and reheat temperature might stay at the low point but not go any lower. If it did not go any lower it might not cause an actuation otdamper l5. In the event the temperatures remained at the low point without starting to close the damper l5, then we provide a time element which would become effective after a certain length of time to make a slight closure of the damper l5 to get the systern oil from its stabilization point.

Referring to Fig. 5, the initial or primary control of the motors l1 and I9 is as previously described through the agency of the Bourdon tubes 23 and 28 and the related contactors 3i and 36. Additionally, however, we provide means to prevent stabilization at any other temperature than that desired. For example, the motors 54, 55, 56 and 51, when energized, are adapted to rotate in a predetermined direction and each angularly position a cam adapted to actuate the contacts 58, 59, 60 or 6! respectively. The necessary reduction gears are provided between the motors and their respective cams, as well as a friction clutch, maximum travel limit, and spring return. The arrangement is such, taking the motor 54 as an example, that when the motor 54 is energized for rotation in given direction it drives the cam associated therewith in predetermined direction and at a speed dependent upon the reduction gears therebetween. The drive is through a friction or slip clutch and the cam is arranged to slowly close the contacts 58 against the action of a spring. When the maximum limit of travel of the cam is reached, as determined by engagement of the contacts 58, a continued energization of the motor 54 will cause the friction clutch to slip, whereby the motor is not damaged and the contacts 58 are retained in closed position. Thus the time length of closure of the contacts 58 is dependent upon the time energiza-' tion of the motor 54 after the contacts 58 engage. As soon as the motor 54 is deenergized the spring returns the movable half of contact 58 and the cam to their initial or starting position, thus breaking the circuit through the contact 58.

It will be observed that the contacts 58, 60 are connected in parallel to the L coil of the motor l8, while the contacts 59, 6i are connected in parallel to the M coil of the motor I8. Whenever the contact 34 is closed the motor 54 is energized. Likewise when the contacts 32, 31, 39 are each closed the respective motors 55, 51, 5B are energized. A momentary closure of any of the contacts such as 34 may not necessarily cause a If however a sustained contactias at ll) would persist, it would resultin a closure of the contacts 58 and correspondingly, an energization of theLcoiI of the motor [8.

It will thus be seen that the condition previously mentioned. cf the possibility of stabilizing at some temperature other than that which is desired, is obviated through the arrangement as proposed in Fig. 5. It too much of. the hot gases are passing through the idle pass I and the superheat temperature and reheat temperature are both low, regardless of the fact that the dampers l4 and ii are wide open, then the Bcurdon tubes 21, 28 responsive to the lowtemperatures would maintain the contacts 34, 39, or either of them,.

in a closed condition, and correspondingly the motors 54, 56 would be energized, resulting in a closure of the contacts 58,80. ,either or both of which when closed are arranged to energize the L coil of the motor iB. SuchJan energization in a closing direction of the damper I! will tend to increase the total heat available in the passes I and 9 over the superheater andreheater to bring the steam temperatures up. I

Thus, in general, Fig. 5 provides that if the dampers l4 and it are wide open, and the temperatures are still too low, a timing device will come into play after a predetermined time interval and make a change in the position of the damper I! to bring the system oif irom stabilization. It will be observed that an interrupting finger is arranged in the neutral connection of the motor I8 so that the positioning of the damper I! is by increments whose frequency and duration may be properly adjustedto prevent overcorrection.

It may be that in certain types oiinstallations or under certain conditions oi' operation it will be desirable to have a somewhat difl'erentsuperheat temperature and/or reheat temperature at diiferent loads. In Fig. -6 we". illustrate an arrangement providing the establishment and maintenance of superheat temperature and reheat temperature varying withzrating. To that end we provide in the superheated steam outlet conduit 2! an orifice 62 producing a pressure difierential thereacross in known relation to rate of steam flow and efiective through the pipes 63, M upon a flow meter generally indicated at 85. The flow meter 65 is of a type designed to move an indicator 66 relative to an index '61 directly in increments of rate of steamiflow through the conduit 2 I. Thus we provide a visual indication of load as represented by rate of superheated ll downwardly, closing the contact 18 and energizing the M winding of the motor ll to accomplish an opening of the dampers l4. Conversely, I

it the temperature of the superheated steam is too high, then the contacts ll will be closed and the dampers I will be moved in a closing direction to decrease the flow of hot gases through the pass 1 over the superheater l 2.

