GB2391266A - Impeller and intake arrangement for a centrifugal pump - Google Patents

Abstract

A centriflugal pump, such as a pump for pumping liquids and slurries containing solid matter, includes an impeller 7 having radially extending vanes 10, an intake plate 13 and a pump casing (see figure 3) including a bowl which receives the impeller 7. The impeller vanes 10 have outer portions 73 which are curved rearward in relation to a direction of rotation, and inner portions 71 which extend radially across an arcuate aperture 14 of the intake plate 13. Also disclosed are a threaded adjuster arrangement for adjusting the clearance between the vanes 10 and an inner surface of the intake plate 13, a seal arrangement (see figure 4) including an annular rotating component and an annular stator component, an intake plate which has a shallow recess in an inner surface to assist with cleaning of the impeller vanes 10 and a pump housing arrangement which is said to reprime the pump when rotation of the impeller 7 is resumed after a stationary period.

Description

( -1 239 1 266

CENTRIF1JGAL PUMP IMPROVEMENTS

Field of the Invention

The present invention relates to a centrifugal pump, and particularly to a centrifugal pump effective for pumping liquids and slumes containing, solid matter 5 Background of the Invention

U.S. Patent No. 57460,482 discloses a centrifugal chopper pump designed for pumping liquids and slurries containing solid matter, including various types of refuse, and for chopping the solid maker which may thereafter be processed for disposal. The pump has external and internal cutters rotated with the internal pump 10 impeller. The impeller has blades or vanes that sweep across arcuate intake apertures for a slicing action of solid matter in the liquid or slurry being pumped. This patent also describes other U.S. and foreign patents that disclose pumps having blades or vanes cooperating with edges of inlet apertures for a chopping or slicing action, or external booster propellers or external cutters, including external blades that sweep 15 across small intake apertures to dislodge or cut solid material clogging an aperture.

Depending on the material being pumped, there still may be problems with solid material working its way between cooperating parts of a pump seal, or becoming wrapped around rotating components of the pump, including the pump drive shaft Some materials are not completely cut effectively in the known designs, 20 and pumps designed for slicing or chopping solid materials may have a loss of efficiency or lower head as compared to units designed for pumping only liquid There also is a need for an effective self-priming pump, particularly in the field of

chopper pumps. Further, chopper pumps are subject to more wear in the area of Me exposed edges of Me impaler vanes and, therefore, require adjustment of the distance

-2 from the vane edges to an adjacent intake plate. In known designs, this adjustment can require removal of the intake plate and changing the clearance by the use of Ol"111. Surnmaof the Invention 5 The present inventirn provides imrrc',e er, for cent; p-L= mi(i nanic'!arly ce"fiQI choppy- pit.-" fir. pu.ll,lrg;;cluiu:; and slurries containing solid matter. In one aspect of the present invention, a modified seal design helps to prevent material from advancing toward relatively rotatable seal components. In another aspect of the invention, modifications are made in the pump intake plate to 10 increase chopping effectiveness and pump efficiency. In another aspect of the invention, an impeller having vanes with a unique shape are provided to achieve improved suction lift. In another aspect of the invention, a self-priming pump is provided. A further aspect of the present invention is the provision of a centrifugal pump having an improved mechanism for adjusting the clearance between the outer 15 edges of the impeller vanes and the interior of an adjacent intalce plate.

Brief Description of the Drawings

FIGURE 1 (prior art) is a fragmentary side elevation of a centrifugal pump of

the general type with which the present invention is concerned, with parts broken away, and FIGURE 2 (prior art) is a bottom plan thereof;

20 FIGURES is an enlarged axial section of a centrifugal pump having an improved seal structure in accordance with the present invention, FIGURE 4 is an enlarged axial section of such seal structure, FIGURE4A is an enlarged top perspective of such seal structure, and FIGURE 5 is a side elevation thereof; FIGURE 6 is a bottom plan of an improved intake plate for a centrifugal 25 chopper pump of the general type shown in FIGURE 1, FIGURE 7 is a side elevation thereof, FIGURE 8 is a top plan thereof, FIGURE is an enlarged fragmentary section along line9-9 of FIGURE 8, and FIGURE 10 is a diiaammatic top perspective of pump blades or vanes and the interior side of an intake plate in accordance with FIGURES 9; 3() FIGUREll is a somewhat diagrammatic bottom perspective of a pwnp impeller having an improved vane structure in accordance with the present invention; FIGURE 12 is a top perspective of a self-priming pump in accordance with the present invention, with parts broken away, and PIGIJRE 13 is a side elevation thereof with parts shown in section;

-3- FIGURE 14 is a perspective of a modified pump structure permitting external adjustment of the impeller-intake plate clearance, with parts shown in exploded ^_laivnship' and vvr; is a perspective view of one assembly thereof; FIGURE 16 is a top perspective of a modified pump having external 5 adjustment mechanism similar to that of the plum.< Of TGTv= US '4 a,,d 1., win, pans shown in exnicle.ll relatinuchip.

