US2656823A

US2656823A - Boiler feed system

Info

Publication number: US2656823A
Application number: US78960A
Authority: US
Inventors: Hillier Harold
Original assignee: G&J Weir Ltd
Current assignee: Weir Group PLC
Priority date: 1949-01-28
Filing date: 1949-03-01
Publication date: 1953-10-27
Anticipated expiration: 1970-10-27

Description

Uct. 27, 19753 HlLLlER 2,656,823

BOILER FEED SYSTEM Filed March 1, 1949 s sheets-sheet 1 l,DU/v1.12 22 Mdm Oct. 27, 1953 H. HILLIER 2,656,323

BOILER FEED SYSTEM Filed March 1 1949 3 Sheets-Sheet 2 VvE/vrai? .HAROLD HILL/El? Oct. 27, 1953 H. HILLIER BOILEE FEED SYSTEM 3 Sheets-Sheet 3 Filed March l, 1949 f? 0W -GLS PER HR.

N. w N ,A a. ,A 6 E E E W\ WQ@ rf .a ao.. MZ @.0 [0U 2 P \P M w .6 m ,6 W @AON WATER FL 'PUMPS 6 AND 6"l o /4 ,M f E e f S w U .2 P 2 a m E @E ,2 0\ 2 ft F/ p M /6 E vom .6 P E M .E 6 A a WATER FLOW-GALS PER Hf?.

/fwfwron HAROLD H/LL IER Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE BOILER FEED SYSTEM Harold Hillier, Glasgow,I

Scotland, assignor to G. & J. Weir Limited, Cathcart, Glasgow, Scotland, a company of Great Britain and Northern Ireland Application March 1, 1949, Serial No. 78,960 In Great Britain January 28, 1949 7 Claims.

manoeuvring and port conditions, circumstances may arise in which the deaeration of the feed water is not as good as during steady normal operating conditions. Further, the extremely' high boiler pressures which are now becoming more commonly used necessitate deaeration of the feed water to the greatest possible extent under all conditions of operation Whether standing, in port, warming up, manoeuvring, or in steady operation.

The present invention provides an improved boiler feed system in which the feed Water discharged by the condensate extraction pump to the boiler feed pump passes preferentially through a deaerator wherein a deaerating action is superimposed upon the deaerating action to which the feed water has already been subjected in the condenser. This deaerator may also be used for port service on board ship when the main condensing plant is closed down, either operating in series with an auxiliary' condensing plant or in parallel, as may be preferred.

In accordance with the invention, the discharge of the main condenser extraction pump is connected direct to the boiler feed pump suction and in parallel also to the float-controlled inlet of a deaerator, with the object of passing the discharge of such pump preferentially into the Ideaerator in which it is subjected to deaerating yaction and from which it is subsequently removed lby a deaerator extraction pump which discharges .into the closed feed line nearer to the boiler feed pump suction than the point in the closed feed line connected to the inlet to said deaerator. With this arrangement the boiler feed pump preferably takes water from the discharge of the de` aerator extraction pump, but can also take water,

, when necessary, direct from the discharge of the condenser extraction pump. The relation of the discharge pressure` capacity characteristic of ,the deaerator extraction pump and the .discharge pressure capacity characteristic of the condenser extraction pump is such that up to the predetermined maximum capacity of the deaerator extraction pump the boiler feed pump takes its supply of water preferentially from the deaerator extraction pump discharge. The quantity of wa- 4 ter passing through the deaerator at any given boiler load is determined by the discharge pressure capacity characteristics of the condenser extraction pump and the deaerator extraction pump under the control of a float-operated water inlet valve on the deaerator, the fioat being operated by the rise and fall of the water level in the bottom of the deaerator whereby a fall in the float increases the flow of lwater into the deaerator and vice versa.

