The Development of High-Head Outlet Valves

DEPARRIENT OF 'llB INTERIOR
BUREAU OF REC W.IATICPJ

'ru U

~ V ~ P I ~OFNHIGK-HEAD'
T
OUTIJJT VALVIE
( ~ y d r a u l i cLaboratory Report Hyd. 240)

0

J. W. Ball, Hydraulic Engineer
and
D. J. Hebert, Hydraulic Engineer

BRANCH OF DESIGN AND CONSTRUCTION
Denver, Colorado

19Y

(prepared f o r presentation a t the 1948 meeting
of t h e Xnternatianal Asaoc i a t i o n of Hydraulic
Structures Research t o be held in Stockholm,
Sweden, June 7 t o 9, 1 9 U . )

Ensign Balanced Valve

Cavitation-erosion of Ensign Valve and

Conduit, Shoshone nam, Wyo,

Cavitation-erosion of 84-inch Needle Valve, Alcova Dam, Wyo.
I n t e r n a l Differential Needle Valve
Differential Needle Valve
Revised Needle Valve

iievised Tube Valve

Hollow-jet Valve
Hows11-Bunger Valvs
Radial Gate, Davis Dan Outlet
Jet.-flow Valve
Shasta Tube Valve
Discharge I'rom Sbasta Dam Outlet a t N f Capacity

Discharge from Shasta Dam Outlet at Half Capacity

A review of t h e developnent of vnl.ves, from t h e crude stone g a t e s
d

used over 2,000 years ago, t o the sleek modern giants wnich a r e capable

of c o n t r o l l i n g e n t h e r i v e r s , would be a f a s c i n a t h g kopfc.
c;ountries have contributed t o t h i s developnent,

Many

The United Skates has

made its contribution i n t h e phase dealing with l a r g e gates and high-

head r e g d a t i n g valves,

A brief h i s t o r i c a l review of t h e developient

of valves i n ~ a r i o u scountries would be appropriate and would serve as a
background against wnich t h e more recent developments could be viewed,
The space a l l o t t e d t h i s paper and t h e t h e a v a i l a b l e f o r i t s p ~ e p a r a k i o n
w i l l not permit an adequat 9 treatment , This paper w i l l df scuss only t f t e

developneni; of high-head outlefb valves i n t h e United S t a t e s with partic-dar
reference t o t h e work of t h e Bureau of Reclamation, and i t i s hoped that
o t h e r papers o r discussions w i l l c o n t r i b u t e m a t e r i a l covering t h e experisnce of other c o u n t r i e s ,

Conditioas requiring t h e developen* of high-

head regulating valves a r e common t o many coun%ries and it. w c d d be
m t e r e s t i n g and i n a i r u c t i v e t o compass t h e s o l ~ i t i o n swhich have been
reached,
Definition of O . ~ t l e tValve

In s p e a k b g o r writing of de-aices f o r ~ o n t ~ r o l l i nogr regulating
.A

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the flow of vrater through m o u t l e t in a dam,, t h e words *gatet3 and ttvalven

are used,

There i s soma measvwe sf confusion as t o whether the dietine-

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t i c n between gate and valve should be based on function o r design farm,

I

For t n e purpose of discussion i n t h i s paperp t h e terms =ll be used to
express function,

The term ngate,n unless q u a i i f i e d as a r e g u l a t h g gate,

used p r i n z i p a l l y t o allow t h e passage of t h e f u l l capacity of an o u t l e t
-a

o r t o shut ii, off completely.

I n a few cases, t h e term lBregulatL-lnggatett

w i l l be used t o designate a gate which performs t h e function of a va,l.~e,~
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The requirements introduced by t h e n e c e s s i t y of operating a g a t e vfider
emergency conditions, which n u s t be accommodated in a design, do not
a l t e r t h e primary function.
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f u l l y opened position.

A gate i s predominantly in a fulluUr
closed

The term "valvev1w i l l be used t o designate

a c o n t r o l l i n g device designed primarily f o r t h e purpose of regulai;ing
t h e amomt of flow through an o u t l e t from zero t o m a x i ~ ~ udischarge,
n

It, therefore, i s required t o operate a t p a r t i a l l y opened posi.tZions and

this r e q u i r m e n t i s l a r g e l y t h e c o n t r o l l i n g f a c t o r in i t s design,
Current pracbice i s t o ca1ibrat.e models of valves so t h a t t h e valves
may be used a s metering devices.
NFZD FOR HIGH-CAPACITY HIGH-HEAD OVTU3T VALVES
As t h e s i z e of dams and r e s e r v o i r s was increased

it became necessary

for economic reasons t~ design p r o j e c t s f o r m u l t i p l e use, such as flood

control, i r r i g a t i o n , power development, and river regulation for naviga+,lono Se-aeral o r a l l of t h e multiple uses of stored waters nigh& be
i t v o l ~ e din one p r o j e c t ,

The rigorous dsmands imposed by such multiple

use of a stsorage dam and reservo= required that, t h e o u t l e t s be designed

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t o give c l o s e regula5ion of t h e rate at. which

s t w e d watera be released,

Since the increase in dam height was accompanied by an increase in t h e
w

s ~ z eof o u t l e t s , many new deszgn problems were poved not only by the

higher pressures and veloci'ties, but also by t h e larger s i z e of the

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were made t o meet the challenge of new conditioss.
Regulation was obtained h some eases by providing numerous o u t l e t s
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controlled by g a t e s such a s those used jin Grand Coulee Dmm, on t h e
Columbia River.

Lhe State of Washington, where increases o r decreases

h flow could be obtained i n f i n i t e increments equal in value t o t h e

capacity of a single! outlet,. Variation Ji.n t h e value of an b.crement was
obtained by i n s t a x l i n g o u t l e t s a t d i f f e r e n t l e v e l s and t h u s d i f f e r e n t
heads.

This method was not conpletelY s a t f s i a c t o s y f o r reasons which

will be discussed nubsequently.
A more economical method of accomplishing regulatiori consisted of

providing fewer ancl l a r g e r o u t l e t s with valves which could be used t o
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r e g u l a t e t h e quantity of flow t o any required value,

The requfremen~s

of valves f o r such a use were t h a t they could be b u i l t and used in
l a r g e s i z e s (high cepacity when f u l l y opened) and could be operated
m d e r high heads and a t any opening without amage to t h e valves.

Valves which had been developed and used f o r relakively low heads,
t h a t i s , heads up t o 100 f e e t , proved t o be e n t i r e l y inadequate, expensive
t o maintain, and ofr,en dangerous when they were used f o r high heads (119,
The developnent of valves t o p = r f o m this function of regulating highcapacity high-head o u t l e t s w i l l be discussed in this paper.

W

Y EXPERIENCE %ITH BALANCED VALVES

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One of t h e f i r s t fnp~ovementsin t h e design of l a r g e o u t l e t valves
w

w a s t h a t of reducing t h e e x t e r n a l power required f o r operation"

The

f o r c e s involved were t h e hydraulic thsuat on *be skat-off element and

.