Through the agency of the now meter 65 and the, linkage I3, 14, 15 the left-hand end of the contact beam 12 is positioned upwardly or downwardly, thus decreasing the distance between the contacts H or 18, as the case may be, and resulting in the maintenance of a difierent superheated steam temperature at difierent rates of steam flow. An adjustment 7! is provided to vary the ellect oi the flow meter movement upon movement 0! the contact bar 12.

In like manner the flow meter 88 assists the Bourdon tube 2! in control of the motor 18 to the end that the superheat temperature maintained is in desirable relation, varying directly or inversely or in desired degree, with rate of reheat steam outflow through the conduit 26.

The motor I8 is under the control of a contact member 8| jointly positionedby the Bourdon tubes 23, 20 through the agency of links 16, 80 as have previously been described in connection with other figures of the drawings. a

It will be evident that with the arrangement of Fig. 6 we may provide any desired functional relation between temperature of the superheated steam and its rate of flow, or between tempera ture of the reheated steam and its rate offlow. In other words, we may arrange to maintain superheated steam temperature varying directly or inversely and in any amount relative to rate i of steam flow, or we may arrange thatthe relation between rate of flow and temperature of the flowing steam may be in any desired curved relation depending upon the design of the linkage interconnecting the flow meter and the Bourdon tube for jointly positioning the contact members. 7

In Fig. 7 we have provided an arrangement particularly adapted ior emergency conditions,

, energize the winding of a relay 83 shown in enersteam iiow leaving the superheater II. A similar rate of flow meter 68 is responsive to the pressure diil'erential existing across an orifice 8! in the reheat steam outflow conduit 26 and is adapted,

to position an indicator 10 relative to an index ll directly in terms of rate 01' flow of reheated steam leaving the reheater ii.

A freely floating contact bar 12 is positioned at one end by the flow meter through linkage 11, I4 and 15. From the Bourdon tube II is pivotally suspended a link 16 to which is pivotally connected the other end of the contact bar II. A contact carried by the bar 12 is adapted to cooperate with either the contacts TI, I8 Joining respectively to the L and M windings oi the motor H. The arrangement is such that in case the superheated steam temperature is lower than desired, the Bourdon tube 23 will move the link gized position in Fig. 7. In normal operation (as shown in Fig. 7) the neutral of the contact bars ll, 36, II is connected to one side of the power source through the lowermost and closed contact of the relay ii.

If there is a, sudden loss of load to below 25% of maximum, the pointer 66 passes beyond the end of the contact segment 82 and the relay 83 is deenergized. Its consequent movement opens the circuit to the neutral, thus deenergizing contact arms 3|, 36 and BI, and closescircuit through the L windings o! the motors l1 and I9 and the M winding of the motor ll, whereby the dampers I4, I! are immediately positioned in a closing direction and the damper I5 is positioned in an opening direction. This action servesto protect a by-passing of a greater portion of the hot gases of combustion through the idle pass 8, and until the boiler operator or automatic equipment has made the necessary changes in firing rate, subsequent to the sudden decrease in output, whereby the total volume of heated gases is reduced below a dangerous value.

The arrangement of Fig. 7 further provides that upon starting up, and until a certain predetermined rate of steam flow is attained, the damper IE will be in an open position and the dampers l4, It in a closed position. Thus the gases will pass through the idle pass 8, be cooled by the economizer l9, and pass through the damper I to the air heater H. This obviates the possibility of damage to the superheater I2 or the reheater I3 by an excessive flow of hot gases when there is not a sufilcient cooling of the reheater or superheater by steam flowing therethrough in'sufllcient quantity.