FIGURE 17 is a perspective of another modified pump having external adjustment mechanism, and FIGURE 18 is an enlarged fragmentary perspective of a part thereof.

10 Detailed Description of the Preferred Embodiment

FIGURE 1 and FIGURE 2 show a centrifugal pump of the general type with which the improvements of the present invention may be used. As indicated in FIGURE 1, the pump includes an upright drive shaft 1 received within a column 2 forming a reservoir for oil or other lubricant. The bottom of the reservoir is closed 15 by conventional anti-friction bearings 3 and a seal 4 which includes a spring 12. The bottom portion of the column 2 is bolted to a pump casing 5 having a downward opening cavity or bowl 6 receiving the pump impeller 7. Such impeller consists of: a cylindrical shroud disk or plate 8 projecting radially from the impeller hub 9 fixed to the cave shaft; the primary pumping vanes or blades 10 projecting downward 20 from the shroud plate; and vanes or ribs 11 projecting upward from the upper face of the shroud plate opposite the primary pumping blades 10.

The bottom of the pump bowl is closed by an endplate 13 clamped or bolted to the bottom of the pump casing and having inlet apertures 14 which, as best seen in FIGURE 2, are arcuate and concentric with the axis of rotation of the drive shaft and 25 the impeller.

An optional addition for a pump of the type shown in FIGURE 1 and FIGURE 2 is a disintegrator or booster propeller 15 located opposite the end plate 13 from the impeller 7. The booster propeller 15 has blades 16. Also, the impeller vanes 10 may have sharpened edges cooperating with edges of the inlet apertures 14 30 and, particularly, with "cutter bars" 14' formed as part of the endplate 13 and extending radially across the intake area of the plate.

general, rotation of the impeller creates suction at the intake side of the endplate for drawing a Liquid or slurry into the pump casing. The slurry is accelerated outward and circumfercutially to an outlet 18 that extends generally 35 tangentially to the remainder of the pump casing.

! FIGURES is a vertical section of a pump of the general type shown in FIGURES 1 and 2 with some parts deleted (including the bottom endplate which -would close the occur L'Oiiom or fine pump Dowi 6j As described above, the upright drive shaft 1 extends through a column 2 and is supported by thrust bearings 3. An 5 improved seal 4 closes the top portion of the pump chair.,, 5 to.',hich Ale loo_. e,.d of the. co!'mn is h!t.ed. The r''-P Lo.: -_c_i';., Hi_,,pCllCt 7 --..ich inelucs ule radial shroud disk or plate 8, primary pumping vanes or blades 10, and vanes or ribs 11 at the top of the shroud plate. In the design of FIGURE 3, special upper cutters are provided to cooperate with the upper vanes 11. Nevertheless, it has been 10 found that material may work ifs way into the area of the seal 4 Tough, stringy material may become wrapped around the seal area and affect operation of the seal and shorten its effective life.

The primary components of the seal 4 are best seen in FIGURE 4 which is a vertical section along line 1 of FIGURE 5, and FIGURE 4A. The seal 4 includes 15 an upper one-piece gland 42 having external threads for mounting of the gland in the lower portion of the column 2 (which, in some applications, could be the upper portion of the pump casing). Pins 44 couple the gland 42 to the stator component 46 which encircles the drive shaft and which is biased downward by a helical compression spring 48. The bottom portion of the stator carries the stationary seal 20 face member 50. The rotating seal face component 52 is carried by a sleeve 54 which is coupled to the drive shaft such as by set screws 56.

