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TECHNICAL PROGRESS REPORT NO. 1 ,10 OCTOBEH 19M A Zippered - Pipe Principle for Irrigation Water Supply BESSEL D. VAN'T WOUDT HAW AII ACIUCULTUHA L EX PEIUI\I EN T STATIO \ UNIVERSITY OF HAWAII

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TECHNICAL PROGRESS REPORT NO. 1,10 OCTOBEH 19M

A Zippered - Pipe Principle forIrrigation Water Supply

BESSEL D. VAN'T WOUDT

HAWAII ACIUCULTUHA L EX PEIUI\IENT STATIO \ UNIVERSITY OF HAWAII

TEC. HN ICA L PROGR ESS R EP ORT NO. 140 J U N E 1% ,1

II AWAII AGBI CULT liB AL I~XPElmll; : NT STA T IONCOLl"~G I<: 010' THOPICAL AGIUCULT lJHI<:

UNI VI':BSIT Y OF IIAIVAIIl lo uo lu lu , lI a waii

A Zippered - Pipe Principle forIrrigation Water Supply

BESSEl D. VAN'T WOUDT

INT HOI)UC'1'I0 N

A fe w ye ars a go t he lI awa ii Ag r icu lt ura l I'; xp er inle nt S ta t ion re c ei ve d

fed era l re s e a rc h nlo ne y viu t he Be gio na l He s e al'(;h Con lllJit te e o f t he I\'e s te r n

S tu tcs for work on fund a me nt a l us pe c ts of s pri n k le r irri ga t ion . T his o p por tu­

ni ty wa s util iz e d for s l ud yin g c crt a i n Iundu mcn tu l as pe cts o f irr igat ing by

me ans o f mo vi ng s us pen ded pi pe . T he u s pc c t wh ic h is d is c us s e d here i s

th at o f s u pp lyin g wa ter t o a mo v ing p ipe l ine .

A l pr es en t 1\\ 0 s ys te ms o f s us pe nded, movi ng liTiga ti o n p ipe a rc in f ield

us c . In o ne , u lruu in um p ip e is mount c d a t in t erval s o n whe e ls, t he pipe bein g

a t w he e l-a x le he ight or u ho ut :3 fe e t a bove th e gr o und s urfa ce . Thi s wh c e l­

moun te rl p ip e, up 10 12 0 0 fe et in len g t h , c a n be move d pe rp e nd icular ly t o it s

long axis by a t ra ct ive u n il a l t he m id d le o f t he l ine . AI pr es e n t , wa ter is

su pp li e d b)' a l la c h ing t he p ipe l in e to d ifferent h)'dran ls b y hand or b)' " hang ­

ing th e positi on o f a pn mp s upp lyin g t he l ine . Th is s ys t em IS mu in lv us ed

for pa sture irr ig a t ion .

IUr. Bt':-; Std D. ",a ll 't \\'oud t is A s si st a nt Agric ult ural J<:ll gillt~ t' r u t th e Ha wu i i A gri cu l tu ral "::0;­

p e r itue n t St atioll aud \ SSi s t il ll t l 'ro f t's s lIr or A gri c u ltura l 1' :ll girl( · t ~ r in g , Un ivers i t y of [ Iu w a i i ,

In a no the r sys te m, pipe I S ca nt ile vered, up to 150 fe et , on each side of

a ce ntra I trac tor. T he can t ile ver ed s pri nk lc r mac hines a re us ed for irr iga t ing

pi neapple on t he isla nds of ~'lo loka i a nd La na i a nd the y ha ve re ce nt ly be e n

intr od uc ed in oth e r places t oo. On rela t ivel y f lat la nd, where grade c ontro l ispos s ible, th e tractor pumps wa ter from a diteh t hrough a f lat tened foot va lve .

On ste eper land, where th e desired d itch grad e ca nnot be a tt a ined , water is

supp l ied by coiling and unc o il ing ru bbe r t ub ing a ttac hed to a fix ed hydra nt.The huge c o i ls on th e ca nt i le ver ed machin es c ou ld be e l imina ted and a n op ­

port unity c ou ld a lso be cr eate d to s upply movin g wh e e l-mounted p ipe with

water, if it were possi ble to develop a pipe w ith a movin g d is charge ou tl et,

as s uggested in figu re 1. A z ippe re d pipe, now us ed on a ircra ft ca rr ie rs forca ta pult ing plan es int o th e a ir (U. S. Navy, 1957) , has be en s ugge s te d for

th is purpos e . Th is paper re po rts on the outc ome ofa mode l study of th is pos­s ibility .