*Numbers I n parentheses r e f e r t.o bibilography a t end.

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t h e e a r l y deslgns large mechanfms, i n some cases approaching t h e s i z e of
t h e valve f t s e l f , supplied t h e power f o r operation.

In l a t e r designs,

t h e power f o r operation was obtained by supplying pressure t o s p e c i a l

compinrtments within t h e valves and u t i l i s i n g t h e shut,-of f elements as
h y d r a u l i c pistons.

known

ris

This method of. overcoming t h e hydramaliethrust i s

balancing, and t h e valves using this principle are ' h o r n as

balanced valves,

I.n general, a balanced valve i s one in which t h e

h y d r a u l i c thrust. on t h e regul.ating elemeat i s non-existent, or i s

balculced auf~omaticallyat all openings of t h e valve, making it necess a z y only t o overcome sliding f r i c t i o n t o attain d i f f e r e n t degrees of

r e g u l a t i o n o From t h i s d e f i n i t i o n it i s evident t h a t t h e term "balanssd

valveu does no* define a partied-ar type, but signifies a feature of
desilq.

A valve i s considered t o be balanced p a h i a l l y when t h e

pressures from t h e discharging f1G.d d o cot counteract completely t h e
hydra.ulic t n r u s t on the shut.-off pl?rnger.

The needle valve and :its v a r i a t i s n s , particularly t h a t know as
t h e Ehsign valve, w e d f o ~ ?
bhe prodment engineer who contrib-dted much

l;c its development, were anlong t h e f i r a t of the balanced %ypeused in
t h e Lhited Statss.

Generally, t h e needle valve xaa used a t t h e and of

,a conduit while the Ensign valve was mounisd or. the r e s e r v o i r f a c e of

a dam or pl-aced a t some intiemadiat.8 p o b % in t ~ outiet
e

tunnel.

The

Fasign valve was used most extensively In e a r l y high-head i n s t a u a t i o n s
by t h e Bureau of Reclamation,

The use of l a r g e needle valves, such as

t h e Lamer-Johnson and others, placed a t t h e ends of conduits, followed
ac

a result of difficulties experienced with t h e Ensign valve.

The Ensign valve consisted e s s e n t i a l l y of:
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a body, or. s t a t i o n a r y

bull-ring cylinder; a hollow c y l i n d r i c a l plunger having a bull r i n g a t
one end

a support r i n g

and a needle t i p with a seat r i n g at t h e other;

b

with r i b s t o support t h e body of t h e valve; and a discharge t h r o a t connected
t o a s t e e l o r concrete discharge conduit, Figure LA,
Usually t h e valve was mounted on t h e reservoir face of a dam v1it.h t h e
t h r o a t embedded in concrete and t h e discharge conduit extending t o t h e
downstream face, but i n some s p e c i a l cases it was .installed in a l a r g e
pipe o r tunnel.

In e i t h e r setting the water surrounding t h o valve flowed

between t h e sapport r i b s , past t h e seaby support, and sealing rings, onto
t h e needle-tlp surface where it was d i r e c t e d axially through t h e t h r o a t

into t h e discharge conduit.

Regulation was a t t a i n e d by varybg

p o s i t i o n of t h e cylindrf cal plunger,

the

The hydraulic t h r u s t on t h e needle

t i p was balanced by r e g u l a t i n g the pressure in 'he

chamber. at t h e back

of t h e plunger* Water reached this chamber by way of a clearance gap

a t t h e downstream end of t h e bull-ring cylinder, through t h e clearance
space between t h e plunger and tine bull-ring

cylinder,

The pressure a$

i;he back of t h e plunger for any opening was r e g u l a ~ e de i t h e r by an

ordinary valve and d r a m pipe or a s p e c i a l device co,mected through
t h e closed end of t h e bull-ring z y l h d e x ,

..

With sufficient pressure

at t h e clearance gap, it would be possible t o move the plunger in either
direction by c o n t r o l l i n g the flow tnrough t h e drain l i n e
special c o n t r o l device,

OP

r e s e t t i n g %he

Increasing t h e fiw though the drain lowered

w

t h e operating presswe and opened t h e valve while decr-sasbg the flow

ralsed t h e pressuw and d o s e d I;,

This system waa effective for opn!ng

movement of t h e plunger,
Y

I f for any reason t h e plunger should start t o

close, t h e movement would withdraw the resistance tube from t h e recess

in back of the plunger.

The r e s u l t i n g reduction in t h e flow in t h e drain

I

passage would lower t h e pressure in t h e cylindsr and check t h e closing
movment.

Although of simple and apparent sound design, t h e d.evice

proved unreliable i n practice and only by careful manipulatiorl of t h e
control valve was it possible t o a t t a i n even approximatte regulation of
t h e flow.

Apparently the point of balance was not well-defined and

s n a l l accumulations of sediment in t h e clearance gap around t h e b u l l
ring, in t h e control tube i t s e l f , o r t h e control valve, r e s u e d in an
unbalancing of forces which caused movement of t h e valve pluiger.

The

use of the resistance tube control was abandoned in l a t e r h s . t a l l a t i o n s
because of these d i f f i c u l t i e s , and a new devics known as t h e sleeve control

was developed t o replace it, Figure 1 C ,

The sleeve c0nt.x-01 received i t s name from a peculiarity of i t s
design.

A movable tubs or sleeve within t h e control pipe was attached

t o t h e back of the cylinder,
be extended into

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This externally controlled sleeve could

retracted f r o m t h e cylinder, against or away from

a special seat. attached t o the back of t n e valve plunger,

The withdrawal

of t h e sleeve from t h e seat fzcreased t h e flow from t h e back of t h e valt-e
plunger, reduced the pressure, and allowed t h e hydraulic thrust
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on %ha

plunger i;fp t o open t h e valve,. As t h e valve opened, t h e seat again
approached t h e end of the sleeve, decreased t h e flow, increased t h e

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pressure in t h e cylinder, and again balanced t h e hydraulic t h w t on
t h e piunger t i p .

The plunger stopped a t a pint w h e ~ et h e space between

Closure

cylinder just balanced the h y d r a u c f o r c e s on t h e plunger t i p .

of t h e valve was accomy~lishedby oxtending t h e sleeve toward t h e s e a t ,.

This control proved so successfuZ that, ' h e principle, with s l i g h t
v a r i a t i o n s and improv'ements, has been adapted t o many of t h e more recent
c o n t r o l devices.

The development of t h i s c o n t r o l took place during t h e

period from 1909 t o 1923, when t h e Ensign valve was being used f o r Bureau

of Reclamation projects.
Cavftat ion Erosior~
Operation o f ' t h e valves during t h e same period disclosed another and
more serious prdblem.

Sevepal high-pressure o u t l e t s t r u c t u r e s , designed

by t h e Bureau of Reclamation in t h e e a r l y part of t h e twentieth century,

were provided w i t h 58-inch Eqsign balarice valves f o r flow regulation.
The o u t l e t s at, t h e Roosevelt Dam in Arizona, t h e Arrowrock Dam i n Idaho?
t h e Pathfinder and Shoshoae Dams in 'LYyomlng, and the Elephant Butte Dam

in New Mexica are t y p i c a l i n s t a l l a t i o n s .

