US2736265A

US2736265A - higgins

Info

Publication number: US2736265A
Authority: US
Publication date: 1956-02-28
Anticipated expiration: 1973-02-28

Description

Feb. 28, 1956 5, Ns 2,736,265

CENTRIFUGAL PUMP Filed June 4, 1952 INVENTOR. DOA/4L0 I ,U/GG/A/J.

A GENT.

United rates CENTRIFUGAL PUMP Donald S. Higgins, Balboa, Calif., assignor to Shellmaker Inc., Los Angeles, Calif., a corporation at California This invention relates generally to the fluid pump art and more particularly to centrifugal pumps. Specifically, the invention is concerned with, a centrifugalpump designed particularly for use in a dredge operative to draw or suck mud, sand and other sediment from a harbor or river bed and force the same through a duct leading to a collecting scow, a river bank or other point of use or disposal.

Dredges of the suction type currently used for dredging harbors, channels and rivers usually include an inlet pipe which is lowered to the river or harbor bottom and frequently provided with a steel grating or head and a rotary cutter or drill. The mud or silt is drawn upwardly through the inlet pipe or duct through the action of a centrifugal pump of large capacity located on the deck of the dredge, the suction pipe being connected to the suction or inlet part of the pump. As the pump is operated, the mud or like material is drawn upwardly from the bottom of the waterway and discharged through a duct to be conveyed thereby to the point of use or disposal.

As is well known by those versed in the art of dredging, centrifugal pumps designed for this purpose have the very serious disadvantage that their closely fitting and relatively movable components are continuously subjected to abrasion caused by minute particles of sand or other material which invariably lodge between the closely fitting faces of the pump housing and the impeller. Such abrasive action of the sand has the deleterious effect of causing scoring or other wear between the parts and this eventually-results in loss of efficiency of the pump. 1 That is to say, when the wear occurs in the surfaces normally separating the high pressure discharge side from the low pressure inlet side, arvery serious loss of discharge pressure ensues, due to the fact that the high pressure water is forcibly returned to the inlet side of the pump. This loss of volumetric flow is further aggravated and constantly multiplied due to the fact that the water in returning to the inlet side of the pump provides a carrier for additional sand particles which are floated into the space between the closely fitting surfaces to increase the abrasive action. This deficiency of dredge pumps is, therefore, a very serious one which results in inefiiciency and eventual inoperativeness of the pumping unit. In actual practice, efficient pump operation can be expected over a very short period of time, it being frequently necessary to discontinue operation of the pump after a period of but a few hours and to overhaul the pump by installing new liners therein. Such interruption in the operation obviously results in loss of time and this is reflected in the over-all cost of the dredging. While new parts for the pump may be kept available for installation, or the dredge be provided with an extra or auxiliary pump, the upkeep of such pumps requires the constant attention of skilled mechanics.

Various expedients have been proposed for alleviating the condition discussed above, that is, for reducing wear between the relatively movable pump surfaces, one such atent .2 means being in the nature of hardened steel wear plates or rings and while these may make for a higher degree of efliciency, they do not prolong the operative life of the pump to any appreciable extent. As a general rule,

therefore, the problem has been considerably a practically unsolvable one and for this reason the condition continues to be tolerated by dredge operators.

It is therefore an important object of this invention to alleviate the deficiencies and disadvantages of dredging and like centrifugal pumps used for pumping sand or other abrasive material by providing a centrifugal pump having meansembodied therein for practically eliminating wear between the pump impeller and the adjacent wall of the housing, so as to render the pump highly efficient almost indefinitely. This object is best attained by providing means for producing and maintaining fluid pressure in the clearance space between the impeller shroud and the casing wall adjacent the impeller eye. In accordance with the invention, said fluid pressure is in excess of that produced in the volute and discharge end of the pump so that the water pressurized in the volute, and the sand particles suspended therein,

efficient operation over long periods of time withoutrequiring overhauling, rebuilding or renewal of its components.

Another objectof the invention is to provide a centrifugal pump of the character referred to in which the wearresisting means comprises a resilient ring disposed at the interior of the front casing wall and provided with a pair of concentric beads or fins on its inner face for engaging the corresponding face of the front shroud of the impeller. The beads define, with the shroud and casing wall, a circular channel or pressure chamber into which fluid is introduced under pressure exceeding that of the fluid discharged by the pump. The fluid pressure existing in the annular sealing chamber thus provides, in effect, a'buifer or fluid partition between the high and low pressure sides of the pump to positively guard against'reverse flow of fluid from the discharge side to the inlet side of the impeller.

' Another object is to provide a pump of the class indicatedin which "the annular beads of the resilient sealing ring are lightly compressible against the shroud of the impeller so asto produce a substantially fluid tight seal. A related object is to provide means for adjusting the ring axially toward and away from the impeller so as to attain the proper degree of compression of the sealing beads thereagainst. In accordance with the invention, thislmeans consists of a plurality of push bolts on the pump casing and engageable against a metal reinforcing ring forme d integrally with the resilient sealing ring.