Heat exchange apparatus may be provided in the discharge line from the condenser extraction pump for heating the feed water before it can pass into the deaerator, and deaeration may be A effected in the deaerator by the flash of such heated feed water, the boiling pressure in the deaerator being maintained by a connection to the main condenser whereby vapour and noncondensable gases can flow to the main condenser, or by means of a steam ejector which discharges into a condenser from which the air can escape to the atmosphere. An air ejector may be arranged to discharge to the main condenser whereby boiling pressure can be ensured in the deaerator without any heating of the condensate before it passes into the deaerator.

Additional heating steam may be supplied to the deaerator so that deaeration is assisted by heating of the water in its passage through the deaerator, air and non-condensable gases being withdrawn'as mentioned above.

The capacity of the deaerating vessel may be equal to the capacity of the boiler feed pump or the capacity of the deaerator may be less or greater than the boiler feed pump capacity by a predetermined amount. For port use, on board ship,

. a feed supply pump may be arranged to draw Water from a feed tank and discharge through the float operated valve to the deaerator, the arrangement being such that all feed Water to be deaerated must pass by way of the feed tank to the deaerator or from drainage lines direct into the deaerator wherein it is subjected to deaerating action before it is delivered by the deaerator extraction pump to the suction of the boiler feed pump. Feed pumps of different capacity may be available for port use and for sea service, respectively, or there may be provided restriction means whereby under port operating conditions the sea service feed pump is restricted to a capacity not exceeding the capacity of the deaerator. Again, a direct connection may be made from the boiler feed pump suction to the main feed tank through a non-return valve which will normally be kept closed by the pressure of the deaerator and condenser extraction pumps, but will permit the feed pump to draw water direct from the feed tank in case of emergency.

With the arrangement proposed all feed water in normal operation will be subjected to the deaerating effect of the main condenser and subsequently to the deaerating effect of the deaerator whereby the maximum possible deaeration is obtained before the feed Water is delivered by the boiler feed pump to the boilers. In the event of derangement of the deaerator the boiler feed pump will take water direct from the condenser extraction pump, such water having been sub- Y jected to the deaerating action of the main condenser. In the event of derangement of both the condensing plant and the deaerating plant, the feed pump can draw water direct from the feed tank.

The accompanying drawings illustrate convenient arrangements of apparatus according to the invention. Fig. 1 is a diagrammatic arrangement of a closed boiler feed system provided with additional means for deaerating the feed water in accordance with the invention. Fig. 2 illustrates the preferred arrangement of discharge pressure capacity characteristics for the condenser extraction pump and the deaerator extraction pump. Fig. shows diagrammatically two or more boiler feed systems in accordance with the invention connected so that they may be operated satisfactorily in parallel.

Fig. 4e and 4b illustrate the rpreferred arrangements of discharge pressure capacity characteristics for the condenser extraction pump and deaerator extraction pump when operating two or more closed feed systems in parallel in accordance with the invention.

Referring to Fig. 1, the turbine I exhausts its operating steam into the condenser 2 in which the steam is condensed and from which it passes to the base of the condenser inwhich a well 3 is formed. A steam passage 4 is provided from the top to the bottom of the condenser so that the exhaust steam can passfreely to and across the bottom of the condenser, and so that all condensate must pass through such steam before reaching the well ,3 inthe base of the condenser. Air and other non-condensable gases are drawn off through air off-takes 5 arranged substantially remote from the water level in the base of the condenser so that a negligible air pressure exists on `the surface of the water, in the well 3. All condensate passing through the condenser is thus subjected to the deaerating action of the steam in the base of the condenser before it is withdrawn by the condensate extraction pump 6. The condensate extraction pump discharges through heat exchange apparatus such as the air ejector 1 and the feed heater 3 to the point 9 Where it is provided with alternative paths direct to the boiler feed pump I0 or to the deaerating apparatus II. The well 3 in the condenser 2 is provided with a float I2 coupled as illustrated diagrammaticallyv yto y make-up and overflow valves I3 and I4, respectively. When the demand of the feed pump I!! is less than the condensate formation in the condenser 2 and the y Water level in the deaerator II is high a rise in Water level in the condenser 2 takS 131266 Opel" ating the oat I2 which opens the overflow valve I4 and allows surplus water to pass from the condensate discharge line leading from pump 6, after the outlet from the heater 8, by way of pipe I5, the overflow valve I4 and the pipe I6 to an external feed tank I1. When the demand of the feed pump I0 is in excess of the condensate formed in the condenser 2 the water level in the base of the condenser will fall and the float l2 Will open the make-up valve I3, permitting Water to pass from the feed tank I1 by way of the pipe I6, the make-up valve I3 and the pipe I8 into the condenser 2 where the water will be sprayed and deaerated. The make-up water passing into the condenser 2 will fall to the base of the condenser from which the extraction pump 6 will discharge it into the closed feed system.