The o u t l e t s were s i m i l a r l y

arranged with t h e valves placed on o r near t h e ups+,ream f a c e s of %he dams,

I n a l l cases t h e valves discharged into t h e o u t l e t conduits.

After short

periods of operation, par%fcuiarly where t h e head was in excess of 100
f e e t , inspection revealed considerabie damage t a t h e needle tips and to
t h e t h r o a t liners and discharge conduits immediately downstream,

The

damage was s o severe i n many cases, a s shown i n Figure 2, t h a t it Ha?

considered dangerous t.o continue operation of t h e o u t l e t facilities,

It was recognfzed t h a t the destruction was in some way connected
with the presence of low a b s o l u t e pressures (high var=uums). The t a m
llcavita$ion'l was actually used to describe erosion instead of t h e

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Many attempts were made t o
b

effective.

eliminate or minimize the damage but few were

A t first, the o u t l e t s were maintained by replacing c e r t a i n

damaged p a r t s o r by patching t h e p i t t e d areas.

The concrete surfaces

a

were chipped and the holes f i l l e d with various concrete mortars, while
t h e p i t s i n t h e metal surfaces were f i l l e d w i t h a material eonsistfng

of powdered iron, ammonium chloride, and sulphur, known a s ttsmooth-on.lt
The l a t t e r proved unsatisfactory and arc-welding various metals i n t o
t h e c a v i t i e s was t r f ed.

With few exceptions, th6 patches eroded more

rapidly than t h e parent materials.

When it was realized t h a t t h e p i t t i n g

was connected with sub-atmospheric pressures, attempts were made t o
eliminate them,

Concrete l i n e r s of various shapes and s i z e s were placed

in t h e conduits below the valves t o reduce t h e j e t expansion and fhus
r a i s e t h e pressures.

When t h e l i n e r s were of s u f f i c i e n t thickness and

emended t o t h e end of the discharge conduit, no damage occurrred when
the vzlve operated

2t

full capacity.

The l i n e r s wer'e h e f f e c t i v e a t

p a r t i a l openings.

The p o s s i b i l i t i e s of relieving t h e sub-atmospheric

pressures by introducing a i r ware a l s o explored,

Several venting

arrangements were t r i e d with l i t t l e success because they were illpropzrly
locatedo After %he apparent f a i l u r e of most of these attempts, t h e
o u t l e t s were operated a s l i t t l e a s possible,

A s t h e multiple use of stored waters increased, it became more =d
more d i f f i c u l t t o avoid unrestricted use of t h e valves,

A method f o r

avoiding some of thr; restrict.ions w a s devised a s a r e s u l t of model
1

studies of the Shoshone o u t l e t .

These studies established t h a t most of

t h e damage resulted from operation within a fairly we12 dafined zone,

Iln operational schedule avoiding t h e c r i t f c a l < v a l v e settings has helped.

valve with a re-designed needle and vent system, a s shown i n Figure 18,
have indicated t h a t i f e x i s t i n g Ensign valves a r e a l t e r e d t o conform,
they could be operated without r e s t r i c t i o n .

These a l t e r a t i o n s would

be ccnsidered only f o r e x i s t i n g valves since t h e Ensign valve has been
long abandoned f o r o t h e r reasons, such as cost and i n a c c e s s i b i l i t y .

DEVELOPlJiETiT OF IJFEDLE AIJD TUBE: VALVES
Since the valves i n s t a l l e d a t t h e dam faces or i n t h e conduits were
subject t a serious damage, t h e design of o u t l e t s was revised t o that of
needle valves placed a t the downstream end of t n e conduit,

Large balanced

needle valves were undergoing developnent about t h e time t h e t r o u b l e was
experienced % + t h t h e Ensigr. valve, and the Bureau of Reclamation began
using them i n s t r ~ c t u r e sb u i l t i n t h c e a r l y 19201s,
Meedle Valves
A needle valve (2) usually c o n s i s t a of an outer s h e l l , o r body, a

s t a t i o n a r y cylinder supported on ribs or vanes; and a closing o r regulati n g element telescoping e i t h e r i n s i d e o r outsides t h s skationary cylinder,

Figure 4,

I n t h e case of a balanced valve, provision i s made f o r

~ e g u l a ~ i nt hge pressure i n chambers behind the plunger,
I'lany of t h e e a r l y need15 valves were q u i t e l a r g e f o r t h e amount of
water handled a ~ most
d
of them were s a t i s f a c t o r y f o r operafiori a t moderate

heads with r e s p e c t t o c a v i t a t i o n erosion.

~ c n s i d s r a t i o nof coat and s i z e

stimulated changes in design direc'c.ed toward reducing t h e weight. pe;
second-foot of water handled,

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An appreciable r e d u c t i o ? ~I n t h e s i z e of

t h e valve proper was accomplished by eliminating t h e annular external.
r i n g around t h e plunge^,

h addition t h e introduction of balancing

.

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A design i n c o r p o ~ a t i n gt h e s e changes r e s u l t e d i n

t h e o v e r a l l length,

a valve known a s the i n t e r n a l d i f f e r e n t i a l needle valve, Figure k ,
Movement of t h e plunger was accomplished by manipala.ting the
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pressures in t h e chambers i n s i d e the valve,

The pressure i n t h e i n t e r -

connected Chambers A and C was regulated by varying the c a p a c i t y of a
drain i n t h e needle with a manually controlled s l i d e valve,

I

Pressure

i n Chamber B, wh?-ch was connected t o the conduit, remained fixed.
Leakage i n t o and from the c h m t e r s through various clearances prevented
operation of t h e control a s intended,

The difficu1,tLes were corrected
I

by separati& Ckmbers A and C and c o n t r o l l i n g t h e pressure i? Chamber B
a s well a s that

1

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Chamber C ,

fixed c a p a c i t y d r a i n ,

In addit.ion Chambe?

A was connected t o a

The multiported c o n t r o l de-cce f o r accomplishing

t h e required chamber pressures was known as t,he paradox z c n t r o l and it
was a f f i x e d t o t h e bottom of t h e valve,

A separate water shpply l i n e

was brought t o t h e paradox s o n t r o l and t h i s permitted hydraulic
operation of t h e valve i n the absence of water is-. t h e conduit,.

