|Publication number||US2275500 A|
|Publication date||Mar 10, 1942|
|Filing date||Mar 8, 1939|
|Publication number||US 2275500 A, US 2275500A, US-A-2275500, US2275500 A, US2275500A|
|Inventors||Frank S. Broadhurst|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (7), Classifications (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
March 10, 194-2. F. s. BROADHURST 2,275,500
PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Fild March 8, 1939 4 Sheets-Sheet 2 wz s/vm? 117777585, V k S i g F5a72 ,Zsaaq ans wrf/vraf? 4 Sheets-Sheet 3 Marh 10, 1942. F. s. BROADHURST PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Filed March 8, 1939 wwm NM Emzi Sflraadu March 10,1942. F. s. BROADHURST 2,275,500
PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Fi'led March 8, 1959 4 Sheets-She et 4 x g, f
mmnmmu F I 224% 2/4 I 206 226 h l J 204 2 2 F7421 sigma/2m! 1770 IVEYJ Patented Mar. 10, 1942 PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Frank S.,Broadhurst, Watertown, Mass, assignor to De Laval Steam Turbine Company, Trenton, N. J a corporation of New Jersey Application March 8, 1939, Serial No. 260,469
This invention relates to priming systems for centrifugal pumps.
In cases where there is no supply of liquid availableto prime a centrifugal pump by gravity flow, or where it is undesirable or impossible to prime the pump by the use of an auxiliary Water pump, it has been customary to provide the centrifugal pump with an air pump in the same casing to evacuate the main pump and so render it self-priming. A system of this character is very unsatisfactory for several reasons, among which may be mentioned the fact that the centrifugal pump is driven for an appreciable time without priming, which may result in damage to labyrinthine packing, the fact that there is absorption of considerable power by the air pump which is running throughout the operation of the main pump, and the fact that scoring and plugging of the air pump may occur due to grit, dirt, seaweed, etc. in the Water being pumped, some of which is passed through the air pump for sealing purposes. i Ithas also been customary to prime centrifugal 13111111351011 the delivery side, sometimes with the provision of float valves or the likedesigned to prevent the passage of liquid to. a vacuum pump after the centrifugal pump is primed and operating. The valves under such conditions are exposed to high pressures and are liable to damage by impact and blocking by solid or semisolid material jammed against them, for example, in the handling of sewage.
In general pumping, and particularly in the pumping of driven walls, air is carried into the centrifugal pump with the liquid. This air is separated by the centrifugal action of the pump and accumulates adjacent the shaft. When the accumulation reaches such extent as to substantially cut off the intake passages, the pump will loselits prime and with previous priming systems it was. necessary to shut down, the pump, reprime, and then restart the pumping operations.
In my application Serial No. 11,867, filed March 19, 1935, there are disclosed priming arrangements for centrifugal pumps which overcome the aforementioned objections to prior priming arrangements. The present invention relates to priming systems of this general type in which priming is efiected byevacuation of the suction side of. a centrifugal pump. The present invention, however, involves various improvements on the systems described in my prior application whereby the operation of the vacuum pumpsis still further reduced, normal operation, even though it involves a considerable accumulation of gas, being accompanied with no operation of the vacuum pump or pumps unless abnormally high quantities of gas enter the system. Under normal conditions, the evacuation only takes place in the initial priming of the system on starting. Thereafter accumulated gas is removed automatically by the action of the centrifugal pump itself.
Subsidiary to the broad object of the invention just indicated are various secondary objects having as their ends the proper rapid and reliable operation of the priming system to take care of modern centrifugal pumping installations which are designed to operate automatically over long periods with little or no attention. Specifically, the subsidiary objects of the invention relate to the provision of arrangements for taking care of abnormal gas accumulation, for handling water carrying sediment or floating material, and for maintaining proper operation despite surges attending unusual conditions in the supply or discharge lines. Additionally, provision is made for the operation of pumps in parallel or the operation of pumps receiving their liquid from different supplies, and particularly under circumstances in which any one or more of a series of pumps primed by a common system may be subjected to an abnormal accumulation of gas.
In such case the other pump or pumps may Figure 3 is a wiring diagram showing the electrical connections in the arrangement of Figures 1 and 2;
Figure 4. is a view similar to Figure 1, but illustrating a modified form of the invention;
Figure 5 is a similar view, partly in section, but showing the invention applied to the priming of a plurality of centrifugal pumps;
Figure 6 is a diagrammatic View illustrating still another modification of the invention particularly applicable to the pumping of liquid containing relativelylarge quantities of gas or dirt,
of the pump. Figure 2 shows a section of a portion of the upper casing of the centrifugal pump,
which, in the illustration is a double suction pump, the suction :bells being indicated at it and the discharge volute being indicated at M, though it will be obvious that the invention is applicable to a single suction pump and to multiple stage centrifugal pumps as well as the type illustrated. The impeller of the pump indicated at E2 operates in the pump casing of which the discharge volute M is a part. The pump is associated with the conventional valves including the usual discharge check valve.
