US3217975A

US3217975A - Pump device

Info

Publication number: US3217975A
Application number: US419067A
Authority: US
Inventors: Irving C Jennings
Original assignee: Nash Engineering Co
Current assignee: Nash Engineering Co
Priority date: 1964-12-17
Filing date: 1964-12-17
Publication date: 1965-11-16
Anticipated expiration: 1982-11-16

Description

Nov. 16, 1965 c. JENNINGS 3,217,975

'PUMP DEVICE Filed Dec. 17, 1964 3 hee sh et 1 INVEN TOR. I? w/vg 6, d/v/w/vgs 1965 c. JENNINGS 3,

PUMP DEVICE Filed Dec. 17, 1964 3 Sheets-Sheet 2 JNVENTOR.

Nov. 16, 1965 (2. JENNINGS 3,217,975

PUMP DEVICE Filed Dec. 17, 1964 5 s-Sheet 5 INVENTOR. .Zkv/A/g 0i JZew/w/vgs ATTORNEYS United States Patent 3,217,975 PUMP DEVHIE Irving C. Jennings, Nash Engineering (30., South Norwallr, Conn. Filed Dec. 17, 1964, Ser. No. 419,067 13 Claims. (Cl. 230-79) This application is a continuation of application S.N. 240,371, filed on November 27, 1962, and now abandoned.

The present invention relates in general to liquid ring pumps and in particular to a novel means and method of reducing the surging and horsepower requirements of a liquid ring pump designed for moderate to high vacuum services when the pump is started or operated at low vacuum services.

In pumps of this type, water or other seal liquid is revolved in a circular or elliptical path within a casing by a rotor containing a plurality of shrouded blades which form radially extending open ended displacement chambers. The liquid, following the casing due to centrifugal force, alternately receives from and is forced back into the displacement chambers within the rotor. Stationary inlet and outlet ports cooperate with the rotor displacemerit chambers to permit the air or gas to be drawn into and discharged from the chambers after compression. This general type of pump is well known in the art and is fully described by way of example in applicants prior art US. Patent Nos. 1,797,980 and 1,718,294, and in his co-pending application Serial No. 90,287, filed February 20, 1961, now Patent No. 3,154,240.

In pumps of this general type, which are commonly employed to create sub-atmospheric vacuums, it is conventional to proportion the size and arcuate lengths of the inlet and discharge ports of the stationary central port member in such a manner as to obtain the desired high or low vacuum producing capability, as determined by the intended service of the pump. In general, a pump intended to be employed for moderate to high vacuum service (i.e., a low absolute pressure) would ordinarily have an inlet port extending through a relatively large peripheral arc and a discharge port extending over a relatively small peripheral arc, in comparison to a pump designed for relatively low vacuum services wherein the discharge port arc length would be substantially greater.

When liquid ring pump designed for moderate to high vacuum services, which may be arbitrarily classified as vacuums in excess of approximately twenty inches of mercury, are started or made to operate at vacuums lower than their designed high vacuum capability, the seal water is forced into the rotor buckets prematurely before the outlet ports open and the water is crowded out past the rotor end shrouds into the spaces between the end shrouds and the pump casing. This forcing of seal liquid results in surging and high horsepower requirements when a pump designed for high vacuum is operated at low vacuum. Obviously, such surging is very undesirable and usually requires the selection of a higher horsepower driving motor because the pump is often required to operate at a lower vacuum than that for which it was designed. This undesirable surging and high horsepower requirement is further aggravated by the fact that efficient operation of a high vacuum pump requires a large amount of seal liquid, but at low vacuums the pump cannot handle this large amount of water without the surging referred to. The present invention overcomes the surging difficulties experienced by high vacuum pumps during start up and low vacuum operation and at the same time permits saving of seal water.

To overcome the aforementioned difficulties in the starting of a high vacuum liquid ring pump, or the operation thereof at lower vacuum levels, the present invention employs means for reducing the surging and horsepower requirements by the provision of release means to bleed seal liquid from the rotor end shroud areas of the pump.

In one embodiment of applicants invention conduit means connect directly with said end shroud area and are provided with a pressure responsive valve adapted to open at vacuum levels below approximately twenty inches of mercury.

In another embodiment of the invention, applicants arrangement places the end shroud sealing chamber of the pump in communication with a lower portion of a gasliquid separator connected to the discharge of the pump so that a similar reduction of horsepower and surging is accomplished.

Accordingly, an object of the invention is to provide a novel method and apparatus for lowering the horsepower requirements and corresponding motor size required to 0p crate a high vacuum liquid ring pump.