Further changes i n t h e valvs, ~ n c l i i d i n ga u j o r r-carraagment of
t h e components resulted i n a valve h o r n a s the i n % e r i o r d i f f e r e n t i a l
needle valve,

The p r i n c i p a l change, a s shown i n Figure

5,

w a s a revision

i n the method o'f supporting t h e plunger which p r m i t t e d t h e use of a

.

needle t.elescoping aver t h e fixed cylinder instead of inside, Thia
permitted t h e use of a m a i l e r diameter and reduced the overall diameter
and length of t h e valve,

The change resulr.ed i n a saving of about 25

percent, ifi valve weight,

No basic change was made i n t h e c o n t r o l

d

proportioning of the water passages was accomplished by using a technique
known a s a r e a shaping,

Area shaping consisted of proportionfng t h e flow

passages i n such a way t h a t the a r e a normal t o flow v a r i e d with l o c a t i o n
according t o some predetermined r a t e ,

I n general, t h e a r e a was held

In t h i s portion

constant except f o r t h e downstream portion of t h e valve,
the a r e a was decreased according t o some smooth curve,

Usually t h e

r a t i o of discharge t o a r e a , o r mean v e l o c i t y , was p l o t t e d against
d i s t a n c e from a reference point f o r Cne ?ally op9n p o s i t i o n anlg,
This p l o t provided a means of judging t h e design; a smooth r,ur"re5 w i t h

no r e v e r s a l s , being t h e c r i t e r i o n of good design,

The procedure,

however, d i d not take i n t o account the e f f e c t of c u r v i l i n e a r flow or
i o c a l high v e l o c i t i e s , or t h e nature of the area shaping curve a t
openings o t h e r thar, 100 percent, t h u s its trse d i d zot always assllre
a s a t i s f a c t o r y design.

The water passages of some of t h e f i r s t designs

prepared using t h i s procedu.re contained comparatively abrupt curves
and s l i g h t l y divergent boundaries a t t h e downstream ends of the valve3
f o r c e r t a i a positions ~f t h e r e g u l a t i n g plunger, Figure 4,

The valves

operated smoothly regardiess of t h e s e c h a r a c t e r i s t i c s u n t i l they were
subjected t o nigh heads.

The discharge c o e f f i c i e n t was 0,54 based on

the t o t a l head immediateiy upstream and t h e a r e a of a conduit with a
diameter i,2 times t h a t of t h e valve exit,
Severe subatmospheric pressnreo occurred just downstream from t h e

.

curved boundaries and i n t h e secti0r.s where t h e bo~u'dariesdiverged,
when t h e s e valves were opepated under nigh heads,

As a result, tnere

was nuch damage t o t h e botmdary surface due t o c a v i t a t i o n , Figzre 3,
I

a t Hoover Dam on the Colorado River and t h e Alcova Dam on t h e North
P l a t t e River in Wyoming,

The damage t o t h e valves a t t h e s e p r o j e c t s

motivated a program of model t e s t s tihich revealed the source of t h e
P

cavitation-erosion and provided i n f o m a t i o n f o r r e v i s i n g t h e shape of
the boundary s u r f a c e s t o eliminate it ( 3 ) ,

A 6-inch model was used

f o r t h e i n i t i a l ssudies which e s t a b l i s h e d t h a t t h e improvement would
be made a t t h e expense of capscity, reducing it about 1'7 percent,

The

discharge c o e f f i c i e n t of the design shown in F i ~ r 6e w z s 0,59 based on
t h e t o t a l head ao)i a r e a one diameter upstream from t h e valve, or 0,45
based on t h e t o t a l head and the a r e a of a conduit L,2 t h s s that. of the
valve f o r comparison with the c o e f f i c i e n t of the previotrs design,

The

model served a l s o t o demonstrate t h e d e f e c t s of the area-shaping procedure and helped to introduce t h e flow n e t as a t o o l f o r studying the
d e t a i l s of flow i n t h e passages,

To d e m o n s t ~ a t e%hat t h e improvemen%

was r e a i , two small valves, one patterned a f t e r t h e i n i t i a l design, Flgure
and t h e other shaped to include t h e d e s i r a b l e features i n d i c a t e d by t e s t s

on t h e 6-inch model, Figure 6, were t e s t e d uader heads c p t.o 550 f e e t ,
Both valves were operated at. t h e most c r i t i c a l openings i n d i c a t e d by t h e

initial model tests.

Cavitation erosion of appreciable extent was noted

withrn 6 days on t h e o r i g i n a i design, whereas there was no sip of erosior?
on the revised design a f t e r

84 days of pera at ion,

A t e s t i n g program was planned w i t ' i t h e objective of r e a l i z i n g t h e
o p t i r m balance among t h e f a c t o r s of s i z e , c o s t , .zapa,citp, jet s%abilfty,
and freedom from c a v i t a t i o n e r o s i o n ,

& f a r e such

6

program was i n i t i a t e d

4,

more economical types of valves which w i l l be discussed l a t e r ,

.

Tube Valves

A reduction i n t h e weight of t h e needle valve as well a s a reduction
1.r.

the operating power was realized by s u b s t i t u t i n g a tube f o r t h e needle

pltmger,

There were t m reasons f o r using the tube, from which t h e valve

received its name, tube valve (2).

First,, it eliminated part of t.he area

of t h e needle that was subject t o cavitation-erosion,

and secondly, it

reduced t h e hydraulic t h r u s t against which the valve had t o be operated,
The p r o f i l e of i t s flow passage, designed t o prevent. negative pressures,
wzs determined through model t e e t s and a ratio diagram established,
Figure 7,

The discharge c o e f f i c i e n t of t h i s valve w a s 0.52 based on

t h e t o t a l head and a r e a one diameter upstre'm

from t h e valve,

T'ne par-

formance of t h e tube valve with respect t o j e t s t a b i l i s y ar?d cavitation-.
erosion was indistinguishable from t h a t of t h e revised needle valve
except f o r openings less than 30 percent,,

A t openings l e s s than

30 percent t h e r e was a f l u t t e r i n g of t h e Set which w a s due to t h o

absscce c . f t h e st.abilLzing inflrldnce of the needle tip,
was used

The design

i n a few i n s t a l l a t i o n s where this unstable s h a r a c t e r i s t i c at

sml.1 openings cotlld be t o i e r a t e d .

This type of valve was operated

mechanically by means of a large screw geared within the fixed up-

stream cone and ext.ending do~mstr.eamthrough a tube nut; i n t h e spider
%

attached to the tcbe plunger,
A tube valve designed specifically f o r i n s t a l l a t i o n i n the 0ct1et

I

conduits of Shasta Dam on t h e Sacrantento b v e r 1.n Californiz w i l l be
described l a t e r under t h e heading of ''Valves i n Conduits,!"

The demand f o r a f u r t h e r decrease i n the c o s t - d i s c h a ~ g e r a t i o prompted

.

t h e Bureau of Reclamation t o i n i t i a t e a program of valve deveiopnent which

has conkinued i n t e r m i t t e n t l y f o r t h e past 8 years with much success,

Onc

L

of t h e most notable accomplishments during t h i s period has been t h e
d e v e l o p o n t of t h e hollow-jet valve, a regulating control f o r usc
exclusively a t t h e end of an o u t l e t conduit, which not only welghs l e s s
than t h e tube valve but discharges about 35 percent more water,

--

Hollow-jet, Valve

The hollow-jet valve (4) i s e s s e n t i a l l y a needle valve with t h e needJ.e,
o r closure element, pointed upstream and t h e nozzle o r downstream end of
t h e body eliminated a s shown by the r a t i o diagram i n Figure 8.

