US2391769A - Self-priming pump - Google Patents

Description

Dec. 25, 1945. R. D. CAMPBELL SELF-lRIMING PUMP Filed May 14, 1943 Patented Dec. 25, 1945 UNITED STATE-s PATENT OFI-ice SELF-PRIDHNG PUMP I menare n. campbell. wauwau, wir., mignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation o! Delaware Application May 14, 1943, Serial No. 486,939

15 Claims. (Cl. 103-113) This invention relates to improvements in selfpriming pumps and particularly to self-priming centrifugal pumps in which recirculation of the water for priming is automatically cuto when the discharge conditions oi the pump change as a result oi completion of the priming action.

Centrifugal pumps are impositivo displacement machines and cannot discharge liquids until all ofthe gases have been removed from the suction line and the pump casing. Such gas removal or priming may be accomplished by completely illling the suction line and the pump casing from a source oi liquid at a higher elevation, by removing the gases by the use of a separate evacuating pump or by causing entrainment ci the gases by liquid recirculating within the pump and then releasing the entrained gases to the discharge line thus making the pump self-priming. Seli-priming pumps, after completion of the self-priming action, should of course be as eective as other centrifugal pumps both as to the depth from which liquids can be lifted and as to the eiliciency with which liquids are discharged. It is desirable that such self-priming pumps be operative at all times after the initial starting action regardless of howi frequently the reservoir from which the liquid is obtained, is completely emptied. Thel priming action should be as rapid and smooth as possible to avoid the occurrence of power losses and the production of intermittent stresses in the pump structure.

The recirculating control valve should be 'unaffected by variations in the suction liit during the priming action and is preferably operative only in response to the discharge velocity of the pumped liquid. The valve should close as soon as the need for recirculation of liquid has ceasedy and the valve should be so designed as to be insensitive to operating conditions and not subject to misadjustments during use. It is therefore an object of the present invention to provide an improved self-priming centrifugal pump in which water is recirculated only aiiected by the varying suction lift or discharge head oi' the pump during the priming action.

Another object of the invention is to provide an improved self-priming centrifugal pump in which the wateriiowing through the recirculating valve -is continuously and immediately picked up by the pump impeller, thus preventing an intermittent priming action producing intermittent stresses in the pump structure.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing in which:

Fig. 1. is a vertical sectional view taken on the line I-I oi Fig. ,2 through the axis of both the valve chamber and the pump to show the valve structure and the relation of the valve controlled ow to the owpassing through the pump;

Fig. 2 is a top plan view of the entire self-priming pump structure; v Fig. 3 is an elevation taken from the inlet or suction side of the pump with a portion of the valve chamber wall broken away and with the recirculation control valve shown in vertical section on a plane taken centrally therethrough to illustrate the relation of the valve with the other portions of the structure; and

liig. 4 is a horizontal section taken on the plane of the line IV-IV of Fig. 1 to show the relation oi the port controlled by the recirculating valve with the inlet of .the pump as Well as to show the shape and location of the discharge passage from the pump and leading through the valve.

It will be understood, of course, that the pump may also be placed with the shaft in vertical posif tion or at any other angle to the horizontal.

Referring more particularly to the drawing by A type, it being understood that any known type of impeller may be used. The pump impeller is mounted on a shaft 8 to which power is to be applied by any known driving means (not shown) and the joint between the stationary casing and the rotating hub of the impeller is closed by a packing gland 9. The inlet through the pump v casing 6 into the eye of the impeller is designated at Il and the discharge passage from the usual volute portion of the casing 6 is shown at l2.

Y A chamber generally designated at I3 is mounted adjacent or, preferably, formed integral with, a portion of the pump casing 6 in such manner as to form one side thereof with the pump inlet ii formed in the wall portion between the pump casing itself and the chamber I3, as shown. The casing outlet and discharge conduit I2 `extend outwardly from the volute portion of the casing and upwardly to open into the chamber I3 at one side thereof. Water is admitted to the intake portion of the chamber I3 by way of a suction pipe I4 provided with s, check valve I! and the water thus admitted flows through an inlet' conduit portion defined by walls I6 formed on the inner wall of the chamber and through the inlet II into` the impeller 1, and water is discharged from the pump through the discharge outlet I2' and the other side of the chamber I3 into a discharge pipe I1. The chamber I3 is provided with a cover I8 having a removable plug I3 by way of which the chamber may be initially filled with water, it being understood that such filling is required only the first time the pump is started. It will oe seen that the inlet conduit formed by walls I6 provides a complete and separate passageway on one side of chamber I3 from the inlet pipe I4 to the pump casing inlet II and is wholly separated from the discharge -space within the chamber except for controlled ports to be described.