At the top of each of the suction bells there is provided a connection to a pipe I6, preferably of substantial diameter. For example, this may have a diameter of 1% inches. A large diameter pipe is desirable at this point to provide for the free upward passage of gas. The pipes it communicate with a chamber l8, which may take the form of a rectangular box. Extending from the top of this chamber l8 are tubes 20 passing through thepipes l6 and terminating as indicated at 22 closely adjacent the shaft of the centrifugal pump.
Extending from the top of the chamber 13 there is the evacuating passage 24 communicating with a water jet air pump indicated at 28, there being interposed-in the connection 24 a check valve 28 adapted to prevent reverse flow of fluid back to the chamber l8. The water jet air pump is provided with supply Water under pressure through a passage 39 controlled by a valve 32 actuated by a solenoid indicated at 34, the valve being closed when the solenoid is actuated. The discharged liquid and gas from the water jet air pump are discharged through conduit 36.
Supported in a holder at the top of the: chamber it are electrodes 38 and 4B, the former of which is substantially longer than the latter. These two electrodes are the control electrodes for a relay which is illustrated as of the wellknown Bender-Warrick induction type. This type of relay is provided with an A-shaped core indicated at 6.2 having a coil 44 on its crossbar portion grounded at one end and connected at its other end to the electrode 49. The upper connecting element of the core is provided with a coil 46 permanently connected to an alternating current power line. The legs of the core are adapted to attract an armature 48, which is conventio'nally illustrated as adapted to close a single contact at 50, and thereby connect the electrodes 38 and MI together, and a pair of contacts 52 adapted to cause the energization of the solenoid 34, which controls the valve 32, and also effects the removal of a short circuiting connection for the no-voltage release of the starter 56 for the pump motor 2, this being .accomplished through a suitable relay, which is not shown. The relay may be conveniently enclosed in a box 5% secured to the chamber l8 and connections made through an electrical outlet boX indicated at 613.
Operation of the modification so far described is as follows:
Assuming that the pump is unprimed, the armature 48 will not be attracted by the field member of the relay because the flux produced by the coil it will have its magnetic circuit completed through the crossbar carrying the open-circuited coil 44. The solenoid 34 will, therefore, be deenergized and the valve 32 will be opened. The no-voltage release coil of the starter will be deenergized, and consequently the motor 2 cannot be started.
To start the operation of the unit, water from the air pump supply is caused to flow through the conduit 39, thereby drawing a vacuum in chamber I8. Due to this action, the liquid will be lifted through the inlet 6 into the centrifugal pump (the usual check valve on its delivery side being closed), and will rise through both sets of tubes i6 and 22 immersing the lower end of the electrode 38. Nothing will happen, however, since the electrode 38 is open-circuited at 5B. As soon, however, as the liquid reaches the level of the electrode 43, the coil 4%, now acting as the secondary of a transformer, will have its circuit completedthrough the liquid to ground. Consequently, a counter-magnetomotive force is created opposing the flux through the crossbar so that the flux will tend to take a path through the armature 48, attracting this armature and closing the contacts at 50 and 52. As soon as the contact at 50 is closed, electrode 33 is thrown in parallel with the electrode 40 and Will additionally tend to maintain the closed condition of the relay. At the same time, the solenoid 34 is energized, closing the valve 32 and removing the short circuiting connection from the no-voltage release of the motor starter.
The pump is now primed and the motor is ready to start. Starting may be effected by a hand control of the starter; or; alternatively, the arrangement may be readily made such that upon energization of the no-voltage release coil the motor will start automatically. Since the specific arrangements for automatically starting a motor are no part of the present invention, this may be considered as embodied in the diagrammatic illustration of the starter at 56.
Before passing to the centrifugal pump operation and priming considerations, it might be here noted that the arrangements of the two electrodes 33 and 40 prevent unstable operation since, though the stopping of the vacuum producing means is not effected until the electrode 40 is submerged, the vacuum producing means will not be restarted until the liquid level drops below the lower end. of the electrode 38, inasmuch as this electrode, through the closure of its circuit at iii), acts as a holding control, maintaining the armature 48 in its attracted position. The height between the lower ends of the two electrodes defines a region'through which fluctuations of liquid level may occur without'disturbance to the system. This distance should be made such that normal fluctuations in liquid level due to surges or other cause will not result in restarting of the vacuumproducing .means or stoppage of the driving motor 2. On the other hand, whenever the liquid drops below the level of the electrode 38, the motor 2 will immediately stop, due to short circuiting of the no-voltage release, and will not then restart until the electrode 49 is submerged.
