US 3050008 A
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Aug. 21, 1962 J. J. PACEY ETAL ELIMINATION OF AIR AND VAPORS FROM A CENTRIFUGAL PUMP 2 Sheets-Sheet 1 Filed Dec.
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I mm Aug. 21, 1962 J. J. PACEY ETAL ELIMINATION OF AIR AND VAPORS FROM A CENTRIFUGAL PUMP 2 Sheets-Sheet 2 Filed Dec.
INVENTORS JOHN J. PACAIY G0RG D. ROBINSON J)?- BY 06,4. W14
A T TMNE YS 3,058,008 ELATION on AIR AND vAPoRs FnoM A cnNTnn UnAL PUMP John J. Pacey, Springfield, and George D. Robinson, Jr.,
Agawam, Mass, assignors to Gilbert 8: Barker Manufeaturing tlompany, West Springfield, Mass, a corporation of Massachusetts Filed Dec. 30, 1958, Ser. No. 783,842 4 Claims. (Cl. 103-413) The present invention relates to centrifugal pumps and more particularly to improved means for eliminating air, vapor or gases from the pumping system.
The prime object of the invention is to provide improved and simplified means for eliminating air from a centrifugal pumping system so as to prime the pump or to maintain the pump in operation when a substantial amount of air becomes entrained in the suction line of the centrifugal pump.
Another object of the invention is to accomplish the above ends when working against high back pressures or pressure heads in the discharge line in a centrifugal pump.
The above and other related objects of the invention as well as the novel features thereof will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the particular novelty thereof pointed out in the appended claims.
In the drawings:
FIG. 1 is an elevation showing a centrifugal pumping system in which the present invention is incorporated;
FIG. 2 is a view, on an enlarged scale, of the centrifugal pump unit itself as shown in FIG. 1 (generally indicated by numeral 10) with parts broken away and in section;
FIG. 3 is a section, on a further enlarged scale, taken on line III-III in FIG. 2;
FIG. 4 is a perspective view, with portions broken away and on an enlarged scale, of an air separator seen in FIG. 1;
FIG. 5 is a section taken on line V-V in FIG. 4, and
FIG. 6 is a section on a further enlarged scale, taken on line VIVI in FIG. 4.
The overall organization of a pumping system embodying the present invention may be seen by referring to FIG. 1 in the drawings. Basically, this system comprises a centrifugal pump 18, a positive displacement pump 12 and an air separator 14. A suction pipe 16 extends from a liquid source (not shown) to the centrifugal pump while a discharge pipe 18 provides for delivery of the liquid to whatever point may be desired within the capabilities of the pump 10.
One inherent shortcoming of centrifugal pumps is their inability to draw any substantial vacuum pressure in a gaseous medium. Thus it is that a centrifugal pump must be primed with liquid before it will become operative. This problem has been overcome in the past by the provision of a positive displacement priming pump for initially creating a vacuum in the suction line of a centrifugal pump to draw liquid from a remote source at a lower level and thereby prime the pump. The function and purpose of the priming pump 12 is also the same in the present instance. However, in accordance with the objects of the invention, the pump 12 is characterized by its efiiciency and its effectiveness in priming where there is a high head or back pressure in the discharge pipe 18.
The pump 10 comprises a frame 21) (FIGS. 1 and 2) which is mounted on a base 22. A housing 24 is secured to the frame 24 and is provided with a central inlet communicating with the suction pipe 16 and a tangential outlet communicating with the outlet pipe 18. The housing 24 is closed off by a plate 26 which provides a journal for a shaft .28 on which is mounted a vaned impeller 30.
3,85,888 Patented Aug. 21, 1952 In the preferred form of the invention, the priming pump 12 is also driven from the shaft 28 and comprises a rotor 32 (FIGS. 2 and 3) keyed thereto. The rotor 32 is disposed within a housing 34 secured to the plate 26 which is sealed off at its opposite end by a plate 35 to provide a closed chamber for the priming pump 12. A slide or collar 36 encircles the rotor 32 and is slidably guided for vertical movement relative to the housing 34 by means of lugs 37 with a spring 38 yieldingly holding it in its lower position for reasons which further appear. The rotor 32 is relieved on each of its radial faces to receive thrust rings 39 against which blades 40 hear. The blades 40 are carried by the rotor 32 andare axially slidable relative thereto. The slide 36 at its top and bottom ends is flush with the plates 26 and 35 to define a suction chamber 41 and a pressure chamber 43 on opposite sides of the shaft 28. The slide 36 is also relieved on opposite sides of the shaft 28 to provide for communication with a suction tube 42 and a discharge tube 44 which communicate through passageways in the housing 34 with the suction chamber 41 and pressure chamber 43 respectively. The action of the pump 12 as above described is well known and the rate or capacity of the pump is dependent on the vertical position of the slide 36 and the degree of eccentricity of the thrust rings 39 relative to the shaft 28.