Water

discharges from t h e s h o r t bell-shaped body i n a t,ubular, or hoilow-jet,
t h e outside diameter of &ich remains unchanged regardless of t h e valve
opening,

The jet leaves t h e valve with very l i t t l e dispersion a t any

opening, but the e f f e c t of t h e hollow form i s to d i s t r i b u t e t h e energy
over a c o m p a r a t i v e l y l a r g e Ires, f a c i l i t a t i n g its dissipa5ion and
lessening t h e destructive a c t i o n i n a sti-g

pool,

.-

c.

The c o e f f i c i e n t

of discharge f o r f u l l valve opening i s 6.70, based on t o t a l head and
area one diameter upstream from the vaive.

The proportions of t h e

water passage through the valve t o prevent subatmospheric pressure and
c a v i t a t i o n were evolved from extensive l a b o r a t o r y t e s t s using aerodynamic
9

and h y d r a u 5 c models.

rllso, t h e t e s t s indicated that an increase of

3-1/2 percent i n capacity could be obtained by increasing t h e t r a v e l of
t h e shut-off plunger 5-1/2 percent.

Although t h e pressures on t h e

plunger and body near the scat were decreased by t h i s change, t h e y

o p e r a t ~ si n t h e f u l l y open position, thus a f u r t h e r increase in t r a v e l
t o allow s l i g h t negative pressures i n t h e valve might riot be objectionable,

A t present, this valve is designed t o be operated mechanically with t h e
a s s i s t a n c e of p a r t i a l balancing.

Complete balance was not a t t a i n a b l e

without apecia1 f a c i l i t i e s e x t e r n a l t o t h e valve, but p a r t i a l balance,
within 13 percent g r e a t e r o r l e s s e r than t h e t o t a l hydraulic t h r u s t ,
a t t a i n e d by providing fixed openings i n t h e face of the needle of
t h e shut-off plunger,

Pressure from t h e flowing water i s transmitted

t o t h e i n n e r compartlnent by way of t h e fixed openings t o counteract the
hydraulic force on t h e needle t i p ,

The c o r r e c t l o c a t i o n of t h e openings

w a s established through t e s t s on 6-inch and 24-inch valves t o give t h e

mininnun unbalanced force.

A desirable c h a r a c t e r i s t i c of t h e hollow- j e t

valve i s t h e f a c t t h a t the body s h e l l downstream from t h e s e a t i s never
subjected t o r e s e m o i r head, and need not be a s heavy a s a needle o r
tube valve.

I n addition, t h e valve has been arranged t o f a c i l i t a t e

removal of a l l mechanical p a r t s h i c h might require maintenance.

The

e n t i r e needle assembly which contains t h e operating mechanism m y be
removed without d i s t u r b i n g the s h e l l .

Large castings and cofisidcrable

machining are required a d t h e design i s undergoing f u r t h e r investigat i o n s involving a re-shaping of the water passages and changes which will

permit f a b r i c a t i o n of t h e main p a r t s of t h e valve by welding r o l l e d s t e e l
plates.

.

Ilowell-Bun~er Valve
Although t h e Iiollow-jet valve has replaced most other types f o r
i n s t a l l a t i o n a t t h e , e n d s of o u t l e t conduits in E3ureau of IEeclrunation

balanced valve of simple design a d lightweight, construction, patented
under t h e name of Howell-Bunger

(5), has been used i n several structures.

It,has a discharge c o e f f i c i e n t of 0.85 based on t o t a l head and a r e a one
diameter upstream from t h e valve,

The valve c o n s i s t s of a s e c t i o n of

pipe having a 90-degree cone and valve s e a t attached t o the downstream
end by a spider of r i b s o r vanes; a s l i d i n g closure cylinder telescoping
on t h e outside of t h e pipe section and outer surface of t h e bibs, which
closes against t h e s e a t on t h e cone; arxl an operating mechanism consisting
of a system of s h a f t s and gears, Figure 9 ,

! a t e r passes through the space

between t h e r i b s and discharges outward between t h e downstream edge of the
closure cylinder and the s e a t cone,
a cone with t h e apex d t h i n

The discharging j e t has the shape of

the valve.

Because of t h i s c h a r a c t e r i s t i c ,

t h e valve is best adapted t o conditions where t h e confinement of t h e j e t
and excessive spray a r e not important considerations,

The valve has not

been used extensively i n t h e United States. because most s t r u c t u r e s
include f a c i l i t i e s f o r t h e generation of power and such j e t conditions
a r e undesirable *ere

exposed e l e c t r i c a l equipment i s involved.

I n some

applications the unruly J e t has been contained by concrete walls which
added appreciably t o the cost of t h e valve insta;llation.

The possi-

b i l i t y of improving t h e q u a l i t y of t h e j e t by a t t a c h i n g t h e simple
f a b r i c a t e d hood shorn i n Figuya 9 has been investigated by model t e s t s ,
Tests have shown t h a t unless the hood i s vented adequately a t i t s
upstream end c a v i t a t i o n pressures a r e induced on c e r t a i n p a r t s of t h e
valve and hood,

The hood a l s o introduced a hydraulic t h r u s t which

unbalanced t h e valve and added tremendously'to the power required t o

7
.

i n t e n s e v i b r a t i o n i n t h i s design f o r t h e higher heads has required
excessive bracing and s t i f f e n i n g ,

Moreover, t h e addition of a hood

increased t h e cost t o an amount comparable t o t h a t of other valves,
Where t h e q u a l i t y of t h e j e t i s not an important consideration, t h e
Iiowell-Bunger valve, without t h e hood, i s an economical, high-capacity
control device,
The Butterfly Valve
T h e ' b u t t e r f l y valve (2), used p r i n c i p a l l y f o r closure of power
penstocks, has been adapted as a regulating control a t t h e end of l a r g e
o u t l e t conduits i n a limited number of cases i n t h e United States.

The

b u t t e r f l y valve, deriving i t s name from t h e shape of t h e shut-off element,
i s e s s e n t i a l l y a s h o r t tube containing a f l a t c i r c u l a r l e a f which i s

rotated, by a n e x t i r n a l rnechanisxx~, about a diametrical axis of t h e tube
t o a t t a i n regulation,
The d e t a i l s of b u t t e r f l y valves vary according t o t h e manufacturers
who design, construct, and s e l l them.

A l l of them operatc on t h e sane

basic principle and t h u s the discussion which follows i s applicable
generally,

A dispersion of t h e discharging . j e t a t small openings ard

t h e presence of excessive spray make t h e b u t t e r f l y valve objectionable
f o r most f r e e discharge i n s t a l l a t i o n s ,

This objectionable c h a r a c t e r i s t i c

m y be minimized by t h e use of a hood o r a s p e c i a l confining s t r u c t u r e
containing adequate a e r a t i o n f a c i l i t i e s .

The addition of such a u x i l i a r y

f e a t u r e s add t o t h e c o s t of a valve i n s t a l l a t i o n ,

The capacity of t h i s

valve i s low compared with the newer valves of t h e same size.