The rotating seal component 52 has an upper face that mates with the bottom face of the stator component. In addition, the lower portion 58 of the rotating seal component 52 is of an outside diameter substantially less than the upper portion 60, 25 forming an abrupt shoulder 62 that faces downward. the embodiment shown in FIGURES 3, 4 and 4A, the shoulder extends radially outward a distance less than the distance between the outer periphery of the rotating seal component 52 and the adjacent edge of the opening through the pump casing. Preferably, the radial extent of the shoulder is kept at no greater than one-half the distance from the outer 30 periphery of the rotating seal component and the adjacent edge of the casing opening to prevent chunks, lumps, grit, or stringy or other tough material from becoming lodged between the rotating seal component and the casing.

It has bees found that by including the shoulder62 on the rotating seal component 52 there is a lesser chance of wrapped material collecting in the area of 35 the abutting seal faces. It is believed that this is because the shoulder prevents

wrapped material from climbing axially upward along the rotating seal component.

Once material wraps in the joint between the two seal faces, leakage may occur, causing used',^;!u,e. v. pomps -hi;, rv=Li' sem components not having a shoulder, such leakage and failure is more likely to occur than for pumps having rotating 5 components provided with the shoulder.

As noted above. numbs of the tape.,i'..ch.ic. the p.-cscEl. Irlicnull is concerned may be used for pumping slurries and/or chopping solid or semisolid materials carried by the liquid being pumped. In this regard, the bottom edges of the primary pumping impeller vanes or blades 10 may cooperate with the edges of the 10 intake apertures 14 Ed cutter bars 14'. In addition, in the pas; -he inner face of the endplate 13 has been provided with short radial or angled ribs that project into the pump bowl. The bottom edges of the impeller blades or vanes 10 can be recessed slightly to acconunodate the ribs, the intent being to provide an abrupt chopping action as the blades or vanes sweep over the ribs.

15 An alternative constriction for the endplate 13 is shown in FIGURES 610.

Endplate 13 has the usual arcuate intalce apertures 14 and radial cutter bars 14'. The bottom plan of FIGURES shows the outer face of the endplate 13 as being essentially flat and smooth. The top plan of FIGURE 8 shows a shallow groove 64 which is elongated but not in a radial direction. Rather, the groove extends at an 20 angle 4, to a radius, from its inner edge to its outer edge in a rearward direction with reference to the direction of impeller rotation (represented by arrow A in FIGURE 8).

The cross-sectional shape of the groove 64 is shown in FIGURE 9. The trailing edge 66 of the groove (i.e., the edge first contacted by a rotating impeller blade) is gently tapered into the plate at a very small acute angle c, such as Tree degrees, 25 preferably no more than ten degrees, to avoid creating excess turbulence. The leading edge 68 (i.e., the edge last contacted by the rotating impeller) is angled sharply upward. Preferably, the leading edge is undercut at a large acute angle (3, such as 60 degrees, preferably between 45 degrees and 90 degrees. In a typical pump, the maxims depth D of the groove can be 0.020.100 inch, wide the groove 30 extending completely across the face of Me end plate 13 from a comer of one of the arcuate intake openings 14 to the outer margun of the end plate, or at least to the peripheral margin of the cad plate where it attaches to the pump casing. FIGURE 10 shows the relationship of the internal groove 64 cut in the intake plate 13 to the impeller blares 10 (the shroud plate being cut away for ease of illustration).

-6- Experience has shown that if the impeller vanes are allowed to run against a smooth, flat, unbroken surface, fibrous material will build up between the bottom of the imrellr n.eS qnA All_ _nplac. iviuhi rmsed ribs helps eilrninate this problem, but the shallow relief cut into the impeller blades to pass over the raised 5 ribs causes a loss in pump head due to back leakage in the pump Tossing Ate "i..s_t and angled ramp internal cutter" groove he, the im<-A!le' voles me c.,.c -.uh =.a.

bottoms so that very close clearances (around.005-.0015 inch) can be achieved to cut effectively and to achieve considerably better pumping efficiencies.