The pump outlet I2 opens into a pocket formed in the bottom of the discharge space of the chamber I3 to provide a receptacle for a valve housing having a cylindrical body portion 20 with internal flanges 2| and 22 and an external ilange 23. A spider comprising a central ring 23 and four arms 21 is mounted on flange 22 ofthe valve housing and a centrally apertured screen 28 is mounted on the flange 23 and extends over the spider. The valve housing encloses and guides a movable valve body formed with a hollow cylindrical bottom portion 3| having an ex' ternal flange 32 and with an internal flange 33 from which extends, at right angles thereto, a smaller hollow cylindrical upper valve portion 34 extending above the valve housing. into the chamber I3. The lower valve ange 32 fits into the valve housing and the lower cylindrical valve portion 3| fits into the opening formed by th'e valve housing flange 2| for the purpose of aiding in guiding the valve in its vertical movement. The upper valve extension or nozzle 34 also fits closely in the ring 26 of the spider to guide the vertical movement of the upper valve extension 34. The fit of housing flange 2| and lower cylindrical valve portion 3| in the valve housing also increases resistance to leakage about the periphery of such flange thereby preventing air flow back to the suction space with consequent increase in priming time re'quired and loss of priming efficiency due to only partially eective discharge.

The spaces about the spider arms 21 provide passages through which water may flow from the chamber I3 between the flange 22 of the valve housing and the valve body extension 34 and through a port 36 in the valve housingr 1ocated between flanges 2| and 22 and adjacent the impeller inlet II. The valve body is Joined to a helical spring 31 under tension and having one end thereof fastened to a plate 38 on which the valve housing is seated and retained in the pocket provided therefor. The vertical movements of the valve are also, at least in part, guided by the spring 31. Due to guiding of the valve by the various flanges, the spider and the spring, it is impossible for the valve body to move from a vertical position suiilciently to cause jamming of the valve under any circumstances.

One wall I6 defining the suction conduit within the chamber I3 is provided with an aperture 4I asomo connecting the suction space k42 of the chamber I3 with' the discharge space 43 thereof and the aperture may be closed by a ball check valve 44. If the check valve Il should not seat tightly and allow water to syphon back into the suction pipe -valve Il' is closed and the recirculating control valve 3| to 34, inclusive, is drawn downwardly by the spring 31 into the position shown in Figs. 1 and 3 of the drawing. If the pump is to be started, the space 43 of the chamber I3 must first be filled with water through the' opening which is closed by the plug I 3. The pump can then be started and water from the space 43 is drawn through a priming or recirculatins path designated a, between the valve housing internal flange 22 and the valve cylindrical upper portion 34 to iiow through theport 36 into the inlet II of the impeller 1. Water is, discharged from the impeller through the outlet I2 and passes up through the valve 3I 34 into the space 43 of the chamber I3 in which air separates from the water and passes out through the discharge pipe I1. Separation of gas from liquid in space 43 is promoted by valve extension 34 which acts as a nozzle to discharge the gas liquid mixture with sumcient force to carry the gas bubbles beyond recirculation path a. Entrainment of the gas bubbles-.is

minimized by the screen plate 23 mounted on the valve housing and fitting relatively closely about I' the valve extension 34 thusblocking return of gas bubbles of any size through the recirculation path. The above recirculation of water through' the path a continues until all of the air is drawn l out of the suction conduit space 42 and the sucutes at a speed of 1750 R. P. M.

During recirculation of a gas and water mixture in the path a the spring 31 holds the valve 3I-34 substantially in the position shown with the recirculation or priming ports at least pal'- tially open. However, as soon as the pump is discharging only gas free liquid, the velocity of the discharge acts on the inner surface of the valve nange 33 and raises the valve 3I-34 against the tension of the spring 31 until the flanges 32 and 33 of the valve body are seated on the flanges 2| and 22 of the valve housing thereby closing of! the recirculation path a. Expressed in different language, lifting of the valve results from th'e diierential pressure due to high suction lift and zero or lowy discharge or positive static head thus producing an increase in velocity through the valve. As the valve lifts the velocity decreases to a constant rate and hence the valve can operate under varying suction and discharge heads. Upon closure of valve 3|-34, water flows through the normal pumping path b, that is through the suction pipe I4, the suction conduit space 42, the impeller inlet II and is forced by the impeller 1 into the volute portion of the casing 6 from whichthe water flows through the casing outlet I2, the valve 3I-34, vthe discharge asomo@ The present structure has been found to liave a number of critical characteristics. Thus the recirculation port 36 must be located adjacent to and in line with the impeller inlet Il to allow the impeller 'I to pick up water immediately andcontinuously. Location of the port 36 as shown allows the jet of water issuing therefrom to en train air in the suction space 42 continuously and to carry it immediately into the impeller. There is no release of such entrained air and there is no loss of time or power due to unnecessary turbulence in the suction space 42. If the recirculation port is located in any other position. the suction space 42 must be iilled up to the level at which more than onefhalf of the pump inlet II is under water before the impeller will pick up the water. The impeller then picks up charges of water interspersed with a quantity of air and delivers the charges of water as solid masses to the recirculation path a. Such so-called slugging imposes intermittent stresses on the entire pump structure and its operating means and momentarily causes the valve 3i-38 to lift. As

