US2921564A

US2921564A - Automatic blowdown for steam generator

Info

Publication number: US2921564A
Application number: US546175A
Authority: US
Inventors: George W Mattox
Original assignee: Clayton Manufacturing Co
Current assignee: Clayton Manufacturing Co
Priority date: 1955-11-10
Filing date: 1955-11-10
Publication date: 1960-01-19
Anticipated expiration: 1977-01-19

Description

Jan. 19, 1960 G. w. MATTOX 2,921,564

AUTOMATIC BLOWDOWN FOR STEAM GENERATOR Filed Nov. 10, 1955 2 Sheets-Sheet 1 luvs/V702. 65026:. W. MHTTOX BY HIS HTTORNEKS. HARRIS, mac/1, Fos'rcl? & HHRR/S Jan. 19, 1960 w, 'rox 2,921,564

AUTOMATIC BLOWDOWN FOR STEAM GENERATOR Filed Nov. 10, 1955 2 Sheets-Sheet 2 \92 56 -F@ l,z 0 2:4 I 64 I 86 52 I08 [/2 //a 25 I46 107 1/4 2K; v

. m I06 65 M21 I w I I /20 v 66 I00 I06 /04 7a /NVNTO/?. GEORGE W. MATTOX BY HIS ATTORNEYS.

HARRIS, K150; FosrsR 3: HARP/5' United AUTOMATIC BLGWDOWN FOR STEAM GENERATOR :George W. Mattox, El Monte, Califi, assignorto Clayton Manufacturing Company, El Monte, Califi, a corporation of California Application November 10, 1955, Serial No. 546,175

7 Claims. (Cl. 121-382) "The present invention relates in general to steam gen- :erating equipment and, more particularly, to a blowdown system for a steam generator or boiler. While applicable to various steam generators or boilers, and particularly to those which have a pulsating unit which can be used .to control the blowdown function, the invention will be particularly exemplified as applied to a closed steam generating system wherein the feed or make-up water introduced into the system is always maintained in balance with the amount of water withdrawn from the system in the form of steam so that a substantially constant volume of excess water is always present in the system, the excess water being constantly circulated throughout the system. Such a steam generating'system .is exemplified in the copending application of Perry Arant, Serial No. 432,631, entitled Balanced Feed Water System for Steam Generators, and assigned to the same as- .signee as the present application. It should be clear,

dered operative to introduce make-up water into the sys- :-'tem by a control means which responds to the water level in the accumulator. The control means may render the feed pump inoperative to introduce make-up water into .the system, when the amount of water in the system is up to the desired value, in various ways, as by by-passing the make-up water discharged by the feed pump-back to the inlet of the feed pump, by rendering a pumping element of the feed pump inoperative, or by stopping the feed pump entirely.

In such a steam generator, impurities concentrate in the excess water in the steam generating system with the passage of time, even with 'properconditioning of the make-up water introduced into the steam generating system to balance the water withdrawn in the form of steam concentration of impurities occurring primarily in the accumulator due to steam-Water separation in the accumulator and to discharging the make-up water in a zone below the water level in the accumulator where the water temperature is such as to precipitate out many of the impurities which may be present in the make-up water. conventionally, the impurity concentration is reduced from time to time by periodically blowing down the steam generating system manually soas to bleed oil the impurity-laden water in the system.. Such manual blowing down of the system is preferably accomplished by means of a manual blowdown valve communicating with the lower end of the accumulator. 7,

With the foregoing manual blowdown procedure, whenever the impurity concentration in the excess water in the system reaches a level such as to tend to produce scale formation, corrosion, embrittlement, or carryover of contaminants into the steam discharged by the system, it is necessary to shut the steam generator down while the manual blowdown of the system is accomplished, which is obviously undesirable.

In view of all of the foregoing, a primary object of the present invention is to provide means for blowing down a steam generating system automatically while the steam generator is'in operation. With such a means, the impurity concentration is kept within acceptable limits for prolonged periods of time to eliminate frequent shutdowns, which is an important feature.

More particularly, an object of the invention is to provide means for bleeding off water from-a steam generatingsystem in proportion to the introduction of makeup Water into the system so that impurities are removed at a rate proportional to the rate at which they are introduced.

' Another object is to provide a steam generatorblowdown valve means for bleeding off impurity-laden water, this valve means being operated whenever feed water is being introduced into the system, thereby attaining a concentration removal rate proportional to the. concentration introduction rate.