The main feed pump I0 discharges the water supplied to it by way .of the heat exchanger I9, and the boiler feed regulator 23 into the boiler 2I. Heating steam, which may be bled steam from the main turbine I, or exhaust steam, or heating steam from any source, may be supplied to the heat exchangers 8 and I9.

The deaerator II is provided with a deaerator extraction pump 22 which discharges by Way of a pipe 23 to the closed feed system Where it enters the closed feed system at the point 24. The point 24 is on the down-stream side of the closed feed system relatively to the point 9, so that water discharged by the deaerator extraction pump 22 preferentially flows into the suc tion of thek feed pump I0 and any Water which is not taken by the boiler feed pump I0 passes by way of the pipe 25 and pipe 26 to the deaerator inlet valve 21. The valve 21 is controlled by the float 28 which follows the water level in the base of the deaerator I I. Water passing through the float-controlled valve 21 passes by way of a heat exchanger 29 into the top of the deaerator VII where it passes through spraying nozzles 30, or perforated plates. into the body of the deaerator which may be provided with spraying trays 3l through which the water cascades to the base of the deaerator. The feed water, in passing through the heat exchangers 1 and 8 is heated before it is sprayed into the deaerator I I. A certain proportion of vapour, together With any non-condensable gases, is Withdrawn from the top of the deaerator II and passed by Way of a pipe 32 to the main condenser 2. Alternatively, the non-condensable gases `may be Withdrawn by a steam-operated ejector 33 which discharges into the de-vapouriser 29, the resultant condensate being drained through a trap 34 into the deaerator II, in which latter case, the air and non-condensable gases are discharged to the atmosphere. If desired, heating steam from any suitable source may be passed into the deaerator through a pipe 35 provided with a control valve 33 to maintain a desired predetermined pressure in the deaerator II Y If the feed pump I0 is driven by a turbine 31, the exhaust steam from such turbine maybe led into the deaerator or a suitable heat exchanger as shown, surplus exhaust steam from the turbine passing by way of a surplus steam valve 33 to the main condenser.

With a suitable selection of the capacityand the discharge pressure of the deaerator extraction pump 22, all water passing to the boiler feed pump lil is preferentially taken from the discharge of the deaerator extraction pump 22. When the water in the condenser is at a level between its upper and lower limits, the valve I4 is closed and the water discharged by the condensate extraction pump is constrained to pass by way of the pipe 26 and float-controlled valve 21 into the deaerator Il from which it is withdrawn by the deaerator extraction pump 22 and discharged to the suction of the boiler feed pump i9. If the capacity of the deaerator extraction pump at any time is greater than the quantity of water required by the boiler feed pump, the balance will pass backwards by way of the pipe 25, the pipe 26, and the float-controlled valve 21 into the deaerator H, wherein it is subjected to a repeated deaerating action.

For auxiliary or harbor use there may be provided an auxiliary feed pump 39 and a deaerator supply pump 4D so that in harbour or when the main condenser 2 is shut down, all feed water can be taken from the feed tank l1 by the pump 40 which will discharge the water through the iloat-control1ed valve 21 into the deaerator Il from which the deaerator extraction pump 22 will discharge the water by way of the pipe 23 to the suction of the auxiliary feed pump 39 which will then discharge the deaerated water through the heat exchanger I9 to the boiler. The auxiliary feed pump 39 may be driven by a steam turbine 4I which exhausts into the heating steam supply line 35 to the deaerator H, any surplus steam passing by way of a surplus steam valve 42 to the auxiliary condenser 43. auxiliary condenser 43 may be provided with a condensate extraction pump 44 which discharges any condensate from the auxiliary condenser through a heat exchanger 45 and a pipe 46 to the feed tank i1, preferably into the suction of 1' the deaeratcr supply pump 40.