The action just described would obviously be unsatisfactory if continuous priming, i. e., continuous removal of gases did not take place independently of the water jet air pump 28. As a matter of fact, the arrangement of the pipes l6 and 20 effects continuous removal of normal amounts of gas which might accumulate by the action of the centrifugal pump itself.
Assume that priming has taken place with the resulting rise of the liquid to the level of the electrode 40 and that the motor 2 has then been started either manually or automatically to drive the centrifugal pump. The check valve 26 will have closed upon interruption of flow of the air pump operating liquid through 30 by the action of valve 32.
It will be noted that the lower end of the electrode 40 is substantially below the upper ends of the tubes 21:, providing a substantial gas space. As the liquid flows into the impeller from the suction bell, asuificiently high velocity is created due both to the approach andthe rotation of the liquid in the bell by the shaft as to create a substantial ejector action at the lower ends 22 of the tubes 29 where they approach theshaft. A partial vacuum is thus produced which in typical installations may be of the order of about 4 feet of water. The oreation of this partial vacuum removes the gas from the space at the upper end of the chamber l8 in such fashion that the gas is entrained in fine bubbles in the water in the suction bell and is hence carried without separation to the impeller l2 to be discharged thereby. This provides a rise of liquid from the suction bells through the pipes 16 and withinthe chamber I8 to the upper ends of the tubes 20, whereupon during continued operation there occurs a recirculation of liquid from the suction bells into the chamber and thence through the tubes 20 to their lower outlets adjacent the shaft. A differential pressure of the amount indicated is thus continuously maintained between the upper end of each of the suction bells and the lower ends 22 of the tubes 20. If gas accumulates and floats upwardly through the pipes IE, it will be removed immediately by reason of this ejector action and consequently the liquid level during normal operation with normal amounts of gas entering the device will remain near the'upper ends of the tubes 20.
If larger amounts of gas enter with the incoming liquids, it is possible that this .gas may be separated centrifugally within the suction bells, with the result that the lower ends of the tubes 20 may be surrounded by gas rather than liquid. As soon as this occurs, the ejector action at the tubes 2|] will cease and consequently an equalization of pressure will occur in the systemsubject only to the centrifugal action which takes place. The static head of the liquid, however, above the suction bell will cause the gas surrounding the lower ends of the tubes 20 to be forced upwardly therethrough into the upper portion of the chamber I8, producing a drop in the liquid level therein. Since the chamber l8 has a volume substantially greater than the total volume of the suction bells, it will be obvious that the liquid level will not drop to any great extent before the lower ends of the tubes 20 are again exposed to liquid with a renewal of the ejector. action. The accumulated gas will then be rapidly drawn off in a fine state of subdivision so as to pass into the impeller without reseparation, and consequently the liquid not beexpected to occur for a long interval.
. of the pipes I6 will be obvious.
level willbe restored to normal at the level of the upper ends of the tubes 20;
As a result of the ejector action, and also the possibility of removal of centrifugally separated large quantities of gas, the continuous removal ofaccumulated gas takes place with the result that only ,under the most abnormal conditions will the liquid level in the chamber l8 fall below the lower end of electrode 38 to close down the system. Under such conditions, as soon as the electrode 38 is cleared by the liquid, the jet air pump will reprime the system and, if the motor 2 is automatically controlled, it will restart as soonas the electrode 49 is submerged.
If the motor 2 is not arranged to be self-starting, then it is desirable to have some signal indicate the stoppage of the system to an operator, who may thereupon promptly restart it if the causeof the loss of prime has been corrected. In thecase of bilge pumps it is desirable to have manual starting since the failure of prime will be generally due to the removal of all the liquid in a bilge, and necessity for restarting would The tubes 29 preferably extend upwardly near the top of the chamber I8 so as to leave a minimum air space at the top of the tank preventing drop of liquid level to any substantial degree upon the occurrence of surges.
While reference has been made to priming with the motor stopped (as is generally desirable with centrifugal pumps) it will be clear that the prim ing system will opera e just as well with the motor runningjas may be the case in some instances ;where such type of priming is desirable and the centrifugal pump is of a type which will not be damaged by dry running for substantial periods of time. Ifthe motor is run-- ning when initial priming is taking place, the removal of centrifugally separated gas will take place as indicated above, withthe ultimate result that the conditions heretofore described will be established.
The reason for the relatively large diameter A large passage for the upwardly floating gas is desirable for its rapid accumulation at the top of the chamber l8. This should be free to occur without any possibility of having the passages through pipes I6 contain plugs of gas. On the other hand, the tubes 22 may be of relatively small diameter, since then a better ejector action is secured with a resulting fine dispersion of the gas so that it will be carried along by the liquid without again separating in the suction bells.