Another object of the invention is to provide an oscillatory blowdown valve means which cyclically opens and closes a blowdown outlet communicating with, the steam generating system, and to provide means for oscillating the blowdown valve means to alternately open and close the blowdown outlet whenever make-up water is being introduced into the system by the feed pump. This oscillating or pulsating action of the blowdown valve means results in self-cleaning thereof to assurea uniform blowdown rate, which is an important feature.

Another object is to provide a feed pump which includes means for producing pressure pulsations concurrently with the introduction of make-up water into the steam generating system, and to apply these pressure pulsations to the oscillatory blowdown valve means to oscillate same between its open and closed positions. With this construction,;whenever the feed pumpis rendered operative to introduce make-up water into the system, the blowdown valve means is automatically actuated to bleed impurity-laden water oifjfrom the system,

thereby attaining a blowdownrate proportional tOj'thQ make-up rate, which is an important feature.

Still another object of the invention is to provide'a feed pump having a pulsation chamber and having means for producing pressure pulsations in such chamber whenever the feed pump is operative to introduce make-up water into the steam generating system, a related object being to provide an oscillatory blowdown valve means which includes a valve member movable toward and away from a valve seat and having connected thereto 7 tions either by rendering the diaphragm or piston nonoscillatory, or by by-passing the make-up water dis charged back to the inlet of the feed pump. Another alternative would be to stop the feed pump completely whenever the amount of excess Water in the'steam 'gcn crating water is at the desired value.

In order to bleed off water of maximum impurity fi ncentrationis ata;ma'ximu'm. This zoneis'justbelow the .water :level in the;accumulator, the im'purrtyzc'oncen- .t ation being-a maximum in this zone due'tothe release orprecipitation of impurities in the accumulatorat the wate'rrjlevel thereinupon steam-water separation in the 1 accumulator. I More particularly, an object is topr'ovide a skimmer .Which; communicates at its, other end .with the blowdown valve .means.

' ".Ah important object'of .thetinvention is to so locatea duct which communicates at one end with the accuimn ';lator in azone just below the; water level therein, and

heat-transferring ,relation with vthewater in the' lower regions of, the accumulator, the lower end of "the skimmer duct being connected to the .blowdown valve means. Since -a substantial vertical temperaturegradient or Stratification exists in the water zone of the accumulator, due pri- .marily torthe introduction' of makeup water into this zone. thereof,. the impurity-laden water. flowing downwardly through the skimmer duct during blowdown is -cooledmaterially so that it can'be safely. dischargedat .any suitable point of disposal, such asa-sewer, which 7 exemplary embodiment of the invention which is illu's-r trated in the; accompanying. drawings and which .is

described in detail hereinafter. ings:

Referring to the draw- Fig. 1 is' a diagrammatic View .of a steamy generator 5 .whiehl embodies means'of the present invention for automatic blOWdQWn at a rate proportional to the make-up rate; V 1 I I Fig; 2 is a view,partially in section and partially in elevation, of a feed pump embodying one means of oscillating 1a blowdown valve" means of the invention during feed-water introduction; and

4 Eig.3 isra sectional view. of a blowdown valve means.

f. he invention.

' 1 Referring particularly to Fig. l-of'the drawings, -th e illustratedsteam generatorincludes a closed system comprising a steam generating unit or boiler 10, an accumulatoror'steam separator 12 and a circulating pump 14, all connected in, series, with the circulating pump downstreamfrom the accumulator and upstream from the boiler. Thelsteam generating systemis provided with a steam outlet:16.con.nectible to a load, and includes a; feed water inlet .18 through which make-up water is introduced; by a .feed pump 20 the operation of which i is regulated zby a control .means 22 responsive to.-the waterlevel inthe' accumulator 12, the circulating pump 14 and the feed .pump. 20. being combined in a single pumping unit 24 in the particular construction illustrated.

. The steam generatingfsystemalso includes a blowdown outlet 2dlcontr olledjby a blowdownvalve means 28 responsive to theintroduction of make-up water into the a system by thefeed pump 26*, as hereinafterdescribed.

