US3005417A - Pneumatic system for pumping liquid - Google Patents

Description

Oct. 24, 1961 w. A. swANEY PNEUMATIC SYSTEM FOR PUMPING LIQUID 2 Sheets-Sheet 1 Filed April 26, 1957 Oct. 24, 1961 w. A. SWNEY PNEUMATIC SYSTEM FOR PUMPING LIQUID '2 Sheets-Sheet 2 Filed April 26. 195'? WWA. mA l MW /l/.S ATTORNEY 3,005,417 PNEUMATIC SYSTEM EUR PUMPING LIQUID William A. Swaney, Pittsburgh, Pa., assigner to United States Steel Corporation, a corporation of New Jersey Filed Apr. 26, 1957, Ser. No. 655,271 7 Claims. (Cl. 10S- 238) This invention relates, as indicated, to a pneumatic System for pumping liquid and, more particularly, to a system for pumping corrosive and abrasive materials at relatively high temperatures and pressures.

In many chemical processing operations requiring the transfer of liquid from one location to another, the liquid to be handled will often have such abrasive and corrosive properties that it is not adapted for handling by gear pumps or other forms of conventional pumping equipment. In addition its characteristics may be such that its handling by such equipment will result in uncontrollable pressure pulses and deviations in rate of ow of a nature which may make control of temperature or other processing factors extremely difficult. As an example of one highly abrasive and viscous liquid for which the pumping system of this invention is particularly adapted, mention may be made of pitch produced as the residue of a coaltar distillation procedure.

One of the principal objects of this invention is, accordingly, to provide a system which is especially adapted for pumping highly abrasive and viscous liquids at high pressures without pulsation or variation in the rate of ow. A further and related object is to provide a pumping system of this character in which a gas under pressure is used to pneumatically pressurize liquid and force it from one location to another. A still further object is to provide a system in which an inert gas such as nitrogen is utilized as the pneumatic pressurizing medium.

To the accomplishment of the above and other ends, the pumping system of this invention, according to a preferred embodiment, is comprised of at least two, preferably three, feed tanks which are filled with the liquid to be handled and then pneumatically pressurized to pump it through a delivery conduit. ln a manner to be described, each of the feed tanks is provided with an identical arrangement of valves for effecting the liquid filling and feeding operations thereof. In addition each of the tanks is provided with upper and lower limit switches, which are responsive to the level of fluid in the feed tanks, and a motor driven controller operated in a timed manner for actuating the feed tank valves to effect a sequential discharge or feeding operation thereof. More specifically the valve control mechanism, which includes the level responsive limit switches and the controller, operates in such manner that emptying of one of the feed tanks initiates discharge of fluid from a succeeding tank, with the valve control mechanism thereafter operating to fill the tank which has emptied with fluid and to pneumatically pressurize such fluid therein as an incident to its being conditioned for a subsequent cyclical and sequential feeding or pumping operation.

Other objects and advantages of theY invention will become apparent from the following description and the accompanying drawings, in which:

FIGURE 1 is a diagrammatic showing of a preferred embodiment of a pneumatic system for pumping liquid in accordance with the principles of this invention;

FIGURE 2 shows an interlocking control circuit for effecting sequential operation of the pressure tank feed valves of the system shown in FIGURE l; and

FIGURE 3 is a diagrammatic and developed showing of one of the timed controllers associated with each of the pressure fced tanks in the system of FIGURE 1 which illustrates somewhat graphically the manner in 3,005,417 Patented Oct.` 24, 1961 which it provides a timed and sequential energization of the control circuits for the filling and feeding valves.

As shown in FIGURE l of the drawings, the preferred embodiment of the pneumatic pumping system of this invention is comprised of three pressure feed tanks A, B and C. In a manner to be described, these tanks, after being filled with liquid to be pumped, are pneumatically pressurized to force the liquid therein under pressure through a delivery conduit. The feed tanks are sequentially operated and connected with the delivery conduit in such manner that it is always connected with and receiving fluid from at least one tank while the remaining tanks are being filled and conditioned for a subsequent liquid feeding operation. Although this can be accomplished by a system having only two pressure feed tanks, the use of three feed tanks is preferredfsince this number reduces the size of the tanks and thereby the cost of the apparatus for a given pumping capacity, facilitates the intermediate operations of filling and pressurizing the tanks, and provides a smoother transition of the liquid feeding operation from one tank to another.

