US2684664A - Boiler feed system - Google Patents

Description

July 27, 1954 H. HILLlER 2,684,664

, BOILER FEED SYSTEM ,Dri ginal Filed March 1, 1949 s Sheets-Sheet 1 PUMPZZ ,9 PUMP6 M QQ vs, 0 v. 5 QQ A Mrzwzav-waawaawaae luvs/v70)? 0.4mm HILL 'IER July 27, 1954 H, HILLIER 2,684,664

BOILER FEED SYSTEM Original Filed March 1, 1949 3 Sheets-Sheet 2 M/VEIV T 0!? HAROLD HILL IE I? July 27, 1954 H. HILLIER BOILER FEED SYSTEM Original Filed March 1 1949 3 Sheets-Sheet I5 PUMP 22 OR 22" PUMPS 22A/VD 22" PUMPS 6" AND a" DISCHARGE PRESSURE LBS PER 30. INCH W47'ER FLOW-GALE. PER HR.

PUMP 22' OR 22" PUMPS 22' AND 22 'PUMPS 6' AND 6" D/SCHARGE PRESSURE 6 LBS. PER 50, INCH WATER FLOW-GALE. PER HR.

l/V VE N TOR HAROLD HILL/ER Patented July 27, 1954 UNITED STATEd TENT OFFICE BOILER FEED SYSTEM Harold Hillier, Glasgow, Scotland, assignor to G. & J. Weir Limited, Cathcart, Glasgow. Scotland, a company of Great Britain and Northern Ireland Claims priority, application Great Britain January 28, 1949 Claims.

This invention relates to boiler feed systems with provision for removing gaseous impurities from the feed water.

This application is a division of my pending application Serial No. 78,960 filed March 1, 1949 for Boiler Feed System now Patent No. 2,656,823

granted October 27, 1953'.

It is known to make use of a deaerating or steam regenerative type condenser for the purpose of deaerating all condensate passing through such condenser, the condensate being thereafter conveyed tothe boilers through a closed feed system wherein the pressure on the discharge side of the condensate extraction pump is maintained substantially above atmospheric pressure so as to avoid any possible ingress of contaminating air. During standing conditions and starting up, and on board ship during rapid 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 deaerator in which it is subjected to deaerating action and from which it is subsequently removed by 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 pref erably takes water from the discharge of the deaerator extraction pump, but can also take water, when necessary, direct from the discharge of the condenser extraction pump. The boiler feed system claimed herein includes a non-return valve in the closed feed line between the condenser extraction pump discharge to the deaerator and the deaerator extraction pump discharge to the boiler feed pump, whereby to prevent the deaerator extraction pump from discharging back into the deaerator. 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 pro-determined 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 water 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 floatoperated water inlet valve on the deaerator, the float 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 water 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 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 vapor 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 1 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 arrangements 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 subjected 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. l 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. 3 shows diagrammatically two or more boiler feed systems in accordance with the invention connected so that they may be operated satisfactorily in parallel;

Fig. 4a. and Fig. 4b illustrate the preferred 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.

reaching the well 3 in the 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 l and the feed heater 8 to the point 9 where it is provided with alternative paths direct to the boiler feed pump H3 or to the deaerating apparatus Ii. The well 3 in the condenser 2 is provided with a float I2 coupled as illustrated diagrammatically to make-up and overflow valves l3 and H3, respectively. When the demand of the feed pump [ii is less than the condensate formation in the condenser 2 and the water level in the deaerator H is high a rise in water level in the condenser 2 takes place operating the float l2 which opens the overflow valve l4 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 E5, the overflow valve H3 and the pipe IE to an external feed tank If. When the demand of the feed pump Ill 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 [2 will open the make-up valve i3, permitting water to pass from the feed tank I! by way of the pipe 16, the make-up valve 13 and the pipe It 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 l0 discharges the water supplied to it by way of the heat exchanger [9, and the boiler feed regulator 25] into the boiler 2 I. Heating steam, which may be bled steam from the main turbine l, or exhaust steam, or heating steam from any source, may be supplied to the heat exchangers 8 and [9.