The dis-

charpe c o e f f i c i e n t f o r t h e designa intwhich t h e valve diameter i s the

valve, c a v i t a t i o n on t h e downstream surfaces of t h e balve l e a f i s a
d e f i n i t e p o v s i b i l i t y when it i s operated near the wide-open position
and a t high heads.

This i s due t o t h e shape of t h e c i r c u l a r l e a f , which

i s q u i t e t h i c k on t h e axis containing t h e pivot s h a f t a d decreases i n
thickness from t h i s a x i s t o i t s o u t e r circumferenca,

Near t h e wide-open

position, t h e l e a f presents a shape s i m i l a r t o an a i r f o i l which causes
a l o c a l zone of intense subatmospheric Fressure and cavitation.
The R e g u l a t i n ~Radial Gate
The r a d i a l gate and i t s v a r i a t i o n s have been us& extensively f o r
c o n t r o l l i n g t h e flow i n spillways and t h e flow from l a r g e o u t l e t s under
low heads,

In 1944 a r a d i a l gate was designed by the Wlreau of Reclamation

f o r use i n a conduit t o c o n t r o l t h e flow

frbm

i n Davis Dam on t h e Colorado ,%ver, Figure 10,

t h e l a r g e high-head o u t l e t s
S t t ~ d i e son a 1 t o 30 scale

model (6) of a g a t e and o u t l e t indicated t h a i t h e r a d i a l g a t e was s u i t a b l e
f o r such use,
position,

The gate offered no r e s i s t a n c e t o flow a t t h e f u l l y opened

Therefore, t h e discharge c o e f f i c i e n t of 0,90 r e s u l t e d from

t h e design of conduit upstream.

There was no measurable v i b r a t i o n and

t h e flow was smooth a t a l l openings,

Although t h e Davis Dam i s i n t h e

construction stage and it w i l l be many months before t h e o u t l e t s w i l l
be placed i n operation, it i s t h e consensus t h a t t h e design has excellent
possibilities,

However, t h e p r ~ b l e mof s e a l i n g r a d i a l g a t e s under high

-heads has not been s a t i s f a c t o r i l y solved.

The samc problem e x i s t s in

t h e case of c o a s t e r gates and r i n g s e a l gates,

The s e a l design now being

used most extensively, t h e so-called music-note s e a l , i s n o t e n t i r e l y
satisfactory,

Tests a r e now being conducted by d i f f e r e n t organizations

t o obtain a s o l u t i o n t o t h e problem,

One of t h e most recent developments i n valves, regulating the flow

-

from l a r g e high-head o u t l e t s , - i s one known a t t h e present,time a s t h e
jet-flow pate o r valve (7).

It was developed by the Wlrsau of Reclamation

for use i n the intermediate and upper t i e r s of o u t l e t s i n Shasta Dam in
C;tlifornia *en

t h e s p e c i a l tube valve developed previously f o r t h i s

purpose and used i n t h e lower t i e r proved t o be t o o costly.

The valve

c o n s i s t s of a s l i d e g z t e i n a s p e c i a l h m s i i ~ ghaving an o r i f i c e a t the
upstream side, and a c i r c u l a r , rectangular, or horseshoe opening a t the
downstream s i d e ,

It was designed t o fit a conduit with a diameter lo?

times t h e diameter of t h e o r i f ice.

A s shown i n Figure

ll,t h e required

s i z e of conduit a t t h i s point may be obtained by expanding from a smaller
conduit i n an easy t r a n s i t i o n ,

The conduit downstream may be of any
(P

desired shape, so long a s a s a t i s f a c t o r y t r a n s i t i o n i s made and an
adequate vent sys-tiem i s provided t o a e r a t e t h e j e t a t p:i%ial
The

openings.

vent in^ system show1 i n t h e f i g u r e i s an adaptation t o conditions

i n t h e Shasta o u t l e t where t h e expander and t h e vent conduit were

-

a l r e a d y i n s t a l l e d when t h e valve type was changed,
s t r a t e the marked reduction i n valve s i z e ,

It serves t o demon-

I n a new i n s t a l l a t i o n t h e

vent system would be Inore simply designed t o d e l i v e r a i r a t a point
immediately downstream from t h e gate.

.

,

The unique f e a t u r e of t h e valve i s t h e use of a c a r e f u l l y planned
j e t contraction,

A s water flows frm t h e l a r g e r conduit through the

o r i f i c e a contraction of t h e j e t around i t s e n t i r e periphery is produced
Y

1

a t any opening.

I

This permits c m p l e t e v e n t i l a t i o n of t h e ,jet and

I

/

eliminates flow i n t o tte gate grooves which i s t h e u s u a l s m c e af d-ge

and v i b r a t i o n i n the case of a s l i d e gate,

remains i n contact with a s p e c i a l s e a l contained i n t h e o r i f i c e s i d e of
t h e valve housing,

Sealing a t t h e upctream face v i r t u a l l y eliminates

t h e hydraulic downpull fame so troublesome i n gate valves with t h e
conventional downstream s e a l ,

The proportions of +,.his valve were

established through extensive t e s t s on a 6-inch model under heads up
t o 350 f e e t t o insure against cavitation-erosion.

The valve i s of

simple construction, i s capable of operating a t any opening, and has a
r e l a t i v e l y high capacity,

The discharge c o e f f i c i e n t i s about 0.80 f o r

t h e f u l l y open position, based on t o t a l head i n and the a r e a of a conduit
with a diameter equal t o t h a t of t h e valve o r i f i c e ,

The f i r s t valves

of t h i s design have been placed I n operation very r e c e n t l y a t Shasta
Dam and u n o f f i c i a l r e p o r t s i n d i c a t e t h a t the design promises t o be one
of t h e best used by the h r e a u of Reclamation f o r regulating t h e flow
from l a r g e high-head o u t l e t s .

The Shasta valves operdted 1 6 t h very

l i t t l e back pressure so t h e s u i t a b i l i t y of the valve i n o u t l e t s with
high back pressure i s s t i l l open t o question,

Its adaptability f o r

t h e l a t t e r type of instsll.ation w i l l no doubt be explored i n t h e f u t u r e

when i t s use under these conditions i s desired,

The possible use of t h e jet-flow valve f o r adaptation t o f r e e
discharge conditions was a l s o studied i n t h e model,

The J e t was rough

compared t o those of t h e needle and hollow-jet valves and f o r i n s t a l l a t i o n s requiring a well-contained j e t plunging i n t o a pool it would be
d e f i n i t e l y i n f e r i o r except f o r s p e c i a l cases with unusually large,
i s o l a t e d pools,

However, it d i d show promise f o r i n s t a l l a t i o n s where

i+,
would discharge tangentially ontr? an apron because i t s shape was

roughly rectangular.
21

The usual cylinder g a t e i n s t a l l a t i o n c o n s i s t s of a concrete tower
s t r u c t u r e located i n t h e r e s e r v o i r and one o r more cylinder g a t e s h i c h

.

s l i d e up and d o h over openings through t h e w a l l of t h e tower t o regulate
t h e o u t l e t discharge,

The g a t e has been used i n a limited number of

Bureau of Reclamation s t r u c t u r e s t o regulate t h e release of wat.er from
r e s e r v o i r s (1).