In Figure 4 there is illustrated a modification of the arrangement just described which is essentially the same as that modification except for provision for priming under conditionswhen a high pressure water supply is not available for actuating the water jet air pump. In this modification of Figure 4, the vacuum connection 24 is connected through the check valve 26 to a water jet air pump indicated at 62. This is arranged to discharge into a vessel 64, the discharge taking place through the pipe 66 opening within a chamber separated by a bafile 68 so as to provide for the more ready separation of the exhausted gas and prevention of passage of this is automatically controlled by the same type of electrical connections as were used for the control of the solenoid 34 in the previously described modification. In this case, however, the starting box is so arranged under relay control that the motor I2 will be started whenever the longer electrode 38 is uncovered by liquid and will be stopped only when the electrode 40 is submerged. Thus the motor I2 and the water jet air pump will be actuated only when it is necessary to draw a vacuum under the conditions described in connection with the previous modification.
The two modifications heretofore described will make clear the more general application of the invention to the use of various vacuum producing devices for effecting priming. Any suitable type of wet air pump might be substituted for the water jet air pumps described, and may be subjected to suitable control by the electrodes 38 and 48, as will be obvious. The vacuum connections illustrated, however, would necessitate a wet type of air pump. A dry type could not be directly used because the connections are of such nature that liquid may enter the pump. If a dry type of pump is to be adopted, then provision must be made to prevent passage of. liquid to the air pump. Arrangements for this will now be described in connection with the modifications of Figures 5 and 6.
Considering first the modification of Figure 5, there is illustrated therein an arrangement for the priming of a plurality of centrifugal pumps by means of a dry type vacuum pump. In this modification there are illustrated at 16 and 16' motors driving centrifugal pumps 18 and 18', which may be of any suitable type as indicated above. These pumps receive their liquid through the conduits 88 and 80, respectively.-
The pump 18 has extending through its suction bells and closely adjacent the shaft a pair of tubes 82 corresponding to the tubes 28 of the previously described modification. This pump also has communicating with the tops of its suction bells tubes 84 which correspond to the tubes I8 of the previous modification, but which are illustrated as not concentrically arranged with the tubes 82. (It will be understood that the concentric arrangement of the previous modification plays no particular part in the operation and merely serves for convenience of mounting of a small chamber such as I8.) The tubes 82 are preferably of small bore and the tubes 84 of large bore for the reasons indicated above in connection with tubes 20 and I6. The pump I8 is provided with tubes 82' and 84', respectively similar to tubes 82 and 84.
The tubes 82 and 82 are connected to a header 88 which is joined by tubing 88 to a wet chamber 98 located at a level substantially above the pumps. The connection 88 enters this wet chamber substantially above its bottom as indicated. The tubes 84 and 84' are joined to a header 92 which is connected by a tube 94 withv the bottom of the wet chamber 98. The wet chamber 90 may be built as a, unit with a dry chamber I00, separation being provided by a wall IIlI, though it will be obvious that chambers which are structurally completely separate may be provided. A valve 98 controls flow of gas from the chamber 99 to the chamber. I88, this valve receiving gas from the chamber 90 through a tube 98, which opens at the extreme top of the chamber 98 to thereby avoid the possibility of the passage of any substantial quantity of liquid into the chamber Hill. The valve 98 is controlled by a float I82, being open when the fioat is in its'lower position and closed when the float reaches an upper position in which it is arrested by a stop I84. The arrangement is preferably such that the tube 88 communicates with the chamber 98 above the top of the float I82 when in its arrested position so that when liquid rises to the level of the tube 88 the float will be held'by its full buoyant force against the stop I64 to therebyinsure that it will not bob up and down with slight fluctuations in the liquid level. Preferably it will have closed the valve 96 completely substantially before rising to its ultimate level.
Accumulation of liquid in the chamber I00 cannot be completely prevented since it will be carried over not only as fine spray, but more particularly in the form of vapor which may condense in the tank I88. Since, as in this case, the pumps may be of a type which cannot permissibly handle an aqueous liquid without damage, provision should be made for removing any accumulated liquid from the tank 28 from time to time. In the present case, this takes the form of a water jet ejector I88 connected at I86 to the bottom of the tank I88 with the interposition of a check valve I81 adapted to close and maintain the vacuum in the tank I08 when the jet pump is not operated. The supply line for the jet pump is indicated at III) and may be manually controlled. The discharge is through the pipe II2 into the wet chamber 98. Under usual conditions of operation, this jet pump need be operated only for very short periods at long intervals. A gauge glass may be provided to indicate any accumulation of liquid in the tank I00.
