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
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
End
plug
anch
ored
togr
oun
d
Gas
oline
engi
nefo
r
tra
iler
mov
emen
t
Dis
char
geau
flet
from
zipp
ered
tubi
ng
Att
ach
men
to
fou
tle
tto
tra
iler
fro
mtw
osi
des
top
rov
ide
bala
nced
forc
efo
rsl
idin
g
Tra
iler
Mov
emen
tP
ump
disc
harg
e-
toca
ntile
vere
d
orw
he
el-
mo
un
ted
pipe
Gas
olin
een
gine
for
pum
p
Jet
and
brus
hes
for
zip
pe
rcl
eani
ng(2
pla
ces)
Ste
el-
wire
rein
forc
ed
zip
pe
red
tub
ing
Hyd
rant
FIG
UR
E1.
Tra
iler
-mo
un
ted
pum
pfo
rw
ate
rs
upp
lvfr
om
zip
pe
red
pip
eto
mo
vin
gc
anti
lev
ered
or
wh
ee
l-m
oun
ted
irri
gat
ion
pip
e.
No
teth
at
dis
char
ge
ou
tle
tof
zip
pe
red
pip
eis
fix
ed
totr
ail
era
nd
that
tub
ing
mo
ves
pa
st
ito
nm
ov
ing
the
tra
iler
.
FIG
UR
E2
.M
od
elof
zip
pe
red
pip
e.
No
teo
pen
ing
for
acco
mm
od
atin
gm
ov
ing
dis
ch
arge
ou
tlet
and
me
tal
bar
sw
ith
wir
esco
nn
ecti
ng
ou
tlet
tosl
ide
rs
on
zip
per
.T
he
reis
asl
ider
onea
chsi
de
ofth
ed
isch
arge
ou
tlet
.
Zip
per
Slid
erD
isch
arge
Ou
tlet-
--
--I-
l---
-Pr
essu
reG
age
(2pl
aces
)A
ir-
Reg
ula
ting
Va
lve
From
eof
Dis
chc
rge
Ou
tlet
Air
Sp
ace
Infl
ated
Cyl
inde
r
(2pl
aces
)
Zip
per
30
'(8
pla
ces)
Hou
sing
for
Infl
ate
dC
ylin
der
(2p l
aces
)
Flo
wD
irec
tion
~"
'I
Ste
el-
Rei
nfor
ced
Tubi
ngW
all
Wir
efo
rop
enin
g
and
clo
sing
zipp
er---
--
--"'",
FIG
UR
E3
.C
ross
secti
on
thro
ugh
disc
har
ge
outl
et
ofz
ipp
ere
dp
ipe
.N
ote
po
srt
ron
of
infl
ata
ble
cy
lin
der
sa
nd
slid
er
att
ach
men
ta
tu
pp
eran
dlo
we
r
su
rfa
ce
ofzi
pp
er.
Zip
per
iso
pe
ne
da
tri
gh
t-h
and
sid
ea
ndc
lose
da
tle
ft-h
an
dsi
de
as
the
dis
ch
arg
eo
utl
et
mo
ves
toth
eri
gh
t,a
ndv
ice
vers
a.
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
~_.
k
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 .
9
TA
BL
E1.
Co
effi
cie
nt
offr
icti
on
,,u
,of
buty
lru
bber
slid
ing
ove
rbu
tyl
rub
ber
Su r
face
Surf
ace
Dry
,In
div
idu
al
cond
itio
n,
con
dit
ion
,m
ois
t,o
rM
ea
su
rem
en
tsA
ver
ag
e
Tr
eatm
ent
Surf
ace
1S
urfa
ce2
we
tof
,uof
).l
mo
lded
mo
lded
dry
1.0
0;
0.9
0;
0.8
50
.92
2c
alen
der
edc
ale
nd
ere
dd
ry0
.80
;0
.70
;0
.70
;0
.67
0.6
0;
0.6
0;
0.6
0
3ce
llo
ph
ane
cell
op
han
ed
ry0
.64
;0
.65
;0
.35
;0
.49
cure
cu
re0
.35
;0
.47
.\ce
llo
ph
ane
cell
op
hane
we
t0
.70
;0
.70
;0
.65
;0
.73
:::>c
ure
cu
re0
.72
;0
.87
5ce
llo
ph
ane
cell
op
han
em
ois
t3
.99
;2.
00
;0
.75
;1.
42
cure
cure
2.40
;1.
25;
0.8
1;
0.7
5;
1.7
0;1.
20;
0.9
0;
0.7
5;
0.6
2;
0.8
5;
1.25
;2
.00
6ce
llo
ph
ane
cell
op
han
ed
ry0
.50
;0
.50
;0
.50
0.5
0
cu
rec
ure
,tr
eat
ed
wit
hs
ilic
on
spra
y
cel
lop
han
ec
ell
op
ha
ne
we
t0
.40
;0
.40
;0
.40
0.4
0
cure
cure
,tr
eate
d
wit
hs
ili c
on
spra
y
(Co
nih
ille
d)
TA
BL
EL
(Co
nti
nu
ed)
Surf
ace
Su
rfac
eD
ry,
Ind
ivid
ual
con
dit
ion
,co
nd
itio
n,
mo
ist,
or
Me
as
ure
me
nts
Av
era
ge
Tre
atm
ent
Su
rfac
eI
Sur
face
2w
etof
jJ.
of
jJ.
8m
old
edm
old
ed,
trea
ted
dry
0.6
0;
0.6
0;
0.6
00
.60
wit
hsi
lico
n
spra
y
9m
old
edm
old
ed,
tre
ated
wet
0.3
0;
0.3
0;
0.3
0;
0.3
1w
ith
sil
icon
0.3
5sp
ray
10m
old
ed
mo
lded
,tr
eate
dm
ois
t0
.60;
0.8
0;
0.5
0;0
.51
wit
hsi
lico
n0
.47
;0
.40
;0
.40
;sp
ray
0.4
0
11c
ell
op
ha
ne
Tefl
on
we
tor
0.2
0;
0.2
5;
0.2
5;
0.2
7c
ure
dry
0.3
0;
0.3
0;
0.3
0;
0.2
0;
0.3
5;0.
35
;
0.2
2
12m
old
edT
efl
on
wet
or0
.20
;0
.30
;0
.25
;0
.24
dry
0.2
3
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