The deaerator H 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 Rd 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 suction of the feed pump it 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 27. The valve 2? is controlled by the float 28 which follows the water level in the base of the deaerator H. Water passing through the float-controlled valve 2"! passes by way of a heat exchanger 25? into the top of the deaerator i l where it passes through spraying nozzles 38, or perforated plates, into the body of the deaerator which may be provided with spraying trays 3| through which the water cascades to the base of the deaerator. The feed water, in passing through the heat exchangers i and 8, is heated before it is sprayed into the deaerator ii. A certain proportion of vapor, together with any non-condensable gases, is withdrawn from the top of the deaerator l i 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 'valve 42 to the auxiliary condenser 43.

which discharges into the de-vaporizer:29,-the-resultant condensate being drained through a trap 34 into the deaerator l i, 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 36 to maintain a desired predetermined pressure in the deaerator l I.

If the feed pump H! is-driven by a turbine 31,

the exhaust steam from such turbine may be led into the deaerator or a suitable heat exchanger asshown, surplus exhaust steam from the turbine passing by way of a surplus steam valve 38 to the main condenser.

With a suitable selection of the capacity and the discharge pressure of the deaerator extraction'pump 22, all water passing to the boiler feed pump I0 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 H from which it is withdrawn by the deaerator extraction pump 22 and discharged to the suction of the boiler feed pump It). If the capacity of the deaerator extraction pump at any time is greater than the quantity of water required by the boiler feed pump, thebalance will pass backwards by way of the pipe 25, the

pipe 26, and the float-controlled valve 27 into 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 4! which exhausts into the heating steam supply line 35 to the deaerator l I, any surplus steam passing by way of a surplus steam The 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 ll, preferably into the suction of the deaerator supply pump 40.

It will be seen that, in the main condensing system, all water passing through the condenser '2 is subjected to the deaerator 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 B is preferentially diverted through the deaerator l I from which it is removed by the deaerator extraction pump 22 whence it is discharged into the suction of the boiler feed pump to, the arrangement being such that all water passing to the boiler feed pump issubjected to the deaerating effect of v ensured. In the event of derangement of the deaerating plant II the condensate extraction pump 6 can discharge water direct to the suctionof the boiler feed pump Ill through the pipe 25. In the event of the closed feed system being deranged, the boiler feed pump Hi can draw water direct from the feed tank I! by way of the pipe 23, the non-return valve 49 and the pipe 50 connecting to the feed tank 11. 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 thecapacity 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 of smaller capacity. Fig. 2 shows the preferred relative 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 difference in pressure between the vacuum in the condenser and the vacuum in the deaerator, and after allowance is made for this, the deaerator extraction pump 22 is designed for a discharge pressure capacity characteristic 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 atall flows between zero and maximum feed flow. Provision may be made for variable speed of the driver of the deaerator extraction pump 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 pressures at the boiler feed pump suction will be determined by 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 fora common discharge pressure and the fiow required through the boiler feed D p- Assuming, for example, that the boiler feed regulator 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, then the quantity of water passing to the boilers will be equal to OK which is the quantity of water discharged by the condenser extraction pump, which passes through the deaerator, and the quantity of water discharged by the deaerator extraction pump is equal to CL where the quantity OK passes into the boiler feed pump while the quantity KL passes back through the floatcontrolled inlet valve 2'! on the deaerator into the deaerator again. The quantity of water dis charged by the condenser extraction pump 6 is the quantity of water which passes through the boiler feed pump l0, so that, if the feed regulator closes further until noflow is passing into the boiler, the pressure will rise to the line AM at the suction of the boiler feed pump, no water 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 seen that the flow through the deaerator varies between the maximum feed flow OF and a minimum flow ON while the flow from the condenser extraction pump 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 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 deaerating apparatus II. The arrangement is such therefore as to ensure the maximum possible deaeration of all feed water discharged by the boiler feed pump to the boilers.

The characteristic CD may be arranged to be more closely similar to the characteristic AE, or the point of intersection between the two char acteristics may be arranged to be less or greater than the maximum feed flow OF to the boilers.