Each of the tanks A, B and C has identical apparatus for controlling its liquid filling and feeding operations and, in the following description, identical elements therein have been given .similar designations. Each tank control apparatus includes four valves, a till valve 1, a vent valve 2, a pressurizing valve 3, and a feed Valve 4, which are normally closed and are actuated to open position in response to energization of control windings R. Energization of the windings R is under the control of a timed controller 5, a bottom limit switch BLS, and a top limit switch TLS. The limit switches BLS and TLS are actuated in response to the level of liquid in the tanks with which they are associated and are preferably float actuated. The switches BLS are normally open switches, which are closed in response to the level of the liquid falling to a predetermined level, and the switches TLS are normally closed switches, which are opened in response to the liquid rising to a predetermined level. Each controller 5 is operated by a clock motor M which is started and continues to run upon energization of its control winding R. In the following description and in the drawings, small case letters a, b, and c used as a sux indicate the pressure tank with which the different control elements are associated and the use of the letter R as a prefix to a numeral indicates the winding controlling the operation of the element designated by such numeral.

The system of this invention is adapted as shown in FIGURE 1, for example, to pump fluid continuously from a reservoir 6 through a delivery conduit 7 which has a throttle valve 8 for regulating the rate of liquid flow. The feed valves 4 when opened upon energization of their respective control windings R provide connections between the feed tanks, A, B and C and a manifold 9 which delivers the fluid through the valve 8 to the delivery conduit 7. To fill the feed tanks, the fill valves 1 when opened upon energization of their respective control windings R provide connections for the feed tanks with a fluid supply manifold 10. The manifold 10 is connected with a return conduit 11 and cooperates therewith to provide a fluid circuit through which fluid is circulated from the reservoir 6 by a centrifugal pump l2. A normally open valve 13 in the return conduit 11 hasV a control winding 13R effective upon energization for operating it to its closed position. Energization of the winding 13R is effected in conjunction with energization of the windings R for the fill valves 1 in a manner to be described such that the valve 13 is closed each time one of the ll valves 1 is opened. Closure of the valve 13 in this manner causes all of the fluid being pumped by the centrifugal pump 12 through the manifold to be diverted through the aou-5,417

. 3 open .till valve l into .the feed tank with which .itis connected.

A closed pneumatic circuit, preferably using nitrogen as apressurizingmedium, is .utilized for'pressurizing the spacesi14 at'the upper Vendsiof the feed tanksA, .E and C incident to .liquid feeding 'andiiilling operations thereof. This circuit comprises ian exhaust manifold ,E5 which is connected withthespaces 14 by the vent valves 2. A con- 'duit 16 connects the manitoldlS 'toalow pressure reservoir.17 in which a supply 'ofinitrogen is maintained at a fconstant pressure. Make-upnitrogen isfcd to the reser- -voir 17 .from supply cylinders ll'through -a regulating .valve i9 which ispre'ferably 'adjusted to provide a pressure as indicated of about 15.pounds per .square inch in 'the reservoir 17. The reservoir 17 vsupplies nitrogen to a pump 20 through a conduit v2l which is provided with a Scheck valve -22 for preventing-feed back into the reservoir.17. Thepump 20 compresses and delivers the nitrogen through a conduit 23 to a high 'pressure reservoir 24. 1A regulating valve 12S in the 'conduit 23 is adjusted to -provide a pressure `in the reservoir Z4 of about 1000 pounds per square inch. yThe reservoir 24 supplies nitro- 'gen under high pressure toa manifold 26 which is connected through the pressurizing -valves 3 With'the spaces 1'4in the lfeed tanks A, B `and C. -A closed pneumatic circuit of this character, using nitrogen gas as a pressurizing medium, is preferred since nitrogen will not adversely *aect many liquids to be pumped such as some petroleum iand coal-tar derivatives. In the case of liquids which are not adversely affected by air, the reservoir 17 and its connections with the vpump 2t) 'and the exhaust manifold l5 "may be omitted.