It will be seen that, in the main condensing system, all water passing through the condenser 2 is subjected to the deaerating action of the condenser 2. Such water is subsequently discharged into the closed feed system by the condenser extraction pump 6 and the arrangement is such that the water discharged by the pump 6 is preferentially diverted through the deaerator il from which it is removed by the deaerator extraction pump 22 whence it is discharged `into the suction of the boiler feed pump l0, the

arrangement being such that all water passing to the boiler feed pump is subjected to the deaerating effect of the main condenser 2 and also the deaerating effect of the deaerator Il, so that the maximum possible deaeration of the boiler feed water is ensured. In the event of derangement of the deaerating plant H the condensate extraction pump 6 can discharge water direct to the suction of the boiler feed pump I0 through the pipe 25. In the event of the closed feed system being deranged, the boiler feed pump I0 can draw water direct from the feed tank l1 by way of the pipe 23, the non-return valve 49 and the pipe 59 connecting to the feed tank I1. The non-return valve 49 is maintained in its closed position in normal operation by the discharge pressure set up by the deaerator extraction pump 22 and the condensate extraction pump 6. Other non-return or check valves are provided in the system and indicated in the same manner as the valve 49, sometimes adjacent to a cut-off valve.

Referring to Fig. 2, it is preferred that the capacity of the deaerating apparatus should be equal to the maximum feed flow through the feed pump, but for economy reasons it may be acceptable to provide a deaerating apparatus oi.' smaller capacity. Fig. 2 shows the preferred rei- The rcharged by the deaerator extraction ative discharge pressure capacity characteristics of the condenser extraction pump and the deaerator extraction pump. Assuming that the condenser extraction pump 6 is designed for a discharge pressure capacity characteristic shown by the line AB, the point E represents the maximum feed flow required by the boiler feed pump. There will be a diiference in pressure between the vacuum in the condenser and the vacuum in rthe deaerator, and after allowance is made for this the deaerator extraction pump 22 is designed for a discharge pressure capacity characteris- "tic such as CD, where CD intersects the characteristic AB at the point E corresponding to maximum feed flow. This ensures that the pressure at the discharge of the deaerator extraction pump will be equal to or greater than the discharge pressure of the condenser extraction pump at all flows between zero and maximum feed flow. Provision may be made for variable speed of the driver of the deaerator extraction rpump so that the discharge pressure capacity `characteristic CD can be raised or lowered as desired. The discharge characteristics AB and CD are measured at the common point 9 in the 'discharge lines after allowance for friction between the respective pumps and the common point 9 in the discharge lines. The pressure at the boiler feed -pump suction will be determined Iby the balancing of the quantity of Water discharged by the condenser extraction pump and the quantity of water discharged by the deaerator extraction pump as determined by their characteristics for a common discharge pressure and the flow required through the boiler feed pump.

Assuming, for example, that the boiler feed reg-ulator 20 closes and reduces the feed flow to the boilers, so that the main extraction pump discharge pressure at the point 9 moves to GHJ,

