CA2175537A1

CA2175537A1 - Corrosion resistant expansion tank

Info

Publication number: CA2175537A1
Application number: CA002175537A
Authority: CA
Inventors: George M. Celorier, Jr.
Original assignee: Amtrol Inc
Current assignee: Amtrol Inc
Priority date: 1996-02-15
Filing date: 1996-05-01
Publication date: 1997-08-16
Also published as: EP0790411A1

Abstract

A first aspect of the invention is directed to a corrosion resistant expansion tank that is divided into two sections: one that may be precharged with a fluid under pressure (for example, a gas) from a first fluid source; and the other being connected to a second fluid source, for example the hot water source in a hot water heating system.
Accordinq to this first aspect of the invention, the tank comprises a pair of molded plastic tank sections that each integrally include the connection to one of the aforementioned fluid sources; and further include means for separating the interior of the tank into the two sections referred to hereinabove. Examples of such means for separating include application specific membranes (such as diaphragms and bladders of varying types) that are impermeable to the fluids stored in the separate tank sections. Further aspects of the invention relate to apparatus for securing the means for separating within a tank and to processes for cost effectively manufacturing the tanks contemplated by the aforementioned first aspect of the invention.

Description

~ 2~75~37 . .

C~RT~OSTON 1~.5T~TANT ~Xr~N.~TON ~r~NK

n~cKc~QuNn o~ Tl-l~ TNV~.NTION

1. l;.el.cl of tl~e Tnvention Ihe .i.nvcntio~ cn(ral.l.y rel.ates to expans.i.on and stora~e tallks (llereinlfter collect;.vely referrc(l to as ex~ansi.on tanks) used for example in el.oscd hydronic heat.in~J systems ~ressur;.zed water systems eloscd clomestic watcr systems and to ex~ansi.on tanks th.lt store water in water treatment systems etc.

More part:ieularl.y a first aspect ot the invention is direeted to a eorrosion resistant expansion tank that is d:ivi.ded into t:wo secti.ons: one that may be prech~r~ed with a~
fluid under pressure (for e~ample a ~as) from a l~irst ~luid souree; and the othcr l~e:in~ connected to a sceond fluid souree for examr)le tlle hot watcr ~ource in a l~ot water heat-.:i.rl(l systcln.

`` 2~ 75~37 Tanks contcmplated by tl-lis f.irst aspcct of the invention are fab~icate(l from a pa.i.r of molcled plastic tank sections that each int~-Jr;~l]:y i.ncl.ude tl~c connection to one of the aforement;.oned fl.l.li.d sources; alld further include n~eans for separatin~ th~. inter:ior of the tank into the two sect;.ons referrcd to herei.nabove. Exampl.es of such means for separatinq incl-lcle applicat.ion specific mcmbranes (s~lch as diaphragms and bladders of varyinc~ types) that are impcrmeable to the fluids storecl in the separate tank sections.

Furtller aspects of the invent:i.on rel.atc to aprarat-l~ ~or se~ur.illJ the me.lns Jor ser.lrat.i.n~ w.ith.in a tank and to p2-ocess~s for cost cffect.i.vcly manufacturinq the tan~s contemplated ~)y the first aspect of the invention referrecd to hereinabove.

2. I)escr;.pt.ion of t-hc Rcl.at-e(l ~rt Water contclins a.ir :i.n the a~sorbed state in nearly inverse proportion to .i.ts te~mperat~lre. This ai.r Is l..i.beratecl into the systcm when thc watcr i5 hcated and acc~lm~llatcs i.n the compression tanl and other portions of the hcating system.

2 ~ 75537:

A reduction in heatil~q efficiency results, makin~
continuous venting of radiators or conveetors necessary.
The water as it is heated expallds and moves into the compression tank which i.s conllected to the pipi.n~ throuqh which the water is circulat~d. Whcn the temperature of the boiler water reachcs the desircd deqree, thc fi.ri.nq of thc boiler ceases. The water be~ins to cool and contract. ~s i.t cools, that part of the boil.er water i.n direct contact w.ith air in the compression tanlc absor~s some of the air in the tank.

Throu~il therma:L circulation tllis air char~ed water in the compression tan~ is chan~e~ conti.nually 50 that i.n the ncxt heatinq eycle thls re-abs,orbcd air :is liberat~d into the system. This reversible proccss i5 repeatecl as often as the firin~ cyc:l.e ;.s repeated and the boiler watær .is heatecl and cool.ccl. ~5 a re~ciult of th:is ~roccss tllc pressurc in the system varies considerably and evcntually the system may cease to function.

~ xpansi.on tanks ;n clomcst-.ic watcr systems provi~e an ai.r cushion for the s-lpply watcr. The air and water in early systcms were in direct contact. ~ir bei.n~ soluble in watcr, t-he watcr a~sorhs ai.r. The wat-.er :i.n thc ~ystcm mi~ht evellt.ll.ll:ly ahsorh tJle .~.i.r CIlS~l.i.oll in t~lle exl)allsion t~nks, 1C~aV.il1~3 a stat;.c wat-cr system whi.c~l llCCC'S';itatC5 the constant operati.on or rapi.cl cyol.in~J of: a press~lrc pump.

~ 2~75~3~

Subseq~lently an air surqe ch;lmber wa~-, provided whiell was not :
in direet eontact w:itll th2 water, thereby eliminatin~ the need of the pressure pump o~eratinq every time a faueet was turned on.

U.S. ~atent No. :3,0~5,Gl~ diseloses expansion ~ -tanks which i.ncl~lde a ~I~.ir o~ holl.ow body members, ~aeh of whi.ch have an encl and a tub~l.lar slcirt portion. The skirt portions are unite-l in end-t:o-end relati.on to form a tank.
~l'here is a ~lex:ible diaL~hra-JIll ;.n ancl spanni.n~ the tank and vin~ a per.iplleral. port.i.oll :in ~er~ heral enqa-~ement with the skirt of one ol` the body members. ~ eontinuous retainin~ ri.n~ en~Ja~es the per;.plleral port.ion arlcl retains it in en~ac~ement witll the sk.irt of the body member. There is a ~roove in the exterior of the ri.n~ ancl a s~lbstantially complement,-ll eorr~ ation in the ~ki.rt of the bocly member compressin~ the peripheral portion into the ~roove to seeure the di.aphra~m a~a;.nst movement endwise o the tank and seal the diaphra~m to the ~kirt. See also U.5. ratent No.
2,695,753 U.S. ~atent No. 3,5?.~,~75, i.ncorporated herein by referenee, (li.scloses an expans:ion tan)c wh:i.ch includes a hol.l.ow bocly llavin~ a ~-,i.cle wall and end walls and a ].iqllid-.i.mperv:ious l..i.ner hav.in-J an en(l wal.l. all(l a 5.idc wall. coverin~
the correspond.i.n~ encl wal.l ar-cl a porti.on of. tl~c 5i.de wall of -the bocly in adjaeent non-adheri.ll~ rel.ation thereto. 'I`he 2 1 75~37 liner llas a periphcral el-)e portion contactin~ the side wall. There is a flexibl.e di~pllraqm dividinq the interior of the body into two sectiolls. One o~ the sections i.s adapted to receive a 1 iqlli.r.l. The cliaphraqm has a peripheral portion dispose~ in over~.yin-~ relat.ion to the ~eripheral ed~e ~ort.ion of the liner. There is also mcans r~taininq the peripheral portions o~ the diaphr~Jm an~ the lincr aqainst the side portions o~ the di~S~ra~m ancl the liner.
The retainin~ me~ns incl.~ldcs ~ continuous rinq cn~qinq and rcceivinq thc pcr.ipllcr<ll portiol ol- tlle di;lr-l~rlqm. Thc s:ide wall engaye~ the ~cri~hcr)l c~lqe l)ortion of thc li.ner. rllle rin~ an~l w~ll have a complemental r.ib ancl qroove secllrinq t)le diaphra~m to the s:i.dc wal..l. Ihc dill)hraqm :i5 formcd wi.th a l)ead on :its per:iphera:l. port.ioll w.ith the ~)eai hc.in~
received between the ri~ ancl the qroove.

U.S. Patent No. 5 3~36 ~25 (asi.qned to the s~me assiqnee as the i.nstant invention; also i.ncorporatecl herein by reference) is an improvement over the expansi.on tank disclosed in U.5. ~atent No.~ 52~ ~75. ~ e retlininq rinq that continuously en~qes the di.apl~r~m ~nd liner to per~orm a secure seal was mo~ified i.n tlle incorporated 5 3~6 ~25 patent.

- 'I'he tanks clescr.il~ccl :i.n l~otl) o.l` tl~e :incorpor.lted pat cnts lS~ ot a del~orm~ l.e di.~l)llra~Jm to (:l.i.vi~lc .1 tlnk i.nto two sect.ions. One scc~.i.on is ~rechar~c(l W.ittl (~as ~nler ~ 21 75~37 pressure so that the diapllraqm is clisplaced to increase or decrease the volume o~ this section accordinq to the var.iations Oe the volume o~ water in -the other section.

~ s indicated hereinbefore wl~en the expansion tank ;i.s incorporate~ in a hot watcr heatinq system the variation in volume is c~used when the l~oiler water is heated and cooled in the normal cyclic operation of the heating system.
If tlle expansion tank is a part of a water system the .
variation :in vo~.ume occlrs as tap water :i.s clrawn and when the pUIllp o~eratcs ~o rer)lac~ tl~ wa~?r drawn from thc tank.
~he liaphraqn1 separates the qas .in tlle one secti.on of the tank from the water in the system.

In desi.~ninq metallic expansion tanks like those descri~ecl in the incorporatc?cl patents i.t is :important to address corrosion ~roblems wllich can have a siqrlificant adverse e~fect on the useful l:i.fe of s~lch tanks. Tank corrosion could becomc a serio~ls probl.em i~ there was direct contact of w-ter (or watcr vapor) wi.th su~stantially the enti.re :inner metal~ic s~lr~ace o~ the water receivinq secti.on of ex~ansion tanks like tl~ose describe~ in the referenced patents. Corrosion i.s act.ive in hot water system expansion tanks )~eca~lse of the el.evatel tcml~eratllre of thc watcr.
W.i.th watcr system ex~ans:i.oll t.lnl~.i thc- coJros.ion var.ics in accorclance Wit~l thc mincral alld oxyqen contcnt. of the wat~?r :in a given ~.ocal:it-.y l`o -olve t-.hese ~ro~l.em<i metal. tanks " ~ 2 1 75$37 :1.ike those deser;1~ed in t11-~ i.neorporatecl patents, use additional components (I.ike the aforementioned liquid-impervious liner, means for securing ~ liner within the tank, ete.), to protect the inner surfaee of the tank section that holds water. Other techniques ~1sed to solve the aforementioned problems incl~1de co~tin~s ~ncl/or surface treatments applied to the inside of a tank.

