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H Y O-257UNITED STATES

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h DEPARTMENT OF THC INTERIOR FILE COPYBlJF,E.fU OF REC!~!r!d.kT 1ONmCV B U R E A U OF R E C L A M A T I O N H'JDT.ALL l C 1 fF';? .!.TORY

70 95 i';: :: * r.O$ ?'I-2

A STCDY OF THE HYDRAULIC CHARACTERISTICSOF CONTROL DEVICES FOR THE UNDERDRAIN

SYSTEM OF THE FRIANT-KERN C ANA LCENTRAL VALLEY PROJECT, CALIFORNIA

Hydraulic Laboratory Report No. Hyd.- 257

R E S E A R C H A N D GEOLOGY DIV IS ION

BRANCH OF DESIGN AND CONSTRUCTIONDENVER. COLORADO

APRIL 18,1949


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C O N T ~ T S

P u r p o s e o f S t u d y . . . . . . . . . . . . . . . . . . . . . .C o n c l u s i o n s . . . . . . . . . . . . . . . . , . . . . . .R e c a m m e m E a t l o n s . . . . . . . . . . . . . . . . . . . . . . .A c k n o w l e d g m e n t . . . . . . . ~ . . . . . . . . . . . . . . .T n t r O @ u c t i o n . . . . . . . . . . . . . . . . . . . . . . . .

D e s c r i p t i o n o f P r o t o t y p e . . . . . . . . . . . . . . . .T e s t F a c i l i t i e s . . . . . . . . . . . . . . . . . . . .T e s t P r o c e & u r e . . . . . . . . . . . . . . . . . . . . .

P r e l i m i n a r y I n ~ , s t i g a t i o n . . . . . . . . . . . . . . . . . .I n i t i a l T e s t s o f F l a p V a l v e C o n t r o l . . . . . . . . . .

l u v e s t i g a t i o n o f S e e p a g e Q u a n t i t y . . . . . . . . . . o F l o w o f S e e p a g e W a t e r t o D m d e r d r a i n s . . . . . . . . . .S e e p a g e ~ i o w E q u a t i o n . . . ~ . . . . . . . . . . . . .C o m p u t a t i o n o f S e e p a g e lelow . . . . . . . . . . . . . .P r e s s u r e D i s t r i b u t i o n U n a e r C a n a l L i m i n g . . . . . . . .

I n v e s t i g a t i o n o f F l a p V a l v e s . . . . . . . . . . . . . . . .S e l e c t i o n o f V a l v e f o r A l t e r a t i o n s . . . . . . . . . .C a p a c i t y o f U n a l t e r e d V a l v e . . . . . . . . . . . . . .E f f e c t o f F l a p C o u n t e r b a l a n c e . . . . . . . . . . . . . . .E f f e c t o f F l ~ p W e i @ h t . . . . . . . . . . . . . . . . .E f f e c t o f H i m g i ~ F l a p ov er . C e n t e r o f G ~ a v i t y . . . . .E f f e c t o f S e a t W i d t h . . . . . . . . . . . . . . . . . . .C ha ra ct er is ti cs o f P ro je ct F la p V al ve . . . . . . . . .C h a r a c t e r i s t i c s o f A l l - B r a s s F l a p V a l v e . . . . . . . .C h a r a c t e r i s t i c s o f R e c t a m g u l a r F l a p V a l v e . . . . . . .

I n v e s t i g a t i o n o f W e e p h o l e T y p e U m ~ l ~ a i n C o n t r o l . . . . . .W e o ~ h o l e U m K e r d r a i n C o n t r o l s . . . . . . . . . . . . . .C h a r a c t e r i s t i c s o f W e e p h o l e % rlth R i s i n g D i s k . . . . . . .C h a r a c t e r i s t i c s o f W e e p h o l e w i t h R u b b e r F l ap . . . . . .

APP]~DIX 1F l a p V a l v e s f o r 6 - 1 m c h D r a i n L i m e - - F r i a u t - K e r n C a n a l- -C e n t r a l V a l l e y P r o j e c t . . . . . . . . . . . . . . . . . . . .

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1 Location Map2' Concrete Canal Llning Underdrains3A Electrical W o g ~ray Model3B Flap Valves4 Curves for C0eff1cient p5 Capacity. Curves far Underdrain Flap Valves6 Capacity Curves far Rectangular Flap Valve7 Capacity Curves for Underdrain Weephole


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DEPARTMENT O F THE INTERIORBUREAU OF RECLAMATION

t Branch of Design and Construction Laboratory Repart No. 257Research and Geolc- Division Hydraulic LaboratoryDenver, Colora d s Compiled by: J. C. SchusterDate: A p r i l 18, 1949 Reviewed by: J. W. B a l lSubJect: A study of the hydraul ic c harac ter i s t ic s of ~ o n t r o l evicesfo r the underdrain systsln of th e Friant-K ern CanaL--CentralValley F ~ o J e c t ,California.

PURFJSE OF STUDYThe purpose of t h i s s tudy was t o determine th e adequacy of flap

valves f o r cont;rolling th e flow of seepage water f rm the Biant-Kerncana l lining underdrain system, without exceediag the meximum- allowable pressure of 0.67 foot of w a t e r under the l ining. The programwa s extended tominclude study of th e hydraulic cha rac ter ist i cs of twoother types of und erd rab co ntr ol devices.C.3NCLUSIOmS

1. In any un le rd ra in systam, one of th e f i r o t consider&ionsshould be the prevention of t he underdrain co nt ro l becoming inoper-at iv e 5ecause of c a ~ o s i o ny oxidation or elect rolyt ic act ion,silting, bonding (such as r ~ b b e r o metsl), or bialogfcal growth.I

2. The q ua nt ity of seepage flow t o each &al n fo r anycombination of factars of pennaabi li ty , water table , l e w h of 'drainage section, and drain arrangement governing the flow quantity,should not exceed the capacity of t he c ontro l device f ur t he c r i t i c a lhead.3 . The pressure conditions under the liniag w i l l be more cri t icalwith the canal empty than when it contains enough water t o 6110 t h ee x i t s of th e underdraies, With no water in t he cana l and the invert bf

I th e flow passage of the ex i t s placed 2 inches above the lining surfaces,the head for poducing flow fra the Upderdraine must not be greaterthan 0.21 of a fo ot or th e buckling pres sure of 0.67 of a foot w i l l beexceeded. The allowable head differential w i l l be increased t o 0.67of a foot for the buckling pressure when the exits are si~bsasrged,. Should a pe rf ec t se a l occur between the cont act sup4aces ofth e valve seat, the head required t o open th e f l ap for any appreciablesubmergence would be considerably larger than the maximum of 0.67 foo tused i n t h i s study. The ef fe ct of t h i s type of seal ing was negl igiblefor all valves tested.