A vacuum is maintained within the chamber I00 through connections H4 and H4 containing check valves H5 and H5 by means of vacuum pumps H8 and H8 driven by motors H6 and HE. A pair of these vacuum pumps H8 and H8 is illustrated, since some installations require a very great factor of safety and it is desirable in such case to duplicate the vacuum pump to insure against failure of operation. The vacuum pumps in the present case are illustrated as of the Imo type, i. e., comprising a plurality of screws arranged to be motor driven and sealed to provide air pumping passages by means of oil contained in a tank indicated at 128. Pumps of this type are positive pumps capable of handling large quantities of air which may be separated from the recirculating oil by means of a screen arrangement indicated at 22 and thence pass outwardly through a pipe I24 which may pass to a device for further insuring separation and avoiding loss of oil. These pumps, while using oil for sealing purposes, would be classified as dry pumps, since they are apt to be damaged by a non-lubricating liquid such as water.
The motors H6 and H5 are under the control of vacuum switches I26 and I 28 communicating With the tank I 88 and controlling the motors through a motor starting box I38. The two vacuum switches are again provided for safety purposes. One of them, for example, may be effective to start the motors at a vacuum of 18 inches of mercury and stop the motors at 26 inches of mercury, while the other may start the motors at a vacuum of 16 inches and stop them at 26 inches. Thus the former will normally be the controlling switch, while the latter serves to effect its control only under emergency conditions.
Both of these should be of the snap type, as indicated, to avoid any instability of operation.
. A low water cutoff indicated at I32 may be used for control of the centrifugal pumpmotors to prevent their starting before the liquid rises to a predetermined level in the tank 90 and to cause them to stop if the liquid drops below such level. This low water cutofi may be either float controlled or may be of the electrode controlled type previously described.
In the operation of the modification of Figure 5, assuming the centrifugal pumps stopped, the priming may be initiated by closing the main switch controlling the motors H6 and I I6. The valve 96 will now be opened due to the lower position of the float I 02 and hence a vacuum will be drawn on the system causing the liquid to rise in the centrifugal pumps through the tubes 82 and 84, headers 86 and 92 and then the tank 90. As the rise of liquid continues, the low water control I32 will be actuated to either start automatically the motors I6 and I6 or to render it possible to start them manually. Eventually the float I02 will close the valve 96, thus preventing further entrance of gas into the tank I 00, whereupon the pumps II 8 and 8' will continue to operate until the vacuum switches stop them by reason of the drawing of a high vacuum in the tank. As operation proceeds, the ejector action described in connection with the previous modification will take place at the lower ends of the tubes B2and 82, resulting in further evacuation of gas from the chamber 90 and rise of liquid to force the float I02 against its stop I04. Thereafter the liquid will rise to the level of the connection 88 and recirculation will then take place upwardly through the tubes 84 and 84' and downwardly through the tubes 82 and 82. As small normal quantities of gas accumulate in the tank 90 this gas will be drawnoff without producing any dropping of the float I02 and, therefore, without opening the connection to the vacuum tank I00.
In the event that air is centrifugally separated in considerable amount within the intake bells of either of the pumps, this air will first escape 90 is of considerable size, there may still be no opening of the valve 96. A substantial amount of air may flow into the tank 90 without causing the float I02 to move away frim its stop.
In the event that a plurality of pumps are provided, it will be seen thatall contribute to the maintenance of the primed condition of any one of them. Consequently, even though one may receive. a substantially large quantity of gas, this gas will be rapidly removed by the action of the others, in fact without ever reaching the tank 90, since the ejector action in a companion pump or pumps will merely cause recirculation of the gas upwardly through the tubes 82 in the pump from which the gas flows, into the header 86 and downwardly through the tubes 82 of the pump or pumps which continue to operate normally.
As a result of the arrangement described, the
vacuum pumps H8 and H8 will operateusually only in starting up the system. They will resume operation only if such a large quantity of gas enters the tank 90 as will produce an opening of the valve 96 and reduction of the vacuum to an extent suflicient to throw one of the vacuum switches. By reason of the fact that the system of this by the water jet air pump I08 need be elfected only at long intervals.
At this point it may be remarked that the tubes 82 or 20 may be so formed at their lower open ends as to secure various efliciencies in the ejector action. In the event that they open in a direction perpendicular to the shaft, the ejector action is quite sufficient for most purposes, being, for example, such as to produce a vacuum of the order offour feet of water relative to the pressure in the suction bell. At the same time, they will remove rapidly any gas which may accumulate centrifugally about the shaft. A more eiiective ejector action may be secured if the lower ends of the tubes 82 open closely adjacent the shaft, but in the direction of circulation about the shaft, thus giving rise to a Pitot tube action.