1~or the sake of i.ll.u.strat.io1l onl.y, reference will be macle part.i.cularl.y t:o the :incorporatec1 5,3~G,925 to point out several o~ the mo1e 5i~l11i 1.;.cant ~rol~.lems inl1erent in present day eorrosion resistant metall:ic tanks themselves and the known processes usecl to manufacture s~1ch tanks.

In order to ma1lufacture a steel. expansi.on tank in accordance with the teac11in~s of the :incorporated 5,3~G,~25 patent, both tlle l;ner ancl diapllraqm must J~e sealed i.n a metal tank half (referred to ~s the "water dome" in the incorporated 5,3~6,925 ~atent). ~ retaining ri.ng (yet another internal tank component) i.s usecl as an inside support of a cold formed tan)c seal..

The "air dome" descril~ed in the incorpor~ted 5,3~,9~5 ~atent ;.s tl)en wel.ded to the water dome; wit1l care -needin~ to ~)e exercised in t1~ tank des~ n to ins~-re that the wel(l 1rca .i.s sufJ~ ie~1tly sr~ace~l I r oln thc (li~r)hr~l~ ancl l.i.ner so tl~t these co111pon~nts are not dam.1(led dur.incJ the (_ 2175337 welding process (~ue to the qreat variance ;,n the meltincJ
temperatllres of the materic~ls used, sueh as metal and ruhber).

As those ski.ll.ed in the art will readily appreeiate, eriteric~ such as the choiee of weld arec~, amount o~ weld material used and type o~ joint heinq formed, all affect joint strenqth and tank inteqr.ity. Onee aqain, the coneern about heat transfer, overheatin~ and me].tincJ
comr~onents :installed i.n the tank, etc., a~ect the weld and ~joint tyr)e o~tions ~1vai1..lh:l.e to t:11e tank manu~ct~lrer.

Additional1y, in accordance wi.th the teachin~s of the i,ncorporate~1 r~,~c3~"9~r) p~tent, the liner m~1st ~e sealed to the tank's water connection; and t~)e water connection '~-'-' itself needs to he formed in c~ separate set of cleta,iled process steps, includinq bra~in~ or wel(1in~ the water connection to the water dome tank half.

In s~1mmary, the incorporated ~,3~6,9~5 patent exemplil-`ies several prob:l.em~i .inherent in the structure c~ncl manufc~cturin3 processes associatecl with prior art metallic expal1si,on tanks. 'I`ank i.nsert comr~onents, such as l.i.ners, are req~1i,re~1 :i.n orc1er to r)rov:i.c1e corros,i.on protecti.on;

sepclrc-1te tank i.nscrt s.ec~l.inq -mechcln;.sms, 5uch c-lS reta;.ni.n~
rinqs, are required t-o seal the l;.ners ~nc3 ~ phra~ms wi,thin the tanks; t~e li.ners need to be ~urt-,her sealed at the ~ 21 75337 tank's water connecti.on; the watcr connection (and the ~as connection in many prior art devices) needs to be formed in a set of separate process steps; care m~lst be taken in performing various manufact-lring steps that call for the application of heat to avoid damagin~ the l:i,ners and diaphra~ms bein~ installed l~lrin<J tl-e manuLacturinq process;
and the type and s~trenqth of joints formed durinq-tank construction are to a de~rec affected by the proximity of the internal tanlc componcnts t.hat can l~e affected by wh~tever jo;nt formi,n~J procc~s i.s ~Iscd.

All. o tlle ~roblems rcferre(l to llere.inabovc add complex.i.ty to the tank m~nul-act~lrinq process in terms of number of components and ~rocess steps req-lire~l for tank fabrication; and the care tl)at neecls to he ex~rcised t~lrou~llo-lt tlle tank fa~ricati,on process to assemble thc vari.ous components, apply heat, etc. These problems and the known solutions to these problems ~11. I)ave ~n ,impact on tank reliability, tanlc life and tank manufacturin~ costs.

Those skilled in the art wil,l al50 reco~Jni~.e that corrosion resistant non-metall:ic (~s~lall.y plastic) tanks exist. Such tanks o~vLate tlle neecl for a liner to protect the tank from corrosion; however, many of the sam~ problems referre(3 to llerei,llhefore st..i.l.l al`fect known p].a,ti,c tank desi,qn an(l manulacturi.n~ processes.

. 2175~37 ~ or exampl.e ~lon~atic procluces a plastic tank that i.5 fabri.cated without the use of a liner. Ilowever, a diaphraqm (inserted into a tank half) needs to be secured by a hoop pressed into the tan]c half; and then t}-e two domes (a:ir and c~as) are friction-wclded toqether. ~clditionally, both air and water fittinqs necd to be fastenecl to the tank.
rhus altl-o~qh the need for a liner is climinatcd the Flomatic tank still requires the use o~ an internal tank component (the hoop) to sec~lre the diaphraqm and still requires the additi.on of scparatc a;.r and qas tank connections since these connections arc not moldcd into the tank halves (the domes).

The frict:i.on we].d stcp in thc proccss used to fa~)ricate thc ~lomati.c t;~nk .is alr;o a potentill problem source. -rlhose skilled :i.n the art wi.ll rca(1il.y appreciate such a welcl (a friction wcld) lla5 a low joint e~ficiency.
In applications where jo:int c~ficiency neecls to bc hicJh (hiqh pressure containment s:ituations etc.) to qet an improvcd joi.nt usill~ fr:i.Gtion welcl:inq the welcl surface area necds to be i.ncreased. ~lthouqh not clesirr.tble this a~ditional surf-1ce area could be prov.i.cled for cxampl.e by the use of wider tank componellts hav:inq a qrcater weld surface area.

~175~37 l~nothtr Is:nc)wn r~ i.c tanlc, tl-e "ROm~t,c" l~ure wat~er stora~JL? ve;:;L?l m~nllrlt~ rt?~l l)y ~t:r~lctli?-al l ihers (an 1~.';1 1;` Company) of Char(lon, Ohio, t,alies the form o~ a one ~iece blow moL(lt?cl plcl'~tiC })ott:l(? havincJ ~ d(lcr instal.led ere;ll. 'J'ht? ~t,r~lctl1raL l il;.?rs plastic tank re~ ires i.ts t-,er connL?ct; on to l~c sc.n I e~ a-~cl inst tlle tank ancl aq~3inst t~ .? I~la(7der; t}~e ~asten;!lt-J or wL?~ i-nq on of an air conn~ct;on; ~n~ s t:he ~)ot--t?nl-i-al for lo-;in~J ~.ir ch~rqe in f; c 1-1 ~ISC h~callsc i nhcr cnt~ wcak 1~ i nts at thc a i r steln to ~ottlc int~erl~~lcL? ~n(l .~t thc v~rio~ls ot-llt~r 5cal.~; (wat,er ~-ollllt--~t-it l~l/})l.ttlt~t?r .1~ -)ct r~-~o~ t~ t-o tt~C?

~ n~tt~ ?!.i.t~r~

Otl:c- r L?~lm~lt?S O I t`.llllt 5 t !~ ;tl-~ttC t}lt-?
~3~-~'sL?I)t St.~t-C? o~ ht? Irt .illcl.u(lc t~ .s hy llyclrotccl~ (pl.astic mol ~]ecl ~Ind thell cri mr)c(l on the ollts i~le to secul-e ~ }~l addcr);
met~a I I i ~ lnk.s - }~y We~,scl; Coml~any o t- I)ctr o i t M i ol~ iqan t~-~hr;c.~-te~:~ vi~ pr-oces~ involvillq the wcl-lill~ of two stcel clomes ancl :incital l; n~ ~ }~ kler (th~ rcsul t,~nt tanlis hav inq the l)rOlllC?In'-; ol~ 'it:C?Cl t,,lnl;~, i n qcncr.tl wi t-h r-cq<~rcl to m.~int cllancc, cor-ros;~n ~n-l t tlC? I-)ot-cnti~ or contalnin~tin~
tlle storecl w-~t,er, the r~otential for f:iel-l failurcs due to }31~l(1der sc~l f~ re, ctc.); lllC't-all.iC tarllcs hy l~ell-Ritc (t~cl}~ric.~terl ~-)y, !o-r ~ial~ lc?, cl inollillq l-wo cli.l~llraqmc. in5;clc .~ we l de~l :;t e-- 1 t-ank o~ al t~-~rn.~l, ivel y c~ l i nct~; nq .n ~i i nql C?
hr~ nl l-c~ C?C'n ~IIC ';t ~ ','i .nll(l )11-.' ';t~ I d(-)mc); an~l .~ 2 1 75~37 still other tanks which utilize fasteners to literally screw tank parts toqether.

None of the known tank devices fabricated in metal plastic or of any other material inteqrate both the air and water conncction i.nto ~arts that arc ~lsed to fabricate the outer shcll o~ thc tank; nor clo any of thç
known tank d~vices combine the desirable attributes of proviclinq a low maintenancc corros.ion resistant tank that can bc fabri.catcd usin~ a vcry small componcllt set (thrce components accordin~ to a prcferrcd embod.i.ment of the present invention): and very s.impIe process stcps to assembl.e to aforcmel-t.ic)ne{l cc>mponellt sct.

~ ccorcli.nqly in view of the present stite of the art i.l]ustratcd by tllC excmplary tan~s tauqht i.n thc aforementioned patents and f~lrther illustrated by the commercially ava;.lable tanls described herei.l~above it would be desirable to provi.de a corros.ion rcsistant cx~ansion tank design that (a) inherently resists corrosi.on and eliminates the need for a li.ner to be instal.lecl in order to provide corrosion protection; (b) does not rcq~li.re the lse of separate tank insert sea]:inq mechanisms such as retaininc3 r;nqs or hoops to scal a. I-iaphra-Jm bl.acldcr ctc. wi.thin t-hc ttn~ ) inteqr~t-c-. tanl conllcctiol):; (bct~l qls ~nd watcr connect:ions) i.nto plrtC; th~t a~rc ~Isc(.l to fabri.c~tc the outer s~lel.l of thc tanlc to thcrehy climinate hlvinq to form ~. 2175~37 sueh eonneetions and asso~iltecl seals :in a set of separate proeess steps; and (d) inel.udes apparatus (means) for seeurlnq within an expansi.on tank the means used for separatin~ the interior of t21e tank into two separate portions and at the same time provide for the joinin~ and sealinq to~ether of tank seetions ~Isecl to form the exp~nsion tank fluid eonta.inment vessel .i.tself.

