US2612112A

US2612112A - Condensate return system

Info

Publication number: US2612112A
Authority: US
Inventors: John G Williams
Original assignee: Cochrane Corp
Current assignee: Cochrane Corp
Priority date: 1947-11-24
Filing date: 1947-11-24
Publication date: 1952-09-30
Anticipated expiration: 1969-09-30

Description

INVENTOR.

X42, AT T 0 R N E s S M M M W G N H O J J. G. WILLIAMS CONDENSATE RETURN SYSTEM Filed Nov. 24, 1947 Sept. 30, 1952 Patented Sept. 30, 1952 tsylv n inp uealt mrnoveni er 24, 1947; serial-'Negz'zsasrs z.8ii'Claims. (chaos-155i I This invention-relates to a condensate return system. In one type of"system-provided for ree turning condensatelto a boilerthere is provided a centrifugal pump-arranged to supply water to the nozzle of an 1 ed1'1ctor,+the suction chamber of which receives 'the condensate-- to be pumped. The pressure recovery" tube of the edrictordischarges through a cooler to the boiler and from the cooler there is-a1so provided -recirculation to the intake of the-centrifugal pump. Thetype or arrangement just described is-in'efiicient since all-bfthe net pumping actionis accomplished by the-jet; the 'latte'rbeing energized by the centrifugal' pump which, however-does not have a' net pumping action on the condensate; 'The cooling-is to insure against too high a temperature in the j et but represents a loss of heat in the water or other liquidreturned to the boiler. The advantage of the system just -described"-is -that it is unnecessary "to provide any automatic devices -to keep-the centrifug'alpump primed.

A second type' of-system has 'been' used -in which the centrifugal pump-is-=located-between the eductor' and the return connection to "the boiler, recirculation being effected from the -outilnhni; (inNi -111iants; Philadelphia, Pas zassignorcto a -:Qcchrane: Germination; a..-;c,orpor ationofi lienn- 1 eductors in parallel,"-

let of a the centrifugal pump to the eductor jet.

sult-"in cavitation at the pump. It was necessary,

I, therefore; to provide a; :control stopping the pump when conditions which would give risetocavita- "tio'n existed. The eontr'olsystemwhich was then required 1 added to the complexity of the system. I gI-n 'accordancew'ith the-present inventiona conde'nsate return:systemis'provided having several-i advantages over the foregoing; In comparison with the second system it involves-the use of a simplepressure responsive valve *as its sole -cofiti'ol element' tc maintain proper operation of "the pump. on the other hand; it invo1ves---the 'fifficiency 'characteristicsbf the second'mentioned systemmcontrast with the first; in that the condensate "is pumped by both the eductor' a'nd the centrifug'al'pump. I .4 v

' In accordancewith the'present-:inventiun th is ialso provided. a cooler in: aapl'oper- 1 tm improvethe operation' of the system without exln t'he icase ofi theisystemof the presentinv'ention it; is aiso possi-ble to' operatetwc or more the valve;

f cssive cooling which: would zonly require the'rurtl'iriadditi'on of :heat :in the boiler'."

draining several sources for condensate which maybe at difierent' pressures. 3 The general objects of the presentinvention will be appreciated 'from theforegoing. and other objects of the invention: particularly relating to details of construction and operation will become apparent from th'e following 'description read in conjunctiomwith' the accompanying drawing in which the figure illustrates in diagram and in fragmentary sectionsthe elements and connections of' a: preferred system embodying the invention.

A boiler with" which the return system is -as sociated is indicated at! and it may beeassum'd that the condensate from-the system is-concentrated in an inletpipel-forreturnto-=the* boiler. 'This inlet pipe imay also receive make-up 'waterl or other liquid in conventional fashion; It will, of course, be obvious that the'system' may handle other liquids as well as water thou gh for 'simf plicity of description itwillbe assumedthat the invention is applied toa conventional steam s'ys ,te v 1' An eductor 5 comprisesth'e suctiorr cha-mber 1i, the water jet nozzle- 8 and'the pressure' recbv 'ery= tube 10. "I'he'latter-is' connectedthrough pipe 12 to the inlet of a centrifugal -pumpf-ll which delivers water through --'the line 6 which a recirculating branch extends i-n--t of a pipe 18, a cooling coil 2.0 --and' a' pipe 24 communicating with the educton no'zz1le. The coilis cooled in any suitable iashion and ma-y, for example, befinned for-air cooling or ma "be water cooled as indicated by the-'-ja'cket-='22'.'

