US3250440A - Pumping apparatus - Google Patents

Description

y 1966 R. G. TROUT 3,250,440

PUMPING APPARATUS Filed Dec. 23, 1963 3 Sheets-Sheet l INVENTOR ROBERT G. TROUT May 10, 1966 R. G. TROUT 3,250,440

PUMPING APPARATUS Filed Dec. 23, 1963 3 Sheets-Sheet z INVENTQR ROBERT G. TROUT A'ITORNEY May 10, 1966 R. G. TROUT PUMPING APPARATUS 3 Sheets-Sheet 3 Filed Dec. 23, 1965 mm. ww. 3. QW- \3 mm. NM m w //H i mm r WI. E, N a a "M we mw. m m NN. ----Q M ow. E g V m qmf [J MA hm. mm m ll.. WWI/l All .3 F 2 Nm United States Patent 3,250,440 PUMPING APPARATUS Robert G. Trout, Altadena, Calih, assignor to FMC (Zorporation, San Jose, Calif., a corporation of Delaware Filed Dec. 23, 1963, Ser. No. 332,386 9 Claims. (Cl. 222255) The present invention pertains to a pumping apparatus and more particularly to an apparatus for pumping substantially all of the liquid from a reservoir, without the formation of air vortexes which would cause the apparatus to become air-bound, and while maintaining the vol ume of liquid being pumped per unit of time at a predetermined amount.

The problem solved by the apparatus of the present invention exists in the removal of liquid from a reservoir and, more specifically, liquid cargo from the hold of a tanker. As is well known, the ships hull forms the bottom of the hold in order to maximize the amount of liquid that can be transported. Small external sumps are not used since they would extend below the bottom of the vessel and thereby the subject to damage as well as to increase the drag on the ship. Small internal sumps are not built into the ship since they would result in the loss of considerable space which could otherwise be used to carry cargo.

Conventionally, a high capacity multi-st-age centrifugal pump is lowered into the hold, positioned with its inlet adjacent to the bottom, and operated to pump the liquid therefrom. Although capable of removing most of the liquid with no difiiculty, previously known pumps of this type have been unable to remove the last twelve or so inches while operating at the same high pumping rate. The reason for this inability is that as the liquid level nears the bottom of the hold, air vortexes form in the liquid around the inlet to the pump. These vortexes, and there may be several of them around the pump inlet, may be visualized as whirling funnels of air which have a maximum diameter at the surface of the liquid and converge downward to a tip at the pump inlet'. As a result, air is drawn into the pump with the liquid. This causes the pump to air-bind, that is to fill with so much air that its liquid discharge essentially disappears.

In order to remove most all of this last foot or so of liquid, other procedures must be resorted to. First, the operator usually reduces the rate of flow through the pump; this has the effect of eliminating vortexes at least until about six more inches are pumped out. At this level, a high volume pump is ordinarily unable to remove any more liquid. And yet, these six inches of liquid must be removed since they may represent dozens of barrels of a saleable commodity.

Thus, it has been known to use complicated air separating systems on the centrifugal pump, to pressurize the hold, or to use a low capacity, high head pump, in an effort to strip the hold of these last several inches of liquid. These auxiliary methods and apparatus for stripping the hold are more time consuming and more expensive than regular high capacity operation of the centrifugal pump. Extra labor is required to install the dilferent pumps and apparatus for carrying out these auxiliary methods. The ship is at dockside longer, resulting in higher costs and aggravating congestion at the port.

This background of the problem brings the present invention into sharp focus, for a high capacity pumping apparatus embodying one form of the present invention can remove all of the liquid from a hold, with the exception of about one barrel, while operating at full capacity; and if it embodies another form it can remove essentially all of the remaining liquid.

It is an object of the present invention to provide an improved pumping apparatus.

3,259,446 Patented May 10, 1966 Another object is to provide an apparatus for pumping substantially all of the liquid from a reservoir, without the formation of air vortexes which would cause the apparatus to become air-bound, and while operating the apparatus at a predetermined high rate of flow.

Another object is to provide a pumping apparatus which minimizes the time, expense, and labor involved in pumping liquid out of a reservoir, such as the hold of a tanker.

Another object is to achieve high volume pumping while removing the liquid in a reservoir to a minimum distance from the bottom thereof.