Another object is to provide means for introducing the pressure sealing liquid into the annular chamber formed by the beads of the resilient ring, this means comprising a plurality of tubular studs screwed into threaded holes in the metal reinforcing ring in align-- ment with holes formed transversely in the resilient ring and in communication with the annular chamber, the outer ends of the studs having connected thereto flexible tubes through which the pressurizing liquid flows from a suitable auxiliary pump.

A further object of the invention is to provide in a centrifugal pump a combined sealing and wear-reducing means which is extremely simple in construction and economical to produce, one which is convenient to install in existing as well as in new pumps, and one which is positive in action and requires no special servicing.

sealing ring andassoeiated Parts.

R ferri g I he drawingin detaiL'the-eent-rifug lpump illustrated, by .wayiofyexample, 'ncludes garbase 5 :and a casing ,6 supported thereby. e,:;cas ing 6; has a: front ,wall 7, aback :wall 8 and a; s,crolllike central portion or volute9-provided with a tangential discharge mouth 10 ,to which maybe connectedzatductil {leading :to a point where the pumped- -rnaterial is delivered. As ;shown, the frontwall 7is-connec.t ed,to thecentral portion9 by means of ,bolts 12in theusual; manner. ln-pumps of the type employed for pumping fluids tandy'relatively solid matter which are apt toweorrode and abrade the inner surfaces, the inner; surfaces of the:pump casing are 'provided with liners, such;:as:those.-shown at 1'3, 14, and 15 in Fig. 1.

Adrive shaft is journaled ;in':h earings 21 on the base-5 and extends into the casing figthroughaghole 22 in the back wall 8, a suitable--st11ffi,ng:box ,23; being employed for sealing this-portion-of;thepump. Connected to the inner end of the shaft within gthecasingfi is an impeller'25, of any conventional typeteaidzimpeller having a front shroud 26 and an inlet opening or;eye;27. Secured to ,the forward face-of the shr.oud, -26;is;awear ring 23' The casing 6 is providedawith-a:;tubular ginlet fitting'29 through whichxthe material .toibe pumped is directed intothe center, of the: i,mpeller; said fitting j-being connected to the inlet orsuctionwpipe'plo ofthe-dredge.

The inlet opening in 'the fronttwall-ofthe casing 6'is made larger in diameter than theinternal diameter of the inlet tube 29, thusproviding.an annulartrecess 3'2.v for receiving a resilient ring'33. Asshown, the ring 33;may be substantially square in cross-sectional;;shaperand provided at one side with a metal backing element -or reinforcin g lementbeing"preferably-formed as an insert in the molded ;ring;33 ,and -provided:,with a plurality of threaded holes135-registering with-holes 36cm the ring 33.

At its opposite side, the resilientyiri-ng;,33-;is1rformed With a P of n n r c,annular,.

reqmpressihleiribsor beads

37 and 38. whiletheseubeadsrmay, emf-various cross-sectional shapes, it has heemrfoundnadyantageous to make them semicireularjn f rm;so; as to provide-subn ially poin contact between their:extre.mities1.and the wear ring, 28,0f the impeller ,25. Means; tnibe-presently described, are provided ;for:-adjusting-:the ring -33 toward the wear ring 28:,so-as t0:.C9 P i z fi 1 and 38 lightly thereagainst and, -;si nce-'twiszdesirablehthat theinner bead 37 becompressed'xto qagslightly greater degree, this bead is made to extendgto;;a;islightly;greater distance fromthe inner face oflthe ring :33: than-rthe'outer head 38. It is to be noted byyreferencet-zto;Fig. 3 that-the beads define with the wear ring ZSJanmnnulartChamber 40.

The resilient ring 33 is ;;for,ccd;;.t0W.ard-;the -;wear :ring 28 y m n f p sh-b lt 4z-whiehzareserewed through holes in the flange 43 of the inlet-fitting 29 -:-with :their inner ends engaging the:metal:reinforcing-ringt34.

During operation of the dredge pump water iisintroduced into the I pressure sealingycharnberdfl -rbyzway. of the aligned

holes

35 and 36,;ithepressure'rof:athewwater being in excess .of ;theifluid pressuresrdeyeloped by-zthe pump in the volute at ,thediseharge; ,d;=.thereof. iiSerewed into the holes 35 are ,tubular studststsmrhichlpass' through apertures 46 in theflange=43,nheck:nutsr47: being-screwed it. onto the studs and set up against theflange- .Cnnnected to the outer projecting ends of the tubular studs 45 are flexible tubes 48, these tubes leading from a suitable fluid pressure manifold supplied with pressurized water from a suitable pump, these last-named parts not being shown in the drawing.