Under such low load or emergency condition, r upon starting up, the energization of motors l1, l8, and i9 is continuous and not through an interrupting finger, and motor travel will be limited by the limit switches 20.

It will be realized that we are not necessarily limited to electrical arrangements or electric motors for positioning the dampers. In Fig. 8 we have illustrated the embodiment of our invention in pneumatic means. Referring to Fig. 8, we show therein that the Bourdon tube 29, positioned responsive to the value of superheated steam temperature, is arranged to axially position a pilot stem 84 to vary an air loading pressure within the pipes 85, 86. In like manner the Bourdon tube 28 axially positions a pilot valve 81 to control an air loading pressure within the pipes 89 and 89. The pilot valves 84, 81 are of a type disclosed and claimed in the patent to Johnson No. 2,054,464 and of a general type wherein axial movement results in the establishment of an air loading pressure bearing a definite and predetermined relation to such axial movement. In the present arrangement, an upward movement of the pilot stems 9t, 81 causes a proportionate increasing of pressure within the pipes 85,. 88 and simultaneous decreasing in pressure within the pipes 88, 89.

Pipe 86 is connected to a pneumatic actuator 88 connected to position the dampers l4; while the pipe 89 leads to a pneumatic actuator 9| adapted to position the damper 16. The actuators 99, 91 are spring loaded so that the dampers l4, l6 assume positions'representative of the air pressure applied to the actuators through the pipes 88, 89 respectively.

II the superheated steam temperature tends to rise above that desired, then the Bourdon tube 23 moves its free end in counterclockwise direction, raising the pilot stem 94 and decreasing pressure within the pipe 58. Such a decrease in pressure, opposed by the spring of the actuator 99, moves the dampers M in a closing direction to throttle the flow of heated gases past the suinaflde'creasing oipressure through the pipe'99 within the actuator 9i, and a positioning of the damper 16 in a closing direction to decrease the I heatiri'igeflect upon the reheater I 9.

For a control 01' the'damper i5 we provide the averaging relay 94. Such'an averaging relay is inlet and outlet valve in the chamber 95. It will be observed from a study of Fig. 8 that the pipe 85 connects with the chamber 98 while the pipe 88 connects with the chamber 96. Thus the pressures effective through the pipes 85 and 88 act in the same direction against the spring and for control of pressure within the chamber 95, which pressure is effective through the pipe 93 upon the'pneumatic actuator 92. If the super- .heated steam temperature is too high, then the Bourdon tube 23, in positioning the pilot stem 84 upwardly, causes an increasing pressure ef- Iective through the pipe 85 within the chamber 98. Likewise an increase in temperature of the reheated steam results in an increasing pressure within the chamber 96. Such increased pressures acting against the opposition of the spring will cause an opening of the air inlet valve to the chamber 95, increasing the pressure within the chamber and within the pneumatic actuator 92, thus tending to position the damper IS in an opening direction whereupon a larger percentage of the hot gases are passed through the idle pass 8 and away from the superheater and reheater. The action is somewhat different from those previously described in connection with the electrical embodiments, in that the relay 96 provides a resultant loading pressure through the pipe 93 which is in eiiect an algebraic summation of the pressures within the pipes 85, 88. Thus, if one oi! the temperatures is too high and the other is too low there will be very little, if any, change in the position of the damper l5, and this is correct, for the actual change should occur in the relative positions of the dampers I4 and 18. However, if both temperatures are too high, or both temperatures are too low, then in addition to any changesin the position of the dampers i9, it, there should be and will be a readjustment of the position of the damper i5 to by-pass more or les of the gas by the superheater and reheatcr.