Outwardly of the plate 38 is a bearing housing 46 (FIG. 1) for the shaft 28 which extends therebeyond to a universal coupling 47 providing a connection with the shaft of an electric motor 48. The motor 48 is for convenience sake mounted on the base 22 and may be provided with any form of electrical control desired. In any event for the purposes of the present invention, it is only necessary that the shaft 28 be power driven.
Although the impeller of the centrifugal pump 10 could rotate about a vertical axis, certain advantages in the operation of the priming pump are to be had from mounting the impeller for rotation about a horizontal axis, as illustrated. Thus it will be seen that the suction tube 42 (FIGS. 1 and 2) extends from the priming pump 12 to the top of the inlet pipe 16. For convenience, the suction tube 42 is actually connected to the top of an adapter 50 which is interposed between the pipe 16 and the pump housing 24, the adapter in essence being a part of the pipe 16.
When the pump 10 is started up by energizing the motor 48, the suction pipe 16 must first be evacuated to draw liquid to the pump 10. This function is accomplished by the priming pump 12 which pulls air and/or vapors through the tube 42 to evacuate the pipe 16 and thereby pull liquid into the centrifugal pump housing 24. With the suction side of the priming pump 12 connected to the top of the suction pipe 16, priming of the pump 10 will be most efiiciently accomplished in that only air or vapors will be drawn into the priming pump 12. That is, there will be no tendency for liquid to enter the tube 42 and thus the pipe 16 will be evacuated at maximum efliciency. Once the pipe 16 has been evacuated sufiiciently to prime the pump 10, its centrifugal action will take over to pull liquid through the pipe 16 and discharge it through the pipe 18. With. the
prime established, liquid instead of air will be drawn through the tube 42.
In order to take advantage of other features of the invention, it is preferable that the priming pump discharge tube 44 be connected to the air separator 14 as indicated in FIG. 1. The air separator comprises a compositely formed closed vessel 52 (FIGS. 1 and 4) to which the tube 44 is connected by appropriate fittings intermediate the height of the vessel. An air vent opening 54 (FIGS. 4 and 5,) is provided at the upper .end
of the vessel 52 and a liquid outlet 56 (FIG. 6) is provided at the lower end of the vessel 52. The air vent opening 54 takes the form of a simple hole formed in a plate 55 (FIGS. 4 and 5) at the upper end of the vessel 52 with a flange plate 57 providing means for mounting a pipe or conduit 58 which may extend to an appropriate location for discharge of air and vapors which may be explosive or malodorous. The liquid outlet 56 is formed in a fitting 59 (FIGS. 4 and 6) threaded into the bottom of the vessel 52. The fitting 59 provides means for connecting one end of a return line 60 to the vessel 52. The return line 60 extends to the suction pipe 16, being connected to the adapter 50.
Valve means are provided for the air opening 54 and the liquid outlet 56 respectively. 'In the former instance, a fiat resilient metal ribbon 62 (FIGS. 4 and 5) is secured at one end to the Wall of the vessel 52 immediately below the opening 54. The ribbon valve 62 is curved inwardly with its other end being secured to a block 64 atop a vertically disposed rod 66. It will be appreciated that as the rod 66 is moved upwardly, the ribbon valve 62 will be flattened against the inner wall of the vessel 52 and seal olf the air opening 54. A second ribbon valve '62 is also attached to the block 64. The ribbon valve 62' could be employed to seal off a second air vent opening on the opposite side of the vessel 52, but in the present case it is merely being used to balance the lateral thrust of the valve 62.
The valve means for the liquid outlet 56 preferably take the form of a needle valve cone 68 (FIG. 6) formed on the lower end of the rod 66 which seats in the opening 56. It will be seen that the lower end of the rod 66 is guided for vertical movement by an upstanding skirt 70 formed on the fitting 59 and that the holes 72 are provided to insure flow of liquid from the bottom of the vessel 52 to the liquid outlet 56. It will also be seen that the upper end of the rod 66 is guided for vertical movement by a spider 71 (FIG. 4).
