US2609668A

US2609668A - Method and apparatus for pumping volatile liquids

Info

Publication number: US2609668A
Application number: US56127A
Authority: US
Inventors: Thomas N Dalton
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1948-10-23
Filing date: 1948-10-23
Publication date: 1952-09-09
Anticipated expiration: 1969-09-09

Description

Sept. 9, 1952 f, N. DALTON METHOD AND APPARATUS FOR PUMPING VOLATILE LIQUIDS Filed Oct. 23. 1948 N 6 RO M mu R M 0 ,V "H mN A v .A .M O H T% Y B lllllIII'L Patented Sept. 9, 1952 2,609,668 nuance AND APPARATUS FOR PUMPING VOLATILE LIQUIDS Ihomas NlDalton, Leonia, N. 1., assignmtoli he ML W. Kellogg; Company, Jersey Gity, N.- 'J'., a

corporation of Delaware AppIieation-O'ctoberZS, 1948, Serial N0. 56,127

6 Claims,

*Thepresent invention relates to a'niethod and apparatus for pumping liquids; and'm'orepar} domain to a method and apparatus for pumping highly volatile liquids. v 7 v Considerabledifiioulty is experienced in pump: inghighly volatile liquids such as liquidoxygen, liquid hydrogen, liquid ammonia; liquid-butane, liquid propane, eta, due tovapor binding, or cavi tation, at the inlet of the pump effecting the transfer. This vapor binding, or cavitation, is caused by the liquid boiling-at or near the pump inlet, which in turn is the result of the pressure such a transfer system being lowest ator adjacent to the pump inlet. Such vapor bindin of cavitation, not only prevents the effective transfer-of the volatile liquid, but the bubblesof vapor, formed by the liquid boiling, are collapsed; By: the pressure within-the pump when they come in; contact "with the; pumping'surfaces' and this collapse brings aboutf shock and erosion of said pumping surfaces. The abov-e'm'entioned vapor" binding, or cavitation, is evenmor'epronounced when the pump efiecting' the-manner is located at prabove' the level of the volatile liquid being transferred. v

' One object of the present invention'is to pro-- vide an apparatus for pumping volatile liquids.

Another object of the present invention is to provide a method of pumping volatile liquids.

Another object of the present invention is to provide an apparatus for pumping volatile liquidswhereby said liquids are reduced in temperature prior to entering the pump. I

Another object of thepresent invention is to provide a method of pumping volatile liquids whereby said liquids are cooled prior to entering the pump.

Another object of the present invention is to provide an apparatus for pumping volatile liquids whereby a portion of said volatile liquid is used as a coolant to cool another portion of's'aid liquid prior'to its entry into a pump.

Another object of the present invention is to provide a method of pumping volatile liquids whereby a portion of said-volatile liquid is used as' a coolant to cool another portion of said volatile liquid prior to its entry into a pump.

Other objects of the invention will in part, be obvious and will in part appear hereinafter;

The invention accordingly comprises the methd involving the several steps and the relation and order of one or moreof such steps with respect to each of the others and the apparatus possessing the construction, combination of elements and arrangement ofparts which are ex the scope or theapplie'atiohefwhich 2 r emplifledin merouo'w fig detailed discldsure; fr'd will bei'n dicated'in the claiiiis. I

For a fuller understanding "of the nature and objeets of the invention, reference should behad to the following detailed description taken iii con:

neo'tion with the accompanying drawing where in the single figure is a somewhat diagrammatic View partly in'seetion, of an'apparatus'for p'uimfling volatile liquids. V