Another object of the invention is to provide a novel apparatus for reducing the surging of the seal liquid within the pump during start-up.

Another object of the invention is to provide novel apparatus for a high vacuum liquid ring pump which permits it to be operated at low vacuum levels without surging and without undue waste of seal liquid.

Still another object of the invention is to provide a pressure responsive bleed passage to vent seal liquid from the end shroud seal chambers of the pump as a function of the pressure therein.

Another object of the invention is to provide a liquid ring pump wherein the seal liquid may be bled from the end shroud portion during the periods of low vacuum level operation and resupplied to said portion to supply a large amount of seal liquid as required for efiicient operation thereof at high vacuum levels.

Yet another object of the invention is to provide a novel uncomplicated and self-adjusting seal liquid supply system for a liquid ring pump operating at varying vacuum levels.

These and other objects and advantages of the invention will become apparent and the invention will be fully understood from the following description and drawings, in which:

FIG. 1 is a cross-sectional view of a duplex liquid ring pump incorporating the invention taken along line 1-1 of FIG. 3;

FIG. 2 is an end view of a pump similar to that shown in FIG. 1 showing the seal liquid supply and bleed system of a second embodiment of the invention;

FIG. 3 is an end view of the pump of FIG. 1; and

FIG. 4 is a representative vertical cross-sectional view taken through a pump such as shown in FIGS. 1 or 3.

Referring more particularly to the drawings, a single lobe pump according to the invention shown generally at 10 includes a cylindrical or other shaped single lobed casing member 12 having a pair of identical casing enclosing heads 14 secured at opposite ends thereof. A main drive shaft 18 rotationally mounted in a pair of bearings 20 supports a rotor 16 which is suitably keyed to the shaft. A pair of packing and gland assemblies 22 are fitted around shaft 18 and into heads 14 and central ports 38 to prevent liquid seepage from about the rotating shaft. The rotor 16 is of the duplex variety containing a plurality of radially extending pumping chambers 24 defined therein by blades 26, side or end shrouds 28 and a central partition wall 39, which is in line with a corresponding partition wall 32 in casing 12 to form adjacent crescent-shaped pumping chambers or lobes 34. Disposed at each end of the pump are a pair of inlet passages 36 formed in head members 14, which direct inlet air or gas to a pair of opposed right and left hand port members 38. The port members include inlet passages 46 in communication with the pumping chambers 24 within the rotor, and discharge passages 42 (see FIG. 4) also in communication therewith. Discharge passageways 42 communicate with a header chamber 44 formed ineach head 14 to provide access to several alternate discharge port flanges 52 located on the lower sides and bottom of the head. As shown representatively in FIGS. 2 and 3, suitable cover plates 66 are attached to the bottom and right hand flanges 52 to direct all of the pump discharge from port 42 into discharge chamber 44- and outwardly through passageways (not shown) to the left hand discharge flange 52. As best shown in FIG. 4, a lower portion of lobed pumping chamber 34 communicates through an aperture 50 to an unloading chamber 46 which is shown terminating in right and left hand flanges 4'7 suitably capped by cover plates 48. In operation, the unloading chamber 46 is sealed and would only be vented through conduits or valves not shown whenever unloading or drainage of the pump is desired.

According to the invention, and as best shown in FIG. 1, novel means are provided in the form of a pair of bleed conduits 56, which extend horizontally inward through the discharge chambers 44 and communicate with the annular end shroud seal liquid chambers 54. Each of the conduits 56 include a check or relief valve 58 and a drain conduit 60. In accordance with the invention, in the operation of the high vacuum pump during starting or service at low vacuum levels, the seal liquid is crowded out past the shroud into the spaces 54 between the sides of the rotor and the casing. This results in surging and high horsepower requirements necessitating the provision of a larger than ordinary capacity drive motor. However, in accordance with the invention, the provision of the check valves 58, and adjustment thereof, is effective to prevent these adverse conditions by bleeding off seal liquid from this area of the pump until the vacuum developed by the pump is somewhat above twenty inches of mercury. The setting of the pressure responsive relief valves 58 is such to effect closing thereof when the vacuum developed by the pump is at a moderate or high level appreciably above twenty inches of mercury in the order of its designed optimum operating range.

In FIG. 3, the seal liquid bleed-elf from the shroud chambers 54 is directed through conduit 60 and into the discharge flange area 52 to exhaust in combination with the pumped vapor discharge.

In the embodiment of FIG. 2, an alternate seal liquid relief pipe arrangement for the shroud chambers 54 is shown in the form of a conduit 64 in direct communication therewith. The conduit 64 extends horizontally to a lower portion of a vapor and liquid separation tank 62 into which the pump discharges a mixture of compressed vapor and overflow seal liquid via the main discharge conduit 70.