FIGURE 3 shows schematically the circuits for the "control windings -R of the valves t-dvand timer motor M "fat the unit C and the manner in which such circuits are energized Aby the controllers 5. In this showing the controller Vv5c isillustrated diagrammatical-ly `as comprising'a `drum switch 27 whichhas been unwrapped and shown in '.'plan in the'manner of'a circularcarn development. it has fa circumferential lengthof 360 between the-start (0 min.) "and=stop (l min.) points indicated onthe time scale at ivthe top of this iigureand Athe clock motor upon starting thereof is adapted to rotate it one revolution, or 360, 'from its'start point to itsstoppoint. The drum'svfitch 27 carries five conductor `barsor contacts, designated t-ZS which have 'different arcuate. lengths and have electrical :contacting engagement with stationary contacts 28 as they 'are rotated relative thereto by the'drum 27 'for different Ytimes and intervals'correspondingto their respective locations kand arcuate lengths. yThe arcuatecontacts tit-t and the circuits connected'with the contacts '28 are polarized asindicated andare Vthus energized when connected for the purposesdesignated at'theright of FIGURE 3. 'the vdrum switch 27 is a conventional structure which per se forms no part of this invention and it will'be'understood Athat'other forms of conventional timerswitches, such as disc or cam-operated switches, may be employed for this purpose.

The manner in which the controllers 5 and circuits operated thereby control the filling and pressurizing of the tanks A, Band C will be best understood from an explanation of the operation of the timer 5c for the condition shown in FIGURE l. In this showing the level of liquid the tanks A, B and C indicates that tank A has been illed and pressurized, tank B is being lled, and tank C is being discharged and almost empty. As the level in tank C moves downwardly, float limit switch BLSc closes and, referring to FIGURE 3, energizes control'winding RMC to start clock motor Mc. Just prior to starting clock motor Mc, it will be noted that valve 4c is open by reason of its control winding Ric being energized through drum contact t2, and the space 14C is pressurized by reason of control winding R3c for pressure valve 3c'being energized through contact t5. With both WH'ClIigs`R4C aI1d`R3C i energized, the contents of tank C will be discharging into the manifold 9 connected to the delivery conduit 7.

After starting motor Mc by closure of float switch BLSC, Such switch stays closed until filling of the tank C is initiated to raise the level ot liquid therein. Betoreiilhng of tank C is started, moto-r holding Contact t1 will have completed Van energizing circuit through coil Rit/ic .so that subsequent opening of switch BLSc will not interrupt the operation of motor Mc which wiil continue to operate through the l0 minute cycle indicated. At the end of the l0 minute interval, contact tt will disengage from its stationary contact and deenergize coilRMc to `stopinotor Mc with the drum switch `in the position shown .in FiGURE 3.

After operation of timer Seis .initiated 'as explained above, feed tank C will continue for a period of Bseconds to discharge liquid through its 'open discharge valve 4c into the delivery manifold. At the end of this interval, winding Rdc is deenergize kas the result of timer contact t2 moving out or engagement with the Contact .23. Opening of the energizing circuit for the winding'lic of course results in valve-4c reverting to its closed position to disconnect tank `C with respect to nianioid 9. Momentary -deenergization of Rdc causes holding contact 3de, which is indicated by the broken line 'asbeing operated in response to energization of coil Rdc, to open so that subsequent engagement of .contact t2 with stationary contact 2.8 will not reenergize coil Rec, until called on to do so by limit'switch BLSb in a manner to be described. A few seconds later, Vcontact t5 Vdisengages from `contact 28 to deenergize coil RSC and thereby close valve 3c to disconnect tank'C from the pressurizing manifold 26.

At the end of an interval of 45" Yafter starting of'motor Mc, contact t3 operates to energize RZC which Opens valve 2c to connect the space 14C with the low pressure vent manifold 15. This reduces the pressure in the space 14e and conditions .the tank C for iillingwith huid upon opening of fill valve lc and closure `of lvalve 'i3 in 'a manner to be described. With reference toFiGURE 3, it will be noted that the contact t3 has -a length of about 3 minutes and 30 seconds, and this'iuterval is used in the preferred practice 'of the invention to effect a very slow opening movement of the valve 2c and thus a gradual venting of the pneumatic pressurizing medium in the space 14e to the reservoir 17. Gradual venting in this manner may be effected by using va conventional slow acting valve arrangement comprising, for example, an air operated diaphragm valve for connecting the space 14C to the manifold 15, an expansion chamber for supplying air to the diaphragm valve for atfecting its actuation, and a solenoid actuated air valve responsive to energization of the coil R20 for bleeding air into the expansion chamber and `gradually building up the pressure therein. With a valve arrangement of this character, the opening movement of the diaphragm valve will be proportional to the 'size of the expansion chamber and the rate at which air pressure builds up therein. A similar slow operating valve arrangement is preferred for use as the pressurizing valves 3.