The present invention comprises an lpba iatus for, and method of,- pumpin volatile liquids whereby vapor binding, or cavitation, in the pump is prevented. bycooling the liquid being pumped immediately Jfilii to its entr iii-to Said pump, and Whereina portion. of the same liquid isftd ployed as the -coolant to effect' saidcooling. In the drawing there is shown a tank I!) con mouse a supply of volatile"liquid I2 undef -15ressill-e Liquid I 2 Contained intank- In 15 mam; tained under a predetermined pressure; by means or r'el-iefyalve' m-mounteai-n the top Oriana t0, and has a temperature correspondin to the vapor pressure in said. tank, A liquid to liquid heat exchanger [8 is Idea-ted. ad acent to, and preferably beneath, tank III. .A preferred form of heat eXcl-ian'g'eris disclosed having a heat ab-- sorbing side or chamber eomprising' a body p"or non 21 adapted 'to contain a; coolant liquid, and" a ceoling side comprising a head end I'QYa daptd' to receive and" discharge the liquid to be cooled;

and "a plurality o'f U' -t'iIbesZl-I mounted in tube sheet and adapted to be i'mm'ersed-in the cool ant liquid in body portion 2 n andtb'co'nd'uct the liquid to be cooled from the inlet-p'or'tion of head end [9 through the coolant to the discharge partan or said head end. ram; [6 isconnected by mean orpipe l'fi'to theinle t' p'ort'fOndf the fie ad end I 9 of heat exchanger [8. The disehafrig'epor-' denof head end i 9 is connected hymen-a er pipe 26 to centrifugal pump; 2-2 The bod-y portion Z'l of heat 'eiichanger' i8 issupplied with coolant from the supply of fluid passing-through pipe 16 from tank ID by means ofa ble't-id'er arrangement comprising a length of pipe 2 3' connectedto' pipe [6, a'solenoid operated valve 2'f5 ada'p t'ed to control the amount of fluidpermittedpopase tlinoughf pipe 24; and a second length oi pipezs' adapted to conductnuid' from solenoid d ted valve & 26th) the body portion 2t of heat exchangeplfl;

The lever of the coolant fluid a-say portion 21 is maintainedate-predetermined constant level.

body portion 2| by pipe'32. Pipe 34 connected to the top of switch 30 and the top of body portion 2| to vent the switch 30 and permit the coolant liquid to maintain the same level in said switch 30 as in body portion 2|. Switch 30 is adapted upon the lowering of the level of the coolant liquid in heat exchanger l8 to close an electric circuit comprising a source of power 36,

electric wires

38 and 40, and the solenoid operated valve 26. When this circuit is closed and the solenoid operated valve thus actuated, the valve is opened to permit a quantity of liquid to pass through

pipes

24 and 28" into body portion 2| of heat exchanger 8 to raise the level of the liquid therein to the predetermined depth at which time float actuated switch 30 opens to break the circuit and cause solenoid operated valve 25 to close.

The volatile liquid l2 which is employed as a coolant in heat exchanger I8 is maintained at a predetermined pressure, considerably lower than the pressure maintained in tank H], by means of relief valve 42 mounted in the top of the body portion 2| of the heated exchanger |8. By maintaining the pressure in body portion 2| of heat exchanger H3 at a lower pressure than the pressure in tank ill the volatile fluid is permitted to evaporate and thu cool itself. The temperature that the coolant fluid is reduced to depends upon the pressure that relief valve 42 is set to maintain in body portion.