Under such conditions, however, the separation of centrifugally accumulated gas is not as rapid as before because of the ejector action of the rotating gas. Such ejector action, however, is far less than, that secured by the passage of the liquid past the lower ends of these tubes.
In Figure 6 there is illustrated still another modification of the invention particularly adapted to the case of the pumping of water or other liquid containing sediment and relatively large quantities of gas, for example, in the pumping of driven wells. In this arrangement a motor I34 drives a centrifugal pump I36, the intake passage I38 of which receives liquid from the socalled sand tank I40, which is connected through passage I42 with the supply. Within the chamber I40 are baflles I44 designed to prevent the passage of sediment to the pump, the tank being provided in conventional fashion with a clean-out opening (not shown). centrifugal pump I36 is provided with a pair of tubes I46 extending through its suction bells to a point adjacent the shaft, these tubes I46 corresponding to the tubes 20 and 82 of the previous modifications. In this case, however, there are no tubes provided corresponding to Hi and 04,
inasmuch as the tank I40 serves for the separation of any gas which, in the absence of the tank I40, might separate in the suction bells of the pump. The tubes I46 are connected through a common tube I48 to the upper end of the tank I40, the head of which is indicated at UM, there being built as an upward continuation of it a vacuum tank I56.
Opening just below the top II of the tank M0 is a tube I50 communicating through a valve I52 with the pipe I54 entering the vacuum tank I56. The valve I52 is similar to the valve 96 previously described, and is controlled by a float I58 the upward movement of which is limited by a stop I6I so that when liquid rises to the height of the tube I48 the float I58 will be against the stop I60 and substantially completely immersed so as, to avoid fluctuations of its level and possible ing a supply of water under pressure through I66 and discharging at I68 into the tank I40. Asin the case, of the vacuum pump I08 previously de- The scribed, this vacuum pump serves for the removal of moisture which may accumulate in the bottom of the vacuum tank due to the passage of spray thereto or condensation.
From the top of the vacuum tank there extend vacuum lines I72 and I12 containing check valves I H3 and I16 and communicating respectively with high vacuum pumps driven by motors I'M and IN, this arrangement corresponding to that described in connection with the modification of Figure 5.
For the control of the motor Iii-i there may be provided the level switching arrangement I'Iii connected to the'tank I40 at I18 and IE0. Instead of a float controlled switch there may be provided an electrode type arrangement similar to that illustrated in the first modification. In any event, a suitable switching arrangement is provided to insure either automatic starting of the motor I34 when the liquid rises to a predetermined level or, alternatively, a possibility of manual starting. At the same time, the switching arrangement must provide for stopping of the motor I34 in the event of abnormal drop of the liquid level".
The vacuum pumps are under control of vacuum switches I82 and I84 connected to a common relay or motor starter I86. These switches may be of the same type and act in precisely the same fashion as the switches I22 and I28 of the modification of Figure 5. I
The above indication of the correspondence of elements of Figure 6 with those of Figure will make clear the nature of the operation of the modification of Figure 6. The only substantial difierence is that the circulation eiiected by the ejector action at the lower ends of the tubes I46 will be from the tank I45) through the tube M8 and tubes Hi6 after the liquid level rises to the level of IE8. Any air accumulating in the tank Idll will be drawn oii through the tube 38. As in the previous modification, this takes care automatically of any normal accumulations of air and the float I58 will be permitted to drop to open the valve I52 only upon an abnormal accumulation of air in the tank Mil. If this occurs, then the air will pass to the vacuum tank H36, Where substantial accumulation will result in renewed operation of the vacuum pumps. Under normal conditions, even with considerable accumulation of air in the tank M0 the vacuum pumps will not operate except in the initial priming of the system. If any sufficient amount of air should find its way into the centrifugal pump so as to be centrifugally separated in the suction bells the tubes I46 will take care of this air by permitting it to pass into the upper end of the tank I 4-0. As soon as the ejector action is renewed, this air will then be removed by the centrifugal pump.
In Figure '7 there is illustrated a modification of the invention applied to a gravel packed well of conventional type. Such a well comprises a casing IQI! which has a lower screen portion I92 through which water may enter. Surrounding the screen portion of the well and in general extending upwardly to the surface, there is a packing of gravel indicated at I 9%. There extends downwardly from the surface an outer shield indicated at H33 which is sealed with concrete to a level below the normal static water level, indicated at 283. In general, this static water level is less than five feet to the center line of the pumps;
Pumping is effected by connecting at 202 to the casing one or more centrifugal pumps indicated at 204, driven by one or more motors 206 and arranged to discharge through conventional check valves 208.