The design gave very s a t i s f a c t o r y service under low

heads, but trouble was experienced with cavitation-erosion at, higher
heads.

It has been possible however t o eliminate the ei-osion by making

minor changes i n design,
i t s inaccessibility,

The main disadvantage of t h e cylinder gate i s

The l a r g e tower s t r u c t u r e and d i f f i c u l t y of a e r a t i o n

might be considered disadvantageous a l s o .
Plug Valve
The plug valve i s e s s e n t i a l l y a cone-shaped plug which f i t s snugly
i n t o a housing,

A hole through t h e plug, perpendicular t o i t s axis,

forms a passage which connects two openings i n t h e housing or body of
t h e valve.

A 90-degree r o t a t i o n of t h e plug c l o s e s or opens the passage.

Although used extensively f o r sma31 l i n e s , o r where three-way or fourway i n s t a l l a t i o n s a r e required and where regulz t i o n i s unnecessary, t h e
plug valve has been adapted as a regulating device f o r the o u t l e t s i n

a few American i n s t a l l a t i o n s .

In most of these cases t h e valve was

placed a t t h e downstream end of t h e o u t l e t conduit and discharged i n t o
t h e atmosphere.

The discharging jet disperses widely a t p a r t i a l

openings making it necessary t o provide a confining s t r u c t u r e whea
t h i s condition cannot be t o l e r a t e d ,

The water passage f o r partial

opening contains abrupt changes i n t h e boundary surfaces which are

1
I

cavitation,

I

Special venting systems have been provided t o a e r a t e

some of these zones but i t i s questionable i f t h e problem has been
solved s a t i sf a c t o r i l y , The plug 'valve merits consideration because
of i t s high discharge capacity,

The c o e f f i c i e n t of discharge f o r the

fully open positon i s nearly unity,
INSTALLATION GF OUTLET VALVES I N A CONDUIT

The e a r l y experience of the Bureau of Reclamation with valves
i n s t a l l e d a t t h e beginning of o u t l e t s using Ensign valves was discouraging,

Some of t h e troubles which were experienced have been described

previously,

Damage t o t h e valves and conduits r e s u l t e d i n a departure

from t h e practice of using valves a t the entrance of conduits,

Insteadp

t h e l a r g e r valves operating under high heads were placed a t the ends of
conduits and discharged f r e e l y i n t o t h e atmosphere.

The design of such

o u t l e t s was more complicated and the longer conduits required t o bring
t h e o u t l e t s t o a s u i t a b l e position f o r i n s t a l l a t i o n of f r e e discharge
valves added t o t h e i r cost,

However, t h e higher costs appeared t o be

j u s t i f i e d by the more trouble-free operation.
During t h e past 1 0 years t h e r e has been a trend towards returning

II

t o the p r a c t i c e of placing regulating valves near the entrance t o an
outlet,

The most important s i n g l e advantage of i n s t a l l i n g a c o n t r o l

valve near the beginning of an o u t l e t i s t h e f a c t t h a t only t h a t portion
of t h e conduit upstream from the valve i s under f u l l r e s e r v o i r pressure
during shutoff,

The conduit downstreani from t h e valve i s subjected t o

only nominal pressures r e s u l t i n g from f r i c t i o n a l l o s s e s and back pressure
from any construction a t the end of t h e o u t l e t ,

The cost b e n e f i t s that

accrue t o a g r e a t e r o r l e s s p r degree depending on t h e t y p e of dam.
as t h e eliminating of emergency gate9

Other possible advantages

and t h e shortening of o u t l e t s , as well a s possible disadvantages such a s
i n a c c e s s i b i l i t y and venting d i f f i c u l t i e s , a r e s u b j e c t t o diverging
opinion and w i l l not be discussed.
I n some cases t h e free-discharge valves were replaced by r i n g
f o l l u w e ~g a t e s placed near t h e upstream ends of t h e o u t l e t s .

Operation

of these gates was r e s t r i c t e d t o t h e fully opened o r closed positions.
An arrangement of t h i s t y p s was used f o r Grand Coulee Dam.

The o u t l e t s

were placed a t three d i f f e r e n t l e v e l s separated by a p p r ~ x i m a t e l y100 f e e t .
There were 20 outlet.? i n each t i e r arranged i n

19

pairs,

The l a r g e number

of o u t l e t s , sixty, and t h e f a c t t h a t they were s u b j e c t t o three d f f f e r e c t
heads permitted regulation by r e i a t i v e l y small increments.

Each o u t l e t

was provided with two gataes s i m i l a r i n design, one for service and t h e
o t h e r f o r emergency operation.

The severe conditions of s t r e s s and

v i b r a t i o n exerted on t h e s e r v i c e gate dwLzg i t s operation f u l l y j ~ t i f l e d the emergency gate,
A r e t u r n to the use of valves in a conduit was mad3 i n t h e ease

of t h e Shasta Dam o u t l e t s .

Each o u t l e t was 102 inches i n diameter and

sor.sisted of a rounded entrance, a horizontkl. segment of steel-lined
conduit, and a deflector elbow a t t h e end wi-iers it pierced t h e spillway
face,

A s p e c i a l l y designed tube valve was i n s t a l l e d i n t h e o u t l e t a

few dlamezers downstrean. from the $ntrance,

It was intended to be

operated a t any opening f o r regulation and t o have a capacity t h a t would

fill t h e conduit downst.ream when fully opened.

kt t h e end of t h e valve

a i r conduit which supplied a i r during valve operation a t p w t i a l openings.
Because t h e valve was designed f o r operation a t p a r t i a l opening t h e need
f o r an emergency g a t e was v i r t u a l l y eliminated.

A c o a s t e r g a t e t h a t could

be t r a n s f e r r e d t o any o u t l e t by a gantry crane served as a means of closing

i t under emergency conditions, o r f o r t h e purpose of carrying out maintsnance work on t h e valve.
A s p e c i a l tube valve, Figure 12, w i t h a long, s l i m shape and operated

by an i n t e r n a l hydraulic cylinder was developed by extensive t e s t s using

a 1 t o 17 s c a l e model and a 1 t o 5.1 s c a l e model ( 8 ) .

The model t e s t i n g

included a study of a i r requirements and the 6etermlLnation of t h e
appropriake s i z e of a i r supply conduit.
before a completely s a t i s f a c t o r y design

Liwelcpment work was c u r t a i l e d
wp-s

the need f a r
evolved because
-.

t h e valves developed sooner t h a n anticipated.

Oniy f o u r of t h e valves
t

were i n s t a l l e d i n t h e four lowest o u t l e t s at Shasta Dam f o r t h e purpose
of regulating releases during t h e f i l l i n g of ths r e s e r v o i r .