The operation of the above described apparatus is as follows. Float operated switch 30, in con-' nection with solenoid operated valve 26 functions to bleed a supply of the volatile fluid i2 from pipe l6 into the body portion 2| of heat exchanger I8. Body portion 2| of the heat exchanger I8 is preferably not completely fllled with liquid l2 but is provided with a space 21 at the top of body portion 2| to permit vapor to separate from liquid 12 and pass out relief valve 42 without an excessive liquid carry-over. Inasmuch as the liquid contained in body portion 2| of heat exchanger I8 is maintained at a lower pressure than the liquid in tank I its temperature is appreciably below the temperature of the liquid in tank I0. Liquid |2 passes through pipe |6 into the entrance portion of the head end ill of heat exchanger I8, and passes from saidentrance portion through U-tubes 23 which are immersed in the cooler liquid of body portion 2| and is thus cooled to substantially the same temperature as the temperature of said cooler liquid. The liquid leaves U-tubes 23 and enters the exit portion of head end l9 and from there passes through pipe 20 into pump 22. Theresults of cooling fluid l2 in heat exchanger I8 is to lower its temperature an appreciable amount while its pressure is maintained substantially the same as it was before cooling. This leaves an appreciable pressure head above the vapor pressure of the cooled fluid. By lowering the temperature of the fluid a predetermined suflicient amount, by means of heat exchanger 8, a sufliciently great differential between the actual pressure of the liquid and its vapor pressure can be provided so that the suction of pump 22 does not lower the pressure of liquid i2 below its vapor pressure. It will therefore be seen that the apparatus of the present invention will eliminate substantially all vapor binding, or cavitation, at the pump inlet and thus make possible the efficient pumping of volatile liquids. It will be apparent to those skilled in the art that it is possible with the apparatus of the present invention, to locate pump 22 above the surface of 4 the liquid in tank ID, if it is convenient to do so.

It will be understood that any convenient and suitable type of pump can be substituted for the centrifugal pump disclosed. Also any type heat exchanger having suflicient capacity to lower the temperature of the liquid being pumped the desired amount, and of suificient mechanical strength to withstand the pressures involved, can be substituted for the heat exchanger disclosed. Furthermore, any suitable means for controlling the level of coolant in heat exchanger 3 can be substituted for float operated switch 30 and solenoid operated valve 26, as for example, a float operated valve.

The method of the present invention for pumping a volatile liquid comprises cooling said volatile liquid subsequent to its leaving the source of supply of said liquid and prior to its entrance into a pump by separating a. portion of said volatile liquid from the main body or stream being pumped, lowering the pressure of said portion to cause it to evaporate and thus lower the temperature of said portion, and employing said portion thus cooled as a coolant to cool said liquid prior to its entrance into the pump.

The above described apparatus can be modifled, to increase its efficiency and prevent heat leaks into the system prior to the entry of liquid l2 into heat exchanger [8, by causing the cold vapor leaving the body portion 2| of heat exchanger l8 through relief valve 42 to pass around pipe 28, valve 26, bleeder pipe 24, pipe I6, and tank It by means of a jacketing arrangement. Such an arrangement would cause the cold exhaust vapors to precool liquid |2 before it entered heat exchanger I8. This precooling of the liquid will permit its temperature to be lowered a greater amount than would otherwise be possible, and thus permit a greater reduction inpressure at the entrance to pump 22 before vapor binding, or cavitation, takes place.

Since certain changes may be made in the above process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An apparatus for pumping volatile liquids comprising, in combination, a storage container for the volatile liquid, a heat exchanger including a heat absorbing side and a cooling side, conduit means connecting said storage container to said cooling side, by-pass means connecting said con duit to said heat absorbing side, means controlling the flow of volatile liquid through said bypass means adapted to maintain a predetermined level of volatile liquid in said heat absorbing side, vent means in said heat absorbing side adapted to-vent said heat absorbing side to maintain the pressure therein at a lower value than the vapor pressure of the volatile liquid in said container,

a pump, and further conduit means connecting.

said cooling side to said pump.

2.. An apparatus for pumping volatile liquids a heat absorbing side and a cooling side, conduit.

means connecting said storage container to said cooling side, by-pass means connecting said conduit to said heat absorbing side, means controlling the fiow of volatile liquid through said bypass means adapted to maintain a predetermined level of volatile liquid in said heat absorbing side, vent means in said heat absorbing side adapted to vent said heat absorbing side to maintain the pressure therein at a lower value than the vapor pressure of the volatile liquid in said container, and further conduit means connecting said cooling side to said pump.