In accordance with the present invention, the casing I9!) is continued to a substantial height above theintakes of the pumps, say about five feet above the pump house floor. I The extension or the casing as well as the casing itself may be two or more feet in diameter so that there is provided by the extension 2H] a quite large diameter which may act as a reserve pump for available liquid to prime the pumps in the event of any large influx of air.
The extension 2H] is provided with a cover ZIZ. from whichextends a pipe 2 I4 to a vacuum tank 216, having wet and dry compartments M8 and 220, respectively. Since this tank and its various associated parts may be identical with the tank assembly heretofore indicated at Hill in Figure 5,
the various parts thereof need not be described.
The dry portion 220 of the tank is connected to vacuum pumps 222, as heretofore described, under control of vacuum switches, and the wet compartment 2| 8 is connected through pipes 224 to tubes 226 closely approaching the pump shafts as previously described, so as to give rise to an ejector action during operation of the pumps.
The operation of this modification is quite similar to that of the modifications previously described. The vacuum pumps create a vacuum to cause the supply liquid to rise into the wet chamber 2I8 until the float therein closes off the vacuum communication. Thereafter, as the pumps run, they maintain by ejector action the vacuum above the level of the liquid in the Wet compartment, causing the float valve to rise against its stop and produce ultimately a circulation of liquid from the extension 2) of the casing through the wet compartment and to the pumps through the pipes 224 and 225. Thus accumulation of air in the extension 2H1 is drawn ofi? without having the communication between the tanks 2I8 and 220 reopened under normal circumstances. Even a sudden large influx of air will not interfere with operation by causing the centrifugal pumps to lose their prime because of the large volume provided by the casing extension. Any such large amount of air which may enter the casing will be taken care of gradually bythe ejector action and, of course, by the volume pumps if the influx is such as to cause the float valve to open. A suitable low level safety. arrangement may be provided to stop the centrifugal pumps in case the liquid level becomes dangerously 10w within the casing extension.
It will be understood that the various elements of the device, particularly the vacuum pumping arrangements, may take various forms. For example, water jet ejectors or even steam jet air pumps may be used throughout the arrangement, or either wet or dry types of mechanical vacuum pumps may be used. In' the event that wet types are used, no precautions need be taken to avoid the passage of water to the pumps, and accordingly the general type of arrangement indicated in Figure 1 can be adopted. The adaptation of this to a sand chamber or tank of the type indicated in Figure 6 will be obvious, as will also be its adaptation to the priming of a plurality of pumps.
It will be noted that the various modifications described above have in common the characteristic of maintaining abovethe pump a quite substantial supply of liquid sothat, in effect; the
pump is maintained primed by what is during operation a flooding arrangement. Thus, while the invention contemplates a suction priming system, it is differentiated sharply from such priming systems as merely raise the liquid to the level of the pump, but whichwould permit the pump and subjected to an ejector action of liquid being handled by said pump to cause rise of liquid in said chamber substantially above said predetermined level, said last means comprising a tube opening closely adjacent the shaft of said pump and subjected to the ejector action of liquid ad-;
jacent said shaft, and arranged to provide flow of centrifugally separated gas adjacent the shaft to said chamber during its evacuation by the first mentioned evacuating means. i
2. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage to thereby prime the pump; means controlled by rise of liquid in said chamber to a predetermined level to stop the evacuation of said chamber by said means; means connected to said chamber and subjected to an ejector action of liquid being handled by said pump to cause a rise of liquid in said chamber substantially above said predetermined level; and means for effecting further evacuation of said chamber by the first mentioned evacuating means only when said liquid level falls substantially below the level to which it rises under the action of said last named means.
3. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage to thereby prime the pump; means for stopping the evacuating action of the last means when the liquid has been so raised; means connected to said chamber and subjected to an ejector action of liquid being handled by said pump to maintain a partial vacuum in said chamber after evacuation by said evacuating means ceases; and means for effecting further evacuation of said chamber by the first mentioned evacuating means only when the liquid level drops substantially below a normal level attained under the action of said means subjected to ejector action of liquid.
4. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage to thereby prime the pump; means controlled by rise of liquid in said chamber to a predetermined level to stop the evacuation of said chamber by said evacuating means; and means connected to said chamber and subject to an ejector action of liquid being handledby said pump to maintain a partial vacuum in said chamber, said last means comprising a tube opening closely adjacent the shaft of said pump and subjected to the ejector action of liquid adjacent said shaft, and arranged to provide flow of centrifugally separated gas adjacent the shaft to said chamber during its evacuation by the first mentioned evacuating means.
5. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump for accumulation of gas contained in the liquid being pumped; means for evacuating said chamber to raise liquid therein to a level above the intake passage to thereby prime the pump; means connected to said chamber and subjected to an ejector action of liquid within the intake passage and being pumped to maintain a partial vacuum in said chamber, said last means comprising a tube opening closely adjacent the shaft of said pump and subjected to the ejector action of liquid adjacent said shaft; and means; effective to close communication between the chamber and said evacuating means when liquid in the chamber reaches a predetermined level below the level of connection with the chamber of the means subjected to said ejector action of liquid.
6. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage thereby to prime the pump; means controlled by rise of liquid in said chamber to a predetermined level to stop the evacuation of said chamber by said means, and controlled by drop of liquid to resume evacuation of said chamber by said means; and means connected to said chamber and subjected to an ejector action of liquid being handled by the pump to evacuate the chamber to maintain the liquid being handled by said pump to effect continuous removal of gas accumulating in said chamber to maintain at least said predetermined level of liquid which is effective to stop evacuation.
8. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage thereby to prime the pump; means controlled by rise of liquid in said chamber to a predetermined level to stop evacuation of said chamber by said means; and additional evacuating means connected to said chamber and effective when the pump is handling liquid to cause a rise of liquid in said chamber substantially above said predetermined level and to the connection of said additional evacuating means with the chamber so that liquid flows from the intake passage through the last named means during operation of the pump.
9. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage thereby to prime the pump; means controlled by rise of liquid in said chamber to a' predetermined level to stop evacuation of said chamber by said means; and additional evacuating means connected to said chamber and subjected to an ejector action of liquid being handled by said pump to cause a rise of" liquid in said chamber substantially above said predetermined level and to the connection of said additional evacuating means with the chamber so that the liquid is circulated from and vacuum tank when the liquid rises to a predetermined level in said chamber; and means connected to said chamber and continuously subjected to an ejector action of liquid being handled by said pump to effect continuous removal of gas accumulating in said chamber and to maintain at least said predetermined level of liquid there- 11. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage thereby to prime the pump, said evacuating means comprising a vacuum tank connected to said chamber, and a pump for creating a partial vacuum in said tank; means for closing the connection between the chamber and vacuum tank when the liquid rises to a predetermined level in said chamber; means for stopping the action of the vacuum pumpv when the vacuum in the tank is substantially higher than the vacuum corresponding to rise of liquid to said predetermined level; and means connected to said chamber and continuously subjected to an ejector action of liquid being handled by the centrifugal pump to effect continuous removal of gas accumulating in said chamber and to maintain at least said predetermined level of liquid therein. i
12. In combination, a centrifugal pump; means providing a chamber connected to the intake passage of the centrifugal pump; means for evacuating said chamber to raise liquid therein to a level above the intake passage thereby to prime the pump; means for stopping the evacuating action of the last means when the liquid has been so raised; and means connected to said chamber and subjected to an ejector action of liquid being handled by said pump to maintain a partial vacuum in said chamber after evacuation by said evacuating means ceases, said last means comprising a tube opening closely adjacent the shaft of said pump and subjected to the ejector action of liquid adjacent said shaft.
13. In combination, a centrifugal pump comprising a casing having intake and discharge passages, a rotor, and a shaft carrying the latter; means providing a chamber connected to the intake passage of the centrifugal pump; and means connected to said chamber and subjected to an ejector action of liquid being handled by said pump to cause rise of liquid in said chamber, said last named means comprising a tube opening closely adjacent the shaft of said pump at the intake side of the rotor and subjected to the ejector action of liquid rotating adjacent said shaft.
14. In combination, a centrifugal pump comprising a casing having intake and discharge passages, a rotor, and a shaft carrying the latter; means providing a chamber; means connecting a lower portion of the chamber to the intake passage of the centrifugal pump; and additional means connecting the chamber to the intake passage of the centrifugal pump comprising a tube communicating with the upper portion of said chamber and opening closely adjacent the shaft of said pump and subject to the ejector action of liquid rotating adjacent said shaft.
FRANK S. BROADHURST.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US2790393 *||Mar 29, 1952||Apr 30, 1957||Waterous Co||Priming valve assembly|
|US2810350 *||May 31, 1956||Oct 22, 1957||Flood City Brass & Electric Co||Automatic pumping system|
|US3431708 *||Apr 25, 1967||Mar 11, 1969||Moretrench Corp||Vacuum line closure method and device for separation chambers in ground-water pumping systems|
|US4067663 *||Aug 13, 1976||Jan 10, 1978||The Chemithon Corporation||Sewage pump priming system|
|US4183721 *||Jan 13, 1978||Jan 15, 1980||Jenoff, Inc.||Apparatus for automatically water charging a centrifugal fire pump|
|US8967274 *||Jun 28, 2012||Mar 3, 2015||Jasim Saleh Al-Azzawi||Self-priming pump|
|US20130104596 *||Jun 28, 2012||May 2, 2013||Jasim Saleh Al-Azzawi||Self-priming pump|