A float 74 is mounted on the rod 66, being axially fixed thereon by cotter pins 76. When liquid rises in the vessel 52, the rod 66 is raised, lifting the needle valve 68 off its seat and at the same time or shortly thereafter closing the ribbon valve 62. For present purposes it would also be feasible to have an arrangement wherein the air vent opening is closed before the liquid outlet is opened when the level of liquid rises in the vessel 52, the prime consideration, in accordance with other aspects of the invention, being that the valve 62 be closed before the level of the liquid is sufiiciently high for foam thereon to escape through the opening 54. In other words the opening 54 must be spaced a substantial distance above the level of liquid to allow for collapse of foam so that only air or vapors escape through the pipe 58.
The operation of the priming pump 12 in combination with the air separator 14 is as follows: When the motor 48 is energized, the pump 12 is set into operation and immediately begins to draw air through the suction tube 42 thereby evacuating the suction pipe 16. At this point, it will be noted that a check valve 78 may be provided in the discharge pipe 18 to insure evacuation of the suction pipe 16 and also to enable a high head to be maintained at all times on the discharge side of the centrifugal pump 18 when such is necessary or desirable.
Air or vapor is thus drawn from the pipe 16 and pumped by the positive displacement priming pump 12 to the air separator 14. When starting up, there will be little or no liquid in the vessel 52 so that the liquid outlet 56 will be closed while the air opening 54 will be open. Thus the evacuated air will be discharged to atmosphere through the pipe 58. This action continues until suflicient liquid is drawn into the suction pipe 12 to prime the pump 10. It will be noted that the priming action of the pump 12 is nowise affected by the back pressure in the discharge pipe 18. Thereafter, once the centrifugal pump 10 is operative, the priming pump 12 will begin to draw liquid from the suction pipe 16 and discharge it into the vessel 52 (FIG. 1). As the level of liquid rises in the vessel 52, the float 74 (FIGS. 4-6) Will be raised, first opening the valve 68 allowing liquid to flow through the return line 60 back to the suction pipe 12. Further rise of the liquid level will cause the ribbon valve 62 to close off the air opening 54 and, after priming, the normal condition of the air separator is for the air opening to be closed and the liquid outlet to be open. Thus it is that a small amount of liquid is bypassed from the centrifugal pump 10 during its normal operation.
The amount of liquid bypassed is minimized by making the outlet opening 56 sufliciently small so that liquid will not flow therethrough as fast as it is delivered into the vessel 52 by the pump 12. This means that a pressure is built up in the vessel 52 which is a back pressure effective on the pump 12 and built up in the discharge chamber 43 of the pump 12 (FIG. 3). This back pressure is transmitted through a passageway to the bottom lug 37 of the slide 36 and tends to raise the slide against the action of the spring 38. As the slide is raised, the eccentricity of thrust rings 39 is reduced and the capacity of the pump 12 is likewise reduced. Thus a balance is obtained wherein the rate of flow into the vessel 52 equals or approximates the rate of how through the liquid outlet 56. This balanced condition is of course obtained by having the proper strength in spring 38 so that the slide 36 will rise in response to the proper back pressure built up in the vessel 52.
While workable systems may be developed without any substantial back pressure in the vessel 52, the described relation is preferred. Thus when there is a back pressure, there is a minimum tendency for foam to form and the flow of liquid through priming pump 12 and the air separator 14 is continuous.
The air elimination means above-described for evacuating the suction pipe 16 in initially priming the pump 10 is equally eifective in scavenging air and vapors which for one reason or another may become entrapped in the suction pipe 16 during normal operation of the pump 10. Thus air or vapors will rise to the top of the tube 16 and be drawn therefrom by the priming pump 12. These scavenged gases are forced into the closed vessel 52 causing a gradual lowering of the liquid level therein. When the float 74 is lowered sufficiently, the ribbon valve 62 will open the air opening 5'4 and the scavenged gases will be exhausted to atmosphere. Thereafter, as further liquid is pumped into the vessel 52, the ribbon valve 62' will close and the condition of the air separator 14 will revert to that above described for the normal operation of the pumps 10 and 12. If a really large amount of air is entrapped in the suction pipe 16, the action of the air separator is essentially the same except the level of liquid in vessel 52 will more than likely drop far enough so that needle valve 68 Will close off the liquid outlet 56. Thus there is always a safeguard against air being bled back to the suction pipe 16 through the return line 60.
Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:
l. The combination of a centrifugal pump having a power driven shaft on which is mounted an impeller, a horizontal suction pipe leading to said impeller, an adapter interposed between said suction pipe and said centrifugal pump and a variable capacity priming pump, a suction tube leading from the top of said adapter to the suction side of said priming pump, and an air sepa rator, said air separator comprsing a closed vessel of substantial height having an air opening at its upper end and a liquid outlet in its lower wall, a discharge line for discharging fluid from said priming pump into said vessel, said discharge line being connected to said vessel at a point intermediate its height, a ribbon valve for closing said air opening, said ribbon valve being connected at one end to the wall of said vessel immediately beneath said air opening, a vertically disposed rod within said vessel to the top of which the other end of said ribbon valve is connected, said vertically disposed rod having a needle valve formed on its lower end for closing said liquid outlet, a return line connecting said liquid outlet with the suction pipe of said centrifugal pump, said liquid outlet being of a size less than that required to pass liquid at the normal rate of delivery of liquid into said vessel by said priming pump whereby pressure will be built up in said vessel and means responsive to said pressure in said vessel for reducing the capacity of said priming pump to balance the rate of discharge of liquid into said vessel in accordance with the rate of flow of liquid through said liquid outlet, a float secured to said vertical rod and operable to raise the needle valve to open said liquid outlet and also raise the said other end of said ribbon valve to close oil? said air opening Whenever the liquid in said vessel'rises above a given level which level is spaced a substantial distance beneath said air opening sufficient to prevent any foam which might build up in the liquid in said vessel from reaching said air opening, said rod being free to follow said float as it follows the height of said liquid below said given level to thereby close said liquid outlet and open said air opening.
2. The combination of a centrifugal pump, a variable capacity priming pump having an inlet line from the suction side of the centrifugal pump and a discharge line back to the said suction side, and an air separator in said discharge line, said separator comprising a closed vessel with an air vent opening in its upper end and a liquid outlet spaced a substantial distance beneath said air vent, valve means for opening and closing said air valve, valve means for opening and closing said liquid outlet, liquid level responsive means actuating both said valve means for closing said air vent While opening said outlet and for opening said air vent while closing said outlet, the level of liquid suflicient to cause closing of said air vent being substantially below said vent in order to block entrance of foam thereto, said separator vessel outlet being of lesser size than said discharge line from the priming pump into the vessel, and said priming pump having means responsive to pressure in said vessel to reduce the capacity of the pump and balance the rate of flow into the vessel in accordance with the rate of flow from the vessel.
3. The combination of a centrifugal pump, a variable capacity priming pump having an inlet line and a discharge line connected to the suction side of said centrifugal pump, and an air separator in the said discharge line, said separator comprising a closed vessel the inlet of Which is intermediate the top and bottom thereof and the outlet of which is at the bottom, said outlet being of less size than required for receiving liquid at the normal delivery rate of said priming pump, said vessel having an air vent at the top substantially above said vessel inlet, a valve for said air vent and a valve for said vessel outlet, float means in said vessel controlling operation of said valves in response to the level of liquid therein for simultaneously opening one valve while closing the other, said priming pump having means responsive to pressure in said vessel to reduce the pumping capacity thereof.
4. The structure of claim 3 in which said float means includes a vertically disposed rod extending upwardly in the vessel the top of said rod being connected to said air vent valve and the bottom of said rod forming a valve to close and open said vessel outlet.
References Cited in the file of this patent UNITED STATES PATENTS 1,551,362 Barton Aug. 25, 1925 1,591,388 Jennings July 6, 1926' 1,890,317 Durdin Dec. 6, 1932 1,910,775 Saxe May 23, 1933 2,064,988 iRisser Dec. 22, 1936 2,150,125 Nelson Mar. 7, 1939 2,313,773 Samiran Mar. 16, 1943 2,318,264 Smith May 4, 1943 2,511,351 Laidley June 13, 1950 2,535,583 Kroll Dec. 26, 1950 2,881,708 Wernert Apr. 14, 19 59