Another object is to control the maximum velocity of liquid flowing through a circumferential passage into the inlet of a pumping apparatus which passage is defined between the bottom of a reservoir containing the liquid and the apparatus.

These, together with other objects, will become apparout upon reference to the following description and accompanying drawings in which:

FIG. 1 is a fragmentary diagrammatic transverse section of a tanker and shows a pumping apparatus including a vortex hood embodying the present invention mounted on the tanker and projecting into the hold thereof.

FIG. 2 is an enlarged side elevation of a portion of the pumping apparatus with portions being broken away and in section and shows specific details of a frusto-conical form of the vortex hood in closely spaced relation to the bottom of the hold.

FIG. 3 is a transverse section taken on a plane at a position indicated by line 3-3 of FIG. 2.

FIG. 4 is a plan view of a frusto-pyramidal form of the vortex hood for use in certain installations instead of the hood of FIG. 2.

FIG. 5 is a diagram contrasting the results achieved with the subject apparatus and with conventional apparatus.

FIG. 6 is a view similar to FIG. 2 but shows another form of the pumping apparatus.

Referring more particularly to the drawings, a portion of a tanker 10 is schematically shown in FIG. 1 and is provided with a hold or reservoir 12 having a bottom 14 and being capable of containing a cargo of liquid, a small amount of which is indicated at 15 in FIG. 1. The tanker has a bulkhead 16, constituting one wall of the hold, and a deck 18.

A pumping apparatus embodying the present invention is generally indicated by the numeral in FIG. 1. The illustrated pumping apparatus includes a high volume, high head, multistage centrifugal pump 26 having a rotary power source 27, such as a steam turbine or electric motor, a tubular housing 28 terminating in a lower suetion piece 29, and a vortex hood 30 connected to the suction piece. The present invention is primarily concerned with this vortex hood and particularly its relationship to the bottom 14 of the hold 12 or other reservoir.

The housing 28 of the pump 26 includes a discharge casting projecting downward from the power source 27 and having an outlet 36 and a horizontal deck flange 37. The pump is supported on the deck 18 of the tanker 10 by a riser 39 that rests on the deck, receives the housing, and bears the weight of the pump since the deck flange rests on the riser.

The housing 28 also includes a column pipe connected to the discharge casting 35 and projecting through the riser 39 and downward through thehold 12. A bowl assembly 46, also constituting part of the housing as defined herein, is connected to the pipe and projects toward the bottom 14 of the hold. Guides, such as 48, encircle the pipe and are attached to the bulkhead 16.

The pump 26 also has a drive shaft (FIG. 2) connected to the rotary power source 27 and extending downward through the housing 28. Impellers 52 are secured to the drive shaft within the bowl assembly 46, in a well known manner. It is thus evident that the tubular housing provides a liquid duct(s) 55 having a lower inlet 56 at the lowermost impeller and an upper outlet 36.

The suction piece 29 (FIG. 2) is frustum-shaped and includes an upper neck 60 bolted to the bowl assembly 46 in circumscribing relation to the inlet 56, an imperforate intermediate wall 61, having an inner convex surface and an outer concave surface, diverging outward and downward from the neck, and an outer up-turned rim 62 provided with an external annular groove 63. An O-ring 64 is fitted in this groove for establishing a primary seal with the vortex hood 36, as will be sub sequently evident.

Vertical ribs 66 are secured to the outer surface of the suction piece 29 in circumferentially spaced relation therearound, and each rib has an aperture 67 located adjacent to the rim 62. A spider 69 is secured to the inner surface of the wall 61 and mounts a bearing 70 which rotatably journals the lower end portion of the drive shaft 50.

The vortex hood 30 can have various shapes. A frustoconical vortex hood is identified by the numberal 30a in FIG. 2. This'hood has an upper inner neck 75 encircling the rim 62 of the suction piece 29 and being in releasably slidable, fluid-tight relation therewith by virtue of the O-ring 64. The hood 30a also has an imperforate intermediate Wall 76 diverging downward and outward from the neck 75, and a lower outer circular edge 77 having a predetermined circumference c, to be subsequently described in more detail, and being closely spaced at a distance s from the bottom 14 of the hold 12. For reinforcement, ribs 79 are secured externally to the neck, wall and lower edge of the hood.

