US3519369A

US3519369A - Pump priming system

Info

Publication number: US3519369A
Application number: US761023A
Authority: US
Inventors: Frank G Weis
Original assignee: Union Tank Car Co
Current assignee: Smith and Loveless Inc; Union Tank Car Co
Priority date: 1968-09-20
Filing date: 1968-09-20
Publication date: 1970-07-07
Anticipated expiration: 1987-07-07
Also published as: FR2018560A1; BE739110A; DE1947573A1; GB1264715A

Description

` July 7, 1970 F. G. Wens 3,519,369

PUMP PRIMING SYSTEM Filed Sep'.. 20, 1968 2 Sheets-Sheet l I' s w /J/ /7 f I I I I I 'I 'f j i ff 1| 4Z N 4^ r" m 1| ii lng/ 2li; l 1]/ .mm digi fyf/5 W 20 ifi-f 4% if /Z l/ \\/f C) z ,ff o 0 r O l: O wma/me ll /Fw/z July 7, 1970 F. G. wr-:ls

PUMP PRIMING SYSTEM 2 Sheets-Sheet 2 Filed Sept. 20. 1968 United States Patent O 3,519,369 PUMP PRIMING SYSTEM Frank G. Weis, Kansas City, Mo., assignor to Union Tank Car Company, Chicago, Ill., a corporation of Delaware Filed Sept. 20, 1968, Ser. No. 761,023 Int. Ci. F04d 1/00, 9/00 U.S. Cl. 417-36 6 Claims ABSTRACT F THE DISCLOSURE A priming system for a vertical shaft centrifugal pump. The system includes vacuum means connected to a priming chamber. The priming chamber is connected to a pumping chamber through the top wall of the pumping chamber in a low pressure area thereof. An electrical priming circuit actuates priming and terminates it when liquid has completely filled the pumping chamber and reaches the electrode extending into the priming chamber.

BACKGROUND OF THE INVENTION This invention relates in general to pump construction and, more particularly, to a vertical shaft centrifugal pump. It deals specifically with a priming system for a vertical shaft centrifugal pump.

A simple and, accordingly, desirable means for priming a vertical shaft centrifugal pump is with the use of a vacuum priming system. Heretofore, however, a problem consistently encountered in vacuum priming centrifugal pumps of this type has been locating a Vacuum attachment point on the pump where literally all of the air can be removed. In presently known priming systems of this type, this connection is normally made at the pump I volute discharge where it is subjected to pump operating pressure during the period when the pump is in normal operation. Accordingly, valve means of some type must be employed to prevent the priming system from being filled with the material being pumped.

Where such conventionally vacuum primed centrifugal pumps employing a vertical shaft connection are utilized to handle sewage, and particularly solid-containing liquid sewage, solids tend to enter the connection during normal operation of the pump. These solids often plug the priming connection, as well as fouling the priming system in general.

SUMMARY OF THE INVENTION The present invention is embodied in a greatly improved vacuum priming system for a vertical shaft centrifugal pump. It is, accordingly, an object of the invention to provide a priming system which assures that virutally 100 percent of the air is excluded from the pump cavity during the priming operation. It is another object to provide a priming system for a pump especially suited for pumping solid bearing liquid sewage, wherein the conventional problems of solids plugging the priming ports, as well as fouling other equipment of the priming system, are substantially obviated.

It is still another object to provide a vacuum priming system for a vertical shaft centrifugal pump wherein priming is automatically cut-off once the pumping chamber has been evacuated. lt is yet another object to provide a priming system of the aforedescribed character including a control circuit arrangement which precisely controls priming.

The foregoing and other objects are realized in accord with the present invention by providing a priming system for a vertical shaft centrifugal pump wherein the vacuum connection to the pumping chamber is made behind the impeller in a low pressure region. Because of this posiice tioning of the vacuum connection, liquids normally do not enter the priming line. There is thus considerably less tendency for solids to enter the priming line and clog it and the priming system. Furthermore, a close clearance is built between the top of the impeller and the pumping chamber top wall in which the priming vacuum connection is made, thus also tending to exclude solids from the area of the vacuum connection.

The invention, together with its construction and method of operation, taken with other objects and advantages thereof, is illustrated more or less diagrammatically in the drawing, in which:

FIG. 1 is a diagrammatic front elevational View, with parts in section, of a vertical shaft centrifugal sewage pump incorporating a priming system embodying features of the present invention, and

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

Referring now to the drawing, and particularly to FIG. 1, a vertical shaft centrifugal pump assembly is illustrated generally at 10. In the present illustration, the pump assembly 10 is adapted to be incorporated in a sewage pump station. As such, it is designed to draw solidbearing liquid sewage from a receiving tank (not shown) through an inlet elbow 11 and pump the sewage from a discharge nozzle 12 to suitable sewage treatment means.