With the arrangement of FIG. 2, during periods of surging and pump start-up, seal liquid is forced outwardly through conduit 64 against the head of any liquid that has accumulated in the lower portion of the separation chamber 62. As the vacuum developed by the pump rises somewhat above twenty inches of mercury, a vacuum begins to build up between the rotor shrouds and the casing in the area of spaces 54. As this occurs, seal liquid is drawn back through conduit 64 from the lower portion of the separation chamber 62 to supply the necessary large amount of seal liquid directly to the shroud areas 54 required for efficient operation of the pump at high vacuum. Additional make-up seal liquid as ordinarily required by all such pumps is supplied through the normal seal liquid supply pipe 68 to the conical port members 38 or to the pump inlet in the usual manner to keep the pump cool. The quantity of water supplied through conduit 68 is relatively small and constant regardless of the vacuum drawn by the pump. In effect, in the embodiment of FIG. 2 applicants arrangement has provided a novel surge chamber in the form of the lower portion of the separation tank 62 in communication with the end shroud chambers 54 via conduit 64.

In further explanation of the phenomenon occurring in high vacuum liquid ring pumps that is solved by applicants novel arrangement, reference should be made to FIG. 4. As can readily be seen, the peripheral arc of the discharge port 42 is selected and oriented with respect to the lobe to open when the vacuum reaches the terminal pressure (i.e., atmospheric pressure in the usual case). When a pump of such arrangement is operated at lower vacuums the seal liquid is forced into the rotor chambers 24 prematurely, and thereby compresses the air to an ultimate pressure higher than the terminal pressure. During this time, and in View of this excess compression in view of the operation of the pump which has been designed for high vacuum at low vacuum, water is forced out around the rotor side shrouds 28 into the chambers 54 and builds up a pressure therein which prevents the escape of excess water in the lobe casing and causes surging and high horsepower requirements. It is this seal liquid forced into the chambers 24 that is relieved by the

vent conduits

56 or 64 of applicants novel arrangement.

While applicant has described several preferred embodiments of his invention as employed with a single lobe pump of the duplex rotor variety, it should be understood that the novel concepts therein may be employed with any liquid ring pump wherein a surging condition arises. Furthermore, while applicant has chosen for description purposes the definition of moderate to high vacuums to be in the range of twenty inches of mercury and above, and low vacuums to be those vacuum levels less than twenty inches of mercury, it should be understood that this is a rather arbitrary division between high and moderate vacuums and low vacuums and that the concept of applicants invention is applicable to the solution and prevention of surging in any pump regardless of its absolute vacuum operation level.

While several alternate embodiments of the invention have been shown and described in detail to illustrate the application of the novel concepts thereof, it should be understood that the invention may be embodied otherwise without departing from such principles.

What I claim is:

1. In a high vacuum liquid ring pump of the type having an annular rotor including a plurality of radial blades and end shroud portions to form in combination therewith a plurality of radially extending open ended displacement chambers, and a lobed casing member enclosing said rotor, including a stationary central port member having inlet and discharge passageways therein in communication with the inner boundary of the displacement chambers of said annular rotor, and end wall portions cooperative with the rotor end shroud portions to form rotor shroud seal chambers therebetween, the improvement comprising, conduit means in communication with said rotor shroud seal chambers and means for removing seal liquid from said seal chambers through said conduit means to prevent surging when said high vacuum liquid ring pump is operated at relatively low vacuum levels.

2. A liquid ring pump according to claim 1 wherein said last-mentioned means includes pressure responsive check valve means in said conduit means.

3. A liquid ring pump according to claim 1 wherein said last-mentioned means includes a gas-liquid separation tank connected to said conduit means.

4. The method of reducing the surging and horsepower requirements of a liquid ring pump having a rotor and a casing thereabout designed for moderate to high vacuum services when said pump is started or operated on low vacuum services comprising the step of bleeding seal liquid from the spaces between the rotor end surfaces and the pump casing during the start-up cycle of said pump and during operation of said pump at relatively low vacuum compared to its designed moderate to high vacuum capability.

5. The method of claim 4 including the additional step of sensing the pressure of the surging seal liquid and effecting the said bleeding of seal liquid from the spaces between the rotor ends and easing at vacuum levels below approximately twenty inches of mercury.