- Cons der ng the. steam generatingsystemin more detail,

the boiler; 10 i'ncludesra continuous heating coil-'30 hav s s nc nletiend 32- and an 1 outlet end..34, hi n. 1110 mguntingaihgelicfl water-wallx'sectionfis. A thermo statically controlled: burner 40 evaporates wateridthej coil ,towardztheoutletend thereof:

The steam generated within; the 1 heating" coil 34 is hGQtingcoil'fiOfas it fiowsfromthe-inlet end SZof-the discharged-into the-aoc'umulatorn through a discharge ding 'a number of spiral. pancakese'ctions 36 'sur- 3 means 42, the latter being mounted on the upper end of heating coil by a pipe 48. The'discharge means 42,

.which may he of any suitable type, separates the steam generated in the heating coil 3% from thewater passing therethrough, whereby the steam zone in the accumulator, above the water level 46, contains substantially dry steam, the water discharged by-the'discharge means 42 descending to the water zone below the water level 46. The steam outlet 16 communicates with the interior of the accumulator 12 at the'upper end of the steam zone therein to minimize water carry over into the steam outlet. The water level '46 Within the-accumulator 12 may be determined visually through a sight tube communicating with the interior of the accumulator above and below the water level; i v

The circulating pump 14 continuously draws water from the Water zone of the accumulator 12 and delivers it to the inlet end 32 of the heating coil 39 While the steam generator is in operation," the inlet 52 of the circu lating pump being connected to the water zone of the accumulator 12 by a .pipe' 54. The pipe 54cornmuni cates with the Water zone of the accumulator at ale'vel intermediatethe'upper and'lower'ends of the water zone soas tocirculate water having a minimumimpurity concentration, the impurity concentration being higher adjacent the water level 46 'due to the discharge of impurities by the dischange means 42 and due to precipitation. of impurities atthe feed-water inlet 13, and being higher nearthe bottom of the accufnulaton'where sludgetends to collect. The outlet 56 of the circulating pump 14 is connected'tothe'inlet end 32of the'heating I coil-30 by 'a pipe 58, thereby completing the closed steam generating system'or loop.

Considering the circulating pump 14in a little more detail, various types may be-utilized, the one illustrated being exemplary only; In the particular construction illustrated, a: standpipe 60 is provided, this standpipe having at its upper end an inlet-outlet check valve assembly-62 which'causes incremental flow from the inlet 52 to the outlet 56 in response to pressure pulsations in the standpipe; Such pressure pulsations in the standpipe are created in a pulsation chamber 64, which communicates with the lower end of the 'sta'ndpipe', by a diaphragm 66 which may be oscillated in any suitable manner. H In the particular construction show'njthe'diaphragm 66 is oscillatedby a piston '68 through a'body of oil trappedin a cylinder 70 when the piston 68' is movedtowa'rd the diaphragm 66 to cover'p'o'rts 72 leading to 'a sump 74 in the pumping unit24. Thepi'ston 68 is reciprocated to oscillat'e the diaphragm 66 in this manner by an; eccentric means g7 6"drivenbya-shaft 78, the'latter, in'turn, being driven continuously in any suitable manner, as by an electric motor 80, Fig. 1, while the steam generator is iniope'ration.

' Considering thefeed pump 20', it is also shown as'ineluding a standpipe, identified by the numeral 82, surmounted by an inlet-outlet check valve assembly, designatedby the numeral 84. This assembly provides an inlet 86"which communicates with a hot well, not shown, through a pipe 88, and provides an outlet 90 which is connected to the feed-water inlet ls'into the accumulator 12 by a pipe 92, the inlet 18 being located in a zone where the water temperaturein the 'accumulator'is such as'to precipitate various impurities. These impurities settleto the'bottom'of'the accumulator, from whichthey may be removed periodically by means of a manual blow-off or blowdown valve 94. Adverting to the feed pump20, the standpipe 82 communicates at its lower end with a pulsation chamber 96 one wall of which is formed by a diaphragm 98. This diaphragm is biased in one direction by-a compression springllltl and is biased in the opposite direction byoil pressure produced in a cy1ind'er'102'by ticularly, as the piston 104 reciprocates, the oil trapped, in the cylinder 102 between the piston and the diaphragm 98 each time the piston covers the ports 106 movesthe diaphragm in one direction, the diaphragm being moved in the opposite direction, upon movement of the piston in the opposite direction, by the spring 100. Thus, pressure pulsations are produced in. the water-filled pulsation, chamber 96, these .pressure pulsations being transmitted through the standpipe 82 to the check valve assembly 84, The latter regulates communication between the inlet 86 and the outlet 90 of the feed pump 20 in such a way as to produce incremental make-up water flow toward the inlet 18 in response to the pressure pulsations. I