2~urthermore it woulcl ~e desi.ral~le to be a2~1e to provide a eorrosiion resi.stallt-. expansi.oll tank d~s.i.~n (ancl relatecl tank manufaetllri.llq ~roeess) in whieh (a) jo.int ~ffieieney ean he inereasecl w.i.thout havi.ncJ to resort to wider tank component~ to obtain a qreater weld surfaee area; (b) the aforementi.oned means for seeur.ln~ is desiqned to hold the means for separati.nJ ~e.~. a diaphra-Jm) in plaee durinq tank assembly and durinq tank operat;on; (e) the a~orement-.i.onecl means ~or seeurinq is ~urther desi~necl to provide a vehiele for ~ormi.nq a stronq i.nter;.or lap joi.nt to repl.aee for exalllpl.e wea).er pri.or art fricti:on welcls etc.; (d) the number of man~lfaetur:inq steps that call for the applicat;.oll o~ heat cluri.n~ the manufaeturinq proeess and the numher of internal tank components that e~n he affectecl 2~y whatever joi.nt forminq proeess is used are mi.nimi.~.ed; and (e) the overal.l compl.exit:y of the t-ank m.~nnfact~lrin~ process :i.5 redueed in terms ot- n~ ter oL ~omponellts ~nd procc-s; ;teps req~l.ire~ for ~1 75~37 tank fabrication to thereby improve reliability tank life and lower tank manufacturin~ eosts.

SUMM~Y 0~ Tlll~ ]NV~NTTON

Aeeord;ngly it is a qencral objeet of the invention to prov.i.de improve(l cxpansion tanlcs For use in hot water heatin~ systems press~lri~.ed water systems an~ the like.

It i.s a furtller qeneral ohject of the lnvention to provide improved expansi.on tanks for use as ind;cated hereinabove whieh are eorrosi.on res:istant.

l~urthernlore it-is a ~eneral objeet of the invention to provide a corros:i.on ~Csist~llt expansion tank tllat may he div:ide(l :into two sect:.i.ons: one that may be prechar~3ed w;th a f~ui(l under pressure (for example a qas) from a first flui.d souree; alld tl~e other he:ill~ connected to a seeond fluid source for examr)le the hot water source in a hot water heatinq system.

It is a sr)ec-i.fic oi~ject of the i.nvention to prov:ide a eorrosion res;.stant expansion tall)c that ean he fabrieated from a pair o~ tan)c sections (preferlbly molded st i.c tanlc scct i.ons) tl~at. cach :i ntc-lral.l.y .i nc~ c t.hc connect:ion to one o~ the aforement;.oned fluid sources; and 1~1 . ~ 21 7;5~37 further include means for se~ratinq the interior of the tank into the two sections referred to 2-ereinabove.

A still f~lrther speci.fie object of the invention is to provide a corrosion resistant expansion tank desiqn that (a) inherently resis~s corrosion and eliminates the need for a Iiner to b~ install.ed in order to provicle corrosion protecti.on; (b) ~loes not req~lire the use of separate tank insert sealinq mechar)isms such as retainin~
rinqs or hoops to scal a di.apllraqm ~ladcler ete. w.ithin the tanlc; (e) inteqrates tlnk collneetiolls (~oth qas ancl water eonneetions) into p~rt; that are Ised to abr:ieate the outer shel.l. o the tanl~ to thereby elim.inate hav.i.n~J to form such eonneetions ~nd associ.ated seals in a set of separ<~te process steps; an-~l (d) i ncludes apparatus for seeurinq within an exp.lnsiol- tank the means used for separatin~ the inter;or of the tank into two separate portions and at the same time provide for the joininq and se~l;.nq toqether of tank secti.ons usecl to form tlle expans:ion tanJc fl-li.d eontainment vessel itself.

I-urthermore :it i.s a specif.i.e ohject of t21e .i.nventi.on to ~rovide ~ corrosi.on resi.stant exp(~nsion tank desiqn (an~ related t:ank man-lfatllrin~ p~-oeess) in W~l:iCh (~) jOillt cl~~ic;~ncy C~ c ;ncreasecl w;.t:hont~llavi.ll~ to resort to wicler t-anl~ Co~ ollCIltS to obta:in a qreat~er weld .urf~lce area; (b) the aforemcnt:ionecl means or see-lri.nq is desi~ned -t ~ 2175~37 to hold the means for separat.incJ (e . q . a cli~phr~m) in plaee durin~ talllc aSSClllb] y and durin~ tank operation;
(e) the aforementioned means for seeurinq is further desi~ned to provid~? a vehiele ~or formin~ a stronc3 interior lap joint to replaee, for example, weaker prior art frietion wel.ds, ete.; (cl) the number of manl.lfaet-lr;.nc3 steps that call for the application of heat dllrincJ the manufaeturinc3 proeess and the number of intern~l. tank eomponents that ean be affeeted by whatever joi.nt formin~ proeess .is used, are minimi~ed; and (e) the overal.l. eompl.exity of the tank man~ etllr.in~ prc)eecis is redule~l in terms of. n~ lber of eomponents and proeess steps requirc?cl for tan]c l-abrieation to thel-e~y improve relia)~.ility, tank li~e and l.ower tank manufaeturi.n~ eosts.

Tlle a~orementioned objeets of the i.nvention are aeh.i.eved in part l~y r)rov:idinc~ a pair of t:ank seetions that intec3rally inelude first and seeond lui.(1 eonneetion means (for examl)le, water and cJas eonneetion means) whieh when joined to~ether (the tank seetions), with a diaphraqm, hlad(ler or other means ror separati.n~J seeured there~etween, form the expans;.on tank fluid eontai.nment vessel. -More part:ie-llarly, a first apeet o:f the :invention is direetecl to .~ eor-rosion :res.istal~t e~r),~niioll tank that is liviclc?(l into t-wo ;e(tionC;~ one c)~ wl~ieh may (a-lt:llo-lcll- not neeessar.il.y) l~e prc?eh~rc~c?(l w:ith a f`l.ll:id ~Incler pre<.;s~re (I.or 2175~37 exampJe, a qa5) from a ~irst fluid souree; whilc the other section i~ connected to a seeon(l fLu:id souree, for example, the hot water so~lrce i.n a l~ot: water heatinq system.

Aeeord.inq to a pre~rred embocliment of the i.nvcntion, the t~nk eomprises a ~air of molded pl~stie tank seetions. Eaeh of the mol.ded pl.astie tank seetions is desi.qn~cl to inteqrally inelu-le tl-e eonneeti.on to one of the aforementioned fl.uid sourees. The tanks are f~lrther des;.c~i~etl to .i.nelude the mellns for s~par.~t.in~ thc tank inter:ior :int:o the two ~;ect:i.ol~s referrell to ~)er-einabove.

~ urther ~spects ot` the :i.nvention relale to apparatus (means) ~or seeurin~ ttle means for separatinc) wit~l;n ~ tank; and to proeesses for eost effeeti.vely ~ -manufaeturinc~ the tanks eontemplated hy tlle aforementioned fi.rst aspeet of the invention.

Aeeordinq to a spee.ifie ~irst embo(li.merlt of the invention, ~ eorros:i.on res:istant expansion tank, eomprises:
(a) a ~irst molded plasti.c tan]c secti.on ;nt.eqrally ineludinq first eonneetion means l~or enabl:incJ ~lui.a from a first ~luid souree to ~e pLaeecl .in fl.u~l commun.i.cat.ion w.i.th a first ~ ter.ior portion o~ tlle ~pans:ion tanlc; ancl (b) a seeond mol.de~ st.i.e tank seetiorl, wl)ieh when joined together with tl~ ~i.rst moLde(l pl.asti.c tallk seet.ion ~orms the ex~nsion tan]c fl~li.(l eontainmellt vc5scl, ;.ntecJral.ly .inelu(li.nq second ~_ 2 ~ 75~37 connection means for enahli.n~ fluid from a second fl.uid source to be placed in i-luicl communi.cation with a second separate interior portion of the expansion tank.

The aforemcntion~ fir.st an~l s~cond conncction means provide passa~cways throu~h which flui.d from the first and second flui.d sourccs rcspectively may he introduced into and may be withdrawn from the expansion tank.

Purtl~crmore accor-(li.nq to thc aforcm~nti.one(t s~eci.f.ic first elDlo(lim~nt. o~ the invcnt.i.on thc tank compriscs means f~or se~aratin~ thc tal-k into the aforemcl~ti.oncd fi.rst ~nd secon(l i.ntcr.ior porti.on-s wllcrc the means for separati.nJ s~ans the interi.or of thc tank ancl is madc of a flexibl.e material that is impermcclbl.c to a pre~etermi.l-e~ set of flui.ls incl.ucl.in~ thosc f.`luids providcd by the aforementioned first and second fluil sources. In practi.ce the means ~or separat:ing can bc rea.l.i7.ed by for example a flexible li~phra~m or bladder.

Stil.l f~lrthcr accord:inq to tlle aforemcntioned sl-)ecific first emhodin)cnt of the invention thc tank includes a means for securi.n~ the means t`or separatin~
(within the tank) v:i.a a joi.nt formed bctween the first and second molded ~l.as~ic tank scct-:i.olls.

ln 2~ 75337 The means for secllrinq accordin-J to yet another asp~ct o~ the invention prefcrably compr.ises: (a) a soc~et integrally formed i.n the first molcled plastic tallk section for rec~ivinc3: (al) a tancJ intec3ral.1y formccl on the aforement.ioned second moldc(3 plastic tan~ SCCtiOIl; and (a2) a joint formin~J matcr:ial clcpositcd into the socket clurinc3 tank assembly for usc in jo.i.ninq aforemcntioned first molded plastic tank secti.on to the second molded p].astic tank section and securin~ the means for se~arati.n~
therel~etwecrl; ~nd (h) a t~ny intcyrall.y fonned in the seconcl moldcl plastic t.anl secti.oll clcsi~llcd for in-;crtion into the sockct f`or use in joininC~ t)-e f.irst moldcct plastic tank secti.on ancl thc sccond mol.(led p:l.ast:i.c tan~ sect;.on toJetller to form the cxpanc--~i.on t nk f.lui.(l containment vessel.