Ythen the quantity of water passing to the boilers will be equal to OK which is the quantity of Awater discharged by the condenser extraction pump, which passes through the deaerator, and

the quantity of water discharged by the deaera- `tor extraction pump is equal to OL where the quantity OK passes into the boiler feed pump while the quantity KL passes back through the oat-controlled inlet valve 21 on the deaerator into the deaerator again. The quantity of water discharged by the condenser extraction pump 6 is the quantity of water which passes through the boiler feed pump I0, so that, if the feed regulator closes further until no flow is passing into the boiler, the pressure will rise to the line AM at the suction of the boiler feed pump, no Lwater will be discharged by the condenser extraction pump into the deaerator, and the deaerator extraction pump will discharge a quantity equal to ON which quantity will flow back `through the float-controlled valve into the deaerator and will be in continuous circulation :through the deaerating apparatus. It will be jseen that the flow through the deaerator varies between the maximum feed flow OF and a mini- 'mum flow ON while the flow from the condenser `extraction piunp varies from the maximum OF to zero. Since the capacity and discharge pressure of the deaerator extraction pump 22 are always equal to or greater than the condenser extraction pump 6, the water taken by the boiler feed pump will preferentially be therwater dispump and will therefore have been twice subjected to the deaerating action of, first, the maindeaerating deaerator II or II which is in operation condenser and, second. the deaerating' apparatus Hf. The arrangementV is such therefore as to ensure the maximum possibleV deaeration of all feed' water discharged by the boilerl feed pump tothe boilers.

' The characteristic CD may be arranged to be more 'closely similar to the characteristic AE, or the point of intersection between the two characteristics may be` arranged to be less or greater thanthev maximum feed flow OF to the boilers.

Referring to Fig. 3, the same numerals are used to" designate similar parts except that a prime suffix is attached to those of the upper system and a double prime su'ix is attached -to those of the lower system in Fig. 3.

When two or more closed feed systems such as have' been described are required to operate in parallel, there are inevitable inequalities in the quantities of steam evaporated by the severalv boilers 2I and 2 I and in the quantities of feed water delivered by the respective feed pumps I and I0". To look after such inequalities, cross connecting pipes `and valves are arranged as shown diagrammatically in Fig. 3. A cross connection I is provided between the external feed tanks I'I and Il" so that any differences in the weight of water discharged through the `external feed tanks I1 and I1 and through the overflow valves I4 and I4 or other sources of supply can balance out through the cross connection 5I.

To permit two or more closed feed systems to be operated in parallel with only one deaerator II' or II" in operation, a cross connection 52 is provided between the-discharges of the condenser extraction pumps 6 and 6" so that the pumps have a common discharge line to the deaerator II or I I" which is in operation. isolating valves are provided so that, if one deaerator is shut down, all connections to that deaerator are closed, and the condensate is discharged by the condenser pump associated with that deaerator through the cross connection pipe 52 to the other deaerator which is in operation with the other condenser extraction pump.

In the same way a cross connection line 53 may be provided between the discharge lines of the deaerator extraction pumps 22 and 22" so vthat the deaerator extraction pump on the can discharge through such connection 53 to any of the several boiler feed pumps Ill and Ill whichrnay be in service. The said cross connection 53 will enable the several deaerator extraction pumps 22' and 22" to deliver in common to a single boiler 'feed pump or more feed pumps which may be in service. Inequalities in the flow through the several condenser extraction pumps 6 and 6 will cause the water levels in the con- ,denser wells to rise or fall, thereby causing the make-up valves I3 and I3l or overflow valves |45 or I4 to open and pass water into or out of the several systems, the differences between the systems being levelled out through the cross connection 5I between the external feed tanks Il and I1". If there are more than two systems, cross connections are provided between all the several pumps and the several feed pumps. One common feed tank may be arranged to serve several closed feed systems, and, where several feed tanks are used, the effect of using the cross connection 5I is to operate the several feed tanks as one common feed tank. The cross connections .52 and 53 enable any single deaerator II or II to be in operation or two or more deaerators to be'v inoperation infparallel withv a common dis'- charge to any feed pump or feed pumps which are in operation.

The action of the float-controlled valves is such that the whole system is completely automatic from no load to full load and vice versa, and. the operation of the float controls ensures that the pumps in the system have a satisfactory suction head at all times and are constrained to operate at all times along their natural discharge pressure characteristics, while the changes in flow through the deaerator are reduced to a minimum so that the pressure and temperature conditions in the deaerator are the optimum for efficient deaeration and the satisfactory operation of the pumping units.