PHOCEDUHE AND HESULTS

A Goodri ch zipper No . double 450 was mou nted , by vulcan izi ng , onto th e

tw o edges (al ong the long ax is ) of a s hee t of non -reinforc ed , extruded butyl

rub be r wi th mo lded s urface . Th e s hee t ha d a t hi cknes s of 3/ 16 in ch and wa s

6 fe et lon g. On c los ing th e z ipper the s heet formed a t ube, 6 fee t lon g. Both

ends of th is tubi ng were sea le d by pl a tes and , by add ing inte rna l sea ls, th e

z ippe re d -pipe sec t ion could be s ubjec te d to hydr ostati c press ure . Th e te s tsc t-up a llo we d on ly 3 fe e t of head t o be appl ie d, a nd at thi s pre s sure the

z ippe r proved wa te rt ight. T he man ufac ture r's da ta s ho w that t he z ippe r ha s

a cross w ise s tre ng th of 225 p. s. i. (p ounds pe r sq ua re in ch) , a nd a le ng th­

wis e s tre ng th of 25 0 p.a . i . As th e z ipper has be en design ed for a irt ight sca l­

ing of a irc ra ft ca bi ne ts, an d c ons ider ing a lso th e prese nce of a rubber ov er ­la ppi ng flap a t th e ins ide of t he z ippe r , it ca n be ass umed that th e z ippe r I S

wa te rtight a t fi eld preSS llres norma lly encountered in irri gation pipe .

This z ippe r ha s tw o s lide rs ; eac h s l ide r can be pl a ced in a ny posi tion

with respe ct t o th e oth er, s o th at a n ope ning of a ny s ize ca n be made a ny

pla ce a lo ng th e length of th e tubin g (fi gure O. By me ans of four wires, th etw o zi ppe rs are ope ne d or clos ed on moving th e di s ch arge outlet. Thes e wire s

a re a ttac he d a t one e nd t o th e out le t a nd at th e other e nd to th e s lide rs ,

(fi gur e s 2 a nd 3). Tw o wires a re a ttac he d t o eac h s l ide r ; one to th e upper

s urface a nd one to the lower s urfa ce. As th e d isc ha rge out le t is mov ed alon gthe pip e, th e zipper o pe ns a head of it a nd clos es behind .

4

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Th e di s charge outl et is thus located within a n ope n ing In th e tubin g,

bUI within th is ope ni ng wa te r is dis ch arged thr ou gh th e o ut le t onl y . A s a tis ­

fa ctory fun ction in g of th e prin c ipl c of a movin g outlet is thus depend ent ona wa ters e al a t both th e upstream a nd th e d own stre am e nd of th e out le t . In th e

6 -foo t - long mode l , a n a t te mpt wa s mad e to pr ovi de such a sea l by movin g th e

tubin g wall a s hor t distan c e a way from th e outlet betw e e n a n interi or, hol­

low f iberg lass cy l inde r a nd a n exter ior, woode n cy l inde r. A lso , in a s epa rate

cx perime nt (fi gure 4) , th e tubin g wall wa s moved betwe en a n e xter ior metal

r ing with ball bea rin gs e mbe dde d a t its inte ri or pcri phcry a nd an o pposi te( int e ri or) metal cy l inde r. In both of these a tte mpt s , th e Forc e required to

move th e tubin g past th e sea l pr ov ed excess ive . On usin g a n e x ter io r a nd a ninteri or cy l inde r with ball bea rin gs opp osi te eac h other (and th e rubber mov­

ing in betwe en) , no pr oper wa ter s e u l wa s o bta ine d e vc n though th e movin gfor cc wa s much s ma lle r .

A more sa t is fac tory s o lution was found by insert ing a hollow, a lr- In­

flat cd rubber c yl ind e r (Sca l Well , Wcstern Br a s s Works) within th e tubin g.

By re gulating the ai r prc s surc w ithin t he cylind er , a good waters cal couldbe obta in cd while the c y li nde r mov ed up a nd d own th c tubin g by a pplyi ng a

for ce of a pprox imate ly :3,5 pounds (figure 4) . As two cy l indcrs are requ ircd,

onc on cac h side of th e di s ch arge outl et (fi gure :3 ) , th e total forc e to be ap­

plied t o mov e a di s ch a rge outlct through a zi ppc rc d tubing would be a ppro x­

ima te ly 70 pounds. The for ce re qu ired to ope n a nd cl os e th e z ipper is ne gli­g ib le.