l .soon as each slug passes into the discharge space @3, the stresses on the pump are relieved and the valve 3i-34 is retracted byl the spring 3l thus causing hammering of the valve. Under such conditions the pump cannot prime smoothly and 3i--3d. Such action would vary as the suction lift varies and would vary the action of the valve. But if the cross-sectional area of the port 38 and the other controlled portions of the recirculation path a are made smaller than the cross-sectional area of the valve chamber as dened by iianges 2i, 22 and body 20 of the valve housing, a' pressure is built up in the valve chamber and neutralizes the effect of th'e variable suction lift on the valve. The valve 3i--34 is therefore actuated only responsive to the velocity of ilow through the valve and a single spring 31 satisfactorily controls valve movement over the entire range of the suction lift. Further,v the smaller port area increases the gas liquid mixture velocity beyond the point at which th'e gas may separate and also limits the ow to the impeller to :prevent iiooding thereof.

'The stroke of the valve 3l34 between closed and wide open position,` that is the space between the' flanges of the valve housing and the valve, should be kept to relatively close limits. Ii the valve travels less than inch the spring tension must be increased beyond the ten pounds found satisfactory 'in-practice and the valve then slams open and shut. And an increase in the valve stroke beyond 3/4 inch makes it necessary to increase iiange area 33 to such an extent that much turbulence is caused and eiciency is lost in ow through the valve. Such stroke limitation also prevents the valve from moving other than in a vertical direction and becoming jammed.

The nozzle portion 34 of the recirculating valve must extend above the bottom oi.' the discharge space 43 for a suilicient distance to allow complete separation of the air from the recirculating water outside oi the recirculation path a and thus permit escape of such entrained air up through the discharge pipe I'l. Ii' the valve is made too short the entrained air is recirculated with the water and no priming action takes place.

A ratio, dependent on the tension of the spring 31, z nust be maintained between the area of the inner surface of the iiange 33 of the recirculation contro1 valve, on which the velocity pressure of the water acts to shut oil the valve, and the area oi' the portion 34 of the valve through which the pump discharge must flow. The ratio, having a given spring tension, must be such that the valve is closed as soon as the volume ci.' water pumped is greater than th'e volume oi' the water which can return through the recirculation port 38.

And the discharge head is related to the area of the bypass port 36. For higher discharge heads, the port must be made smaller because a greater quantify of water flows through th'e recirculation path, increasing the velocity of the air-water mixture beyond the point at which the air is readily released. The velocity must be kept down either by decreasing the port area or increasing the volume of space 43.

Although but one embodiment of the present invention has been illustrated and described, it

` will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit oi the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet ofsaid impeller and separated from a, discharge space receiving the discharge from said. casing, a hollow valvel member defining a passage through which the entire discharge from said casing is conducted to the discharge'space of said chamber under all conditions of pump operation. said valve member being slidably mounted to control a port connecting the suction and discharge spaces in said chamber, and spring means cooperating with said valve member to maintain communication between said suction and discharge spaces through' said port when said pump is inoperative and during priming thereof.

2. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a bail check valve controlling an aperture in the wall separating the suction and discharge spaces in said chamber to break any syphon action in the suction space, and a valve member conducting the entire discharge from said casing into the discharge space of said chamber and controlling a port connecting the suction and discharge spaces in said chamber.

3. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, and a hollow valve element mounted for sliding movevided into a suction space connected with the iny iet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, said port being adjacent to and in line with the inlet of said impeller, and a hollow valve element mounted for sliding movement in said valve housing for conducting therethrough the entire discharge from said casing into the disy charge space of said chamber and controlling the recirculation of liquid between the spaces through said port.

5. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a

chamber mounted adjacent said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the discharge space of said chamber, said housing having a plurality of internal flanges and a port between the flanges connecting the suction and discharge spaces in said chamber, and a valve mountedV in said housing for conducting the entire discharge from said casing into the discharge space of said chamber, said valve having flanges seating on the flanges of said housing to control recirculation of liquid between the spaces through the port.

6. In a self-priming centrifugal pump, a cas-V ing, an impeller rotatable within said casing, a chamber mounted adjacent said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, and 'a valve mounted in said valve h'ousing for conducting the entire discharge from said casing into the discharge space of said chamber and controlling the recirculation of liquid'between the spaces through the port, said housing and said valve having a plurality of interengaging flanges with the upper of said valve flangesv having an area greater than the area of the discharge passage through said valve to cause closing of said valve responsive to the velocity of the discharge therethrough.

7. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the bottom of the discharge space of said chamber and having a port connecting the suction and discharge spaces in saidl chamber, and a valve mounted in said chamber and controlling the recirculation o!v liquid between' the spaces through the port. said housing having a plurality of nanges with the upper one of the flanges having extensions therefrom fitting closely about said valve and said valve having a plurality of flanges with the lower one of the flanges fitting closely into said housing to guide movement of said valve.

8. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the bottom of the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, and a valve mounted in said valve housing for conducting the entire discharge from said casing into the discharge space of said chamber and controlling the recirculation of liquid between the spaces through the port, -said housing and said valve having a plurality of flanges, the movement of said valve being limited by engagement of the flanges thereof with the'flanges -of said valve housing.

9. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on'said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the bottom of the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, and a valve mounted in said valve housing for conducting the entire discharge from said casing into the discharge space of said chamber and controlling the recirculation of liquid between the spaces through the port, said housing and said valve having a plurality of interengaging flanges, the lower one of said housing flanges fitting closely about said valve and the lower one of said valve flanges fitting closely in said housing to reduce leakage from the discharge space to the suction space of said chamber.

10. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a chamber mounted on said casing and divided into a suction space connected with the inlet of said impeller and separated from a discharge space receiving the discharge from said casing, a valve housing mounted in the bottom of the discharge space of said chamber and having a port connecting the suction and discharge spaces in said chamber, a valve mounted in said valve housing for conducting the entire discharge from said casing into the discharge space of said chamber and controlling the recirculation of liquid between the spaces through theport, said housing and said valve having a plurality of interengaging.

anges with the upper of said valve flanges having an area greater than the area of the-discharge passage through said valve to cause closing oi said valve responsive to the velocity of the discharge therethrough, and a spring joining said housing and said valve to allow closing of said valve only at a predetermined velocity.

1l. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a suction and a discharge conduit associated with said casing, a hollow valve element defining a passage through which the entire discharge from said casing is conducted to said discharge conduit-underI all conditions of pump operation, said valve controlling a port connecting said suction conduit with said discharge conduit, and means for regulating movement of said valve responsive to the velocity of ow through said valve.

12.. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a suction and a discharge conduit associated with said casing, a valve housing mounted in said discharge conduit, said housing having a plurality of internal flanges forming a valve chamber, a port connecting said valve chamber with said suction conduit, said port being of less cross-sectional area than said valve chamber, and a valve mounted in said housing for conducting discharge from said casing to said discharge conduit and controlling said port.

13. ln a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a suction and a discharge conduit associated with said casing, valve means controlling an aperture between said discharge conduit and said suction conduit to break any Siphon action in said suction conduit, and a valve for conducting the discharge from said casing to said discharge conduit, said valve controlling a port connecting said suction conduit with said discharge conduit.

14. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a suction and a discharge conduit associated with said casing, a valve housing mounted in said dis-- charge conduit, said housing having a plurality of internal flanges and a port between said flanges connecting said suction and discharge conduits, and a valve mounted in said housing for conducting the entire discharge from said casing into said discharge conduit, said valve having flanges seating on the flanges of rsaid housing to control recirculation of liquid between said conduits through said port.

15. In a self-priming centrifugal pump, a casing, an impeller rotatable within said casing, a suction and a discharge conduit associated with said casing, a port connecting said suction and Adischarge conduits, said port being adjacent to and in line with the inlet of said impeller, and an annularvalve element having-a tubular portion dening a passage through which the entire discharge from` said casing is conducted to said discharge conduit under all conditions -oil pump operation, said valve element being exposed to pressure of uid discharged from said pump and being actuated in responseto velocity of flow through said valve element for controlling said port.

RECHARD D. CMPBELL.

Images