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~ a t i o d ast Iro n Pipe c&nPang.,and the PTockhest Valve c&np& w i l lnot operate sat1sf a c to r i l y under the low-pressure dlff rential requbedi n the Fr iant -Kern ins ta l la t io n when ~ h e ansl Is empty.6. The valve with the 4-pound bronze flap, furnished by the projectfo r te s t ing , w i l l aperete sa t is f ac t or i ly provided that the seepwe flowi n t o a single dra in does not exceed 0.01 cubic foot per ser,ord,' andt h a t t h e re i s no corrosion Etnd a minimum f2 i c t i o n a l r e s i s t a nc e In thehinge. By cou nte rba lan ci~ q h e f l ap of t h i s valve, it i s possib le t omake it open under extremely a n d l beds and increase the capaci ty t o0.06 cubic foot per second for the 0.21-foot head.7. Assumin& no corrosion and a minimum f r i c t i o n a l r e s i st a n ce i nth e hinge, the thre e heavy cammercial valves can Be made t o open atheails l e s s than 0.21 foot by counterbalancing the f lap s, but t hedibchesge capacity for t h i s maximum allowable headWUe very small(approxlmatel;p 0.03 cubic foo t per second f o r th e National Cast I ron

pipe Company valve).8. A "sloppy" f I+ , hould be provided i n the hinae of any f l a pvalve used i n an underdrain system where opera tio n under smal l heads

i s required.9 . A l ightweight f la p ( 3 pouods o r l e a s ) w ith i t s hinge overth e center of gra vit y could be ueed t o replace the heavy fla pe of thevefves alxeady ins ta l led .

10. A f l ap valve with a rectangular flow passage and Ligb.tweightf l a p will have be t te r operat ing character ic t ics t h w one w i t h acircular opening having the sawe area and Invert elevation.U. A weephole through the canal liaing, controU ed by a rubberf lap , ie a feas ib le meas of pas ;ing seepage flow f"rcun beneath thecanal. The mater ia l of tihe fl ap , t he weight of the flap, and theposit ion of t he hinge point are hpo r ta n t desiga fac to rs .13. An underdrain control consisting of a I jghtweight r i s i ngdisk on a stem and supports, covering a weepholo in the canal l in ing ,might be used i n cases whore the water i s f re e ofmoes, s i l t , . orother Zebris.

1. Suf fic ien t fi e l d information, including groundwater elevati onsand type and permeability of a o i l a , be obtained f o r determining theadequacy of all cana l underdrain systems pr io r t o construction.


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2. A l ightweight f lap (3 pounds or l e ss ) with i t s hinge over thecente r of gra vity be used t o replace th e heavy f la ps of t he valvesal ready ins t al l ed i n the Friant -Kern Canal, and t ha t add i t iona l ou t l e t sbe provlded fo r the ex is t ing long drains , & od d act ual f i e l d condi-t i on s ind icate seepwe flow in excess of th e capac ity of t he present

3. A ' sloppy" f i t be provided i n the hinge of any f l a p va lveused i n an underdrain system operating under low heads.4. Should th e f la p valve be used t o c on tro l seepege flow f r o m aca na l underdr ain systerm, th e valve should have a rectangular f lowpassege and l ightweight f l a p and be ins ta l le d wi th the in ver t of thepassage as near the surface of the l i ni ng as possible.5. E the use of a nonmetal flap i s contemplated, t he sea lin gcha rac ter i s t ic s should be inves t igated before the des ign i s adopted.Information concerning p la st ic mate rials i s contained i n Appendix 1.6. If the flap-controlled weephole underdrain i s considered, af inishe d f l a p should be s tudied i n the laboratory before the des lgni s adopted.

Engineers from the C a n e l s and Mechanical Dlvlsions ,snd the EasthMaterials Laboratory collaborated i n the canal underdra in inve~t iga-t i o n s disc ussed i n t h i s r e ~ o r t .


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Description of PrototypeThe F!riant-Kern Canal, Central Valley Project, Cal i fornia , ( ~ i g u r e )has been designed with a 3-1/2-inch rei nfo rce d con crete lin in g. Thisl ining can withstand a macimum d i f f e r e n t i a w a h r pressure of 0.67 ofa foot without buckling. To protec t the l in in g %ainst buckling duet o a di f f e re n t i a l wate r p ressure resu l t ing fram a high watertable orrains torm , 6-inch open-jointed sewer pipe d r a i n s have been providedbenea th the f loor o f the cana l ( ~ i g u r e ) . At; intervabs along thecourse of th e canal, th e drainpipes pass upwan-d through the bottoml i n i ng and ar e vented by f l a p valves. Each valve consists of 4 bodyconnected by a f lange to the end of a dra in and a f la p which i s f r e et c swing out from the body seat when InternaJ. pressure from t he dre in-pipe acts upon i t . . The $avert of the valve Slow passage has beenplaced approximately 5-46 of a fo ot above the lower s id e of t he bottoml i n i n g i n o rd er t o f a c i l i t a t e t h e ins ta l la t ion of the valve, and t oassure a minimum interference by moss or accumulating s i l t . For safe tyof th e l in ing , the f la p valve must open and be capable of dischmgingthe drainage flow a t heads not greater than 0.21 of a foot when thecanal i s empty and the invert of the dra in i s 2 inches above the lining.The d if fe re nt ia l head should not be greate r t h a n 0.67 of a f ~ o t hent h er e i s s u f f i c ie n t w a t e r i n th e canal t o submerge the valve. Sincel i t t l e was known of the operat ing cha ra cte ris t ic s of f l a p valves a t

s m a l l heads, it was requ ested t h a t se ve ra l of t he commercial desig nsinwtalled i n the Friant-Kern Canal be t es t ed i n the laboratory.T es t Fac i l i t i e s

A 20-foot h orizo ntal len gth of 6-inch standard pipe terminated bya flang e ins ide of a box i n xfiich th e water depth could be va rie d w a sprovided t o tes % he ga tes i n the laboratory. Water was supplied bya vex-tical 8-inch propeller pump and measured by an or i f i ce -ventur imeter. A 1-inch standard pipe vent was placed i n the 6-inch pipe t ofa c i l i t a te applying pressure to the valve f lap . Pressures weremeasured by a water manmeter connected t o a pibzameter lo ca te d onepipe diameter upstream f=m the extrame end of the valve body and i nthe bottom of the 6-inch pipe. To fa c i l i t a te obtaining the pressurere qu ke d to open the valve, a s et of el ec tr ic al contacts completingth e cIrcu:',t t o a m a l l light bulb was attache d t o the fla2 and body.The s l w t e s t movement of the f la p would break th e con tac t which wouldi n te r ru p t t he c m e n t t o t h e b ulb and indicate the opening of thevalve.