To pos sibly red ucc th is [o rcc , th e eoe ffic ic nt of fri ction wa s detcrmincd

fo r rubber s l id ing ov c r (tr eated a nd un trea te d) rubbc r . Th e treat mc nts g ivc n

a nd th c rcs ults obta ine d arc sh ow n in ta bl e 1. It is no ted th at ru bbe r s l id ing

ovcr rub bcr s prayed with Tcflon s howe d the lea s t fri ct ion a nd th c lea s t var i­a b il ity in fri ct ion, whet her th e s urfaces we re dry or mo istc ne d . S il icon -s prayed

rubbe r s howe d s l ig ht ly h igh er fr ict io n tha n T eflon- s pra yed ruhbe r ,

Both the T efl on- and t he s il icon-s praye d surfaces produccd a fl e x ible

fi lm , as was e v idenced in tests on th e inflatable cy li nder. T he for ma t io n of

the fi 1m a ppe ar ed to be una ffec te d , whe n th e d ia me te r of t hc c y Iinder was

in crca s cd fr om :34 to 42 inc he s , I~i thc r of these spra ys cou ld th e re fore re'du c e

th c movin g forcc of 70 poun ds if th c fil ms coul d stand up t o wea r und er fi eldcond it io ns .

It is of intercs t to not e from tab le 1 th a t un trcated rubber s ho we d con­

s idera blc va riat ion in the coe ffi cic nt of fr ic t ion in th c prcs en cc of wate r, In

somc cases moi s t s urfn c cs s howc d more fri cti on th a n dry surfaccs . Th is ap·

peared to bc caus ed by vac uum pockc ts that de vc lop bc twc e n moist or wet,untrea ted rubber surfaces when they a re s lid ing over cac h ot he r. On s l id ing,

thcsc pocke ts nc e d be climinatcd agai ns t atmos phcr ic prcs s urc.

8

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F IG URE 4 . Mod el s tudies of wa t ers eal fo r i s ol atin g di s ch a r ge outl et from ma in b od y of z ip­

pered tub in g.

At le ft: Exterior ri ng wi th ba ll b eari ng s emb edded a t periphe ry of rin g, opposit e int eri o r

metal c yli n d er.

A t cente r: Exterior a nd in te rior me tal r in g wi th ball beari ngs opposite each othe r.

At righ t: Holl ow, in fl a t abl e cylind er us ed as seal .

While th e inflated cy l inder led to a sa tis fac tory s ea l whe neve r pre s surewithin th e rubber tubing remain ed fix ed , a ny increa s e in pres sure w ith in th etubing ca used it to ex pa nd more than th e c y l ind er did, so that th e sea l a f­ford ed by the inflated cy l inde r be cam e ineffe cti ve. Therefore, e ithe r pre s surewi th in the tubin g must be c ontro ll cd , or mat eria l for th e tu bin g wa ll must bese lec te d that is flexibl e yet ex h ibi ts littl e variat ion in diameter w ith var ia­t ion in pres sure. T hi s can be ass ure d by the us e of ru bber re inf orced with,for instan ce , ny lon fiber s .

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CONC LUSIONS

T he concl us io ns dr a wn from t he model s tud y a rc :

( I) A di s ch a rge out le t ca n be moved w it h in a z ippe re d t ub ing wit hreas ona ble for ce .

(2) T he s iz e of the dis c harge out let ca n be va rie d a t w il l.

(:3 ) A z ippe rc d t ub ing is probab ly le ak proof a t d is ta nces fro m th e out­le t , a t field pre s s ures .

(/0 T he Goodr ic h z ippe r t ested is s u ita b le, in a ge nera l way, but for

t he devel opm en t of a f ie ld model req uire s s mooth ing of the inn ers ur face .

(5) T he di s ch a rge outle t ca n be ma de leak proof by insert ing two, in­fla ted holl ow cy linde rs, one on each side of t he outlet.

(6 ) Hei nforced tu b ing , or equiva le nt mate ri al , must be s elected w it h

suff ic ie nt crosswise a nd len gth w is e strength, so tha t tbe t ub ing

s ho ws ne gli gib le vari ati on in d ia me te r wit h var iat ion in pre s s ure

wi t hin a g ive n ra nge and ca n wit hstand th e force req uired t o mov eth e tubin g pas t th e d is c harge out le t.

HEFEH EN CE

ll n it ed St a tes Na vy . 1957 . T he s te a m ca ta pu lt- it s hi story an d opera t io n.NA VA I~H 00-80 '1'-69.

UNIVERSITY OF HAWAIICOLLEGE OF TROPICA L AGRICULTURE

HAWAII AGRICULTURAL EXPERIMENT STATIONHONOLULU, HAWAII

THOMAS H. HAMILTONPres ident of th e Unive rsity

DALE N. GOODELLActing Dean of the College and

Acting Director of th e Experiment Station

GEORGE STAN FORDActing Associate Director of th e Experiment Station