The deaerator may be operated without any additional heating and to ensure adequate deaeration there may be provided an ejector 58 to withdraw the air and non-condensable gases from the deaerator and discharge to a suitable place under vacuum such as the main condenser 2.

Referring to Figs. 4a and 4b, it is preferred that the capacity of the deaerating apparatus should be equal to the maximum feed flow through the pump but for economy reasons it may be acceptable to provide a deaerating apparatus of smaller capacity. Figs. 4a and 4b show preferred relative discharge pressure capacity characteristics of the condenser extraction pumps and the deaerator extraction pumps suitable for the parallel operation of two or more closed feed systems in accordance with Fig. 3.

Referring to Fig. 4a, the condenser extraction pump discharge pressure capacity characteristic is shown by the line AB, where point E represents the maximum feed flow required by the boiler feed pump of one system. If two condenser extraction pumps are in service in parallel operation, the combined discharge pressure capacity Vcharacteristic of the two pumps is as shown by the line ABZ, where point E2 represents the combined maximum feed flow required by the boiler feed pumps of the two systems. If one boiler feed pump only is in service, the pressure developed by the combined condenser extraction pumps at the maximum feed flow for that boiler feed pump is as shown by the point P.

The deaerator extraction pump is preferably designed for a pressure capacity characteristic such as CD, where CD intersects the maximum feed flow line at the point Q, where this point is equal to or greater than the point P. This ensures that the pressure at the discharge of the deaerator extraction pump will be equal to or greater than the discharge pressure 0f the Vcondenser extraction pump at all flows between zero and maximum feed flow with one boiler feed pump in operation.

If there are in operation two boiler feed pumps and two deaerator extraction pumps, the combined characteristic of the two deaerator extraction pumps will be as shown by the line CD2 where Q2 is the discharge pressure of the two pumps at the maximum feed flow corresponding to two boiler feed pumps in operation,

It will be seen that there is a considerable difference in pressure between the discharge pressure capacity characteristic CD of a deaerator `extraction pump and the charatceristic AB of according to Fig. 3 to prevent such an occurrence, the

non-return valves

59 and 60 being maintained in their closed position in normal operation by the discharge pressure set up by the respective deaerator extraction pumps 22 and 22 which are in excess of the discharge pressure of the respective condenser extraction pumps 6 and 6". In the event of a failure of either or both deaerating plants, the non-return valve or valves will open and permit the condenser extraction pump or pumps to discharge direct to the suction of the boiler feed pump or pumps.

Referring to Fig. 4a, it will be seen that there will be a difference in pressure between the characteristics of the deaerator extraction pumps and the condenser extraction pumps under any conditions of working which will maintain the said non-return valve in the closed position during normal operation.

Referring to Fig. 4b, the conditions illustrated in Fig. 4a may in some systems result in excessively high discharge pressures from the deaerator extraction pump. The condenser extraction pump driver may therefore be provided with means whereby the speed of that pump can be varied.

The line AB shows the discharge pressure capacity characteristic for the condenser extraction pump when operating under the solo system, the line AB2 representing the combined characteristic of two condenser pumps operating in parallel. Means is preferably provided for varying the speed of the condenser pump, so that the combined characteristic is lowered to db2 where ab is the characteristic for each pump operating alone. This will enable the deaerator extraction pump to be operated at a discharge pressure capacity characteristic corresponding to CD with a combined characteristic for two pumps corresponding to CD2, the said characteristic being substantially lower than the corresponding characteristics in Fig. 4a.

For solo operation the condenser extraction pump may be operated along the line AB with the deaerator extraction pump operating along the line CD. For parallel operation between the two systems, the condenser pump characteristic is lowered to ab with a combined characteristic of abZ in connection with which either a single deaerator extraction pump with a characteristic of AB or two deaerator extraction pumps with a characteristic of ABZ can be operated satisfactorily.