1

An e l e c tr i c analogy t r a y was used t o determine th e amount ofseepage flow which might be expected t o en ter th e underdrains. Thetray, 1 nch i n depth, having s ides of s t r i p p la st ic which represented


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of 18 fe et , and a sid e slope of 1-1/4 t o 1, was conatructed on 8, 50- by50- by 3/8-inch glass p l a t e t o a scale of 1/2 nch 1 foot (~Lg;ure ~ ) .m e remaining portion of th e -tray ~ounilRry a 8 formed by ' p l a c i q ~ l as ti cs t r i p s on the v er ti ca l cente rlin e below the canal bottom,, along ahor izon ta l l i ne 8 inches above the floor and outside of tne c m a l w a l l ,and on an arc of 40-inch ra di us between th es e two li ne s. The ce nt er ofthe 40-inch radius w a s a t the inters ection of th e canal centerl. ine andth e horizon'tal l in e 8 inches above the canal. floor. An elect rcde wasplaced alord th e curved boundary t o repre sen t t he maximum poten t ia lof the groundwater. TWDmall. electrodes represented one and one-halfdr ai n f i l t e r s of a three -dra in sya-tcsm and the minimum poten t ia l a t th ecana l bottam. The el ec tr ol yt e used In the model w a s ta p waterapproximatelr 1/2 inch i n depth.Test Procedure

Each fla p valve was bolted t o the flange i nsi de the bcx and w a t e rintroduced slowly in to the 6-Inch pipe t h r o w the 1-inch vent un ti lt h e f l a p wss forced open by t he pkeesure i n the pipe. The headrequired t o ope= the fl ap was read from a w a t e r manometer a t th ei n st a nt th e in d ic at or l l g h t s i # f i e d t h a t th e f lap star ted t o open,The same +oceaure was followed whether t he v alv es were submerged orunsubmerged.

Accepted st8nda;rd procedures were followed i n the e l e c t r i canalogy - tray tes ts ,

PRELIMINARY II?VESTIG.ATIOlJI n i t i a l Te st s of Flap Valve Control:

The i n i t i a l te s ts on the four valves received from the proJectind.icated t h a t none would ba e n t i r e ly satisfactory for the underdrainsys'tezn.The opening heads were excessive f o r the unsub~~erged ,ondition 9 sth re e of t he valves, Table I, and i t vas not cer ta ln that the capacl.ty

o f any of th e valves was adequate, sinc e th e qu antit y of seepage flowwas UIlknoWn.


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D i f fe ren t i a l Pressure in f e e t of water,head refe rred t o invert of 6-inch pipeManufacturer Submsrged Una~ brnm ~ed

Fr ian t Valve No. 13141(manufacturer mhown) 1 0.03 0.UIowa Valve Campany 1 0.093 0.31Nat ionel Cast *on PipeC ~ P W , 0.23 0.48

Flockhart Valve CompanyNo. 5149 0.47

Note: A check of the r e l i a b i l i t y of the values given above watsmade by computation using balanced m a e n t s about - the hinge point, onefo r th e weight of th e fl a p and one for the force produced by t he waterpressure. Good agrement was obtained.

Tbe invest&t ion resolved int o tbr es parts: (1) o determine w h a tqua ntit y of seepage flow migb;t be expected t o enter the drains; (2) t odetermine if the valves had sufFficient capacity withln the require d headrange; and ( 3 ) t o d e t e m n e i f the i n ~ t a l l e d alves could be made t ooperate sa t is fa ct or i ly by making minor a l t e ra t lops . The program wascontinued on the basis of these three pxloblams.

m r I w I o m OF SEEPAGE wmmFlow of Seepage Water t o Underr3,rains

The capa city of t h e Friaat-Kern Canal underdrain syetesl was l imitedby t he e l eva tion of th e ha inp i pe ex i t s and t he res i s t ance o f t he flepvalves; therefore, It w a s very important t o determine t he quan tity ofseepage flow t o be expected t o ent er th e imderdrains. E l sc t r l c d o g gt e s t s were made for that purpose.Seepage Flow Equation

The eqwtion, Q = m b , may be used t o comg~&e the seeptge flow t othe c d nderdrains, providing d l t s f a c t o r s can be evaluated. Inthe equation


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K - percola t ion ra te ( fe et per year) ,H = height of watertable i n feet above drain f i l t e r

b L - length of cana l secti on i n fe et , measured along th elongitudinal cante r l i n e&ape fac to r , dependent upon desig n and foundationconditions

The factor, , cannot be determined from p hy si ca l m e a ~ ~ ~ e m e n l xf ani n s t a l l a t i o n b ut can be obtained thrcugh e le c tr ic amPog3~s tu di es W c hconsider the Plow of c m e n t i n a conductor analogasls t o f lw of waterthrough granulm material (Ohmls b w and DIPcyss Law fo r seepage flow).dIn the case of the e le ct r ic a l analogy tray, 8 i s t h e r a t i o of t h er e d s t a n c e of a square uni t of the model t o the resis tance of the m&el(both co nt a i ni q the same depth of e l e c b o w e ) .