~ ccorcliny to a preferrc!cl cl~ o~l.imcnt o~ the i.nvent:i.on the socket and tanc~ l`urtl~cr comprisc (a) a first socket surface and first tanq surface respectivcly desi~3ned to accommodate the installat.i.on and sccurinq of a porti.on of tlle means for separat;.ny thcrc~etwecn w:ith the means for separatinc3 beinc3 shaped to facili.tate the enc3acjcmcnt of a portion o~ the mcans for ~.eparatiny w:ith at lcast a portion of t~)e first socket surface durit~q tank asc-,emhly; anct (h) a secon-t soc);et surl~ce ~n(l -;ecc)llcl tany sllr-t~acc rcspcctively wh:i.ch whcn juxtapo5cd rOrlll a citop. ~urther~nore thc sccond soc~et surfacc anct seconcl tanJ sur~.lce .II-C ~rcferahly 1.~

C 2~75~37 l.ocated in proximity to thc exterior wall of the tank (in relation to the com~ination of the socket, the portion of the m~ans for separatinq l~c.i.nq secured and the tanq itself, the aforementione~l comhinat:ion beinq located toward the interior wall of saicl tank).

~ urthermore, accorcl:i.nq to furthcr aspects of the invention, the aforementioned joint forminq matcrial may bc characterized as a material that inclucles a thermoplastic, sllch as commcrc:ia'Lly ttlcrmor).l..3sti.c cc)m~ositc matcr;als formect as ~ m.ixture of tllc~rmo~last.i:c ancl mctLll ~artic3es: or a wel.c~i.nq mater:i:al whi.ch ~-lows upon bci.nq hci~tcd. One ~articularl.y ~l~e~ll. wcldin~ m.ltcrial. conteml~l..ltccl l>y t~c .i.nventi.on is a mi.xt~lre of thermoplastic and mctal parti.cles.

Furt}~er yet, accorclinq to a preferred emhocl;.mcnt of the invention, tlle aforemcntioncd sockct ancl tancJ are clesiqnecl such tllat weklinq mater.ial depositcd in the socket, ~Ipon bei.nq heatecl ancl ~lpOn beinq compres~ed t>y the socket -ancl tanq bein~ forcecl toqct-hcr ~lnt:il. the aforementioned stop is reached, flows from the point of depo~it in the socket away from the stop ancl toward thc coml~ination of the socket, the portion o~ the means for separ.lt.in~ beinq secured and t~)e tanq, to form an interior 3.ap joint.

~( 2175~37 .

Accor~in~ to one emboclim~nt of th~ invention, the interior lap joint forms a wel.d th~t joins the tan~ and socket, together; but does not include the means for separatinq as part of the joint. I~or example, a means for separating m~de of r~ ber wou:l(l not be include~ in welds contemplated by this emboclimcnt of the invention. llowever, accordin~J to another embo~l.i.ment of the invention, the interior lap joi.nt forms a weld that joins the tang, socket and th~ aforement;one~l means for separatinc~, to-~ether. Such a wel.d eo~lld be empl.oyed wl~ere the material usecl to ~abricate tlle mealls for se~arati~ as a mcltin~ temperat~lre that approximates tl~at o~ the tank sections (the tanc3 ancl socket port-;.ons thereo~) and wcld materiAI.. ~or example, the meclns for separatincJ co~lld he fabri.catecl us:inc~ a fl~xi.b].e tl~ermoplast.i.c m;ltcria.l. s~lc~h as a thermop].astic elastOlllCr/tl-CrlllOSCt rUi)t-er COlllpO5ite.

~ ccord:inc~ to an alternate emhodiment of the inventi.on, a corrosion resistant expansion tank contemplated hy the teachinc3s herein compri.ses: (a) a first molded pl.astic tank sect;on incl~ld:i.nq a ~.irst tank connection i.ntec~ral].y molded therei.r~ )) a seconcl moldecl plast;.c tank sect;on, wh;ch wl~en jo;.ne(l to~etl~er w.i.tl~ the ~irC~t lllOldeC
plast;.c tank sect;i.on l~ornls tl~e ex~ans:ion tank fl.~l.i.d containment vessel., .incl~ J a seconcl tank connect:ion int~ral Iy mOI(lC'(l tl~C?rC'i.n; ((`) InC?anS for separatinc~ the tank .into a first i.nterior- port.i.on and a seconcl :interior portion, ~ 21 75~37 the means for separatinq )-)einq secured betwecn the first molded tank section and the sccond mo~ded plastic tank section; and (d) means for securinq the means for separatin~
in a joint formed between thc first molded tank section and tlle second molded plastic tallk section.
.

~ ccordi.nq t.o this al.ternate eml~odimcnt of the invention, the f:irst molde-;l pl-~st:i.c tank section further compri.ses (a) a qas dome whi.cll m~y he connectecl to a qas source vi.a tlle fi.rst tank cc)llnccti.oll :inteqrally moldcd in tlle first mol.de~l ~l.asti.c tan)c sect.i.on whcrc;n _aicl ~as clom~
i.nclu(les a seal.i.ng surfacc; (b) tl-e seconcl molded plastic tank section furthcr comprises a water dome c~esiqnecl to fit into the qas clome which may be connectc~ to a water source vi.a the secon~ tank connect;on inteqrally molded in the second moldecl pl.lstic tank section; (c) at least a portion o~ thc means for separatinq .i.s formecl to fi.t onto (an(l/or "into" de~i.ned hcrci.n to be :includcd in the term "onto") the sealinq surface of the ~as clome; and (d) the portion of the means for se~ar~t:i.n~J i.s seal.ed bctween the qas dome and the water dome by li.tti.nq thc port.ion of th~ means for separatinq into the sealinq surface and thcn jo;.nin~ the ~as dome and sa:id water dome toqether to form a lap joint by compress:inq a matcr;.al that inclu~es a thermopl.astic (or some othcr wcl-1in-~ m~t-r.i.~l) until. 1~ stop is re~chccl.

( 21 75~37 ~ s indic~te~ tlereinbefore, further aspects o~ the :invention are directecl to the apparatus (means) for securin~
the means for separatin~ within a tank per se (the novel mcans for sccur.inq havinJ heell described herein~eforc); and to processes for cost cffectively manufacturin~ the tanks contemplatccl ~y tlle various emboclimcnts of tl-e ;nvcntion referrcd to hereina}~ovc.

In particulL1r the invcntion contcmpl.atcs a proccss for manufacturinq ~ corr~s:ion res.;.st~nt e~ansion tank, compris;n~ thc ;teps of~ ) fabri~ati.nq a fi.rst plastic tank section th~t inteqra~.ly incl.udcs f;.rst tank connect.ion me~ns; (h) fabr.ic.lti.n~ ~ second pl~st;.c t~nl-secti.on that intc~rall.y .i.ncl.udcs scconcl tank connccti.on means; (c) inserti.n~ hetwc?en thc first plast:i.c tank section an-l the secon~l pl.ast;c tank secti.on, means for ;cparatinq the tank into a first interior portion ancl a second i.nterior port.i.on; and (d) joi.nincJ the irst plastic tank section and the second plastic tank section wi.th thc means for separati.nc3 nsertecl tllcrc~etwecn, to therc?hy form the expans.ion tank flu:i~l containment vessel with the means for separatinc3 s~cured therein.

~ urther cxem~lary process steps contcmplated by tlli.s ls~ect o r ttlC ~ VCIlt_iO~ lll(l~ t~ ? '-;t:CpS O f-:
(1) inte~r~l.ly f-orlllinq .~ sock-t i.n tlle f..i.rst pllst.ic t~nk section for receivill~J the clcLos;.t of a joint ~ormin~

` (~ 2175~37 material and for receivinq a tanq formed as part of the second molded plastic tank ~cction; and (b) :inte~rally forminq a tang in the second molded plastic tank section that when inserted into the socket and joined therew.ith form the expansion tank fluid con-tainment vessel.

Accordinq to a preferred embodiment of the invention the step of forminq a socket further comprises the step of formincJ a fir-st sockct surfacc ancl the step of forming a tan~ furthcr comprises tl~c step of formin~ a first t~n~J sllrfacc whcrc.i.n tl)c f irs~ soc~e~ s~rfl~cc ~ln(l tllc first tan~ surface are dcsi~ne(l to accommodatc tlle in;ertion ~ncl secur;n~ of a port;on of tlle melns for scparatin~ :
therebetween.
. .

lurthermore accorclinq to a ~referred embodiment of the invention the portion of the means for se~aratinq to be secured is shaped to facilitate its enqa~ement with at least a portion of the first socket surface durinq tank assemhl.y; and at least a porti.on of the first tanq surface i.s rouqhened to enhance the abi.l;ty of tlle portion of the means for separatinq to be secured between the first tang surface and the first socket surface.

~ ti.-l.l t~lrthcr thc prcf.`errccl cmbod.i.mcllt of tlle il~v~ ion ~(>I-l~:c~ ; t:~c l`o~ wil~-J l~ lrin~J ~.~c~
(a) lorm;n~ a sccon~l soclet ;~lrfacc lnd second tancJ surface 2~

~ 2175~37 wherein the second sock~t surf;lce and the second tan~
surface when juxtaposed orm a stop; (b) formin~ the second socket surf~ce and second tanq surface in proxim.i.ty to the exterior wall of tlle tank (i.n rcl.at;.on to thc first socket surace and the f;rst tan~ surface which arc formed in proxi.mity to the intcri.or wall. of thc tank; and (c) shapin~
the socket ancl tan~ such ti~at wcl.clin~ matcri.al. deposLtecl in tlle socket upon bei.n~ he.lted ancl upon l~ein~ compressccl by the socket and tan~ bci.n~ forcccl to~ethcr ~lntil the stop is reached flows rom thc po.i.nt of dcpos;.t in thc socket away from the stop (towar(l the combinclti.on o~ tllc soc~kct the portlon o~ the means for separatin~ bein~ sccllrcd and tan~) to form an inter:ior lap joint.

~ urthcr yet accorcl:i.n~ to a prc~erred em~odiment of the i.nvention thc first pl.asti.c tank sectiorl and the seconcl pl.ast.ic tank scct:i.on are formed vi.a an injccti.on molclin~ process; and the aforementioned manuacturin~ step of joininq further comprisos the steps of: (a) dcpositin~ a weldi.n~ m~terial (such as the aforement:i.oncd mixture of thermoplast.ic and mctal parti.clcs) into thc socket;
(b) heatinq the weldin~ materi.al; and (c3 comprcssin~ the heated weldin~ material hetween the socket and tancJ until the stop is reacllcd.

~ ~ 21 75~37 f An alternati.ve process for man~Ifacturin~ an expansion tank, as contempl.atecl by the invention, comprises the stcps of: (~) fabricating a one picce mol.clcd p1astic ~as dome includ;.ng an inte~rall.y ormecl socket, further includin~ a sealin~ surface, and gas connection;
(b) fabri.catin~ a one pi.ece mo1(1cd plasti.c water clome includin~ an inteqrally ~ol mecl tan~ and water connection;
(c) fittin~ a diaphraqm onto the sea1in~ surface o~
the socket; (d) clepos;tin~ a welcl:i.n~ mater:ia1 i.nto the soc~kci-; (e) h~.3t~ J ~.hc wcl.(I.i~ materi.l'I; alld (f) compressi.Il~3 thc heatc(I wc1diIl~J mater:i.al ~etwecn the socket ancl tan~ ~Intil a stop formed by the sockct and tan~ is reache~.