When the pumping apparatus 25 is used for removing liquid 15 from the hold 12 of a tanker 10, the hood 30a is preferably permanently secured to the bottom 14 of the hold. For this purpose, blocks 78 are welded to the underside of the lower, outer edge 77 and to the bottom in circumferentially spaced relation to eachother. The outer edge of the hood and the bottom of the hold define an annular flow passage 80 having an area about equal to the product of the space s and the circumference c, it being noted that the circumference of the flow passage is actually slightly less than the circumference of the outer edge because of the blocks; however, in order to simplify the discussion herein, reference will be made only to the circumference c of the outer edge since the two are nearly the same.

With the vortex hood 30a secured to the bottom 14 of the hold 12, the pump 26 can be inserted into the upper neck 75, thereby being coupled to the hood in fluidtight relation, or can be withdrawn from the hood in order to be removed from the hold. In the coupled position of the pump, an annular pocket 81'is defined between the neck of the hood and the outer surface of the suction piece 29. As the liquid level in the hold drops below the neck, a quantity of liquid 82, hereinafter referred to as the sealing liquid, is captured in this pocket and constitutes a secondary seal in overlying relation to the primary seal established by the O-ring 64. Although the O-ring, in itself, is capable of providing a sufiicient seal between the suction piece and the hood, insertion and removal of the pump may damage the primary seal 64 so that the secondary seal insures fiuid tight coupling. The apertures 67 allow the sealing liquid 82 to flow through the ribs 66, and the upper neck 75 of the hood has overflow holes 84 which control the level of the sealing liquid. In this manner, a substantially uniform depth of sealing liquid is maintained in the pocket, circumferentially of the rim 62, in accordance with the secondary sealing effect required.

It is also to be noted that the vortex hood 30 can be permanently attached to the pump 26 without affecting the operation of the pumping apparatus 25 according to the present invention. However, because of its relatively large circumferences c, as will be subsequently more evident, and because it is not required for proper operation of the pump where stripping a reservoir is not desired, the hood is preferably not permanently attached to the pump.

Another shape of the hood 30 is illustrated in FIG. 4. Here is shown a frusto-pyramidal hood 39b which is useful for certain installations where the available area cannot accommodate a circular hood 36a having the desired circumference c. The hood 30b has an upper neck 75b, an intermediate imperforate wall 76b including panel portions 86, and a rectangular lower-outer edge 77b having a circumference c. For the reasons described above, blocks 88 are secured to the outer edge 77b for spacing the outer edge at a distance s from the bottom 14 of the hold 12 and, if desired, permanently attaching the hood 30b to the bottom.

The selection of the dimensions s and e is of primary importance to the successful practice of the present invention in retarding vortex formation and resultant entry of air into the pump inlet 56. Naturally, the dimension s should be as small as possible since, for practical purposes, when the liquid level falls below the edge 77, or 7717, air will be drawn into the inlet whether or not any vortexes have formed. However, other factors, such as unevenness of the bottom, may require the dimension s to be more than the optimum amount.

Once dimension s is determined, it is possible to calculate the circumference c from the equation Q=kcsv, where Q=the rated capacity of the pump 26 k the pump constant v velocity of flow through the passage A high capacity pump, such as the multi-stage centrifugal pump 26, having a pressure head capable of lifting liquid from the bottom of the hold to the outlet 36, is selected so that Q and k are known.

As for the velocity v, it was discovered during development of the pre'sent'invention that the velocity of flow through the passage 80 should not be greater than about one foot per second if detrimental vortex formation to prevent air binding of the pump to be retarded until the liquid reaches a minimum level. With Q, k, s and v known, 0 is readily obtained by solving the above equation. Once Q and s are selected, therefore, the opti mum value of 0 actually depends on the important velocity factor.

It is obviously not practical to state herein all of the various combinations of pump capacities and dimensions s and c that will effectively strip the hold 12 or other reservoir of liquid. One example of the subject apparatus 25, together with the foregoing information on how to determine the important parameters, will suffice to show others skilled in the art how to practice the present invention under conditions which differ from those of the example. Thus, assume that the pumping apparatus 25 is to be used for removing kerosene from the hold 12 of the tanker 10, and that because of space limitations, it is necessary to use the frusto-pyramidal hood 30b instead of the frusto-conical hood 30a. The bottom 14 of the hold is surveyed and other factors considered in arriving at a distance s of about /2 inch. In order to obtain the desired lift, a nine-stage, turbine driven centrifugal pump 26 having a volumetric capacity of 500 gallons per minute and operating at 1760 r.p.m. is employed. With the pump capacity Q and the distance s determined, the circumference c is readily calculated, as above explained. Accordingly, the length and width of the outer edge 77b used in this installation is respectively five feet and two feet; it is also to be noted that with these dimensions, the distance between the bottom 14 and the neck 75b is approximately two and one-half inches.