Referring to Fig. 3, the same numerals are used to designate similar parts except that a prime sufiix is attached to those of the upper system and a double prime suflix 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 several boilers 2| and 2 I and in the quantities of feed water delivered by the respective feed pumps Hi and To look after such inequalities, cross connecting pipes and valves are arranged as shown diagrammatically in Fig. 3. A cross connection is provided between the external feed tanks ll and Il" so that any differences in the weight of water discharged through the external feed tanks H and I1 and through the overflow valves i4 and M" or other sources of supply can balance out through the cross connection 5|.

To permit two or more closed feed systems to be operated in parallel with only one deaerator H or H" 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 H or ii" 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 that the deaerator extraction pump on the deaerator i i or I I" which is in operation can discharge through such connection 53 to any of the several boiler feed pumps l9 and it! which may 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 fiow through the several condenser extraction pumps 6 and 6 will cause the water levels in the condenser wells to rise or fall, thereby causing the make-up valves l3 and. [3 or overflow valves 14 or I l to open and pass water into or out of the several systems, the differences between the systems being levelled out through the cross connection 5| between the external feed tanks H and N. 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 5| is to operate the several feed tanks as one common feed tank. The cross connections 52 and 53 enable any single deaerator H or H" to be in operation or two or more deaerators to be in operation in parallel with a common discharge 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 eficient 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 41), it is preferred that th 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 ca pacity 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 characteristic of th two pumps is as shown by the line AB2, 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.

l'he 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 9 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 with one boiler feed pump in operation.

If there arein 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 pumpv and the characteristic AB of the condenser extraction pump, and, to avoid overloading the deaerator extraction pump in back flowto the cleaerator,. non-return valves 59 and 60 are preferably provided in the system according to Fig. 3 to prevent such an occurrence, the non-return valves 59 and 69 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 is 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 A132 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 (1172 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. la.

For solo operation the condenser extraction pump may be operated along the line AB with the deaerator extraction pump cperating along the line CD. For parallel operation between the two systems, the condenser pump characteristic is lowered to cab with a combined characteristic of M72 in connection with which either a single deaerator extraction pump with a characteristic of AB or two deaerator extraction pumps with a characteristic of A132 can be operated satisfactorily.

Since the capacity and discharge pressure of the deaerator extraction pump or pumps are 10 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 ate 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 2 and subsequently to the deaerating action of the deaerator H, 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.

I claim:

1. 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 to the 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, 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 level in the deaerator and closing on a rise of the water level in the deaerator, and a non-return valve in a portion of the feed line between the entry end of the water supply conduit and the discharge connection from the deaerator extraction pump, said non-return valve being arranged in the feed line to permit flow therethrough toward the boiler feed pump and prevent flow in the opposite direction.

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 having its suction side connected into the lower portion of the condenser for withdrawing condensate therefrom, a boiler feed pump having its discharge side connected into the boiler for delivering feed water thereto, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied to the boiler by the boiler feed pump, a conduit for supplying water to the deaerator from said feed line one end of which is connected into said feed line downstream of the condensate extraction pump, the other end of said conduit being connected into said deaerator, means associated with the deaerator for collecting the deaerated water produced in the deaerator, a deaerator extraction pump having its suction side connected into the lower portion of said means associated with the deaerator for withdrawing deaerated water therefrom and having its discharge side connected into said feed line between the point of connection of the feed line with the suction side of the boiler feed pump and the point where said conduit is connected into the feed line, said deaerator extraction pump delivering deaerated water into the feed line and to the boiler feed pump, a nonreturn valve in the feed line between said points, said non-return valve being provided in the feed line and arranged therein to prevent flow of water from the deaerator extraction pump into the deaerator in the normal operation thereby to avoid overloading the deaerator extraction pump, said non-return valve being maintained in closed position in normal operation by the discharge pressure of the deaerator extraction pump and being opened in the event of failure of the deaerator thereby permitting the condenser extraction pump to discharge directly through the feed line to the suction side of the boiler feed pump, a control valve in said water supply conduit for continuously controlling the flow of water from said feed line into the deaerator, a float responsive to changes in the level of a body of deaerated water, said means associated with the deaerator, said float being operatively associated with said control valve for respectively opening and closing said control valve on the fall and rise respectively of the water level in the body of deaerated water under all conditions of operation, whereby a body of deaerated water is maintained in normal operation for delivery by the deaerator extraction pump to the feed line and the boiler feed pump.