~ `he invention, as excmplifiecl by tlle various aspects thereof dcscr.i~ed here;.Ilahove, ~~eat-~res (when compared with the pr:ior art clescribcd here;.nbcfore):
~a) fewer parts; (b) f~ id connectioIls mol(led .into the'tank secti.ons (domcs) that when jo.ined (thc tank sect:ions) form the containment vessc3. itsc].f; (c) tlle use of plasti.c materials that clo not rcqui.re 1iners or sca1s; (d) a diaphra~m (or bl.a(l(ler, etc.) captured bctwcen the dom~s; (e) a simp].i~'ied set of prod~Ict;.on processes; (f) a tank that is corrosion resistant ins:iclc and O~It; (~) a tank that does not retluirc o-Itside f.in;sI~;.Il~ (e.~., pa-iIltin~) ~or ~inish ~rot-cct:ion; (Il) a rc1.iaI~.e tank thllt: c.~n ~.~f-el.y )~e ~It.ili.~cd for a variety of applications i.ncludin~ watcr stora~e c ` 21 75~37 - I

applications and hiqh pre~s~lre environments due to the inherent stren~th of the lap jO.illt formed ~Isinq the proeess deseribed llereinl~eforei an(:l (.i) a tank th~lt ean be taken apart by reheatinq the aforementioned interior l~p joint for inspection repair and/or recyclinc3 purposes.

These and other ol~jects emhodiments and features of the present invention and the manner of o~tai.ni.nq them wi.ll. beeome ap~arent to those sli.lled in the art and the invention itself will ~e hest ~Inderstoocl ~y referenee to the fol.~.ow:inq neta;lcd l~escr;ption rea(l in conj~lneti.on with the aecompanyinq ~raw;.nq.

~TI~ n~ CRTII`ION 0~ AW.NC

~ IG. 1 is a vertical cross-section view of an expansion tan) contemplated by one em}~odiment of the invention. IIC. 1~ is a vertical. cross-sect;.on v-iew of the tank depi.eted in I~IG. 1 carryinq an a:i.r charqe.

IIC. 2 is all enl.arqecl vert.i.cal. parti.al. cross sect;.onal view of a portion of the e~pansion tank depicted i.n I~IG. 1 depictinq exemplary means for see~lrin3 a means for separatin~3 (the interior of the tank ;.nto two portions) between the tan~ sections wherci.n t.he ~lepict~d means for seeuri.nq holds tlle means for separat;.n~ (e.q. a cliapllraqm) in plaee durinq tank assemhl.y d~ i.nq tank.operclti.on alld 2~ 75~37 provides a vehicle for formin~ a stron~ interior lap joint to replace, for exampl.e, wealcer pri.or art friction welds, etc. More particularly, i.n FIC. 2 depicts port.ions of the tank sections and means for separatin~ prior to these components be;.ncJ joined and secured toc~ether.

FIG. 3 and FIG. 3A clep;ct the components shown in FIG. 2 joined to~ether and securec~ in accordance with a fi.rst and second èmbodiment of the invet-tion, respectively.

I~IC. ~ is a vert.ic.ll cross-scct-.ion v:iew o~ an alternate emhocliment of an expansion tank contemplatecl by tlle invention in wl).i.ch one of tl-e f`luicl connect:i.ons is shown molded in a cl:i.ffcrent port:i.on ot- onc o~ the tank scctions.

FIC. ~ clep.icts, in the form of a fl.ow clia~ram, a set of tank manufacturin~ process steps contcmp.lated by an illustrative embod.iment the invention.

FIC. 6 depicts, in the form of` a flow clia~ram, a d;.fferent sct of tank manu~acturin~ process steps (c1i~ferin~
from the set of steps clepi.cte~cl in FIG. r~), as contemplated l~y an alternate embocl;.ment the inventi.on.

~ 2~

2 1 75~t37 Dl;~ l' r..l;~ I)F'S CR T r'r T ON

An illustrative eml)oliment of a corrosion resi.stant tank of the type eontemplated by the invention will ~e set forth herein~f`ter with referenee to ~I~S. 1~

It is intended t-.hat the followi.n~ deseription of the tank means for securin~ used in the tank (clurin~ the tank eonstrl~etion process and dur:in~ tank operation) ete.
all dc~.i.eted l-:CCS. 1-;l w.i.ll t-each thc l-r.i.nci~als of t))e invent.i.oll. Tt~ose ski.lled in tlle art will readil.y a~preciate that the teaching is bei.n~ set forth in the context of an exemplary tan~ structure only ancl that ~ucl~ structure may be v~rie~ i.n praet.ice without depart:inq from the spi.ri.t or scope of the invention wh.ich is intencled to ~e lim.i.ted by the clai.ms only.

In partieular those ;k:i.lle~l in the art should readily ap~reeiate that in t~lC eontext of-` presentin~ the i.l.lustrative embod.iment of. tllc invention certai.n terms will ~e use~ for the salce of illustrat.i.on only. Ior example reference will sometimes be macle herein to a;.r ~as and/or water as the f-lu-ids to he contained ;.n the tclnk;
but these partic~llar ~lu.i.ds are meant to be il.lustrati.ve ;.n natl~re onl.y since ~.IlC tanks contempl..lte(l ~y thc :invent.i.on lllay ~)e usecl clS fluid COllt.l inment ves~ ls ;n ~Jcncral (wi.ttlOut li.mitation as to the typc of flu;.ds t~ei.n-J eonta.i.ned ~ 29 f~ - 2 1 75~37 there.in). A further example is that specific references are made hereinafter to a "diapl~ra~m" as a means for separatin~
the interior of the illustrative tank into two sections;
however, alternate means for performin~ the des;red separation (like a bladcler) are contcmplatcd by the invention as well.

F;nally, bcfore clescribin~ the ;.nstant .invention and for t}lC sake of- complctcncss, re~erencc sholll.d bc made to the ~reviously incorporatecl 5,3~6,925 patcnt, i.n part;.cular to ~IC. 3, ~TC. ~ and thc dcscr:ipti.on thercof in tlle 5,3~3G,925 patcnt, f~or an cxplallat:ion oJ hot. watcr heat;n~ systcms ancl prcss~lr:iY.cd water ~ystcms in ~eneral (shown ;.n schematic form in ~TC. 3 arld lTC. ~ of thc i.ncorporate(l rc~erence), in Wlli.CIl tl-e tan~ tau~ht herein may be used.

r~eference shoulcl now be made to ~IG. 1 which, as indicatecl herei.nhefore, is a vertical cross-section vicw of an expansi.on tank contemplatecl hy one em~odiment of the invention.

~ ccorclinq to thi~ :i.l.l.ust--ative embodimcnt of thc inVCIlt.iOn (al.SO a prercrrc(l c~ o(l:imcnt of~ thc invent;on), a cor~os.ioll res:i.stant expansion tank ]oo as ~;hown :in rIG~ ]
incl.u(lcs: {a) a fir-st molcle(l plasti.c tank scct:ion 1.0]., ~ 2i75~37 intecJrally includi.nq f irst: conl1eet.iot1 means 102, for enabl ;nq fluid from a first fluicl souree (not shown) to be plaeed in fluid eommunication with a f-irst interior portion 103 of e~pansion tank 100; clnA (b) a seeond molded plastie tank section 104, wh;.ch when joi.ned toqether w.ith f~rst molded plastic tank secti.on 1.()'1 forms the expansi.on tank ~luid containment vesst-~l 1()0, inte~ral1.y inclu(linq seeond connection means 105 for en~ .i.n~ fluid from a seeond fluid source (not shown) to he ~l.ace~1 i.n fluid communieation with a seeond separate interior port ion 10-. of expansi on tank 100 .

I; irst eonnection mcans 102 and second connection means 105 provide pass~c~eways through wh,i.ch flu.id from the first and seconcl flu:id sources respeetively, may be introduced i.nto ancl may l~e withdrawn from expansion tank 100. Aceordin~3 to one emboc1iment of tl1e invention, f.irst connect:ion means 102 and second connection means ] 05 are threaded (as st)own for example at ] 15 in FIC. 1) to permit easy instal.lation o~ v~.1ves (not shown) into the t,lepicted passa~eways . Exemp],ary tank lO0 shown i n EIG . 1 also ;neludes tank stand member 120 (and corresE onclin~ portion 1'~0a of that member in the dep:i,ctec1 vertical cross-section view), wh.ieh is prefera~l.y i.nt.egr~l 1y f~ormed (althou~h this .is not ~ re~ 'irement to pract,.ict.~t1 the i~nvel1t.it n) as part of t.lnk sect.i.on 101 to serve (~ se ~pon wl~icll the t.~nk may he rested in an ur~r:i~ht posi.tion.

~ 2 1 75~37 Furthermore, accorclin~ to the aforementioned preferred embodiment of thc invention, tank 100 includes means for separatin~ (shown as 107 in FIC. 1) tank 100 into the aforementioned first ancl second interior portions (10~
and 10~ res~ect.ively, with fi.rst interior portion 103 bein~ -located betweell means ~or scr)aratin~J 107 and thc intcrior wall of tank section 101); where means for separatin~ 107 spans the inter:ior of tank 100 and is inacle of a flexi.ble mater:ial that is imperm~al-le to a precleterminc(l sct of flu;ds, includin~ those fl~li(ls provi.dc~l by the aforementioned first and second fl~lid sources.

In pract;ce, means ~or se~aratin~J 107 can be realizecl by, for exam~le, a flexihle diaphra~m, hladder or some other applicati.on specific mcmhrane that separates a the expansion tank into two chambers. ~or many water storaqe and watcr heatinq applications it is des;.rahle that separate water and air chambers be formed usin~ a materia'l that ;s not permeahIe to ~a5 ancl whi.ch allows the a;r chamber to be prechar~ed. ~ vertical cross-scction view of the tank depicted in ~IG. 1 carryi.n~ an ~ir char~e, is il.lustratecl :in ~IC. I.A where means for separat:i.n~ 107 (in tank 125), is shown deformed by the air charqe at 126.

2 1 75~37 . Still further w;th reference to ~IG. 1, accordin~
to the aforementioned prcfcrred embod:iment of the i,nvention, tank 100 incl,udes means for securing (shown as 110 in FIG. 1) the means for scparati.n~ 107 (withi,n tank,100) via a joint forme~ between fir~-t mo].ded plastic tank section lol and second molded plastic tank section 10~.