The hood 3% is, of course, attached to the bottom 14 of the hold 12 when the latter is empty, but assuming that the hood is in place and that liquid is in the hold, the pump 26 is installed. The pump is operated at its rated capacity of 500 gallons per minute and pumping continues at this rate until air vortexing occurs. With the present invention, vortexing doesnt occur until the liquid level is about where it is shown in FIG. 1, that is, between the neck 75b and lower edge 77b of the hood 30b, this usually being two or three inches off the bottom 14. At this low level, less than one barrel of liquid may be all that remains in the hold. These results are in contrast to those achieved by conventional pumping equipment where air vortexing and resulting binding of the pump has usually occurred when there are still dozens of barrels of liquid remaining in the hold.

FIG. 5 is a diagram which contrasts the results obtained by conventional equipment (on the left) and results obtained by use of the present apparatus (on the right). The conventional apparatus includes a pump which may be identical with the pump 26 but for purposes of separate identification herein is given the numeral 95. A conventional suction piece 96 is attached to the lower end of this pump and usually has a maximum diameter D about the same as the diameter of the bowl assembly of the pump. The minimum spacing of the suction piece from the bottom 14 is usually A to /2 of D. Under these circumstances, air vortexes 97 and resultant airbinding of the pump occur when the liquid is about at the neck of the suction piece 96; this may be thirteen to fourteen inc-hes off the bottom, just to give an example for comparison purposes. In order to remove any more of the liquid with the pump 95, it is necessary to reduce its pumping capacity whereupon the liquid level may be reduced to that indicated by the dashed line 98 just above the lower end of the suction piece. Any further removal of liquid must be accomplished by other apparatus or methods, as suggested in the introduction to the specification.

By way of contrast, the subject pumping apparatus is shown diagrammatically in FIG. 5 on the same scale as the conventional apparatus 95. The pump 26 can be operated at its full capacity until the liquid level is below the neck 75, or 75b, of the hood 30, at which time air vortexes 99 may form. It will be evident, therefore, that the subject pumping apparatus removes more liquid in less time than a conventional pumping apparatus, it being noted that the same pump is used in each apparatus.

Another form of pumping apparatus embodying the present invention is illustrated in FIG. 6. Since the pump employed in the form of FIG. 6 is the same as the pump of FIGS. l-S, with one exception, the same reference numerals are applied to corresponding parts with prime suflixes added. The one exception is that the shaft 50' has an end portion 51 extending out of the inlet 56.

Asuction piece 105 has an upper neck 106 bolted to the bowl assembly 46', an intermediate wall 107 diverging downward from the neck, and a lower outer rim 108 provided with an external groove 109 in which is placed an O-ring 110. Ribs 112 are secured externally to the suction piece, each rib having an aperture 114 therein. As described so far, the suction piece 105 is identical with the suction piece 29.

This form of the pumping apparatus 25 includes a main vortex hood 120 which is identical with the vortex hood 30a and so is described only by briefly identifying its neck 121, its intermediate wall 122, and its lower outer edge 123 which is fixedly held in predetermined space relation to the bottom 14 by blocks 124.

The significant, distinguishing feature of this form of the apparatus is an auxiliary pump 130 of low capacity although having as high a pressure head as the pump 26. An example of a pump that is suitable for this purpose is a regenerative turbine vane pump. The form of auxiliary pump disclosed has only one stage and operates at a capacity as low as ten to twenty gallons per minute, although having a very high head as stated. The auxiliary pump includes a concave-convex mounting shroud 131 rotatably receiving the end portion 51 of the shaft 50' and rigidly secured to the suction piece by circumferentially spaced webs 132. A hearing 133 is mounted within the shroud in surrounding relation to the shaft. The pump includes a casing 135 bolted to ribs 136 depending from the shroud. The casing has a chamber 138 which is provided with a radially disposed inlet 139, on the left of the shaft as seen in FIG. 6, and a radially disposed outlet, not shown, which is circumferentially displaced from the in let. An impeller 142 is positioned within the chamber and issecured to the shaft. The casing has a lower orifice 144 in alignment with the shaft for balancing pressures above and below the impeller and for draining liquid from the chamber. Such a pump, per se, is known and not described in any greater detail.