Since, as hereinbefore suggested, it is desired :to main tain the amount of water in the steam generatingsystem substantially constant by adding make-up water at a rate suflicient to balance the steam demand, the feed pump 20 is rendered operative to produce pressure pulsations in the pulsation chamber 96 whenever the water in the,

accumulator 12 tends to drop below the desired water level 46, the water level being sensed by the coiitrol means 22, which governs the operation of the feed pump 20 in a manner about to be described. The control means may be of any suitable type, and preferably includes -a switch, not shown, which is actuated whenever the water level varies from the desired level 46. The control means 22 is electrically connected, by an electrical conductor means 107, to a means 108, Fig. 2, for preventing pres-- sure pulsations in the pulsation chamber 96 whenever the water level in the accumulator is at or above the desired level 46. The means 108 may comprise a valve 110 controlled by a solenoid 112 to which the switch of thecon-r trol means 22 is electrically connected by the conductor means 107, the valve 110 controlling communication between the sump 74 and a port 114 communicating with the cylinder 102 between the ports 106 and the diaphragm 98. With this construction, whenever the water level attains or exceeds the desired level 46, the control means 22 is actuated and operates the solenoid 112 to produce opening of the valve 110 so as to permit the discharge of oil from the cylinder 102 into the sump, thereby preventing displacement of the diaphragm 98 by the piston 104 and preventing pressure pulsations in the pulsation chamber 96. Thus, make-up water is introduced into the F steam generating system by the feed pump 20 only when necessary to maintain the desired water level in the accumulator 12, no make-up water being introduced at other times even though the shaft 78 and eccentric means 76 operate continuously.

The foregoing merely represents one way of producing pressure pulsations during the introduction of make-up water. Pressure pulsations may be prevented in other ways when no make-up water is being introduced into the steam generating system. For example, instead of an oil by-pass as shown, a make-up water by-pass governed by the control means 22 may be utilized, 'Alternatively, the feed pump 20 may be driven independently of the circulating pump 14 and stopped whenever no introduction of make-up water is necessary.

The steam generator thus far described in detail, is,

except for the automatic blowdown means to be described hereinafter, generally similar to the steam generator disclosed in specific detail and claimed in copending application Serial No. 432,631, supra. Reference is hereby made to said copending application for a more specific disclosure of the steam generator, minus the automatic blowdown means of the present invention.

As suggested earlier herein, the automatic blowdown means, which includes the blowdown outlet 26 controlled by the oscillatory blowdown valve means 28, bleeds oif impurity-laden water from the accumulator 12 whenever the feed pump 20 is operative to introduce make-up water into the system along the avenue hereinbefore described. Thus, the blowdown rate is always proportional to the make-up rate so that the rate of impurity removal is proportional' to the rate of impurity introduction into the system. Consequently, the impurity concentration level is maintained within acceptable limits for prolonged periods of time with only infrequent necessity for manual blowdown, by means of the manual blowdown valve 94, to completely clear the system of impurity-laden water.

Considering the automatic blowdown means in more detail, the blowdown outlet 26 is connected to a pipe 116 which, in turn, is connected at its other end to the blowdown valve means28, the latter controlling flow from the pipe 116 to a waste pipe 118 leading to a suitable point of disposal for the impurity-laden water, such asasewer. I

The valve means 28 includes a valve body 120 having ports into which the

pipes

116 and 118 are threaded, there being a connecting passage, indicated generally by the numeral 122, which extends through the valve body 120 from the pipe 116 to the pipe 118. Disposed within the valve body 120 and forming part of the passage 122 is a velve seat 124, shown as a separate member pressed into a counterbore 126 in the valve body. valve seat is engageable by an oscillatory valve member 128 having a stem 130 which is of smaller diameter than and extends through the valve seat and through a guide bore 132. The stem 130 of the valve member 128 is connected to a member 134 having an annular flange 136 which serves as a seat for a compression spring 138, the other end of the spring being seated in a counterbore .140 in the valve body 120. As will be apparent, the spring 138 biases the valve member 128 toward the seat 124, and thus tends to close the passage 122 through the valve body 120.

Considering the manner in which the valve member 128 is moved 01f its seat 124, the member 134 is seated against one side of a diaphragm 142 clamped between one end of the valve body 120 and a closure 144. The opposite side of the diaphragm 142 is exposed to the pressure in the pulsation chamber 96, as by means of a pipe 146 threaded into the wall of the pulsation chamber and threaded into the closure 144. Thus, pressure in the chamber 96 tends to unseat the valve member 128, this unseating tendency being opposed by the spring 138 and by the pressure in the steam generating system applied to the outer end of the valve member 128. The area of the diaphragm 142 is sufiiciently large that, whenever pressure pulsations occur in the pulsation Chamber 96 in response to the introduction of make-up water into the system, the valve member 128 is moved off its seat. The distance that the valve member 128 may move off its seat 124, which determines the rate at which impurity-laden water is bled olf from the sys tern, is determined by an adjustable stop means 148 engageable by the outer end of the valve member 128 to limit its movement off its seat. The adjustable stop means 148 is shown as including a threaded stop 150 adapted .to be locked in any given position by a lock nut 152.