Another consideration for centrifugal pumps of the type with which the 10 present invention is concerned is that such pumps rely on atmospheric pressure to push material into the pump's low pressure area This low pressure area is created inside the pump inlet toward the center of the rotating impeller. Centrifugal pumps are limited by whatever absolute pressure is available at the pump inlet. Each pump design requires a certain minimwn amount of absolute pressure at the pump suction 15 pressure above the vapor pressure of the pumped liquid to be able to generate its normal head and flow characteristics. Any pressure less than this minimum causes the pump to cavitate and lose discharge head. The pressure available is referred to as "Net Positive Suction Head A. vailable" (NPSHA) and the minimum NPSH required to allow the pump to work as rated by the manufacturer is "Net Positive Head 20 Suction Head Required" (NPSHR). lithe lower the NPSHR of any given pump, the better able that pump is to effectively pump hot water (such as condensate pumps in a power plant) or to provide a high suction lift to the pump (as required in self-priming pumps). Centrifugal pumps are normally designed with an unobstructed suction 25 opening, which promotes a lower NPSHR. Some chopper pumps have significant suction blockage (i.e., stationary cutter bars extending diametrically across the suction opening, plus a hub at the center of the impeller to support the cutting/pumping blades). This blockage results in a pump requirin. more NPSH than any standard centrifugal pump of equivalent hydraulic size. FIGURE 11 illustrates 30 modifications including a particular i;mpeiler vane shape that helps to minimize suction opening blockage and thus reduces NPSHR. The majority of the portion of the impeller vane which is exposed in the arcuate intake or suction openings 14 extends radially (rather than at an angle or in a spiral) from the impeller hub (the radial portion is identified as 71 in FIGURE 11). Eliminating the angled or spiraled 35 portion in this area results in blocking less of the intake opening. In addition, the

l impeller hub 9 is tapered from the back or shroud plate 8 down toward the inlet opening so that only the width of the impeller blade blocks the inlet. At or near the ouicr penpnerai edge of the suction opening, the vanes mre swept back into a curve described by a logarithmic spiral, with either a constant or varying vane angle and 5 continue to the outside Ewe. or the il,yGllcr This outer section is identified as 73 In FIc'T=!!).,,e or,, -Amy, Awn the inner racial portion 71 and the outer curved portion 73, can include a forward inclined leading edge 75, which facilitates cutting against the stationary cutter bars 14' and any cutter provided (including an intema] cutter recess as described above) on the inside surface of the end plate.

10 In addition, a "cutting nose" can be provided on the impeller hub with sharpened cutting teeth 70 on its outer diameter to cooperate with the center or inner edge portions of the cutter bars 14' Close clearances are required for this cutting to be effective. The nose has a rounded exposed portion to keep material from collecting on it. The purpose of the cutting nose is to prevent intake opening 15 blockage. Certun materials, such as rags, may lay over the outside of the stationary shear bars 14' and start blocking flow into the pump, unless the cueing nose is used.

Another aspect with which the present invention is concerned is adapting a pump of the general type described above into a self-priming pump. FIGURE 12 (perspective view) and FIGURE 13 (vertical section) illustrate these changes 20 diagrarnatically. With reference to FIGURE 13, the centrifugal pump unit including the pump casings and intake formed by end plate 13 is mounted in a two-

compartment housing76. In each of FIGURE 12 and PIGIJPE 13, the housing compartment 78 at the led is the suction chamber and the housing compartment 80 at the right is a discharge chamber (in FIGURE 12 part of the outer wall of the 25 housing 76 is broken away). The center wall 82 of the housing between the suction chamber and the discharge chamber is formed with an opening to accommodate the endplate 13 of the pump through which material is drawn inward. The discharge port 84 of the pump is shown in FIGURE 12.

At the bottom of the pump casing, an additional port 86 is provided to 30 communicate win the housing discharge chamber, namely, a rreprime port". This provides for open commucanon between the discharge chamber arid the interior of the pump casing 5.

The suction chamber78 has an upper suction port 88 with a check valve assembly 90. In general, the pump housing 76 is designed such that it will always 35 retain a proper amount of water required for reprirning of the pump. After Me pump

/ -8 shuts down and the water in the suction line is allowed to drain back into the sump, the pump reprices as follows: ax - A- '^... > A,* 4 " as I'M -vv'aG1 as - Talkie liO-f.I-'e Cumuli-' side of the housing. This water is combined with the water in the discharge side of 5 the housing and recirculated through the pump casing by way of the repAme port 86.

This recirculation of water through the pump causer Any Or in the: S'JCt'n idle to he drawn into the pump, mixed with the water being recirculated, and then allowed to separate from the water (in the discharge chamber) as it is waiting to be recirculated through the pump casing again. As the air is drawn out of the suction Line, a vacuum 10 is created and water from the sump is forced into the suction line by annospher,c pressure. Once the suction line is completely filled, the pump housing begins filling and forces any remaining air out of the discharge chamber. At this point, the pump is completely palmed.