t about the time contact t3 operates'to deenergize coil RZC and close vent valve 2c, timing contact t4 operates to energize a circuit which includes 'coils Ric and vpump 12 is returned to the kreservoir 6 through return conduit l0. With reference to the ll circuit for the'co'il 1c in 'FIGURE 3, it will be understood that the similar circuits for the ll coils operated by the `timers 5a and 5b include a coil 13R which is energized to-close the vvalve 13 when either of the tanks A or VB is to be filled.

After-ffillings-fthe tank C,I the conta-ct t energzes contact t1 moves out of engagement with the contact 28 connected to motor operating coil RMC. Motor Mc thenv stops -with the drum 27 in its` zero position as shown in FIGURE 3. In this position, contact t2 is connected with` the circuit for coilR4c and this circuit will be energized to: open feed. valve 4c and repeat the emptying' and ill'- cycle of tank C in response to emptying of tank B and, closurey of limit switch BLSb. As explained above,

energization of coil Rlc by closure of'BLSb is effective to establish a holding circuit through holding contact 31a which closes in response to. energi'zation of coil R40.

From the. foregoing, it will be` apparent that theY bottom limit; switches BLS interlock the operation of the tanks by placing a succeeding tank on feed in response to emptying of another tank. This is accomplished by an interlocking; energizing circuit of the type shown diagrammatically in FIGURBZ. This: 'gure shows the; energizing circuit for each of the feed valve control coils R4. The coil Rdc is connected across the line L1--L2 by limit switch BLSb as explained above; the coil R411 by limit switch BLSc; and the coil R4!) by the limit switch BLSa. From this, it will be apparent that emptying of tank A places tank B on feed; emptying of tank B places tank C on feed; and emptying of tank C places tank A on feed. Intermediate the times of emptying and being placed on feed, the controller 5 for each tank takes over and effects the filling and pressurizing operations essential to condition it for a subsequent feeding operation as explained above.

Since the valves 1-4 and their control windings and energizing circuits therefor have been shown diagrammatically, it will be appreciated that such showing does not provide safety interlocks for preventing untimely operation of the system components or signal elements for indicating the operating condition of the apparatus. In cornmercial embodiments of the pumping system of this invention, interlocking safety controls are required to insure opening and closing movements of the valves 1-4 in a predetermined sequence. In addition, signals in the form of lights and audible alarms should be provided to indicate the operating condition of the apparatus and to warn of improper operation resulting, for example, from a sticking valve. The provision and operation of signals and safety controls of this character require the use of control relays in the energizing circuits for the control windings R. Accordingly it will be appreciated that such windings, in commercial embodiments of the invention, will not as a general rule respond directly to the feed tank operations or actuate the valves 1-4 directly as shown diagrammatically in the drawings, but will operate through intermediate relays and control circuits. While modifications for these and similar purposes are contemplated and have been used in the practice of this invention, they do not involve a departure from the essential principles of the invention as disclosed above and shown diagrammatically in the drawings.

While several embodiments of my invention have been shown and described it will be apparent that other adaptations and modiiications may be made without departing from the scope of the following claims.

I claim:

l. A pneumatic system for pumping iluid comprising, the combination with a fluid supply conduit, a fluid delivery conduit, and a plurality o-f liquid feed tanks respectively adapte-d to be lled with Huid from said supply conduit and to-discharge such fluid under pressure :into said delivery conduit, of a plurality of separate valve means respectively controlling the filling and discharge operationof; said tanks each oft said separateI valve means'v comprising a discharge, valve connecting `One of said tanks withV saiddelivery conduit, aV lill valve connecting Y vtially timedintervals for closing its discharge valve and operating its,v llt valve and its pneumatic valve means to, thereby ll it. with gas-pressurized liquid, and means providing for successive operation of said tanks comprising a. lower limit control in each of said tanks which is: actuated inresponse to the. fluid therein falling to a predetermined level and includes means for actuating the motor driven-controller for; such tank andvr for opening the. discharge valve of a succeedingY tank, said motor driven controllers operating, respectivelyV at a predeterminedtimed, interval. after actuation,V by said lower limit contr-,olsy to closey said discharge valves.