The auxiliary pump 130 (FIG. 6) also includes a discharge elbow 150, preferably cast integrally with the suction piece 105 and the mounting shroud 131, having a lower end 151 connected to the outlet of the chamber 138 and an upper socket. 152 above the suction piece. An auxiliary discharge tube 154 has a lower end threaded into the socket, projects upward alongside of the pump 26, and has an upper outlet, not shown.

An auxiliary vortex hood 160 has a neck 161 bolted to the shroud 131, an intermediate downwardly diverging wall 162, and a lower outer edge 163 maintained in spaced relation to the bottom 14 by blocks 165 that are secured to the auxiliary hood. It is to be noted that the auxiliary hood is fastened to the auxiliary pump 130 and not to the bottom, in contrast to the main hood 120.

The lower edge 163 of the auxiliary hood 160 is prefcrably spaced even closer to the bottom 14 of the hold 12 than the outer edge 123 of the main hood and defines a flow passage 166 with the bottom. It is, of course, obvious that the circumference of the lower edge 163 is less than the circumference of the lower edge 123.

In operation of the form of pumping apparatus illus trated in FIG. 6, the main pump 26' is operated at its full capacity in order to remove liquid from the hold 12 until the liquid level drops below the neck 121 of the main hood 120 where air vortexing occurs, as described above. Since the auxiliary impeller 142 is on the main pump shaft 50', this auxiliary impeller rotates along 'with the main impellers 5.2. However, the auxiliary pump does not take effect until the main pump entraps so much air that it ceases to discharge. Thereafter, the main pump continues to work, but liquid is actually being pumped out of the hold by the auxiliary pump and through the discharge tube 154.

Since the capacity of the auxiliary pump 130 is only fractional relative to the capacity to the main pump 26', the velocity of flow through the passage 166 is less than one foot per second even though the circumference of the edge 163 is considerably less than the circumference c. The advantage of the auxiliary pump is that no shutdown of the pumping apparatus 25' is required to evacuate the hold of substantially all liquid, even though the rate of removing the last two or three inches of liquid by the auxiliary pump is slower than removing a corresponding amount of liquid by the high capacity main pump. In considering the operation of the auxiliary pump, it is to be noted that atmospheric pressure forces liquid up into the auxiliary vortex hood and mounting shroud 131 to the inlet 139 as long as no air is admitted under the edge 163 of the auxiliary hood.

Although the subject pumping apparatus has been described with the suction piece 29, or 105, connected directly to the bowl assembly 46, or 46, it is to be understood that the bowl assembly could be located remotely from the suction piece, and that the latter could be directly connected to the column pipe 45. It is also to be understood that although the subject apparatus is particularly suited for use with the multi-stage, high capacity centrifugal pump described, the principles of the invention are applicable to other types of pumps.

From the foregoing, it will be evident that a pumping apparatus according to the present invention is capable of pumping substantially all of the liquid from a reservoir, without the formation of air vortexes which would cause the apparatus to become air-bound, and while maintaining the volume of liquid being pumped per unit of time at a predetermined amount. As applied to stripping the hold of a tanker, the subject apparatus is advantageous in withdrawing the maximum amount of liquid cargo in a minimum of time and with a minimum of expense and labor.

Although preferred embodiments of the present invention have been shown and described, it will be understood that various changes and modifications may be made in the details thereof without departing from the spirit and scope of the appended claims.

Having described the invention, what is claimed as new and desired to be secured by Letters Patent is as follows:

1. A pumping apparatus comprising a main pump having an inlet, outer wall means circumscribing said inlet and diverging therefrom to an outer edge, and an auxiliary pump mounted within said wall means in spaced relation to said inlet of the main pump, said auxiliary pump having an auxiliary inlet and inner wall means circumscribing said auxiliary inlet and diverging to an inner edge spaced circumferentially inward from said outer edge.