A connection 28 from-the centrifugal; {pump output line I 6 to' the boiler -2 contains a pressure responsive vaive- 26- including i the valvemeinber 30;"- the s-temof which -is connected to a* dia phragm 32 in a' housingprovided-with chambers 36' and 40 connected respectively througli-lines 38 and- 42 to the suction chamber cr me-edema and-to the output side-of the-centrifugal-pump. A spring 34 acting upon an adjustable c6l lar on the valve stem urges the" valve toward closed position. As will be evident-apredetermined'eic'essofpressurein the chamber 40-over 'the 'pre's sure in the chamber 36 -will-be -required' to pen Consideringthe sy'stemsdfar' described; con taining a single educter, thezoperat-ion is 'as 'fol lows: J

-Assurne that opera +011 -is"--takin g--place witha certain 4 quantity of condensate enteringthe *inl'et pipe 4. Obviouslythis sa-n'ie -'quar tifty of' li'" d m "p e' Op ning amne vaiv bm diiferent inlet pressures at the eductors which may be draining condensate near saturation temperatures, it is necessary to apply different rates of cooling to the water passing through the several jets.

In the figure there is shown in construction lines the paralleling of the cooler-eductor combi- V .nation heretofore described "with asecond such adjust itself so that the pressure gain of the.

eductor and of the pump in series will give this 4 required pressure in line 18.

Now assume that the quantity of liquid enter-. 1 x

. :ing the eductor at 4 becomes less. The quantitypassing valve 30 would now be less and the pressure drop across this valve would be less, than before. A readjustment must therefore occur,

the pressure in line l8 now dropping until the lower pressure difference between line l8 and inlet! produces a partial closure of valve 30 to increase the pressure drop for the decreased de- -liv ery of; liquid so as to reattain apressure equi- .::librium as, previously set forth. Under these condi t ions-the pressurein line 18 will be lower than 'Whatis required for proper operationis a large change in'valve position for a small change in the pressure ,inline l8iso that the changes in pressure in line l-B for considerable'changes in quantity of liquidc ltering at 4 will be small, so that the pressure recovery across the eductor is-mainvtained sufficiently high: to preventcavitation at the pump. This end is, of course, secured by providing a weak spring a .34. Y eductor is much less efficient than a cenl i filgal pump, and consequently it is desirable to get therequired pressure rise primarily in'the pump; the eductor is accordingly chosen to secure large-volumetric delivery with little regard for pressure recovery except that sufiici'ent pressure recovery is provided to avoid cavitation even under the condition of no liquid entry at 4. In other words, the system is arranged forcontinuous draining by prevention of cavitation of the pumpat all times, there being then no necessity g-forstopping the pump. 1 I 3 -v 'fhe cooler provided in ,theposition illustrated insures -most efiective operation of the eductor. The suction pressure in the eductor cannot be lower than the vapor pressure of the water used to; energize,the jet. If 'it was lower the jet would explode by flashing action, choking the throat of the pressure recovery tube and preventing .the entrance-of anycondensate tothe suction chamber. Q, The cooler insures thatthetemperature of the wa ter energizing the'jet nozzle is lowerthan theboiling point corresponding .to the pressure atthe suction chamber inlet sothat the jet water maycondense a small-quantity of free vapor and reduce the pressureat the throat of the eductor to-produce a velocity, entrance head for thewater to be pumped. v I, The describedsystem lends itself to muitijet installations drawingcondensate from a plurality of sources, each ctr-which maybe ata difierent pressure 'l he proportions of the Jet and tube in each suction chamber are selected to accommocombination, theelements i8,- 20, 24'; 5, 4 and [2 of which correspond to the unprimed elements previously described. As will be obvious more than two of such combinations may be put in 'parallelJ'The only requirement of any such multiple. arrangement is that the differential pressure regulating valve will have its control connections 'tO the discharge of the centrifugal pump and to theinlet of that eductor having the lowest pressure rise through the tube. In other word'athese control lines will be connected across the lowest pressure of difference between the several drain pressuresand the pressure at the discharge of the centrifugal pump. a

While theoretically, as described above, it is more desirable to apply the required amount of cooling to the water issuing from the jet, in prac- ;tice it may often be found more convenient to v.cooiqthe tcondensateentering the eductor. ,R,e

ducing the temperaturerof the condensateybeing drained is quite effective, z and since the pressures of condensate entering the eductor are relatively low, it is possible many;, times to select a cheaper heat 'exchangerdue to the lower mechanical strength required. Thus the-particular point of cooling is a matter sub ject to exercise; of choice in theinterests of-economy, g a ;It will be evident from the above that a simple system is provided to secure a condensate, return system ofhigh efiiciencyand of proper operating characteristics. It. will be evident that various 'changes may be'made-in thev system as will be evident to those skilled'in-the art without depart- .ing from the scopes-of the'invention as defined in the following claims.-