Two conditions had t o be con sid erd la determining the value of :(1) he ef fe ct of changing the depth t o an Iztpervious layer; and (2) theeffect of changing the h e w t of the watertable above the underdrainf i l t e r . Curves were plo tte d showing the va ria tio n i n g for the tkabove conditions ( ~ i g u r e ). The maximum value obtained w a s 0.n for .th e one-half sect ion of t h e c ar d. which assumed pervious ma te ri al ofi a f i n it o d b e n s l o n ~ nd a watertable coincident with the top of theca ie l . A flow net construc%ed by using dat a f r o m t h e e l e c t r i c d o g ytr ay indicated th at t he discharge would be di str ib uted so th atapproxima'iely one-fif th of the seepage water flowing t o the c dunderdrain system would enter the center dr ai n while two-fifths wou ldenter each o f t ho two outside drains.Computation of Seepage Flow

By using the f low dis t r ibut i on ra t io and appropriate values of $ ,it 1 8 po ssi ble t o compute th e seeyege flow in to any crystem of under-dra ins which i s geametrically slrmilar t o the one tes ted, i f thewatertable, leng th of drainage section, aad perc olati on r a t e ar e known.A l l of these aata are not avai lable f or specif ic se ct ior s of th e Fr lant-Kern C a n a l ; thus i t i s not possible a t t h i s t lme t o p ~ e d i c t he dischargequant i t ies f or the We rd ra ln systems of that s t ructure .

d . W. Lane, 'Model Stud ies df the Imperial D8. Desl l t ing Worksand Structures i n AU-Americas Canal, I Hydraulic Laboratory R e m No.Hyd 7 - 9 9 , p. 93 , Bureau of Reclamation, Denver, Colarado, May 1, 1946.J. N. Bradley, J. R . Drisko, and D. J. Eebert, Preliminary Rep o r t

No. 2, '1M 471, "Hydraulic and Elec t r ica l Analogy Model Studies of theRoposed Imperial Dam and Appu~te-t Works--All-American C d 1 . o ~ e c t ~Bureau of Reclam tion , Denver, Colorado, July 15, 1935.


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frcun probable marimum values of p , H, K, and Z, which might occurd o ng the course of the c d , s 0.80 cubic fo ot per cecond. Thevalues of g , H, K, and L used i n camputing th i s quan tity are asfollows:8L = 0.77 maximum value from elect r ic analogy t rayLests (f igure 4 )

K " 4,125 f e e t per year, Table 2, Earth MeterialsLaboratory Report No. EM-78, October 12, 1945H = 16-foot depth of cana l or assuming water tablecoincident with top of canalL = 500 feet, Sec. AA, Figure 2

It seems very improbable th a t t he above vd u e s would ever e xi stat one location. If such condit ions do exi st , the most lo gi ca l solu t ionwould be t o decrease the dra in leagth L. The height of the d ra in exit s,being 0.46 fo ot abovs the bottom of th e lin in g, l imits the head forproducing flow t o 0.21 fo ot f o r the unsubmerged dr ai n exi t; thus th ema;rcirmrm len gth of d ra in can be determined S the capaci ty of the dr ainunder t h i s head i s known. The ca pac ity must inclyd e the influe nce ofany res t r i c t i on , s9ch as f la p gates or other controls , p laced a t t heex i t of the drain . discharge for an open unsuhaerged drain undert h is head i s 0.096 cubic fo ot per second., or about 15 p e r c ~ n t f thexuaxlmum possib le flow; thus, th e pressure head f o r th9 maxim= valueswi3L be excessive, even f o r the un rest r ic te d drain unless the length1,s Umitea to about 65 f e s t or the permeability coefficient does notexceed 490 fe e t per yea r.

It nust be pointed out that the values of P determined i n t h i sstudy are ap plicable only t o canal cross-sect ions geometrical lys i mi la r t o t ha t t e s t ed and that these values are f o r a one-halfsect ion of the canal . Additional te s t s would be required t odetermine values for other cross-sect ions and underdrain mangernen6s.Pressure Distribution Under Canal Lining

A deturmlnation of the pressure d is t r ib ut i on on the l ining, tha ti s the effectiveness of th e d rains f o r reducing pressures throughoutthe underside of 'the lining, w a s not made because of l im it at io n simposed by %he temporary e l e c t r i c a l analogy equipment used i n t h i s@ study. It was believed that if, ressure a t any point under theli ni ng exceeded the buckling pressure, the l in in g would r a is esl ig ht ly from the surrounding so i l t o form a free water path between-tb.e poi nt i n queetio n and the underdrain f i l ter , thereby rel ievice


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+&is path by the seepage flow and so the nimber of prossure-relievingcyc les without damage to t he l i n in g m y e limited. A d e ta i l e dpressure-distribution e t uQ could be made i f th e need should ever a r i s ei n th e design of unaerdrain systems.

bINVESTIGATION OF FLAP VALVES

Selection of Valve f or A lterati onsIt became evident during the preceding tests, that nothing couldbe gained by using a valve with s greater capaci ty than an unobstructeddrainpipe; therefore, t h i s cri te ri on was used f o r determining theadequacy of tlll valves tested. With a determination of approximateseepege flow quantities, i t became necessary t o fi nd i f any of thevalves had suff ic ie nt capaci ty t o d ischarge t h i s f h w with in therequired head range, and t o f i nd i f the in st al le d valves could be

made t o opera te sa t is fac to r i l y by minor a l t era t io n of t h e i r par ts .Since all of th e valves were of similar design (Figure 3B) and hads im i h r hydraulic chara cte rist ics , the National Cast Iron PipeC n m p a ~ ~alve was studied for the ef fe ct s of t he various al ter at ion s.This valve was chosen because it required a gr eat er head t o open thanany of th e o th er va lve s when discha rg in g unsubmerged, and any sobutionobtained From t h e t e s t s o n it would be appli cable t o the other valves.Capacity of unaltered va lve

A head-discharge curve for cm pl et e suhmergencewas obtained f o rth e Nation al Cast I ro n Pipe Cumpang f l a p valve (curve a, Figure 5 ~ ) .It was found t ha t t he di ff er en ti al head required t o maintain flow wasindependent of th e depth of ta i l* -a te r , and th at the capacity of thevalve f o r submerged flow was adequate fo r pass ing th e seepsge water.