Since the capacity and discharge pressure of the deaerator extraction pump or pumps are always equal to or greater than the condenser extraction pump or pumps, the water taken by the boiler feed pump will preferentially be the water discharged by the deaerator extraction pump and will therefore have been twice subjected to the deaerating action of, first, the main deaerating condenser and, second, the deaerator. If necessary, the boiler feed pump can take water direct from the condenser extraction pump discharge.

The systems above described operate entirely automatically from no load to full load, the iioat controls operating to ensure that the several pumps in the system have a suction head at al1 times greater than that at which they will operate satisfactorily, and the pumps are constrained to operate at all times along their natural discharge pressure capacity characteristics. Under normal operating conditions, the whole of the water discharged to the boilers is first subjected to the deaerating action of the condenser j ing the water normally supplied to 10 2 and subsequently to the deaerating action of the deaerator I I, and any surplus of water discharged by the respective pumps is subjected to a repeated deaerating action before passing to the boiler feed pump for discharge to the boilers.

It is to be understood that the apparatus shown may be modified in detail and that the constructions illustrated and described herein are typical convenient forms.

What is claimed is:

1. A closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler and having a condensate well, a condensate extraction pump connected into said Well, a boiler feed pump having its discharge connected into said boiler, a feed line connecting the discharge of the condensate extraction pump with the suction side of said boiler feed pump, an external feed water tank, a conduit connecting said tank and said condenser, a valve intercalated in said conduit, a float in said well controlling said valve whereby said valve is closed at an intermediate water level in the condenser well and full open at a lower level to permit passage of makeup water from said external feed tank into said condenser, an overflow conduit leading from said feed line and communicating with said tank and having a valve therein, said float controlling said valve in the overflow conduit whereby said over'- flow valve is closed at an intermediate water level in the condenser well and full open at a higher level to permit the discharge of surplus water to said external feed tank, a deaerator for deaeratsaid boiler,` a deaerator extraction pump connected into said deaerator and having its discharge conduit connected into a portion of said feed line for delivering deaerated water to the suction side of said boiler feed pump, a water supply conduit from said feed line to said deaerator for conducting water from said condensate extraction pump to said deaerator, the deaerator extraction pump discharge conduit being connected to a portion of the feed line between the suction side of the boiler feed pump and the entry ends of the water supply and overflow conduits from the feed line, and a neat-controlled water inlet valve in said water supply conduit responsive to changes in the Water level in the deaerator, said last-mentioned valve opening on a fall of water level in said deaerator and closing on a rise of water level in said deaerator.

2. A closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler, a condensate extraction pump connected into the lower portion of the condenser, a boiler feed pump connected into the boiler, a feed line connecting the discharge of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied tothe boiler by the boiler feed pump, a deaerator extraction pump connected into the lower portion of the deaerator and having its discharge connected into said feed line, a water supply conduit one end of which is connected to said feed line upstream of the discharge connection from said deaerator extraction pump and the other end of which is connected to said deaerator, and a float-controlled water inlet valve in said water supply conduit connected into the deaerator responsive to changes in the water level in the deaerator, said valve opening on a fall of the water ll level in the deaerator and closing on a rise of the water level in the deaerator.

3. The method of operating a closed, feed water system including a. steam boiler, a, condenser for the condensation of steam initially' generated bi' thev boiler anda deaerator for deaerating the water to be supplied to the boiler, which method comprises passing a stream ofcondensate from the condenser into the upper portion of the deaerator for deaeration therein. maintaining. a bodyfof deaerated water in the lower portion. of the deaerato-r, passing Aa stream of deaerated water from the lower portion of the deaerator. passing a portion of said last-mentioned stream under pressure into the boiler asfeed water therefor rand passing the remaining portion or said last-mentioned stream through a conduit into the stream of condensate nowing from the condenser to the dcaerator, deaerating the. combined stream. introduced into, the upper portion of the deaerator comprising the strearn of condensate frorn. the condenser and said remaining portion of; the stream of deaerat.ed water; passed from thev lower portion of the deaerator, withdrawing air and non-condensable gases from the; upper lltlt. of the. deaerator by apply-ingsuction thereto, and deoreas and increasing respectively the, `flow in said combined stream. introduced into the upper portionof the ldeaerator in response to the, rise and fallqrespectively of the level. of the. body of decorated water 1 -n. the lower por-tion ci the deaerator, whereby said body of deaerated water is, maintained in the lower portion of the deaerator as the source of supply of. deaerated feed Water for the boiler- 4,... A. closed feed 'system as claimed in claim 1, including-means `for passing water directly from said feed Water tankA into. said water supplyv oonduit. upstream-of the. float-controlled'valve in said water supply cond-uit.