2. The pumping apparatus of claim 1 wherein a plurality of spaced webs rigidly interconnect said outer wall means and said auxiliary pump.

3. The pumping apparatus of claim 1 wherein a discharge pipe is connected to the outlet of said auxiliary pump and extends through said outer wall means.

4. The pumping apparatus of claim 1 wherein said main pump is a multistage high capacity centrifugal pump and wherein said auxiliary pump is a single-stage low capacity regenerative turbine vane pump.

5. The pumping apparatus of claim 1 wherein said inv ner edge is in a plane displaced axially endward of the outer edge.

6. The pumping apparatus of claim 1 including a reservoir having a bottom, means securing said outer wall means to said bottom with the outer edge spaced from the bottom, and wherein said inner edge is spaced from said bottom.

7. A pumping apparatus comprising a high capacity, high head main pump having an elongated housing terminating in an endwardly opening inlet, a shaft journalled in said housing and having an end portion projecting out of said inlet, means for drawing liquid into said housing through said inlet, and other frustum-shaped wall means in circumscribing sealing engagement with said housing and diverging therefrom to an outer edge; and a low capacity, high head auxiliary pump having a pump casing mounted on said outer wall means around the end portion of the shaft and in endwardly spaced relation to the inlet of the main pump, said casing having a pump chamber positioned so that a plane passing through the chamber is substantially normal to the shaft, said chamber having a radially opening inlet and a radially opening outlet, an impeller secured to the end portion of the shaft and positioned in said chamber, inner frustum-shaped wall means connected to the casing in circumscribing relation to the inlet of the auxiliary pump and diverging downward to an inner edge spaced inward from the outer edge of the outer wall means, and a discharge pipe connected to the outlet of the auxiliary pump and extending through both'of said wall means.

8. In an apparatus for pumping liquid from a liquid reservoir having a suction piece providing an inlet submerged in the liquid, the inlet being circumscribed by a peripheral edge that is spacedfrom the bottom of the reservoir, anr whereupon, during entry of liquid into the inlet during pumping, one or more air vortexes form in the liquid and converge from the surface thereof to said edge when said surface is at a predetermined level above said edge whereby it is ordinarily necessary to reduce the volume of liquid being pumped per unit of time below the rated capacity of the pumping apparatus in order to eliminate said vortex formation, the improvement of means for eliminating said vortexes at said predetermined level and retarding the formation thereof until the liquid surface is below said level comprising an imperforate hood having an upstanding neck surrounding said inlet in spaced relation therewith and projecting down and out from said peripheral edge to a lower outer edge spaced closer to said bottom than said peripheral edge and defining a flow passage with said bottom, said flow passage having an area that is large enough to substantially reduce the flow velocity with respect to the flow velocity in said inlet so as to allow liquid to be pumped therethrough at said rated capacity while preventing air vortexes from forming until said surface is below said level, said suction piece and said hood being releasably slidably coupled in fluid tight relation, said suction piece and said neck forming an annular pocket therebetween, and liquid in said pocket to establish a secondary seal between said neck and said suction piece.

9. The means of claim 8 wherein said neck has an overflow passage communicating with said pocket.

References Cited by the Examiner UNITED STATES PATENTS 1,943,603 1/1934 Hartman.

2,533,697 12/1950 Stewart 222-464 X 3,151,565 10/1964 Albertson et al. 222-385 X FOREIGN PATENTS 1,020,237 11/1957 Germany.

RAPHAEL M. LUPO, Primary Examiner. HADD S. LANE, LOUIS J. DEMBO, Examiners.

Claims (1)

1. A PUMPING APPARATUS COMPRISING A MAIN PUMP HAVING AN INLET, OUTER WALL MEANS CIRCUMSCRIBING SAID INLET AND DIVERVING THEREFROM TO AN OUTER EDGE, AND AN AUXILIARY PUMP MOUNTED WITHIN SAID WALL MEANS IN SPACED RELATION TO SAID INLET OF THE MAIN PUMP, SAID AUXILIARY PUMP HAVING AN AUXILIARY INLET AND INNER WALL MEANS CIRCUMSCRIBING SAID AUXILIARY INLET AND DIVERGING TO AN INNER EDGE SPACED CIRCUMFERENTIALLY INWARD FROM SAID OUTER EDGE.

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