Considering the operation of the oscillating blowdown valve means 28, it will be remembered that pressure pulsations occur in the pulsation chamber 96 when, and only when, make-up water is being introduced into the steam generating system, pressure pulsations in the chamber 96 when,and only ber 96 being prevented at other times by the means 108. The pressure pulsations produced in the chamber 96 during the interval of introduction of make-up water cause the valve member 128 to rapidly and repeatedly oscillate between its closed position in engagement with seat 124 and its open position in engagement with stop 150, the position of which determines the rate at which stop impurity-laden water is bled off. Preferably, the stop 150 is adjusted to provide a blowdown rate of 3 /2% to 4% of the evaporation rate. This oscillating action of the valve member 128 results in self-cleaning of t e valve member and its seat 124, whereby operation of the valve means 28 is not adversely affected by the impurityladen water passing therethrough into the waste pipe 118. In other words, this self-cleaning action permits the valve means 28 to maintain a uniform blowdown rate for each intermittent period of time, which is an important feature of the invention.

Another important feature of the invention resides in the location of the blowdown outlet 26, which is shown as including the open upper end of a skimmer duct or tube 154 positioned in the water zone of the accumulator 12. The upper end of this skimmer duet communicates with the water zone in the accumulator below the water lever 46, in a zone where the impurity concentration is relatively high, due to thedischarge of impurities above the water level by the discharge means 42, and due to precipitation of impurities from the feed water introduced by the feed water inlet 18. By locating the inlet end of the skimmer duct 154 in a zone of high impurity concentration in this manner, maximum impurity removal with a minimum of water removal is attained. The skimmer duct 154 extends downwardly in the water zone of the accumulator 12 to, or substantially to, the lower end of the accumulator in heat-transferring relation with the water in the water zone, the lower ,end of the skimmer duct being connected to the pipe 116 leading to the blowdown valve means 28. The water in the water zone is subject to considerable vertical temperature stratification due to the introduction of the feed water into the system by way of the accumulator 12. For example, the temperature at the lower end or" the water zone in the accumulator may be in the neighborhood of 100 F. when the temperature in the upper end of the water zone is of the order of 300 to 400 F.

Consequently, as the water which is bled off passes downwardly through the skimmer duct 154, it is cooled very appreciably due to the temperature Stratification in the water zone of the accumulator, and the temperature of the impurity-laden water discharged into the waste pipe 118 is therefore sufficiently low to permit disposing of it in a sewer, or the like, which is an important feature.

Thus, the present invention prov-ides an automatic blowdown means which discharges impurity-laden water in response to the introduction of make-up water into the system so that the blowdown rate is proportional to the make-up rate to obtain a rate of impurity discharge proportional to the rate of impurity introduction into the system. By using an oscillating blowdown valve means 28, such valve means is self-cleaning so that its operation is not adversely affected by the impurityladen water passing therethrough, whereby the blowdown valve means will operate without attention for prolonged periods of time. Also, by utilizing the temperature stratification in the accumulator 12 to cool the water which is bled off, it may safely be discharged into any convenient means of disposal.

Although I have disclosed an exemplary embodiment of my invention herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims hereinafter appearing.

I claim as my invention:

1. In combination: a closed steam generating system including a boiler, an accumulator and a circulating pump in series; a feed pump communicating with said system for intermittently introducing make-up water thereinto, said feed pump including means for producing pressure pulsations in the make-up water as it is introduced into 'said system; means controlling the introduction of makeup water into said system by said feed pump for maintaining the amount of water in said accumulator substantially constant; and oscillatory blowdown valve means communicating with said'accumulator for bleeding water therefrom, said blowdown" valve means including an oscillatory element for controlling flow from said accumulator, said element normally occupying a closed position and being operable by means responsive to said pressurepulsations to rapidly and repeatedly move from closed to" open position in response to the introduction of make-up water into said system.