5. fiA Closed feed system for a. steam Aboiler Ainl-.uding a, Condenser for the condensation of steamA initially generated in the boiler, a conde.rasatev extraction. pump having its. suction side connected intothelower portion of the condenser fOr' withdrawing condensate therefrom, av boiler feed; p11-.inn having its4 discharge side connected into the boiler fondelii/.ering feed water thereto, l-ineconncctng' the discharge sdeofthe condensate extractionpump with the suction eide of. the boiler feed pump, a deaerator for deaerat'-y ing the water normally supplied to. the-boiler by the boiler feed pump, a conduit for supplying water tothe deaerator from said feed line one end Vof which is connected into said feed line. downstream of the condensatevextraction .pump the other end of said conduit being connected into. said. deaerator, a deaerator extraction pump having its suction side connected into the `lower portion of the deaerator for withdrawing dea'erated Water therefrom and having its dischargev side connected into said feed line between the point ofconnectijon "of the feedlne with the sucl2 tion side of the boiler feed pump and the point where said conduit is connected into the feed lille., said deaerator extraction pump delivering deaerated Water from. the deaerator into the feed line and to the boiler feed pump and forcing any delivered deaerated water in addition to that necessary to supply the boiler through said feed line and into the conduit for supplying water to the deaerator, a valve in said water supply conduit for continuously controlling the flow of water from said feed line into the deaerator, a. float in the lower portion of the deaerator responsive to changes. in the level of the deaerated water in the` lower .portion of the deaeratonsaid float being' operatively associated with said valve for respectively opening and closing said valve von the fall and rise respectively of the water level in the lower portion of the deaerator under all conditions of operation, whereby a body of de- ,f aerated water is maintained in the lower portion or" the deaeratcr for delivery by the'deaeratorextrac-tion pump 4to the feed line and the boiler feed pump..

6. The method of yoperating a closed feed water system including a steam boilerL a condenser for the condensation of steam initially generated by the boilerV and a deaerator for deaerating Vthe water to be supplied kto the boiler,` which method comprises passing a stream of condensate from the condenser into the upper Aportion of the deaerator to Vbe deaerated,passing a. stream of: deaerated water from the lowerv portion of the deaerator, passing aportion of thedeaerated water of said last-mentioned stream under pressureinto the boiler as feed water .therefor and passingthe remaining portion thereof through aconduitntu thel stream, of condensate flowing from the com denser to the deaerator, withdrawing air and non-condensable `gases from the upper part. .of the, deaerator by applying suction thereto, and deaerating the. combined stream introduced intothe upper portion o'f the deaerator .comprising the stream of condensate from the condenser and'said rernaningportion of the stream of dee aeratedA water passed from the lower vportion ,of the deaerator.

"7.; The method'as'claimedjin claim 6.'inoluding maintaining Va, bod;rl of deaerated water in the. lower portion ofj 'the deaerator as a source of supply of deaeratedj'feed'water for. the` boiler, and: introducing heating steam into the deaerator..

HAROLD I References Cited in 'the file. of this patent UNITED STATES PATENTS Number 'Name Date 1,216,747 |leuggart Feb. A'20., 191:7 1,9Q'k735. Campbell May-9j1933 1,932,485 Roe Oct'. 3l, 1933 1,991,929v Hillier Feb. 19:,"1-9'35 ZZ'lAlB; 'Hillier AMar. `13, 1945` 2,388,3444 'Sebard Nov. 6, v1945"