A. pumping system as deiinedi in claim l character,- by the. provision of separate electric drive motors for operating said controllers, means responsive to actuation of each of said lower limit controls for starting one of said electric drive motors, and each of said controllers including means for stopping its said drive motor at the end of'each operating cycle thereof.

3. A pumping system as delined in claim 1 character ized by said pneumatic means comprising a vent valve and a `gas admission valve in the upper end of each tank,`

and a closed circuit connecting said gas admission and. -i

vent valves comprising a low pressure reservoir for receiving gas `discharged from said tanks through said vent` valves, a high pressure reservoir for supplying gas under pressure to said admission valves, and meansrincluding a compressor for pumping gas from said low pressure reservoir to said high pressure reservoir. l

4. A pumping system as defined in claim l characterized by the provision of a reservoir for the fluid to be pumped, a continuously operating pump for delivering illuid from said reservoir to said supply conduit, a return 'y conduit connecting said supply conduit with said reservoir, a normally open How-control valve in said return conduit, and means operated by said controllers for closingI said flow-control valve to render said supply conduit operative to deliver iluid through said lill valves to said ifeed tanks.

5. A pneumatic system for pumping iluid comprising a plurality of liquid feed tanks respectively adapted to be illed with liquid and for the discharge of such liquid under pneumatic pressure, and pneumatic means for pressurizing each of said tanks comprising a vent valve and a gas admission valve in the upper end of each tank, and a closed circuit connecting said gas admission and vent valves comprising a low pressure reservoir for receiving gas discharged from said tanks through said vent valves, a high pressure reservoir for supplying gas `under pressure to said admission valves, and means including a compressor for pumping -gas from said low pressure reservoir to said high pressure reservoir.

6. A pneumatic system for pumping uid comprising a plurality of liquid yfeed tanks, a duid supply conduit, means including a plurality of normally'closed lill valves for connecting said feed tanks with said supply" conduit, means for selectively operating said valves to open position, a reservoir for the fluid to be pumped, a continuously operating pump for delivering uid from said reservoir to said supply conduit, a return conduit connectingv said supply conduit with said reservoir, a normally open now-control valve in said return conduit, and said selective valve operating means including means for closing said flow-control valve in response to operation of any of said nll valves to open position to thereby render said supply conduit operative to deliver uid through the open ll valve into one of said tanks.

7. A pneumatic system for pumping uds comprising, in combination, a iuid supply conduit, a iiuid delivery conduit, a plurality of liquid feed tanks arranged between said conduits and respectively adapted to be filled with fluid from said supply conduit and to discharge such iiuid under pressure into said delivery conduit, a pair of valves in the bottom of each of said tanks respectively controlling the connections thereof with said supply and delivery conduits, pneumatic means for pressurizing said tanks including a pressurizing valve and a venting valve in the upper end of each of said tanks, a separate motor operated controller for each of said tanks operable in a cyclic manner and including a plurality of means respectively eifective during each cycle of operation and at sequentially timed intervals for operating the valves therein, each of said controllers operating sequentially to close the discharge and pressurizing valves of the tank which it controls, to openthe said vent and till valves therein to ll said tank and then close said vent `and ll valves, and then open the pressure valve therein to pressurize the fluid therein for a fluid discharge operation, and a separate means in each of said tanks responsive to References Cited in the file of this patent UNiTYED STATES PATENTS 1,551,639 Brown sept. 1, 1925 1,591,318 Johansen July 6, 1926 1,628,608 Newhouse May 10, 1927 2,093,474 Okell et al. Sept. 21, 1931 2,145,540 Ellis Jan. 31, 1939 2,180,274 Bentleyy Nov. 14, 1939 2,300,039 Yeomaus et al Oct. 27, 1942 2,458,053 yBrown Jan. 4, 1949 2,644,405 Yeomans July 7, 1953 2,669,941 Stafford Feb. 23, 1954 20 2,730,961 Yeomans Jan. 17, 1956 OTHER REFERENCES Pamphlet: Weber Subterranean Pumps-Industrial Types, published 1912, pages 9 to 12.

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