Reference sho~ld now be made to rIGS. 2, 3 and 3A, where means for securinq ll.0 from ~IC. 1 is shown in ~reater cletail. In particular, means 1.10 is shown i,n l'IC. 2 to be holdin~ mcans ~or sel~ar~lt.i.n~ 107 (c.q., a d:iaphra~m) in place durin-J tank ~.isscml~ly. ~l~hc same Incans 1l.0 is clcsi~ned t:o hold means for se~aratinc~ 1,07 in pl,ace dur:inq tan~
operation (illustrated by the diaqram shown in ~IG. 3) and providcs a vchicle ~or form:i,n~ the ~forementi,oncd stron~
interior lap joint (also shown in r'IG. 3, at 150) to replace, for example, the weaker prior '~rt friction welds, etc., di,scussed herei.nbefore.

In FIG. 2, the d~pi,cted portions of tank sections 101 and 10~; and me~ns ~or scr)ar~ti.n~ 107, are shown prior to these components bcin~ joincd ~nd secured. In FIG. 3, the components dcpicted in l'TG. 2 are shown joi.ned to~ether ancl secured i,n accordance witl- a pre~erred cmbodiment o~ the invention.

2 1 75~37 More parti,cular],y, a5 may be seen with reference, to l;'IC. 2 and accordinc3 to yet another distinct aspect of the invention, means `or securin~ 110 (a specifi.c illustrative embodiment of, the preferred securinq mechanism) is shown to inclucle sooket 170, inte~rally formcd in first mol.ded plastic tank sect,ion 101, for receivincJ: (a) tan~
1.71, inte~rally forme(3 on thc aforementionec,l second molded plastic tank section 10~1; and (b) joint forminc3 material 172, deposited into socket 170 durin~ tarlk assemhly, for use in joinin~ f:irst mol,ded pl,ast:ic tank sect,ion 101 to sccond molde~ r~l asti c tanlc sect.ion l.o~ an~l securin-3 mc~ns for separatin~ 107 therebetwecn. T~n~ 171 is shown in I~IC 2 to be intec3ra,1.1,y formec~ in second mol.decl r~l,ast:i~ tarlk section 104 ancl is desiqnecl for i.nsertion i.nto sockct 170 for ~Ise in jo;.ning first molded plastic tank section 101 and second molded plastic tank sectlon 10~1 to~ethcr to form the expansion tanlc fluid contailllllent vessel.

Accordinc3 to a preferred embod.i,ment of the :invent:ion, as may be secn witl~ refcrence to l~TC. 2, socket 170 and tan~ 171 further inc.l.ude (a) t'i,r:it soc)~et sur~ace 175 and first tanq surface 17~, rcspectively, desic3ned to accommodate tlle install,ati.on and secur,i.n~ of a portion of ~-means for separatinc3 107 therebetween, wi,t-,h means for separatinc3 107 bcinc3 sh.tped to fac:i.li.t.lte the encJac3ement of a port ion of thc mean-.i for .-,cl-)arat.i.n-3 w.itl~ at least- a portion of first socket sur.f-`.lce 175 durin-3 tanl~ asscmbly;

~ ~1 2 ~ 75~37 ~, .

and (b) second socket surfacc 177 an~ second tang surface 178 respectivel.y, whi.ch when juxtaposed form stop 19~ as shown in FIG. 3.

F~lrthermore, second socket surface 1.77 and second tan~ surface 1.7~ are preferabl.y located in ~rox.imity to the exterior wall of the tank (;.n relati.on to the combination of socket 170, the portion of the means for separtting 107 being secured and tanq 171 itself, thc aforementioned comhination ~cinq locate(l toward the inter.ior wall 190 of tank 100). ~s w.iLl l~c ex[)l.t.inc(l hcreina~ter, tlt:is arran~ement hel.ps form al~ ;.ntcrior lap jo;nt wh;.ch strenqthens t~c comhinati.on of com~onents thlt ~orm the tank.

~ dditiont:l.ly, accorclinq to further as~ects of the i.nvention, the aforementioned joint forminq material (172) may bc character;.~ecl as a materic-tl thAt includes a tl)ermoplast;.c, sucll as commerciall.y thermo~l.as-t:i.c composite mtterials forme(l .as a mixture of t~ermopl.tst;.c and metal particles; or a wel.dinq material. wh;.cll flows ~lpon beinJ
heated. Weld coil 1~5 is shown in ~IG. 2 and ~TC. 3 as a well known mcans ~or heating joint form:i.ng matcrial 172. One particularly useful commerci.ally avai.l.ab].e weld;nq material conteml~latecl hy the inVentiOIl i.s a m:ixturc of t:hermoplastic and metal ~arti.(~l.es manl~acturc-l hy l~mabon(l (a rc-Jistcrc(l traclem,.trk) ;ystems, a divi.sion o~ Aslllancl Chcmi.(a:l. Company.

2 1 75~37 ~ urther yet, accorclin~ to a preferred embodiment of the i.nvention, the aforemcntioned socket 170 and tan~ 171 are desi~ned such that weldinq materia1 172 deposited in socket 170, upon beinq heated an~ u~?on beinq compressed by socket 170 ancl tan~ 171 l~cin~ forccd to~ethcr unti1 the aforementioned stop 1~9 is reached, flows from the point of deposit in socket 170 away Erom stop 19~ and toward the coml~i.nation of socket 170, thc port;.on o~ tlle mcans for separati.n-3 107 bein~ sccured alld tanq 171., to form the desired interior .lap joinl 1.50 del~.ictccl in ~~[C. ~.

An a1ternate cmt.)ocl;.mcnt ol~ t:hc :inverlti.on is depicted in ~IG. 3A where an interior 1ap joint, 1~1, i5 formed that incl.udes means for sc~aratinq 107 as wel.1 ~s a porti.on of socket 170 and tan~ 171 in thc weld. ~s -inclicated hereinbefore, this eml~odiment i.s fcasib1c where the means for separatin~ .is made, ~or exam~lc, ~ls;.n~ a thermoplastic materia1 that has a me1ti.nq tcmperature that approximates that of the tank sections (the socket 170 and tan~ 171 portions thereof) and the wcl.cl materia1.

Thi.s arran~ement would rel.ax the nced for di.mcnsional controls i.n the sockct and tan~ rthermore, th;.s arr;ln~elllent woul.d cl..im;.nat-c is-;uc.-. invol.vin-J thc coml?ression set of the (~ lra~Jln (Illeall5 l`or ~e~?arat:in-J) mater.ia1 and the entirc ti~nk wou.l.(l I-c rccyc1cab:le without 2 1 7~37 havinf.3 to be taken apart j.f thc means for separatin-.3 were made usinf.3 all recycleab~f=? mat-?rial (such as a tllermoplastic), assumincl any air chargc was first removed.

~ ccord itlCJ to al~ altcrnate characteri~.ati.on of the invention, a corrosion res.i.stant expansion tan)c (like t~nk lO0 of ~IG. 1.) cnntcmplatf?~ y t~lc inventi.on comprises: (a) a first molded plastic tank section (such as t~nk section lOl) includinq a first tAnk connection (l.ike connection 102) .
intec3rally mol-led thcrei.n; (b) a sccond mol.dcd pl.ast;.c tank section (sl~cl~ aci t~ k sectioll lo~), wlli.fl~ wllcn jo:;necl togf?ther with first molclcd 1~1 a5t iC tanli section l.()l forms tlle cxlansi.c)tl tank l.O~f) flllid cf.~ntai.llmf?llt vesse'l, inclucl.i sccond tank connccti.on 105 :intL?-~r.ll1.y molcled thcrcin; (c) means for separating the tank into a first intcrior port.ion an-l a second i.nterior portion (means 107), means for se~arat.i.nf3 1.07 bein~ secllr-?(:l }~etwcen fi.rst mold-?cl tank secti.on lOl and second molded plastic t~nk sect:ion lO~; ~nd (d) mcans for securinf.3 (llO) thf? mcans for separating (107) in a joint (1.50) formecl hetween fi.rst molded t~nk section lOl and second molded plAstic tank section lO~.

.

~ ccord;n-3 to thi.s a1ternate eml~oclimcnt of thf?
i.nventi.on, first mol.df?d plas-tic tank section l()l may he fllrtllCr CharaL'tCri.~.ed as ~1 c3as dome wllich may hf~ connected to ~l J~IS .';C-~lr('~ (nOt~ fwrl) via t-llf' I~ ;t: I:nlll:. L-Onnf'Ct:iC)Il lo~ i.ntegrall.y molcled in ~.i.rst molde(l plasti.c tank section 2 ~ 75~37 101, wherein the qas dome includes a sealinq surface (shown in part at 176 in FIC. 2); alld where second molded plastic tank section 10~ may he further characteri~,ed as a water dome, desi~ned to fit into the gas dome, ,which may be connected to a water source via ttle seconc3 tank connection 105 whicl- is inte~rally mol,decl in second n-olded plastic tank section 10~.

~ ccord.in~ to tl)i.s altcrnate character;.zation of tlle :inventi,on, at least a port.ion o~ means for separatinq 10~ is formecl to f,it onto sealinq s~lrface 17G of the qas dome; ancl that porti,on of mcans for separat:inq 107 is sealecl ~etween the qas dome and thc watcr dome t~y f.itt:i,nq the aforementioned porti.on of thc means for separat.inq (10~) into sealinc3 surracc 176 and then joinin~ the qas dome and saicl water dome toqcther to form lap joi.nt (as shown, for example, at 150 in ~JG. 3 or 151 in I~IC. 3~) ~y compressinq a material tllat ;nc~ldes a ttlermoplastic, such as commercially thermoplastic composite mater:iaJs formed as a mixture of thermoplastic and metal particles (or some other weldin~ material) until stol~ 199 (also shown, for example, in FIG. 3 and FIC.-3~) is reached.

~ n alternate embodilllent of the invcntion is shown :in rIG~ ~ wtlicll, a~ previo~sly :indicate(l, ;.s a vertical cross-secticll view -l' an exp.-ns:ioll tanlc in wl~ich onc of ttle fl~l;d connections to the tank :is shown molcle(l .in a difrerellt 3~

2 1 `75~37 portion of one of the tank sections. This may be observed with reference to location ln9 in ~IG. ~. Dependinq on the application for the expans.ion tank, it may be c1esirable to form a ~iven fluid connecti.on at still other locations in a tank section. FIC. ~ i5 presented ~or the p~1rpose of illustrati.ng one way in which a ~luid connection could be formed in tank section l.Ol, where the formation of the connection differs from the location of connection 102 shown in FIG. l.