For best pumping efficiency, it is believed that gentle changes in the direction 15 of water directed in the suction passageways are desirable. However, when gentle bends are inserted into the suction side of the housing to effect the snore gentle changes in flow direction, the bends and fillets in the suction passageways use up some of the suction coinparunent volume which is needed to store water for effective pump priming. Ellis problem has been solved by providing an angled flow deflector 20 92 in the suction compartment. Preferably, the flow deflector has a downward inclined, generally serniylindrical upper surface that leads from below the suction port 88 to an area adjacent to the pump inlet. However, the inner edge 94 of the deflector stops short of the pump inlet, such that the pump may access water stored below the deflector. The deflector resembles a 180 degree scoop with a flat forward 25 edge adjacent to but spaced from the pump inlet In the illustrated embodiment, a large clean-out plate 96 is provided at the upright side of the suction chamber 78 opposite the pump intake, and the central portion 92' of the scoop is mounted on the clean out, whereas the side portions 92" of the scoop are mounted to the stationary walls of the suction chamber. The side portions and central movable portion of the 30 scoop form smooth continuations of each other when Me clean-out is inserted Thus, the deflector scoop has no exposed edges where stringy materials or lumps or chunks of solid or semi-solid material can become trapped to block flow to the pump. The suction side flow deflector with an access port (i.e., the gap between the inner edge of the deflector and the pump inlet) allows the pump to use stored water below the

( -9- deflector and provides a good compromse between achieving good pump effciency and good pump priming capabilities.

=T=^ 1A."-s*-a.os a sc'-llinE, -imp iw o. use gt:nerai type shown in FIGURES 12 and 13 parnally disassembled. The pump impeller 7 and all rotating 5 components can be mounted or removed from the pump housing 102 by uncoupling a back plate 104 which fits in a rear opening 1Q of the ho''in". TIC sem,!,' 'A shown in FIGURE 15. Returrung to FIGURE 14, the pump intake plate 13 is mounted separately in the housing 102. In one known construction, shims are placed between the margin 108 of the housing opening 106 and the back plate 104 which A carries the rotating pump components to adjust the clearance between the impeller blades and the intake plate 13, particularly the cutter bars 14' of the intake plate.

With reference to FIGURE 16, a similar construction can be provided for the more traditional pump design that does not include the enlarged housing of the self prirning pump. In that case, the intake plate 13 is mounted to the casing 5, and the 15 rear side of the casing has the opening 106 for the back plate 104 which cames the rotating pump components, including the impeller 7.

In accordance with the present invention, small adjustments can be made in the clearance between the impeller blades and the interior of the intake plate 13 without completely disassembling the pump. Rather, the clamp bolts 110 which 20 secure the back plate 104 to the pump housing 102 or casing are loosened, and the distance between the inside face of the back plate and the outside face of the margin 108 of the opening 106 is adjusted by turning set screws 112. In this construction, preferably at least three set screws are provided spaced uniformly around the circumference the back plate 104. The set screws are threaded in the back 25 plate and have exposed ends that bear against the housing or casing margin 108 at locations between adjacent clamp bolts 110.

With reference to FIGURES 17 and 18, the adjustment screws and clamp bolts can be combined in one unit 120, the details of which are best seen in };IGURE 18. I=rger adjustment screws or bolts 122 are threaded into the back 30 plate 104 and have inner ends 124 that bear against the marginal portion 108 of the pump casing flange adjacent to the opening which is closed by the back plate. Each adjustment bolt 122 has a central bore 126 through which a clamp bolt 128 extends, including its threaded inner end portion 130 which can be screwed into the pump casing flange 132 or an inner nut. In this construction, the clamp bolts 128 can be 35 unscrewed sufficiently to allow the adjusting screws or bolts 122 to be fumed for

f -1 snoring their inner ends I24 in or out, thereby moving the impeller of the pump relative to the intalce plate. When a desired position has been reached, the clamp avid 'A uc,...erle" to leek ale ass:mDiy in position. fir fine clearance is incorrect, or if, for example, the impeller blades become worn over time, the clearance can 5 easily be adjusted by unscrewing the clamp bolts and teaming the aj'sti".g h^l.ts in.

the annrn,nnate rlirestnn' folio=ed he' tightening the -!-. belts ic lCc1 'ale Oscar'; in position again.