In general, while we have provided an arrangement and method of controlling the heating of a superheater and of a resuperheater in connection with a steam generating boiler, it will be'understood that we are not to be limited thereby as the invention may equally as well be applicable to vapor generators in general, or to furnaces in general, or to combinations of superheaters or reheaters other than those specifically illustrated and described What we claim as new, and desire to secure by Letters Patent of the United States, is:

l. The combination with a vapor generator having a furnace, threeparallel passes for the gases leaving the-furnace, a superheater in one of the passes, a reheater in another of the passes, the'third pass being an idle pass, means sensitive to temperature of vapor leaving the superheater adapted normally to vary the gas flow through the superheater pass in direction to maintain said temperature at optimum value, means sensitive 'to temperature of vapor leaving air actuator 92 connected by 8 P p 93 0 an the reheater adapted normally to vary the gas aaoavoo gases flowing from the furnace which do not flow that portion of the total gases flowing from the furnace which do not flow through the heater passes will flow through theidle pass.

through thesuperheater and reheater passes will flow through the idle pass,and means responsive to a predetermined minimum rate of' flow of one of the fluids being heated and arranged to render ineffective the said joint temperature'sensitive means when there is no flow through the superheater and reheater passes and direct the total gas flow through said idle pass.

2.The combination with a vapor generator having three parallel gas passes leaving the furnace, one of the gas passes being an idle pass. a superheater in a second pass, a reheater in the third pass, temperature measuring means for thevapor leaving the superheater, temperature measuring means for the vapor leaving the reheater, dampers at the exit of each of the passes,

and control mechanism so responsive to said measuringmeans as to so selectively position said dampers to maintain the temperatures each at a predetermined optimum value that the 9 damper of said idle pass will be in open position tain the temperature of the vapor leaving the and the dampers of said superheaterand reheater pass will be in closed position when the vapor generator is under substantially no load, and the" dampers of all three passeswill beproportionally in open and closed position when said generator is under load.

3. The combination with a vapor generator having a furnace, a vapor generating tube portion at the gas exit of the furnace, three, parallel gas passes leaving the generating tube portion, a vapor superheater in one of the passes,

a vapor reheater in a second pass, the third pass being an idle pass, dampers at the exit of each of the passes, control means for each of the sets of dampers, means measuring temperature of the vapor leaving the vapor superheater, means measuring temperature of the vapor leaving the vapor reheater, means so responsive to the superheated vapor temperature measuring means as will so position the dampers in the pass at the exit of the superheater that the superheated vapor temperature will be maintained at an optimum value, means responsive to the reheated vapor temperature measuring means for positioning the dampers in the pass at the exit of the reheater to maintain the reheated vapor tema plurality of parallel being so jointly responsive perature at optimum value, and means so Jointly responsive to both measuringmeans that the dampers in the idle pass are so positioned that of the passes, a reheater in another of the passes,

the third pass an idle pass means responsive to temperature of the vapor leaving the superheater, means measuring flow of vapor from the superheater, control means for the heating of the superheater jointly controlled by said temperature responsive means and said flow means in such direction and amount as to maintain the'temperature of the vapor leaving the superheater at optimum value, means responsive to temperature of the vapor leaving the reheater, meansmeasuring flow of vapor from the reheater, control means for the heating of the reheater Jointly controlled by said second temperature responsive means and said second flow means in such direction and amount as to mainreheater at optimum value, and means controlling the flow oi gases through the idle pass responsive to both said temperature sensitive means, said last-mentioned means being so Joint- 1y responsive to both measuring means that the flow in the idle pass is that portion of the total gasesiflowing from the furnace which do not 1 how through the heater the idle pass.

passes will flow through a vapor generator having passesfor the gases leaving the furnace, one of the passes being an idle pass, a vapor superheater in one pass, a vapor reheater in another pass, means so sensitive to the temperature of the vapor leaving the super heater as to so control the gas flow through its pass as to maintain said temperature at optimum value, means so sensitive to the temperature oi the vapor leaving the reheater as to so control the gas flow through its pass as to maintain sfaid temperature at optimum value, and time delay means coacting with both said temperature sensitive means in controlling the gas flow through the idle pass, said last-mentioned means to both measuring means that the flow in the idle pass is that portion of the total gases flowing from the furnace which do not flow through the heater pass will flow through the idle pass.

9 t RAYMOND D. JUNKINS.

THOMAS C. TOOMEY. CHARLES B. SMITH,

5. In combination

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