3. An apparatus for pumping volatile liquids comprising, in combination, a storage container for the volatile liquid, a heat exchanger including a chamber adapted to contain volatile liquid and conduit means in said chamber through which volatile liquid is adapted to circulate in heat exchange relation with said contained volatile liquid, vent means adapted to vent said chamber to maintain the pressure therein at a lower value than the vapor pressure of the volatile liquid in said container, a conduit connecting said storage container to said conduit means in said chamber, a pump, further conduit means connecting said conduit means in said chamber to said pump, a by-pass conduit connecting said first conduit to said chamber, and means controlling the fiow of volatile liquid through said by-pass conduit to maintain a predetermined level of volatile liquid in said chamber.

4. An apparatus for pumping volatile liquids comprising, in combination, a storage container for volatile liquid, vent means adapted to vent said storage container when the pressure therein exceeds a predetermined maximum above the vapor pressure of the volatile liquid, a heat exchanger including a chamber adapted to contain volatile liquid and conduit means in said chamber through which volatile liquid is adapted to circulate in heat exchange relation with said contained volatile liquid, vent means adapted to vent said chamber to maintain the pressure therein at a lower value than the vapor pressure of the volatile liquid in said container, a conduit connecting said storage container to said conduit means in said chamber, by-pass means connecting said conduit to said chamber, means controlling the flow of volatile liquid through said by-pass means to maintain a predetermined level of volatile liquid in said chamber to thereby maintain said conduit means in said chamber submerged in said contained volatile liquid, a pump, and a further conduit connecting said conduit means in said chamber to said pump, said maintained chamber pressure being materially less than said predetermined maximum pressure, whereby said contained volatile liquid evaporates at a sufiicient rate to reduce its temperature and thereby cool the volatile liquid circulating through said conduit means.

5. An apparatus for pumping volatile liquid comprising, in combination, a storage container for the volatile liquid, means for venting said container when the pressure therein exceeds a predetermined maximum above the vapor pressure 01 the volatile liquid, a heat exchanger including a chamber adapted to contain a volatile liquid and conduit means in said chamber through which volatile liquid is adapted to circulate in heat ex-' change relation with said contained volatile liquid, vent means adapted to vent said chamber to maintain the pressure therein at a lower value than the vapor pressure of the volatile liquid in said container, a conduit connecting said storage container to said conduit means, a by-pass conduit connecting said first mentioned conduit to said chamber, a valve in said by-pass conduit controlling the flow of volatile liquid therethrough, float controlled means sensitive to the volatile liquid level in said chamber for operating said valve to maintain a level of volatile liquid in said chamber suflicient to submerge said conduit means, said maintained chamber pressure being substantially less than that for said storage container whereby volatile liquid in said chamber evaporates to cool itself and thereby cools the volatile liquid circulating through said conduit means, a pump, and a second conduit connecting said pump to said chamber- 6. The method of pumping volatile liquid comprising, storing volatile liquid in a container at.

a pressure above its vapor pressure, flowing the volatile liquid from the container into the cool side of a heat exchanger, circulating the volatile liquid through said cool side in the form of one, or more, confined streams, diverting a portion of the volatile liquid on its way to said cool side into the heat absorbing side of the heat exchanger and forming therewith a body of volatile liquid completely submerging said one or more streams and in heat exchange relation therewith, maintaining said body of liquid at a pressure below the vapor pressure of the volatile liquid in said container to permit volatile liquid of said body of liquid to evaporate to thereby cool said body of liquid and said confined streams, controlling the quantity of diverted volatile liquid to maintain said body of liquid of substantially constant predetermined height, and flowing the cooled volatile liquid of said stream, or streams, to the inlet of a pump to be pumped thereby without substantial cavitation at the inlet thereof.

THOMAS N. DALTON.

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

UNITED STATES PATENTS Number Name Date 1,371,427 Kerr Mar. 15, 1921 2,021,394 Wade Nov. 19, 1935 2,292,375 Hansen Aug. 11,1942 2,325,931 Avigdor Aug. 3, 1943 2,346,253 De Motte Apr. 11, 1944 2,451,151 Byram, Oct. 12, 1948 FOREIGN PATENTS Number I Country Date 495,795 Germany 1930 668,512 France 1929