While the preferred characteristics of the invention have been described and illustrated, it will be appreciated that various changes can be made therein without 10 deponing from the spirit and scope of the,nention.

Claims (7)

( CLAIMS

1. A centrifugal pump having an impeller (7) rotatable about an axis.

such impeller having a plurality of generally. ad.ally extending 5 vanes (10), and a pump casing including a bowl receiving the impeller and having an inlet side for intake of material into the pump bowl, and a rear side opposite the inlet side, an intake plate (13) mounted on the inlet side of the pump casing and having an arcuate inlet aperture (14), the most radially outward position of which aperture (14) is located a 10 substantial distance inward of the outermost portion of the impeller vanes (10), characterized by each of the impeller vanes (1O) including an inner portion (71) extending substantially radially across the inlet aperture (14) and an outer portion (73) curved rearward in the direction of impeller rotation and positioned adjacent to the inner surface of the 15 intake plate (13) at a location radially outward of the inlet aperture (14).

2. The pump defined in Claim 1, further characterized by the

impeller (7) including the impeller vanes (10) being constructed and arranged so that only the width of the inner vane portions (71) block the 20 arcuate inlet aperture (14).

3. A centrifugal pump having an impeller rotatable about an axis, such impeller having a plurality of generally radially extending vanes, a pump casing including a bowl receiving the impeller and having an inlet 25 side for intake of material into the pump bowl and a rear side opposite the inlet side, the rear side having an opening therein, and a back plate attached to the pump casing to close the opening, the impeller being carried by the back plate, the inlet side of the casing including an intake plate having an intake aperture, the impeller vanes having outer edge 30 portions closely adjacent to the surface of the intake plate adjacent to the pump bowl, the back plate being separable from the pump casing for

removal of the impeller, threaded adjusters extending through the back plate for engagement against the casing adjacent to the rear opening for adjusting the clearance between the outer edge portions of the impeller vanes and the inner surface of the intake plate by turning the threaded 5 adjusters, and means for selectively locking the back plate against the casing to prevent turning of the adjusters.

4. A centrifugal pump having an impeller rotatable about an axis, a drive shaft connected to the impeller, a pump casing including a bowl 10 receiving the impeller and having an inlet side for intake of material into the pump bowl and a rear side opposite the inlet side, the rear side of the pump casing having an opening through which the drive shaft extends, and a seal for the drive shaft in the area through which it extends through the opening in the rear side of the casing, the seal including an annular 15 rotating seal component mounted for rotation with the impeller and an annular stator seal component mounted so as to be nonrotatable relative to the pump casing, said components having respective seal faces in engagement with each other, the rotating seal component being mounted closer to the pump bowl than the stator seal component, and the rotating 20 seal component having a first portion of reduced diameter adjacent to the pump bowl, a second portion of a diameter greater than the first portion remote from the pump bowl and an abrupt shoulder extending generally radially outward between the first portion and the second portion.

2o

5. A centrifugal pump having an impeller rotatable about an axis, such impeller having a plurality of generally radially extending vanes, and a pump casing including a bowl receiving the impeller and having an inlet side for intake of material into the pump bowl and a rear side opposite the inlet side, an intake plate mounted at the inlet side of the 30 pump casing and having an inlet aperture, the impeller vanes having edges closely adjacent to the inner surface of the intake plate facing the

pump bowl, such inner surface of the intake plate having a shallow recess extending generally obliquely relative to a radius from the axis of rotation of the impeller, the shallow recess having an abrupt edge for assisting in cleaning the impeller vanes of material as the impeller rotates and the 5 vanes pass along the inner surface of the intake plate.

6. A centrifugal pump having an impeller rotatable about an axis, such impeller having a plurality of generally radially extending vanes, and a pump casing including a bowl receiving the impeller and having an 10 inlet side for intake of material into a pump bowl, a rear side opposite the inlet side, and a discharge for material drawn into the bowl, the pump casing being mounted in a housing having a first compartment connected to the pump discharge and a second compartment in communication with the pump intake, the housing including an angled deflector leading to the 15 inlet side of the pump bowl, and the first and second compartments of the pump housing being constructed and arranged relatively for retaining a sufficient amount of water after the impeller stops rotating so as to reprime the pump when the impeller is rotated again.

20

7. A centrifugal pump substantially as described herein with reference to Figures 3 to 17 of the accompanying drawings.