The pump assembly 10 is vertically elongated and actually inciudes a lower pump section 15 and an upper drive motor section 16. The drive motor section 16 includes an oversized, heavy-duty electric motor 17. The motor 1'7 is mounted on the pump section 15, and the vertically disposed motor shaft 20 extends downwardly from the casing into the pump section 15.

The pump section 15 includes a heavy-rigid, cast iron base 25 adapted to be bolted to a suitable foundation. The base 25 has four upstanding legs 26 which support a plate 27. The plate 27 has a centrally disposed aperture 28 extending through it, and the pump suction elbow 11 is bolted to the bottom of the plate in registry with the aperture 28, as illustrated.

Bolted to the top of the plate 27 is the cast iron pump volute housing 35. The volute housing 35 has an annular configuration in plan view and forms the side wall of a pumping chamber 36, the plate 27 forming the bottom wall. This configuration is interrupted only by the pump discharge nozzle 12. which, as seen in FIG. 2, forms an outlet from the chamber 36 in the rear, left quadrant of the housing.

A motor section 16 adapter cage di) is seated on and bolted to the top of the housing 35. The base plate 41 of the cage 40 forms the top wall of the pumping chamber 36. A suitable mechanical seal assembly 42 is mounted in the center of the plate 41. The motor section 16 is bolted to the top of the cage 41) in such position that the shaft 2i) extends vertically downwardly through the seal assembly 42 into the pumping chamber 36.

A balanced cast iron impeller 45 of generally conventional construction is mounted on the lower end of the shaft 2t) in the pumping chamber 36 for rotation with the shaft in a well-known manner. The impeller 45 includes a vertically disposed, axial inlet 46 and conventional shrouds bracketing horizontally disposed radial outlets 47.

In normal operation of the pump 10, the shaft 20 rotates the impeller 45, drawing sewage through the suction elbow 11 into the impeller. This sewage is impelled radially of the impeller through the openings 47 and around the pumping chamber 36 housing 35. The sewage is forced out of the housing 35 through the discharge nozzle 12.

As will be recognized, rated pump pressure is effective in the chamber 36 around the impeller 45, and in the discharge nozzle 12. At the same time, however, an annular dish-shaped chamber 55 above the impeller 45, defined between the shroud 56 of the impeller and the base plate 41 of the adapter cage 40 is subjected to relatively low pressure. It is to this chamber 55, Opposite the discharge nozzle 12 from the shaft 20, that the priming system 60 embodying features of the invention is connected. The priming system 60 is a vacuum type system which is designed, in its conventional sense, to draw sewage into the pump chamber 35 before the pump is started to institute normal operation of the pump.

The primary system 60 comprises a primer housing 61 integral with the base plate 41 of the cage 40 adjacent the seal assembly 42 and opposite the discharge nozzle 12. The housing 61 defines a priming chamber 62 which communicates ywith the chamber 55 above the impeller 45 through a port connection `63 in the plate 41.

Connected to the chamber 62 at the top of the housing 61 is a vacuum line 65. The vacuum line 65 is connected to a vacuum pump 66 of conventional construction, through a suitable filter arrangement 67.

The vacuum pump is driven by an electric motor (not shown) through a control circuit 70. Operation of the pump 66 is controlled through the circuit 70 from a control panel 71 where switching equipment is provided to turn the vacuum pump motor on and olf.

According to the invention, the circuit 70 also includes a sensing electrode 75 extending into the chamber 62 through the top of the housing 61. The electrode 75 depends to a preselected point in the chamber 62 and operates to trigger the switching equipment in the control panel 71 when liquid reaches it in the chamber 62 during a priming operation.

In operation, to prime the pump according to the invention, the vacuum pump 66 is energized from the control panel 71 and a suction is created through the chamber 62 and the port 63 into the pumping chamber 36. Solid-bearing liquid sewage is drawn up into the chamber 36. lt rises in the chamber until 100 percent of the air is evacuated and the liquid actually starts filling up the priming chamber 62. When the liquid in the priming chamber 62 reaches the electrode 75, a circuit is completed to the control panel 71 which, in turn, is effective to open the circuit to the vacuum pump 66 and stop the priming operation. The centrifugal pump is then started.

In order to prevent solids from being drawn into the priming chamber 62 during priming, only a small clearance is provided between the roof plate 56 of the impeller and a depending ridge 80 on the plate 41 in the chamber 36. The ridge 80 defines the annular side Wall of the chamber 55. During normal operation of the pump, after the priming function, this small clearance also serves to prevent solids from clogging up the port -63 into the priming chamber 62.