During operation of the dredge, the impeller 25 is rotated with the shaft 24 withinithecasing 6 to draw the sand-laden water upwardly'from the harboror riverbottom :throughthe suction. pipe: 30, the dredged material being forced radially outwardly into the volute bythe rotatingimpeller blades. Thus, fluid pressureis created within the casing 6 and the discharge 10. Also, during operation of the pump,. sealing .water is introduced into the annular channel or chamber 40 by way of the tubes 48, tubular studs 45 and the holes 36, the pressure of this water being greater than that of the fluid pressure de veloped within the pump. Consequently,any'tendency of the-pressure fluid in the casing'6 to=escape intothelow pressure inlet passage, through the :space' normally exist- .ing-vbetween the wear ring 128and theinner surfacet-of :the'front casing .wall"7, 13, is effectively prevented. The :present fluid pressure sealing means thus guardsagainst ;sand;particles,entering saidspace to cause scoring-and abrasion of the adjacent surfaces of the wear'ringend ing-of-thepump, the over-all upkeepcost of the dredge ,-iseffectivelyminimizedand this is an important-consideration.

It is to be noted that the resilient sealing ring-33pm rmallyisurged towardthewear ring128 with-a force which at least ilightly compresses the fins 'or beads 37' and 38 thereagainst to seal the sides of .the pressure chamber '40. Byxsuch sealing, escape of the pressure sealing fluid from ithe chamberAt) into eitherthe inlet or discharge sides of':the pump is minimized. A gentle flow of the'sealing rwater past the beadsmayyhowever, be desirable for the purpose of flushing away minute particles of sand which tmightvtendto lodge against the outer surfaces of the .bea'ds,.and for-reducing wear of the-beads. As previously explained, suchw-adjustmentof the sealingring 33- -towaid and :-.away from the impelleris effected by means of the push-boltst42. When the beads eventually become'worn,

.the ring I33-may be-easily replaced by simply-removing "the. coverdike front wall? andthe sealing ring-carried thereby-rafter which thestuds 45 are withdrawn torelease hearing Anew ring 33-is then installed-by'reversing the above procedure and-the pump is't-husreconditioned :foncontinued dredging service with auminimum ofexpended time, effort and expense involved.

';:In:a ccordance with the patent statutes,'-I have disclosed r-herein-=what I'consider to represent'the best embodiment tof'lthe f invention. It is tolee-understood, however, that -.various modifications might be made in the-construction andxarrangement of :the dredge pump within the spirit of tthe invention. Consequently, I do not wishto be ,limitediin :this respect, but desire to be accorded the v fullzvscope of the appended claims.

I r claim as my invention:

r1. A centrifugal pump for use particularly in pumping liquid containing solid particles, comprisingz-a easing having a forward :wall, an axial inlet port-and a substantially :radialwdischarge port; an impeller rotatable -within said casing and having a shroud disposed adjaeentfbutspaeed gfrom; said Walk-a resilient sealing ring s'lidably mounted inr'a recess in aside :of'said casing;'means-operative-m adjust :saidring toward and away from-"said impeller; said ring having a pair of concentric, annular, compressible beads on its side facing said impeller, said beads having substantially semi-circular ends engageable with said shroud and defining therewith a fluid pressure chamber located in the annular clearance space between said shroud and said wall; and means connected to said sealing ring and communicating with its said chamber for introducing fluid into said chamber at a pressure in excess of the fluid pressure developed within said casing by said impeller so as to prevent passage of the fluid from the pressure side of said casing to the inlet port thereof by way of said annular space, said fluid introducing means including a metal reinforcing ring embedded in said sealing ring and having at least one threaded hole therein registering with at least one transverse hole in the ring communicating with said pressure chamber; and a tubular stud screwed into said threaded hole for conducting pressure fluid to the chamber.

2. A centrifugal pump for use particularly in pumping liquid containing solid'particles, comprising: a casing having a forward wall, an axial inlet port and a substantially radial discharge port; an impeller rotatable within said casing and having a shroud disposed adjacent, but spaced from, said wall; a resilient sealing ring slidably mounted in a recess in a side of said casing; means operative to adjust said ring toward and away from said impeller, said ring having a pair of concentric, annular, compressible beads on its side facing said impeller, said beads having substantially semi-circular ends engageable with said shroud and defining therewith a fluid pressure chamber located in the annular clearance space between said shroud and said wall; and means connected to said sealing ring and communicating with its said chamber for introducing fluid into said chamber at a pressure in excess of the fluid pressure developed within said casing by said impeller so as to prevent passage of the fluid from the pressure side of said casing to the inlet port thereof by way of said annular space, said fluid introducing means including a metal reinforcing ring embedded in said resilient sealing ring and having a plurality of threaded holes therein registering with a plurality of holes in the ring in communciation with said pressure chamber; and a plurality of tubular studs, each screwed into a said threaded hole and adapted to conduct pressure fluid to said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,862,153 Lee June 7, 1932 1,869,955 Daugherty Aug. 2, 1932 2,109,679 Neveling, Sr. Mar. 1, 1938 2,133,487 Spargo Oct. 18, 1938 2,536,292 Kollsman Jan. 2, 1951