~ s in(1icated herein~)e~ore, otl1er aspects of the invention are directed to processes for cost effectively manufact~lrin~ the tank~ contemp~.ated by the vario~1s emhodi.ments of tlle i.nvention re~erred to hereinabove. These~
will now be described with reference to ~IG. 5 and FIC. G.

~ s previo~1sly in~3.icatcc1 ~IC. 5 depicts, in the fo~m of a flow di.aqr~m, a sct o~ tank manufact~1rinq process steps contemplated by an i.ll~1strative embod:iment the invention. ~IG. 6 clepicts, in the form of a f~.ow diaqram, a d.i~ferent set of tanh malll1fact~1rin~ process steps contempl.ated by an alternate embodiment the invention.

In partic~1l.ar, w;.th refcrence to l;~:rc~ 5, it may be seen that one em1~oc1.i1nent c~ tl1e i.nvention contemplates a process for manufact:~1r.inq a corrosion resistant expansion tan1c, comprisi.n~ tlle steps of: (a) fahricat:i.nq a fi.rst . 39 . c 2175~37 plastic tank sect:ion that intcgrcall.y includes f.irst tank connection me~ns (shown as stcp 201 in ~IC. 5); (b) fabricatin~ a second plastic tank section that inte~rally includes second tank connect:ion means (shown as step 202 in ~IG. 5); (c) insertin~ between the first plastic tank section and the second plastic tank section means for separatin~ t~e tank into a fi.l-st interior portion and a second interior portion (shown as step ~03 in FIG. 5);
and (cl) joiniin~ the first plastic tank section and the second p.last;c tanlc section w;.th tlle means for scparatin~
i.nserte(l tllcrcl~ctwccn to thcrc-~).)y form tllc cxpansion tank fl.uid containment vessel witll the mcc~ns for scp~crc~tinq sec~lred t~erein (shown a~ stcp 20~ :in ~IG. 5).

Further exempl~ry process steps contemplated ~y this aspect of the invention ;.ncl~lde thc stc?ps of:
(a) inte~rally formin~ a socket in the first plastic tank section for rece;.vinc~ the deposit of a joint forminc~
material and for receivin~ a tan~ ~ormed as part of the second molded ~].astic tank scot:ion (tll:is is prcfera~ly done as part of step 20~ ]~lt co~lld ~e performcd as part o~ a separate process step); and (h) ;nte~rall.y formin~ a tanc3 in the second moldcd plastic tank secti.on that wtlen inserted into the socket and ~oinel therewith form the expansion tank fluill containmcnt vcssel. (th;.s is preferahly clcne as pc~rt of step 202 ~t co~l:ld l~e pcrformc(l clS plrt o~ a separc-lte process step as well).

~10 : ~ 2175~37 ~ eeordin~ to ~ pre~crred'embocliment of the i,nvention the step of formin~ a soeket further eomprises the step of formin~ a first soeket surfaee ancl the step of forming a tan~ further comprises the step of formin~ a first tan~ surfaee, wherein the first soeket surfaee and the first tan~ surfaee are desi~ned to aeeommodate the insertion and securin~ of a portion of the means for sep~rating therebetween ~ lrthermore, accor~linq to a preferre(l emhodiment of the invention, tlle portion of the means for separating to be seeured is shaped to faeilltate its cn~a~ement with at least a portion of ti~e first sock~t surfaee durin~ tank assembly; and at least a portion of the first tan~ surfaee is rou~hened to enhallce the ab,ility of the port;on of the means for separatill~ to be sccurcd between the first tan~
surfaee and the first socket surface These prcferred proeess steps are optional, but recommencled The step of roughenin~ the first tan~ surfacc may be performed as part of step 202 or in a separate proeess step l~he step of shaping may be performed as part of step 203 cliscusséd hereinabove (the insertin~ step), but al50 may bc pcrformed in ~ separate proeess step not sllown in ~IG 5 since it i,s optional ~11 2 ~ 7~7 `

Still further the preferred embodiment of the invention eontemplates the followin~ manufaeturin~ steps:
(a) formin~ a second soeket surfaee and seeond tancJ surfaee wherein the seeond soeket surfaee and the seeond tanq surface when juxtaposed form a stop; ~b) formin~ the seeond socket surface ancl seeond tan~ surfaee in prox;mity to the exterior wall of the tank (in relation to the first soeket surface and the first tanq surfaee whieh are formed in proxim;ty to the interior wall o the tank; and (e) shapin~
tlle soeket ancl tanq sucl~ that welding material cdeposit~d in the soeket upon bein~ he.lt:ed and ilpon l~cin~ comlressecl ~y the soeket and tallJ ~ein~ forcecl to~ether untiL the stop is reaehed flows from the po;nt of deposit in the ;oeket away from the stop (toward the eom~ination of tlle soeket the portion of the means for separatiny belncJ seeured and tang) to form an interior 1AP jOillt. All of these steps are onee a~ain preferably ~ormed as part of steps 201 ancl 202 diseussed hereinabove; but may }~e perEormed in separate proeess steps as well Iurther yet accorlin~ to a preferrecl embodiment of the invention the first plastic tank seetion and tlle secon~l plastlc tank section are forme~ via ~n injection moldillJ process; alld the aforemelltiolled manufactllrin-J step o~ joinLnq (step 20~ referred to hereil-a~ove) fllrtller comprises the stel)s of: (a) depositin~ a we]clinq materi~l (sucll as the aEorementioned mixt~lre of tllermoplast-ic and ~2 2175~37 met~l. particles) into the sockct; (1) he~tin~ the weld.inq material; and (c) compressin~3 tlle }leated wcldin~ materl~l between the socket and tan~ until the stop is rcached.

~ n alternative process for manufacturi.n~ an expansion tank as contemplated by tl-e invention is illustrated with reference to I~IG. 6. The ~ltern~te process comprises the steps of: (a) fabricatinq a one piece molded plastic ~as dome including an integrall.y formed socket further includin~ a sealinq surf~ace and ~a5 connect.ion (step 301 i.n FIG. 6);(~) fabricatin~ a one piecc molded plastic water dome includ.in~ an intcJrally formcd tang and water connection (step 302 .in IIG. G); (c) f`itt.ing a diaphra~m onto the sealin~ surface of~ the socket (step 303 in FIG. 6); (d) deposjt.Lnc~ a wcld.in~ material into thc socket (step 30~ in lIG. G); (e) lleatin~ thc wc~ c~
material (step 305 in FTG. G); <~nd ( r) com~ressin~ the heated welding material l~etween the socket and tan~ until a stop formed by tl~e sockct and tanq is reachcd (step 30G in FIG. 6).

~ s previously stated the invention (~5 excmplified ~y tllc various ~spects ttlereof describcd hereii~a~ove) features (when compared with the prior ~rt lescri})c~ llereinl~cf~r.e): (a) ~.ewcr parts; (1~) f:luid connectiolls mol(le.l int:o tllc l.ank 5C('t: i.oll'; (domc;) thlt ~/llcn joined (t)le tanlc scctions) f-orm the conta:inmcnt vesse]

. ~3 2175~7 ` ~" I

itself; (c) the use of ~lastic materials that do not require liners or seals; (d) a diaphragm (or bladder etc.) captured between the domes; (e) a simplified set of production processes; (~) a tank that is corrosion resistant inside and out; (~) a tank that does not require outside finishinq (e.9 paintin~) ~or finisll protectiol1; and (h) a reliable tank that can safely be utilized ~or a variety o~
applications includin~ water stora~e applic~tions and high prcssure environments due to the inhcrent stren~th of thc la~ joint formed usin~ the process clcscribed hereinbefore What has been described in deta i.l hereil1above re methods a~paratus and fahrication tccl1niques wh.ich meet all of thc aforestatecl objectives. As previously inc1icatc~1 those skille~ in the art will reco~Jnize that the foreqoin~
description has been prescntcd for thc sake o illustration and description only It is not intel1dcd to be exhaustive or to limit the invention to the precise ~orm disclosed and obviously many modi~ications and variations are ~ossibl~ in li~l1t of the above teachin~

The embodime11ts and examples sct forth herein were presente~ in or(ler to ~est exl~]ain the ~rinciples of the instant invcntion al1c1 its practic11 app]ic1tion to thcreby enable ot1~ers skilled in the art to ~cst utilize the in~tant invel-tiol1 in various e1nbodin1cnts and with various 2~ 75~37 modifications as are suited to tlle particular U5e contemplated.

In view of the above it is, therefore, to be unde~stood that the claims appen~cd hereto arc ;ntcnded to cover all such mo~lfications and variations which fall within the true scope and spirit of the invention.

~5

Claims

1. A corrosion resistant expansion tank, comprisinq:

(a) a first molded plastic tank section inteqrally includinq first connection means for enabling fluid from a first fluid source to be placed in fluid communication with a first interior portion of said expansion tank; and (b) a second molded plastic tank section, which when joined together with said first molded plastic tank section forms the expansion tank fluid containment vessel, integrally including second connection means for enabling fluid from a second fluid source to be placed in fluid communication with a second separate interior portion of said expansion tank

2 Apparatus as set forth in claim 1 further comprising means for separating said expansion tank into said first interior portion and said second separate interior portion.

3. Apparatus as set forth in claim 2 wherein said means for separating spans the interior of said tank.

4. Apparatus as set forth in claim 2 wherein said means for separating is a flexible material.

5. Apparatus as set forth in claim 2 wherein said means for separating is impermeable to a predetermined set of fluids including those fluids provided by said first fluid source and said second fluid source.

6. Apparatus as set forth in claim 2 wherein said means for separating is a flexible diaphragm.

7. Apparatus as set forth in claim 2 wherein said means for separating is a flexible bladder.

8. Apparatus as set forth in claim 2 wherein said means for separating includes a thermoplastic material.

9. Apparatus as set forth in claim 2 further comprising means for securing said means for separating within said expansion tank in a joint formed between said first molded plastic tank section and said second molded plastic tank section.

10. Apparatus as set forth in claim 9 wherein said means for securing further comprises:

(a) a socket, integrally formed in said first molded plastic tank section, for receiving:

(a1) a tang integrally formed on said second molded plastic tank section; and (a2) a joint forming material, deposited into said socket during tank assembly, for use in joining said first molded plastic tank section to said second molded plastic tank section and securing said means for separating therebetween; and (b) a tang, integrally formed in said second molded plastic tank section, desiqned for insertion into said socket for use in joining said first molded plastic tank section and said second molded plastic tank section toqether to form the expansion tank fluid containment vessel.

11. Apparatus as set forth in claim 10 wherein said socket and said tang further comprise a first socket surface and first tang surface respectively, designed to accommodate the installation and securing of a portion of said means for separating therebetween.

12. Apparatus as set forth in claim 11 wherein said portion of said means for separating is shaped to facilitate the engagement of said portion of said means for separating with at least a portion of said first socket surface during tank assembly.