What I claimand desire to protect byLetters Patent isg; 1 I v 1. A system forthe return of condensate from :a;.plurality of sources to a boiler comprisinga plurality of eductors, each having a nozz1e,.a suction. chamber; and a pressure recovery; tube, the several suction v charnbers being; connected to :receive condensate ;from the respective sources, a pump receivingthe combined discharges from the pressure recovery tubes, connections between the delivery sideiof the pump and said nozzles, .a connection between thegdeliver-y side of the pump and the boilen agpressureresponsive valve inthelast mentioned connection, and-said -pres- .sure responsivevalve-having control connections .to .-t hedelivery side of the pump and-tozthat eductor suction chamber having the highest pres- :sure therein. 3: A system for thereturn of condensatef-rom a plurality ofsources to aiboiler-comprising a pluzralityfofeductors, .each; havin a nozzle, asuc-l j tiong chamber and a pressure, recovery tube, the

, severel -suction chambersrbeingconnected;to re date the source pressure and a given pressure rise ceivecondensategfrom the-respective sources a pump receiving the combineddischarges from the pressure recovery-"tubes, connections between the delivery side of r the. pumpzand said nozzles, a cooler in eachof said connections, a connection between. the delivery side, of. the pump andthe a boiler, a pressurearesponsivegvalve in thBgldSli menti n d nnection; andsaidrpressureresp airs; va e"h ving;c ntmlocqnn c ions'to the and to the suction chamber of the eductor to regulate the pressure at the delivery side of the pump and the pressure at the eductor nozzle in accordance with the quantity of condensate entering the eductor chamber.

4. A system for the return of condensate to a boiler comprising an eductor having a nozzle, a suction chamber and a pressure recovery tube, a pump receiving liquid from said pressure recovery tube, a connection between the delivery side of the pump and said nozzle, a cooler in saidconnection, a connection between the delivery side of the pump and the boiler, and a pressure responsive valve in the last mentioned connection, said valve including valve actuating means connected to the delivery side of the pump and to the suction chamber of the eductor to regulate the pressure at the delivery side of the pump and the pressure at the eductor nozzle in accordance with the quantity of condensate entering the eductor chamber.

5. A system for the return of condensate from a plurality of sources to a boiler comprising a plurality of eductors, each having a nozzle, a suction chamber and a pressure recovery tube, the several suction chambers being connected to receive condensate from the respective sources, a pump receiving the combined discharges from the pressure recovery tubes, connections between the delivery side of the pump and said nozzles, a connection between the delivery side of the pump and the boiler, and a pressure responsive valve in the last mentioned connection, said valve including valve actuating means connected tothe delivery side of the pump and to that eductor suction chamber having the highest pressure therein, to regulate the pressure at the delivery side of the pump and at the eductor nozzle in accordance with the quantity of condensate entering the eductor chamber.

6. Asystem for the return of condensate from a plurality of sources to a boiler comprising a plurality of eductors, each having a nozzle, a

suction chamber and a pressure recovery tube, the

several suction chambers being connected to receive condensate from the respective sources, a pump receiving the combined discharges from the pressure recovery tubes, connections between the delivery side of the pump and said nozzles, a cooler in each of said connections, said. arrangement providing a plurality of parallel groups of coolers and eductors in series with said parallel group in series with the pump, a connection between the delivery side of the pump and the boiler, and a pressure responsive valve in the last mentioned connection, said valve including valve actuating means connected to the delivery side of the pump and to that eductor suction chamber having the highest pressure therein, to regulate the pressure at the delivery side of the pump and at the eductor nozzle in accordance with the quantity of condensate entering the eductor chamber.

7. A system for the return of condensate to a boiler comprising an eductor having a nozzle, a suction chamber and a pressure recovery tube, a pump receiving liquid from said pressure recovery tube, a connection between the delivery side of the pump and said nozzle, a connection between the delivery side of the pump and, the' boiler, and a pressure responsive valve in the last mentioned connection, said valve including valve actuating means connected to the delivery side of the pump and to the suction chamber of the eductor, said actuating means closing the valve when the pressure difference between the delivery side of the pump and said suction chamber is not greater than the shut-off pressure head of the pump and opening the valve when such pressure difference is exceeded by reason of the sum of the pressure gains through the eductor and pump.

8. A system for the return of condensate to a boiler comprising an eductor having a nozzle, a suction chamber and a pressure recovery tube, a pump receiving liquid from said pressure recovery tube, a connection between the delivery side of the pump and said nozzle, a connection between the delivery side of the pump and the boiler, and a pressure responsive valve in the last mentioned connection, said valve including valve actuating means connected to the delivery side of the pump and connected to the suction chamber of the eductor, said valve actuating means acting in response to pressures received through said connections to open the valve only when the eductor is receiving condensate.

JOHN G. WILLIAMS.

REFERENCES CITED The following references are or record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,734,567 Dunham Nov. 5, 1929 1,802,383 Jarvis Apr. 28, 1931 1,930,731 Thompson Oct. 17, 1933 2,159,179 Ringgenberger May 23, 1939 2,435,053 Piccardo et al Jan. 27, 1948