Since the port 63 is connected to the chamber 36 in a relatively low pressure area of the chamber, i.e., the chamber 55, there is little effective pressure trying to force liquid into the priming chamber 62. Accordingly, no valve connection is required in the port 63. A simpler and less expensive priming system 60 is the result.

While the embodiment described herein is at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modifications and improvements as fall within the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

1. In a vertical shaft centrifugal pump including a housing defining a pumping chamber, said pumping chamber having a generally annular side wall with a discharge nozzle in one quadrant of its circumference, a top wall through which a vertical drive shaft extends, and a bottom wall defining an inlet port, wherein an impeller is mounted on said shaft within said chamber over said inlet port, said discharge nozzle defining an area of high relative pressure and said inlet port defining an area of negative relative pressure, the improvement in vacuum priming system for drawing liquid into said pumping chamber to prime the pump, comprising:

(a) a priming connection to said pumping chamber displaced from said discharge nozzle and said inlet port in a relatively low pressure area of said pumping chamber, said low pressure being intermediate said high pressure and said negative pressure,

(b) said priming connection connecting said pumping chamber with a priming chamber above said pumping chamber in a position so all air rises from the irnpeller and pumping chamber,

(c) and pump means for developing a partial vacuum in said priming chamber and said pumping chamber wherein liquid is drawn into said pumping chamber to evacuate all of the air therefrom into said priming chamber.

2. The improvement in vacuum priming systemof claim 1 further characterized in that:

(a) said priming connection to said pumping chamber is made through said top Wall, opposite said shaft from the discharge nozzle.

3. The improvement in vacuum priming system of claims 1 or 2, further characterized in that:

(a) said top wall has an upwardly extending depression formed therein so as to define, with the roof of the impeller, a low pressure chamber,

(b) said priming connection being made to said low pressure chamber.

4. The improvement in vacuum priming system 0f claim 1 further characterized in that:

(a) means is provided for de-activating said pump means upon conclusion of priming.

5. In a vertical shaft centrifugal pump including a housing defining a pumping chamber, said pumping chamber having a generally annular side wall with a discharge nozzle in one quadrant of its circumference, a top wall through which a vertical drive shaft extends, and a bottom wall defining an inlet port, wherein an impeller is mounted on said shaft within said chamber over said inlet port, said discharge nozzle defining an area of high relative pressure and said inlet port defining an area of negative relative pressure, the improvement in vacuum priming system for drawing liquid into said pumping chamber to prime the pump, comprising:

(b) said priming connection connecting said pumping chamber with a priming chamber above said pumping chamber in a position so all air rises from the impeller and pumping chamber,

(c) pump means for developing a partial vacuum in said priming chamber and said pumping chamber wherein liquid is drawn into said pumping chamber to evacuate all of the air therefrom into said priming chamber,

(d) said priming chamber extends upwardly from said priming connection,

(e) electrode means extending into said priming chamber to a predetermined point above said priming connection, and

(f) circuit means for initiating operation of said vacuum pump means to draw liquid into said priming chamber where it engages said electrode means and causes said circuit means to de-activate said vacuum pump means.

6. In a vertical shaft centrifugal solids handling pump including a housing defining a pumping chamber, said pumping chamber having a generally annular side wall with a discharge nozzle in one quadrant of its circumference, a top wall through which a vertical drive shaft extends, and a bottom wall dening an inlet port, wherein an impeller is mounted on said shaft within said chamber over said inlet port, said discharge nozzle denng an area of high relative pressure and said inlet port defining an area of negative relative pressure, the improvement in vacuum priming system for drawing liquid into said pumping chamber to prime the pump, comprising:

(a) a priming connection to said pumping chamber displaced from said discharge nozzle and said inlet port in a relatively low pressure area of said pumping chamber, said low pressure being intermediate said high pressure and said negative pressure.

(c) said impellers outer extremities dene with said 2 side wall an annular shaped region within said pumping chamber, said impeller form a close t passage- Away with said top wall inwardly of said annular shaped region, said passageway communicating with said low pressure area, said impeller throwing suspended solids outwardly into said annular shaped region so as to substantially prevent solids from entering said low pressure area and clogging said priming connection,

(d) and pump means for developing a partial vacuum in said priming chamber and said pumping charnber wherein liquid is drawn into said pumping chamber to evacuate all of the air therefrom into said priming chamber.

References Qited UNITED STATES PATENTS 2,166,530 7/l939 Morgan 103-113 2,275,502 3/1942 Broadhurst 10S-113 2,448,717 9/1948 .leffcock 103:*113

0 ROBERT M. WALKER, Primary Examiner U.S. Cl. X.R.