6. A liquid ring pump for producing high sub-atmospheric vacuums comprising, an annular rotor including a plurality of radial blades and end shroud portions to form in combination therewith a plurality of radially extending open ended displacement chambers, a casing member having at least one lobed portion enclosing and rotationally supporting said rotor, said casing including a stationary central port member having inlet and outlet passages therein in communication with the inner boundary of said displacement chambers of said rotor, and end wall portions cooperating with the rotor end shroud portions to form rotor shroud seal chambers therebetween at each end of said rotor, and means communicating with said seal chambers responsive to the pressure therein to bleed seal liquid therefrom when said pump is started or operated at relatively low vacuum levels below its designed high vacuum capability.

7. A pump according to claim 6, wherein said last-mentioned means include a check value adjusted to close at pump vacuum levels above approximately twenty inches of mercury.

8. A pump according to claim 6, wherein said last-mentioned means includes check valve means a check valve adjusted to be closed whenever the pressure in the end shroud seal chambers is less than atmosphere.

9. The method of reducing the horsepower require ment of a liquid ring pump of the character described having a casing and a rotor therein during start-up comprising the steps of withdrawing seal liquid from the interior of said pump from the spaces between the ends of the rotor and the casing, and thereafter returning the withdrawn seal liquid to said spaces when said pump is up to speed.

10. The method of reducing the surging and horsepower requirements of a high vacuum pump to which seal liquid is supplied in proportion to the high vacuum requirements of said pump when said pump is operated at low vacuum comprising the steps of sensing the pressure of the seal liquid within said pump and removing seal liquid from the interior of said pump to prevent the pressure of said seal liquid from exceeding a predetermined pressure thereby reducing the surging and horsepower requirements of said pump.

11. The method of reducing the horse ower requirements during start up and when operating under a low vacuum of a liquid ring pump of the character described having a casing and a rotor therein comprising the steps of leading seal liquid from the spaces in the interior of said pump between the ends of the rotor and the casing and thereafter leading the seal liquid into said spaces when the pump is operating at high vacuum.

12. The method of reducing the horsepower requirements during start up and when operating under a low vacuum of a liquid ring pump of the character described having a casing and a rotor therein comprising the steps of leading seal liquid from the spaces in the interior of said pump between the ends of the rotor and the casing, storing the liquid, and thereafter leading the seal liquid into said spaces when the pump is operating at high vacuum.

13. A liquid ring pump for producing high sub-atmospheric vacuums comprising, an annular rotor including a plurality of radial blades and end shroud portions to form in combination therewith a plurality of radially extending open ended displacement chambers, a casing number having at least one lobed portion enclosing and rotationally supporting said rotor, said casing including a stationary central port member having inlet and outlet passages therein in communication with the inner boundary of said displacement chambers of said rotor, and end wall portions cooperating with the rotor end shroud portions to form rotor shroud seal chambers there'between at each end of said rotor, conduit means connecting said seal chambers and a reservoir adapted to receive and store seal liquid when said pump is started or operated at relatively low vacuum levels below its designed high vacuum capability.

References Cited by the Examiner UNITED STATES PATENTS 1,662,250 3/ 1928 Jennings 230-79 1,718,294 6/ l929 Jennings 23079 1,797,980 3/1931 Jennings 230-79 LAURENCE V. EFNER, Primary Examiner.

Claims

1. IN A HIGH VACUUM LIQUID RING PUMP OF THE TYPE HAVING AN ANNULAR ROTOR INCLUDING A PLURALITY OF RADIAL BLADES AND END SHROUD PORTIONS TO FORM IN COMBINATION THEREWITH A PLURALITY OF RADIALLY EXTENDING OPEN ENDED DISPLACEENT CHAMBERS, AND A LOBED CASING MEMBER ENCLOSING SAID ROTOR, INCLUDING A STATIONARY CENTRAL PORT MEMBER HAVING INLET AND A DISCHARGE PASSAGEWAYS THEREIN IN COMMUNICATION WITH THE INNER BOUNDARY OF THE DISPLACEMENT CHAMBERS OF SAID ANNULAR ROTOR, AND END WALL PORTIONS COOPERATIVE WITH THE ROTOR END SHROUD PORTIONS TO FORM ROTOR SHROUD SEAL CHAMBERS THEREBETWEEN, THE IMPROVEMENT COMPRISING, CONDUIT MEANS IN COMMUNICATION WITH SAID ROTOR SHROUD SEAL CHAMBERS AND MEANS FOR REMOVING SEAL LIQUID FROM SAID SEAL CHAMBERS THROUGH SAID CONDUIT MEANS TO PREVENT SURGING WHEN SAID HIGH VACUUM LIQUID RING PUMP IS OPERATED AT RELATIVELY LOW VACUUM LEVELS.