The head-discharga re la ti o ns hi p fo r t h s unsubmerged valve wasobtained also (curve a, Figure 5B). The heads t o open the valve ebndmaintain flow were excessive. A discont inui ty exis t sd i n the curvea t appr~ xlma tely .2 of a second-foot, which was beli eved caused bya change i n the -flow conditions i n the passage famed between tb,ebody seat and f lap .It was believes tha t the d i scon t inu i ty resu l ted from the contraction

a t th e inn er periphery of th e body se at and the flow conditions inthe expanding passage between the seat and f l a p . The dec rea se i npressure i n the flow passage accmpanied tha contra ction and expansionand created a hydraulic p ul l forc e which tortded t o clos e th e fl ap , thusincreasing t he head required t o maintain flow. This flow conditionexisted until the outwasd movement of the gate by the force of the


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aera ted . When aera ti on occurred th e f l a p moved ou t and the depth ofw ater i n t h e pipa decreased.Effect of Flap Counterbalance

f. The f i r s t a l t e ra t23 3 made t o the Nat iona l Cast Iron Pipe Campanyf l a p valv e was th e ad d it io n of a 5.05-pound counterwei@it suspendedins i de th e pipe on the upstream s ide of f la p (Figure 51, ) . The flapw a s b al an ce d i n a i r by th e counterwgight so t h a t it iuight touch therea t or remain s l ig ht ly open depending upon the a ct io n i n the hinge.In t h i s cond i t ion o f ba lance , the va lve s t a r t s opening a t p r a c t i c a l l yz e r o head. The di sc on ti nu it y ia th e d i scharge curvs was -no td i s ce r n ib l e , p ro bably due t o t h e f a c t t h a t t h e b&%k~nciIIgf t h e f l a ppermit ted it t o be forced open beyond the cr i t ic a7- point by a verylow head and p e rm it te d t h e j e t t o a e r a t e a t a very ma l l dischazge,The discharge was approximately 0.03 of a second-foot when he headi n the p ipe reached t he maximum allowable of 0.21 of a foot (0 .67-footwater on bottom of l i n i n g ) (Curve b, Fig ure 5B). C a l i br a t io n f o r t h esubmerged con diti on showed th e ca pac ity t o be s at is fa ct or y, 0.27 cubicfoo t per secon& fo r a d if f er e nt ia l head of 0.010 fo ot (Curve b, Figure5A)E f f ec t o f Fl ap W e i a t

An 8- by 8- by l / 8 -i n ch b r a s s f l a p w i t h the same hinge point wasmade f o r th e National Cast I ro n Pipe Cmpaqy valve (Figure 5C). Thlsflap weighed 2.59 pounds compared t o t h e 10.60 pounds of the original.A d i s co n t i n u i t y i n t h e d i s ch a rg e cu rv e similar Lo t h a t o bs er ved f o rt h e o r i g i n a l f l a p w a s s t i l l apparent , but occurred a t a Lower head anda disc harg e of approximately 0.04 of a seco d-f oot (curve a, Figure 3 C ) . 'A t a discharge of e~pproximately0.25 of a second-foot and a head of0.8 1 f o o t , t h e f l a p cea sed t o a f f ec t t h e head a t th e p iezometer andthe d ischmge curve coincided with that f o r f ree f low frorm t h e p ipe .Th is a l t e r a t io n was no t a so lu t ion because the he& t o open the va lveand maintain f low w a s excessive when the valve was.not submerged.Ef fec t o f H i ~ i x q lap over Center of Gravitx

The 8- by 8- by 1/8 -inch b ras s f l a p was a l te re d t o move th e h ingepoint over i t s c e nt e r of g r a v i t y ( ~ i g u r e C). This change reduced theh ead r eq u i r ed t o m a in ta in a given d i scharge such th a t t he d i scharge fo rth e 0.21-foot head was approximately 0.10 cu bic fo o t pa r second, ,thesame a s f o r an u n r e s t r i c t ed drain (curve b, Figure 2C). However, ab d i s co n t i n u i f y s t i l l occur red i n the d i scharge curve and t h e maximumhead under the l in ing, a t t h e d i s co n t i n u i t y , was 0.62 of a f o o t ,wh.ich was only s l ig ht ly l e s s than t he maximum allowable. It w a sd e s i r a b l e t o e i th er reduce tbe ,head a t t h e d i s c o n t i n u i ty o r e l im i na t eth e d i s co n t i n u it y , s o f u r t h e r t e s t s were Ioade.


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I t was reasoned t h a t the discon t inui ty caused by the f low condi t ionoccurring between t ho body s e at and f l ap could be e l imina ted by reducingth e width of the s e at . The red ucti on was mads by machining the o r i g i n a l

1 se at of t he Na tion al Cast Ir on Pipe Company valve t o an tuurulm r i n g1/8 inch wide by 1/4 inch deep having an ins ide diameter of 7.12 i nches(Figure 5B) . The pre ssure-d i scha rge re l a t i on sh ip f o r t he or ig i na l f l a pw it h t he a l t e r e d s e a t r i n g i s shown 117 Curvs c , F ig ure 5B . The discon-t i n u i t y i n t h e d is ch a rg e curve was el im i~l ste d,bu t t h e opening head wasdecreasad on ly s l i g h t ly . Thi s s l i gh t dec rease w a s a t t r i b u t e d t o t h ef a c t t ha t t he w a te r p r e s s u r e a c t s over a l a r ge r a r e a on the i n s i de o ft he f l a p .Es t a ob ta ined f o r t he 8- by 8- by 1/8- inch bra ss f la p having th esame hinge point as t he o r i g i na l f l a p , bu t w it h an a l t e re d body sea t ,a r e shown by Curve c , Fi gu re 5 C . There w a s no d i s c on t i nu i t y i n t hea-ischmge curve but th e head t o open and mainta in f low againf it t he

moment of t he g at e about th e hinge po in t was s t i l l t oo l a r ge . Withthe hinge poin t moved forward, th e head-d' ischmge rel at io ns hi p w a st he same a s f o r f r ee d i scharge f rm an open drain (Curve d, Figure 5 C ) .I t i c be li evsd *ha t any of t he fo ur va lves l i s t e d i n Table 1 could bemade t o ope rate s a t i ~ f a c t o r i l y y reducing the se at width and providinga l i gh tweight f l a p h inged over i t s cen t er o f g rav i ty . @om t h e s e t e s t s ,I t w a s concluded a l su t h a t t he most sa t i s fac tor y f l a p valve fo r t hevaderdrain system would be one which has a narrow seat and a l i g h t -weight f la p wi th th e hinge placed over or n e w i t s cente r o f g rav i ty .Cha rac t er i s t ics of P roj ec t Flap Valve

Although th s heads t o open the f la p va ive wi th c as t - s t ee l body and4-pound bronze f l a p receiv ed from the p roJ ect and i d e n t i f i e d by t h entinber, 13141, were wi thi n the spe cifi ed l i m i t s fo r th e submerged andunsuhmerged cop diti on s, th e disch arge cap ac ity w a s very sm a l l f o r t h emsubnergen con dit ion and th er e was a small d i s c on t i nu i t y i n the d i s -chmge curve a t about 0.04 cubi c fo ot per second (Curve a, Figure 5 D ) .Te st s were made t o dete rmin e i f the capac i ty could be increasedsu f f i c i e n t l y by minor a l t e ra t i o ns t o pe rmi t t he use of t h e va lve i nth e Friant-Kern Canal underdrain system. The a l t e ra t i ons cons i s t edof: (1) oun t e r bal a nc iw of t he b ronze f l a p ( ~ i g u r e D), and (2 ) decre as-ing the width of the seat by machining the inne r pe r iphe ry of t he f l a psea t r i ng (F? .gwe 5 D ) .