2. In combination with a steam generating system: a feed pump communicating with said system-for introducing make-up water thereinto, said feed pump including means for producing pressure pulsations'concurrently with said introduction of make-up water into said' system; means for controlling the introduction of make-up water into said system by said feed pump; and normally closed oscillatory blowdown valve means exposed tosaid means for producing pressure pulsations, and operable rapidly and repeatedly by said pressure pulsations'frotn closed to open position and communicating-with a portion of said steam generating system for bleeding ofi water from said portion in response to the introduction of make-up water into said system by said pump. v

3. In combination with a multi-co'mponent steam. generating system: a feed pump communicating with said system for introducing feed'water thereinto, s'aid' feed pump including a pulsation chamber andincluding means for producing pressure pulsations in 'said pulsation cham-' ber concurrently with said introduction offeed water into said system; means responsive t'oithefamou'nt of water in a component of said system for controlling such introduction of feed water into said system'hy said feed pump; and normally closed oscillatory blowdown valve means connected with said system'and exposed to said pulsation chamber and rapidly and repeatedly operable'from'closed to open position by said pressure pulsations thereinfor bleeding off water from said system in response'to the introduction of saidfeed water intosaid system by said feed pump.

4. A blowdown for a closed steam generating system including a boiler, an accumulator and a.circulating pump in series, said steam generating system also: including feed pump means for'introducing make-up water thereinto, and further including control' means for rendering said feed pump means operative to introduce makemp water into said system whenever the water level insaid accumulator is below a predetermined value and for rendering said feed pump means inoperative to introduce make-up water into said system whenever the water level in said accumulator is not below said predetermined value, said accumulator having an outlet, and said blowdown including: normally closed oscillatory blowdown valve means communicating with said outlet; and means responsive to operation of said feed pump means to introduce make-up water into said system for rapidly and repeatedly oscillating said blowdown valve meansbetween its closed position and its open position each time said feed pump means is in operation.

5. In a steam generator, the combination of: a closed steam generating system including a boiler, an accumulator and a circulating pump in series, sa'id steam'generating system also including normally inoperative feed pump means capable of being rendered operativeto introduce make-up water into said system, and .said' system further including control means for rendering said feed pump means operative to introduce make-up water into said system whenever the water level in said accumulator is below a predetermined value and for rendering said pump means inoperative to introduce make-up water intosaid system whenever the water level in said accumulator is not below said predetermined value, said accumulator having an outlet; normally closed oscillatory blowdown val've'means' communicating with said outlet;'and means responsive to operation of said feed pump means to introduce make-up water into said system for rapidly and repeatedly oscillating said blowdown valve means between its closed position and its open position each time said feed pump means is in operation.

6. In combination with a multi-component steam generating system having a steam outlet, a feed Water inlet and a blowdown outlet: normally' inoperative feed-waterintroducing meansoperative in response to a reduction in the amount of liquid in a component of said system below a predetermined value for introducing feed water into said system through said feed water inlet as required to maintain the amount of liquid in said component substantially constant; and oscillatory means connected with said blowdown outlet and being automatically responsive to operation of said feed-water-introducing means for rapidly and repeatedly effecting opening and closing of said blowdown outlet while said feed-water-introducing means is in operation.

7. In an automatic blowdown for a steam generating system having a water zone, a steam outlet, a feed water inlet and a blowdown outlet, the combination of: normally inactive feed-water-introducing means operative in response to a reduction in the amount of water in said Water zone below a predetermined 'value for introducing feed water into said system through said feed water inlet References Cited in the file of this patent UNITED STATES PATENTS 1,576,889 Wulf Mar. 16, 1926 1,582,148 Stockholder Apr. 27, 1926 1,913,195 Donaldson June 6, 1933 2,317,546 McGrath et al Apr. 27, 1943 2,379,841 Thomas July 3, 1945 2,393,079 Wall Jan. 15, 1946 2,400,290 Clancy May 14, 1946 2,442,281 Arant May 25, 1948 2,573,680 Arnold Nov. 6, 1951 2,800,117 Arant July 23, 1957 FOREIGN PATENTS 931,643 France Nov. 3, 1947 589,016 Germany Dec. 2, 1933 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,921,564 January 19, 1960 George W. Mattox It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below..

Column 6, line 26. for "velve" read valve line 69. str out "her 96 when, and only"; line 75, before "stop" nsert the column 7, line 1, after "which" insert stop l1ne 2, strike "stop"; line 19, for "lever 46" read level 46 Signed and sealed this 12th day of July 1960.

(SEAL) Attest: KARL AXLINE RQBERT C. WATSON Attesting Officer Commissioner of Patents