13. Apparatus as set forth in claim 11 wherein said socket and said tang further comprise a second socket surface and second tang surface respective]y, which when juxtaposed form a stop.

14. Apparatus as set forth in claim 13 wherein said second socket surface and second tang surface are located in proximity to the exterior wall of said tank in relation to the combination of said socket, said portion of said means for separating and said tang which is located toward the interior wall of said tank.

15. Apparatus as set forth in claim 14 wherein said joint forming material includes a thermoplastic.

16. Apparatus as set forth in claim 14 wherein said joint forming material is a welding material which flows upon being heated.

17. Apparatus as set forth in claim 16 wherein said welding material further comprises a mixture of thermoplastic and metal particles.

18. Apparatus as set forth in claim 16 wherein said socket and tang are designed such that welding material deposited in said socket, upon being heated and upon being compressed by said socket and said tang being forced together until said stop is reached, flows from the point of deposit in said socket away from said stop and toward said combination of said socket, said portion of said means for separating and said tang, to form an interior lap joint.

19. Apparatus as set forth in claim 18 wherein said interior lap joint forms a weld that joins said tang and said socket, together.

20. Apparatus as set forth in claim 18 wherein said interior lap joint forms a weld that joins said tang, said socket and said means for separating, together.

21. Apparatus as set forth in claim 18 wherein said interior lap joint when reheated is separable to enable said tank to be taken apart.

22. Apparatus as set forth in claim 11 wherein at least a portion of said first tang surface is roughened to enhance the ability of said means for securing to secure said portion of said means for separating between said first tang surface and said first socket surface.

23. Apparatus as set forth in claim 9 wherein said means for securing is operative to maintain the separation between said first interior portion and said separate second interior portion defined by said means for separating during both tank assembly and tank operation.

24. Apparatus as set forth in claim 23 wherein said means for securing is further operative to hold said means for separating in place during and after precharging said tank with a prespecified amount of fluid pressure.

25. Apparatus as set forth in claim 1 wherein said first connection means provides a passageway through which fluid from said first fluid source may be introduced into and may be withdrawn from said expansion tank.

26. Apparatus as set forth in claim 1 wherein said second connection means provides a passageway through which fluid from said second fluid source may be introduced into and may be withdrawn from said expansion tank.

27. A corrosion resistant expansion tank, comprising:

(a) a first molded plastic tank section including a first tank connection integrally molded therein;

(b) a second molded plastic tank section, which when joined together with said first molded plastic tank section forms the expansion tank fluid containment vessel, including a second tank connection integrally molded therein;

(c) means for separating said tank into a first interior portion and a second interior portion, said means for separating being secured between said first molded tank section and said second molded plastic tank section; and (d) means for securing said means for separating in a joint formed between said first molded tank section and said second molded plastic tank section.

28. Apparatus as set forth in claim 27 wherein said first molded plastic tank section further comprises a gas dome which may be connected to a gas source via said first tank connection integrally molded in said first molded plastic tank section wherein said gas dome includes a sealing surface.

29. Apparatus as set forth in claim 28 wherein said second molded plastic tank section further comprises a water dome, designed to fit into said gas dome, which may be connected to a water source via said second tank connection inteqrally molded in said second molded plastic tank section.

30. Apparatus as set forth in claim 29 wherein at least a portion of said means for separating is formed to fit onto the sealing surface of said gas dome.

31. Apparatus as set forth in claim 30 wherein said portion of said means for separating is sealed between said gas dome and said water dome by fitting said portion of said means for separating into said sealing surface and then joining said gas dome and said water dome together to form a lap joint by compressing a material that includes a thermoplastic until a stop is reached.

32. Apparatus as set forth in claim 31 wherein said means for separating includes a thermoplastic material.

33. Apparatus as set forth in claim 31 wherein said means for separating is a flexible diaphragm.

34. Apparatus as set forth in claim 31 wherein said means for separating is a flexible bladder.

35. Apparatus for securing, within an expansion tank, means for separating the interior of said tank into two separate portions, wherein said expansion tank is formed utilizing a first molded plastic tank section and a second molded plastic tank section that when joined together forms the expansion tank fluid containment vessel, comprising:

(a) a socket, integrally formed in said first molded plastic tank section, for receiving:

(a1) a tang integrally formed on said second molded plastic tank section; and (a2) a joint forming material, deposited into said socket during tank assembly, for use in joining said first molded plastic tank section to said second molded plastic tank section and securing said means for separating therebetween; and (b) a tang, integrally formed in said second molded plastic tank section, designed for insertion into said socket for use in joining said first molded plastic tank section and said second molded plastic tank section together to form the expansion tank fluid containment vessel, wherein said socket and said tang further comprise a first socket surface and first tang surface respectively, designed to accommodate the installation and securing of a portion of said means for separating therebetween.

36. Apparatus as set forth in claim 35 wherein said portion of said means for separating is shaped to facilitate the engagement of said portion of said means for separating with at least a portion of said first socket surface during tank assembly.

37. Apparatus as set forth in claim 36 wherein said socket and said tang further comprise a second socket surface and second tang surface respectively, which when juxtaposed form a stop.

38. Apparatus as set forth in claim 37 wherein said second socket surface and second tang surface are located in proximity to the exterior wall of said tank in relation to the combination of said socket, said portion of said means for separating and said tang which is located toward the interior wall of said tank.

39. Apparatus as set forth in claim 38 wherein said joint forming material includes a thermoplastic.

40. Apparatus as set forth in claim 38 wherein said joint forming material is a welding material which flows upon being heated.

41. Apparatus as set forth in claim 40 wherein said welding material further comprises a mixture of thermoplastic and metal particles.

42. Apparatus as set forth in claim 40 wherein said socket and tang are designed such that weld material deposited in said socket, upon being heated and upon being compressed by said socket and said tang being forced together until said stop is reached, flows from the point of deposit in said socket away from said stop and toward said combination of said socket, said portion of said means for separating and said tang, to form an interior lap joint.

43. Apparatus as set forth in claim 42 wherein said interior lap joint forms a weld that joins said tang and said socket, together.

44. Apparatus as set forth in claim 42 wherein said interior lap joint forms a weld that joins said tang, said socket and said means for separating, together.

45. Apparatus as set forth in claim 42 wherein said interior lap joint when reheated is separable to enable said tank to be taken apart.

46. Apparatus as set forth in claim 35 wherein at least a portion of said first tang surface is roughened to enhance the ability of said means for securing to secure said portion of said means for separating between said first tang surface and said first socket surface.

47. A process for manufacturing a corrosion resistant expansion tank, comprising the steps of:

(a) fabrication a first plastic tank section that integrally includes first tank connection means;

(b) fabricating a second plastic tank section that integrally includes second tank connection means;

(c) inserting between said first plastic tank section and said second plastic tank section means for separating said tank into a first interior portion and a second interior portion; and (e) joining said first plastic tank section and said second plastic tank section, with said means for separating inserted therebetween, to thereby form the expansion tank fluid containment vessel with said means for separating secured therein.

48. A method as set forth in claim 47 further comprising the steps of:

(a) integrally forming a socket in said first plastic tank section for receiving the deposit of a joint forming material and for receiving a tang formed as part of said second molded plastic tank section; and (b) integrally forming a tang in said second molded plastic tank section that when inserted into said socket and joined therewith form the expansion tank fluid containment vessel.

49. A method as set forth in claim 48 wherein said step of forming a socket further comprises the step of forming a first socket surface and said step of forming a tang further comprises the step of forming a first tang surface, wherein said first socket surface and said first tang surface are designed to accommodate the insertion and securing of a portion of said means for separating therebetween.

50. A method as set forth in claim 49 further comprising the step of shaping said portion of said means for separating to facilitate the engagement of said portion of said means for separating with at least a portion of said first socket surface during tank assembly.

51. A method as set forth in claim 50 further comprising the step of roughening at least a portion of said first tang surface to enhance the ability of said portion of said means for separating to be secured between said first tang surface and said first socket surface.

52 A method as set forth in claim 49 wherein said step of forming a socket further comprises the step of forming a second socket surface and said step of forming a tang further comprises the step of forming a second tang surface, wherein said second socket surface and said second tang surface when juxtaposed form a stop.

53. A method as set forth in claim 52 further comprising the step of forming said second socket surface and second tang surface in proximity to the exterior wall of said tank in relation to said first socket surface and said first tang surface which are formed in proximity to the interior wall of said tank.

54. A method as set forth in claim 53 wherein said steps of forming a socket and forming a tang respectively further comprise the step of shaping said socket and tang such that welding material deposited in said socket, upon being heated and upon being compressed by said socket and said tang being forced together until said stop is reached, flows from the point of deposit in said socket away from said stop and toward said combination of said socket, said portion of said means for separating and said tang, to form an interior lap joint.

55. A method as set forth in claim 54 further comprising the step of forming a weld that joins said tang and said socket, together.

56. A method as set forth in claim 54 further comprising the step of forming a weld that joins said tang, said socket and said means for separating, together.

57. A method as set forth in claim 54 wherein said step of joining further comprises the steps of:

(a) depositing a welding material into said socket;

(b) heating said welding material; and (c) compressing said heated welding material between said socket and said tang until said stop is reached

58. A method as set forth in claim 57 wherein said welding material further comprises a mixture of thermoplastic and metal particles.

59. A method as set forth in claim 57 further comprising the step of utilizing a means for separating that is impermeable to a predetermined set of fluids.

60. A method as set forth in claim 57 further comprising the step of utilizing a means for separating that is a flexible diaphragm.

61 A method as set forth in claim 57 further comprising the step of utilizing a means for separating that is a flexible bladder.

62. A method as set forth in claim 57 further comprising the step of utilizing a means for separating that includes a thermoplastic material.

63. A method as set forth in claim 54 wherein said first plastic tank section and said second plastic tank section are formed via an injection molding process.

64. A method for manufacturing an expansion tank comprising the steps of:

(a) fabricating a one piece molded plastic gas dome including an integrally formed socket, further including a sealing surface, and gas connection;

(b) fabricating a one piece molded plastic water dome including an integrally formed tang and water connection;

(c) fitting a diaphragm onto the sealing surface of said socket;

(d) depositing a welding material into said socket;

(e) heating said welding material; and (f) compressing said heated welding material between said socket and said tang until a stop formed by said socket and said tang being juxtaposed is reached.

65. A method as set forth in claim 64 further comprising the step of compressing said heated welding material into an interior lap joint that welds said tang and said socket, together.

66. A method as set forth in claim 64 further comprising the step of compressing said heated welding material into an interior lap joint that welds said tang, said socket and said diaphragm, together.