The capac ity of t h e valve was increa sed by counterbalancing th eB b r o n ~ e l a p with a piec e of 3/8-inch-diameter br as s ro d 10-1/2 inc heslong. The inc rease i n capac i ty fo r c he submerged valve was s ub st an ti alwhil e t ha t fo r t he un sube rged condi ti on w a s mall (about 0.03 cubicf o o t per second) (Curve b, Figu re 5 ~ ) . he h 9 d requi red t o open th evalve was neg l igib le f o r both cases .


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machining of the- inne r periphery of t he f l a p s ea t (curve c, Figure 5 ~ ) ,but the di sc on tin ui ty i n Vie discha rge curve f o r unsubmerged flow wasp r a c t i ca l l y e l h i i m t e d .1 The water Barn t he r ese rvo i r a t f i i a n t Dam i s considered to havea s a l t content gr ea t enough t o produce an elect rolyt ic act ion betweenthe cas t - s t ee l body and bronze f l ap of t h i s valve. This act io n wouldmake the l i f e of t h i s valve questionable, i f the valve wore t o remain. cubmerged %or long pe riod s.

The loose f i t i n the hinge of t h i s valve w i l l l e ssen anyposs ib i l i ty o f i t s becamin& inoperable due t o corr osio n.Ch arac terist ics of All-bra9 s Flap Valve

An a l l - b ra s s f iap valve, having a body of 6-inch-inside-diameterby 114 inch w a l l bras s p ipe and a c i rcu lar f la p of 1 /8-inch brass p la tewith the hinge placed v e rt ic al ly above the cen ter of gra vity , was con-st ructed and tes ted (valve e , F igure 3 ~ ) . I t s design was based uponthe result^ of the t e s t s completed thus f a r on tha four f la p valve13received f rom the prodect. No disc onti nuity was observed in theaisc harg s curve which, f o r a l l gr ac tic al purposes, coincided witht h a t f o r an unobstructed drain (Curve e, Figure 5C). Tfais valve wasconsidered entl -ely ss t i sf ac tory so fair as hydraulic char act er is t icswere concerned. It aoes have the disadvrntage i n th a t ca st Iron i sanodic to brass.Character is t ic s of Rectangular Flap Valve

Since i t was found tha t most f l ap va lves a re unsa t is f acto ry f ~ ri n ~ t a l l a t i o n n low-pressure underdrain systems, a valve fo r r ep lac ingthose tilready LnstaJ.led i n the f i iant -Kern C a n a l was proposed by th eMechanical Design Sec tion ( ~ i g u r e ) . This f l a p valve included acast- iron adapter f lange that lowered the valve f low passage invert1-1/4 inches below th e inv ert of the underdrain ex it , and a 1/8-inch

I r e ctangulaz bronze flap and hinge weighing approximatsly 1.5 pounds.The s ea t on th e body of t h i s valve w a s a rect-le with insid ed b en s i o u s 3-114 inches hi& by 7 inches wide, and a seat. width of9/32 inch. A clearance of 1/16 inch between the hi-; p in a d bearingwas provided t o minimize th e p os si bi l i t y of corrosion freezing thehinge. The recta ngu lar e x i t of t hf s valve provided s grea te r a rea incontact with the water for ma l l heads, thus fo r a given depth ofwater, the opening force i s l a r g e r th an f o r t h e c i r cu l a r ex i t .

The opening head f o r th e unsuhmerged re ct an gu la r f l a p valve wa s0.06 of a foo t of water. Since the inv ert of the water passege of thevalve body was about 0.10 fo ot below th e i n ve rt of t he drainp ipe e x l t ,the opening head f o r the f la p did not af fe ct the deptk i n the d r a i n( ~ ~ g u r e) .


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.on the to ta l hiad in the valve body, show that the capacity for thisarrangement i s es se nt ia lly the same as an unobstructed dra in (cur- a,Figure 6 ) . The capacity of an unsubmerged fiiant-Kern Canal underdrain,using th i s f l ap valve a ~ a a g e m e n t ,w i l l therefore be l im ited by-theeleva&ion of the dra in ex it ra$her than the resis tance of the f l ap valve.The cr i t i c a l heads and corresponding capacit ies fo r th ree drain-exitelevations are shown on ~ i g u r e . p he maximum capaci ty fo r the dra inexits placed 2, 3 , and 4 inches above the canal floor are 0.094, 0.036,and 0.004 cub ic foot p er second, re spo ctivo ly. This valve, asconstructed i n the laboratcry, exhibited good seal ing qu al i t i es i npreventin g a rev ers e flow oP water i n to the underdrain. The onlydisadvantage w a s the po ss ibi l i t y of corrosion res ul t in g f rc rm the useof two dissimilar metals.

IIWESTIGATION OF VEEPHOLE TYPE UIVDEEUXAR? CONTROLWeephole Underdrain Controls

A weephole type of unds rdraln w a s inv est iga ted b6cause of theunfavorable opening heads and operat ing cherecter ist ics noted formany of the f l a p valves in . t he te s ts d iscussed previously i n th isr epor t . The advantqes of t h i s type of underdrain, over thatplanned for the Friant-Kern C a n a l , weze: (1 ) t h a t i t s e x it was a ta low elevation w i t f r res pec t t o the' floor of the canal, permittingu t i l i z a t i o n of more of the maximum allowable underlining pressurefor sroducing flow fkom the drains, axil (2 ) possible el iminationof d ra in t i l e . Two devices for control l ing.the f low fram theweephole were teste d: (1 ) a risiw rubber disk and (2 ) a rubberflap (Figure 7).