3. A closed feed system as claimed in claim 2, including an external feed water tank, means for conducting the water discharged by the condensate extraction pump in excess of that admitted to the deaerator by the control valve into the external feed tank, and means for passing water directly from the external feed water tank into said water supply conduit upstream of the control valve in said conduit for delivery through the control valve to the deaerator.

i. The method of operating a closed feed water system including a steam boiler, a boiler feed pump, a condenser for the condensation of steam initially generated by the boiler, a condensate extraction pump having its suction side connected into the lower portion of the condenser, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, and a deaerator for deaerating the water to be supplied to the boiler, which method comprises passing a stream of condensate from the condenser into the feed line and from said line under pressure into the upper portion of the deaerator ior deaeration therein, deaerating the stream of condensate introduced into the upper portion of the deaerator, collecting and maintaining a body of the deaerated water produced in the deaerator, passing a stream of deaerated water from said body of water under pressure into the feed line and through the boiler feed pump for delivery to the boiler as feed water therefor, maintaining a higher pressure on the stream of deaerated water than that on the stream of condensate in said feed line under normal operating conditions and preventing the flow of deaerated water in the feed line toward the condensate extraction pump, passing condensate directly through the feed line from the condensate extraction pump to the boiler feed pump in the event the pressure on the stream of deaerated water falls below that on the stream of condensate delivered by the condensate extraction pump, withdrawing air and non-condensable gases from the upper part of the deaerator by applying suction thereto, and decreasing and increasing respectively the flow in said stream of condensate introduced into the upper portion of the deaerator in response to the rise and fall respectively of the level of the body of deaerated water, whereby said body of deaerated water is maintained under normal operating conditions as the source of supply of deaerated feed water for the boiler.

5. A closed feed system for a steam boiler including a condenser for the condensation of steam initially generated in the boiler, an external feed tank, a condensate extraction pump having its suction side connected into the lower portion of the condenser for withdrawing condensate therefrom, a float-controlled inlet valve for said condenser, said valve being closed at an intermediate water level in the condenser base and full open at a lower level to permit make-up water to pass from the external feed tank into the condenser, a floatcontrolled overflow valve for said condenser, said overflow valve being closed at an intermediate water level in the condenser well and full open at a higher level to permit the condenser extraction pump to discharge surplus water to the external feed tank, a boiler feed pump having its discharge side connected into the boiler for delivering feed water thereto, a feed line connecting the discharge side of the condensate extraction pump with the suction side of the boiler feed pump, a deaerator for deaerating the water normally supplied to the boiler by the boiler feed pump, a conduit for supplying water to the deaerator from said feed line one end of which is connected into said feed line down-stream of the condensate extraction pump, the other end of said conduit being connected into said deaerator, means associated with the deaerator, for collecting the deaerated water produced in the deaerator, a deaerator extraction pump having its suction side connected into the lower portion of said means associated with the deaerator for withdrawing deaerated water therefrom and having its discharge side connected into said feed line between the point of connection of the feed line with the suction side of the boiler feed pump and the point where said conduit is connected into the feed line, said deaerator extraction pump delivering deaerated water into the feed line and to the boiler feed pump, a non-return valve in the feed line between said points, said non-return valve being provided in the feed line and arranged therein to prevent flow of water from the deaerator extraction pump into the deaerator in the normal operation, said non-return valve being maintained in closed position in normal operation by the discharge pressure of the deaerator extraction pump and being opened in the event of failure of the deaerator thereby permitting the condenser extraction pump to discharge directly through the feed line to the suction side of the boiler feed pump, a control valve in said water supply conduit for continuously controlling the how or" water 13 14 from said feed line into the deaerator, a float by the deaerator extraction pump to the feed responsive to changes in the level of a body of line and the boiler feed pump. deaerated water, said float being operatively associated with said control valve for respectively e ces fiited in the fi Of this patent opening and closing said control valve on the 5 UNITED STATES PATENTS fall and rise respectively of the water level in the body of deaerated water under all conditions g g fia gfi of operation, whereby a body of deaerated water 2626005 Sebald Jan. 20, 1953 is maintained in normal operation for delivery

Images