8

Chara cter is t ics of Weephole ~ 4 t h ising DiskA r ising-disk con trol for the weephole, te ste d i n the laboratory,consisted of a rubber disk seal; a cjrc~2a.rmetal plate on top of therubber disk t o prevent i t s being pushed into the weephole by waterpressure from the canal; a guide stem; and a guide bewing with clipst o fa ci l i ta te the renova1 of the device for inspection (Figure 7A ) .This c ont rol was placed i n a 2-inch plastic tube which represented theweephole.The opening head for the disk was recorded as that which producedan evihent flow and not that which caused sl ight leakage f r m beneaththe disk. This head. w a s recorded by a p iezmete r in s t a l l ed i n the

6-inch conduit supplying the water t o the underside o f, th e disk. Waterwas introduced into the supply conduit slowly asd the piezometerreading taken when the disk opened. Since the head req uk ed t o open


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t e s t s were made,with vario us weights placed on top of th e dis k.The opening head f o r th e submerged co ndi tio n appeared t o becons tant a t about 0 .03 of a fo ot f or mov iq pa r t s weighing from 0.11

t o 0.65 of a pound, while th a t fo r the unsubdrged con di t ion var iedfrom 0.02 t o 0.22 of a f o o t . The fa c t th a t the opening head fo r th e .submerged co ndi tion appeared t o remain cons tan t w a s a t t r i b u t e d t o t h ed i f f i c u l t y of determining when the opening act ua ll y occurred.The capa cit ie s of t he unsubmer~edweephole underdrain f o r weightsof 0.11, 0.23, and 0.65 of a pound were app rox ima tel y 0.01, 0.03, and0.05 of a cubic foo t per second f o r the maximum a l lowable l in ingpressur e. The th ree sep ara te curves a t t h e l e f t of F ig ur e 7C show th eef fe ct of the weight of th e moving par ts upon the head req uir ed t oproduce a g iv en d i sch a rg e , w h i le t h e s i n g l e cur ve a t t h e r i g h t i n towhich thi: th re e merge shows the ef fe ct of th e di sk reaching i t s

maximum r i se . The high poi nts i n the curves ar e caused by f lowcor di t i ons between the seat in g surface of th e rubber d i sk and t h el i n in g s u rf ace , s im i l a r t o t h a t d e sc r ib ed f o r t h e f l ap v a lv e underse ct on "Capaci ty of Unal tered Valve" of t h i s repor t . ' The capac i tyof th e unsubmerged ri s i n g di sk con trol , with moving p a r t s weighingup t o 0.2 of a p ~ u n d ,would be half t h a t f o r an uncontrol led 6- inchunderdrain of the type placed. i n t h e ? -Lant-Kern canal.

The pattern of the capacity curves for the submerged weephole andth ree di f f er en t weights of th e moving par ts was similar t o t h a t f o r t h eunsuhmerged condi tion ( ~ i g u r e D). However, t h e head t o produce flowremained sub s ta nt i a l l y below the maximum a l l o w ~, b l e n t i l a f t e r t h e d i*8 .reached i t s maximum r i s e and th e curves merged, th us gi vin g th e same

maximum capaci ty of 0 .067 of a cubic fo ot per second f o r the thre eweig hts. The weight of the moving p a r t s i s n o t s o c r i t i c a l when t h eweephole I s submerged. The possibility of increas ing the capaci ty oft h i s device by increas ing the r i s e o r the s ize o f the weephole w a s notinves t iga ted .

The disadvantages of t h i s c on tro l were t h a t moss s tream ers mightentangle the disk when it i s i n t h e r a i s e d p o s it i o n r e l e ~ s i n g eepagef low dur ing the t ime th a t the cana l ca r r ie s wate r, and t h a t it was onthe f l oo r of the canal wher-; sedimect could in te r f er e with i t soperat ion. A pr ot ec ti ve hood co uld be added bu t no t e s t s were made t od et er mi ne i t s f e a s i b i l i t y .Ch ar ac te ris ti cs of Weephole with Rubber F 3 a ~

A second device cons idered f o r c ont rol l ing t he f low thrcagh aweephole w a s a r ub be r f l a p b o l t e d t o t h e CPKLLi n ig g ( ~ i g u r e ~ ) . Am eta l r e in f a r c in g d i s k w a s placed ou top o f the l /8 - inch rubber f l a p to


18/27

The head t o open t h i s rubber f l a p was determined i n the same manner ast h a t f o r t h e r i s i n g d i sk and it was fownd t o be ne@ igi ble (Figure 7E ) .Discharge curves f o r th e subuerged and unsubmerged condition wereobtained for f l ap s with hinge distanc es of 2 and 3 inches and re inforcingdi sk s woighing 0.04, 0.13, and 0.31 of a pound. The weight of theport ion of the rubber f laps affect ing the operat ing heads w a s 0.07 and0.09 of rt pound for the 2- and 3-inch hinge distances.

i

There were dis con tin uit i es i n the curves sim ilar t o those observedf o r smal l openings i n the i n i t i a l f la p ga%e study. It was believed thata reduction in pressure occurred between the rubber f l a p and l i n i n g a sthe water passed from the tube, thus ixlcreesing the head required t ofor ce water through the weephole. This reduction i n pressure conticuedun t i l the force of t h e w ater l i f t e d t he f l a p and changed the f lowlines.The discon-kinuity of flow i s ref l ect ed i n the discharge curves for boththe submerged and unsubmerged weephole.The maximum capacity a t th e al lowable underl ining pressure obtainedfor t h i s type of co ntrol was 0.06 of a cubic fo ot per second f o r theunsubmerged condition and 0.12 of a cubic foo t per second f o r th esubmerged condition.The head-discharge re la ti on sh ip of the rubber f l a p might followtwo paths, depending upon whether the seepage flow from the weepholei s decreasing or increasing. In ei th er case, the head might becames u f f ic i e n t t o e d a n g e r a 3-1/2-inch-thick lining, unless the hingedistance and weight of the f l a p are properly designed. Tho fl,apshould be lightweight a d the hinge distance m~&emall enough t oeliminate obJectionable head r i s e s i n the region of discontinuity.Further improvement might be realized by using other hinge and s e a ldesigns.


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J. 21. Richardson March 8, 1949Through W. T. Moran and R. F. Blanks

Flap valves fo r 6- inch drain l i ne s--Frlant -Kern Canal- Central ValleyProject .

1. During .December 1948, we had se ve ra l dis cu ssi on s on the que stionof a sui ta ble mater ial for fabr ic at ing the f l ap s of the d raln valves onthe f i iant-Kern C a n a l . A t that t ime, I s w e s t e d t h a t c e rt a in p la s t i c sappeared t o have the desir ed prop ert ies and should be given con side ratio n.2. King Pl as t i c s and Iq erw ers on Manufacturing Company, both ofwhom are lo c al pl as t i cs fab rica tor s, were consulted. Both concernsexpressed the bel ief th at cer tain pla st ics were sui tab le fo r th i s purpose.

Particularly,polyethylene,polystyrene, and saran were proposed. However,since these fa br ic ato rs were not completely fa mil iar with th e long-timebehavior of these materin ls, it was considered advisable to-write themanufacturers for their recommendations.3. After a considerable delay, we have now rec eiv ed r e p l i e s t oour three le t t e r s of inqulry. Although th e o ri g in a l problem has beeneliminated by a charge i n design, t h i s memorandw has been prepared 'toslmrm~rize he manu facturer*b recammendation i n t he event a si mi la rproblem arises.4. Monsanto Chemical Company says f l a t l y th a t they would recammendno pl as t i c materia l where the f la ps w i l l not be available for examinationo r replacement for a period of years. They fe ar also , t h at pla st ic s havenot suff icient impact strength.3 . Dow Chemical Compacy sugg ests t h a t e it h e r sara n or polystyre nemight be used i f th e impact cond ition s ar e not too severe. Bowever, theylack q i n g information, and can only suggest th a t we answer t h i s quest ionby trial.6. W o n t i s samewhat doubtful of the aging char act er is t ics ofpolyethylene, as wel l as the po ssi bi l i ty of cold f low di st or t in g thevalves .7. I n view of t he se opinions, I have now concluded t h a t we havenot su f f i c i en t da t a a t t h i s time on the aging characteristics of thes emater ials t o warrant a f i e l d i n s t a l l a t i o n on a very large scale . There -

I s no proof th a t the materials would not be suitable, and I 'would n o t ,he si ta te t o chance one o f these mate rials i f we had no al t er na te, How-eve r, u n t i l the manufacturers gain more experience, th er e i s no advantagei n our press ing fo r an I ns t a l l a t i on a t t h i s t h e .


20/27

Cmpany (04881~ , m & & ~0, 1949)Letter of Janumy 5 , 1949 f rm Dow Chemlca: CompanyLet t e r of February 15, 1949, from Wo n t and Campany(10013 February 18, 1949)?

.'

1C

C


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/L- E Friont -Kern Canal

Sand orld grovel frlledt re nc h @ ~ o ' ~ f i- - - - - - - - - - - - -mortar over trans-

trenches~continuous- *- \ -~a nd nd gravel f i l led,'. trenches(cont~nuousl"I ' Layer of cernenf mort orover 6" sewer plpe droin.

y -21' - ---1-{ID f k,,..-f -c Underdroin

Alternative transversedrain with ver t ica l s ides- ' "Graded sand and graveS E C T I O N B - B( T R A N S V E R S E DRAIN)

1Unr e in fo rced ~ r o te c t i ve ood .., vc E vUnreinforced protective hood --,

Short radius 45'bends --,;"

- 1" ioye r cemen t mo r ta rF--20" -Q1j l0.t + - ~ n d e r d r a r n# . I ,-I Layer o f c

,' mortar overUnrernforced box 2'x 2-6'" concrete pipe ?nit. --JS E G T I O N A - A ' S E C T I O N A-AALJERNAJIVE SEFTIONT O U T L E T B O X - 5 0 0 ' M A X C R S A T OUTLET D O X - 50 0 PAAX.CRS. wrth vertic al sides-.'

t = 2fWh4in or centrrfuqol pipe. S E C T I O N D - Dt = 3 jm hl lnor precast plpe. (G" SEWER PIPE DRAIN)

Unre~nforced rofectrve hood - .. Unreinforced proiecfivc! hood --. 6"F lap va lve ,,FLOW, \ -=LOW '\ L ,,+-+ ---- a 4- .-A. - +.....-------.-------&-A ---- --.-'+- THIS DRAWING SUPERSEDES DWG. 214-0-14790i 1 : ,;.--" I O ~ alve

wi I II - - - ; I I I II 1 30 Precast reinforced,--.-..--------L4--1-5-a,--__ +----concrete pipe unrt - -- -8 I I I+ 6 ' - - - 216 " - - 4 6 " "

P L A N C- C P L A N E -EALrERNATlVE S E C T I O N

I U N I T E D S T A T ESD E P A R T M E N T O F TH E I N r E R l O RB U H A U OF R E C L 1 A T l O NCENTRAL VALLEY PROJECT- CALIFO RNIAI FRIANT-KERN CANAL-STA. 4646+06 TO 6076+15I CONCRETE C A N A L LINING1 U N D E R D R A I N S


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A. Electric Analogy Tray Model

W I LF - K . C A N A LB. a . Frlant Valve b . Iowa Valve c. National Cast I ron PipeValve d. Flockhart Valve e. A l l Brass Valve

FRIANT-RERN CANAL


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IN EQUATION Q = K H p L


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Flap we@ 106 pounds

COUNTERWFIGHT

ALTERED SEAT0 O n 5 0 0 a's OZO 0 25 0 0 06 0 10

DISCHARG f CFS DISCHARGE CFSA.CAPb CI1Y CU RV E. SUBMERGE0 N.C.I.P. VALVE B.CAPA ClTY CURVE S UNSUBMERGEO N.C.1.P VALVE

Flap w e ~ g h t4 0 5 pounds: ' ;Brass rod f .o; lnchesAS FURNIS HED COUNTERWEIGHT

FRIA NT V ALVE NO. 13141

- b -H.nge over C G.o i flop, Body seor os f ~ r n ~' . H~ngeover C G of f l op , i ~nch ody 5wf

DISCHARGE CFSC. CAPACITY CURVES VI~SUBYERGED N.C.I.P. VALVE WIT^ BRASS FLAP D.CAPACITY CURVES FRlANT VALVE NO. 13141

CAPACITY CURVES FO R UNDE RDRAI K F L AP V AL V E SF R I A N T - K E R N C A N A L .


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:-.2;. 1- elnforclnp dtskalnch Rubber.,:,Can01 l~ n ~n g

A.RISING DISK

Hinge dlstanc~. . . . f lelnforc~nq d ~ s k/ .f lnch RubberB.RUBBER FLAP

##hyd-257(underdrain).pdf

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