The nodel

t e s t s demonstrated t h a t t h e r e was a range of openings varykng from zero
)I

a t low heads t o the range from 65 t o 90 percent opening a t maximum head

of 323 f e e t wherein operation should be r e s t r i c t e d because of t h e
cavitation -erosion vihlch would result,

This r e s t r i c t i o n i n operating

range is thc r s s o n f o r t h e statement made previously t h a t t h e desfs
was not completely satisfactory,

Experience with these four valves

has indicated t h a t they were q u i t e s a t i s f a c t o r y and t h a t t h e r e s t r i c t e d
range was e a s i l y circumvented by using d i f f e r e n t combinations mong t h e
f cur valves , .

.

During construction, one of t h e vabres

p r o d d e d Hith ,piezcmefer

openings sc t h a t pressure msasurmects could be macio'.after it was instnlled.

of a i r flow, which reached a msximum of 40 percent of

.

water

discharge, checked c l o s e l y with t h e respective values predicted from t h e
model t e s t s .

Operation of t h e valves a t p a r t i a l opsnings was reported

t o b e smooth and s a t i s f a c t o r y s o far as conditions a t t h e valve were
concerned,

Inspection of t h e o u t l e t conduit downstream from t h e valve

a f t e r a seasonls operation indfeated no evidence of damage i n t h e
s t r a i g h t section due t o t h e operation of t h e valve i n a conduit,
The i n v e r t of t h e elbow d e f l e c t o r a t t h e end of t h e o u t l e t showed

some evidence of cavitation-erosion.

This was n o t unexpected as t h e

model t e s t s showed t h a t negative pressures would p r e v a i l i n t h i s region
f o r operation a t p a r t i a l g a t e opening.

The damage was n o t g r e a t , probably

because t h e water contained a r e l a t i v e l y high percentage of entrained air
which'would discourage cavitation-erosion,

The sii;uation may be correctsd

by v e n t i l a t i n g the c r i t i c a l a r e a o r t h e erosion r e s i s t e d by weld-filling
t h e damaged areas with a m a t e r i a l such as s t a i n l e s s s t e e l .
The q u a l i t y of t h e j e t f o r such an i n s t a l l a t i o n , where a mixture of

air and water i s discharged from an c u t l e t , a t high v e l o c i t y , i s such
t h a t i t s use would be subject t o some r e s t r i c t i o n .

The d e f l e c t o r elbow

and i t s s e t t i n g ir, t h e f a c e of t h e spillway were designed t o place t h e
j e t along t h e spillway f a z e -with comparatively l i t t l e disturbance and

i t s o operated when t h e valve was fully opened, Pig u ~ e13.

I *

When the j e t

contained a l a r g e p o r t i o n of air, as it d i d a t partial valve openings,
t h e action of the elbow d e f l e c t o r was l a r g e l y n u l l i f i e d .

Shortly a f t e r

emergicg from tha o u t l e t t h e mixed f l u d jet dispersed and a considerable
amount of spray was generated, Figure

2A,

not operated at p a r t i a l openings except when absolutely necessary,

-

.

The

spray from t h e other t h r e e valves did not reach t h e powerhouse s o they
were operated as required.

Every e f f o r t was made t o accomplish t h e

required t o t a l discharge by s e t t i n g - t h e valves a t openings where t h e j e t
had t h e b e s t q u a l i t y ,

For example, two valves would be operated a t 30-

percent capacity, r a t h e r than one at 60-percent capacf t y because theye
was l e s s spray.
Spray conditions made it undesirable t o consider regulated flow f o r

t h e higher o u t l e t s so t h e p o s s i b i l i t i e s of using a l e s s expensive valve
or a non-regulating g a t e were investigated i n l i e u of equipping t h e
remaining o u t l e t s with regulating tube valves.

The r e g u l a t i n g g a t s o r

jet-flow valve developed i n t h e course of t h i s i n v e s t i g a t i o n has been
described previously,

Although it i s not intended t h a t t h e jet-flow

valve be used as a regulating device a t Shasta Dam, i t s performance i n

t h i s respect was studied i n t h e model.

Its performance c l o s e l y p a r a l l e l e d

t h a t of t h e other valves with respect t o flow conditions i n t h e conduit
and the appearance and a c t i o n of t h e j e t a t the end of t h e conduit.

A

f i e l d t e s t of one of t h e Shasta valves i s planned.

1

During t h e s t u d i e s relaking t o t h e s p e c i a l t u b s valves, regular tube
valves, and neodle valves were investigated i n an attempt t o generalize t h e

I

information on t h e performance of valves placed i n an outlet,

They ahowed

promise of operating more s a t i s f a c t o r i l y than t h e ~ p e e i a l ~ t u bvalve
e
because they could be operated at any opening m t h o u t r e s e r v a t i o n s o far
a s conditions i n t h e valve were concerned.

Howeyer, t h e lower discharge

c o e f f i c i e n t s compared t o t h e s p e c i a l tube valve wouid require l a r g e r

e s p e c i a l l y t h e diameter, l e d t o a decision t o use t h e s p e c i a l tube valve
which had a long, slender shape.

For other i n s t a l l a t i o n s , however, e i t h e r

one of these two valves, t h e conventional tube o r t h e needle valve, would
be considered,

Conditions of flow i n the conduit downstream from e i t h e r

of these valves closely resembled those e x i s t i n g f o r t h e s p e c i a l t u b e
valve,

The a i r requirements were nearly i d e n t i c a l i n each case.

The

q u a l i t y of t h e j e t from a conduit containing a p a r t i a l l y closed valve
of any type would be q u i t e similar,

The d i s i n t e g r a t i o n of t h e j e t and

t h e spray r e s u l t i n g therefrom a r e caused by t h e mixture of a i r i n t h e
water which m s u l t s from t h e s e t t i n g and operation of t h e valve r a t h e r
than t h e type.
The model s t u d i e s of t h e regulating gate in t h e conduit r e s u l t e d
i n t h e development of a r a d i c a l l y d i f f e r e n t type of elbow d e f l e c t o r which
does show promise of improving t h e j e t delivered by an o u t l e t , and i n
p a r t i c u l a r an o u t l e t with a f l a t bottom.

The new d e f l e c t o r which was

t e s t e d with a flat-bottomed conduit consisted of a curved re.ctangular
passage which turned the j e t with an open water surface a t t h e j m e r
radius, s t a r t i n g a t a v e r t i c a l o f f s e t i n t h e f l o o r .

The space under t h e

j e t was v e n t i l a t e d t o prevent t h e formation of low pressures.

The j e t

delivered by t h i s d e f l e c t o r appeared t o be more s t a b l e i n t h e model than
t h a t delivered by t h e elbow d e f l e c t o r used a t Shssta Darn.

Since t h e

model did not completely represent t h e conditions t h a t would e x i s t a t
t h e dis1;harge end of t h e prototype o u t l e t , the model r e s u l t s a r e
q u a l i t a t i v e only.

Q u a n t i t a t i v e evaluation of t h e improvement must a w a i t

t h e i n s t a l l a t i o n of an o u t l e t w i t h the revised deflector.

conduit diameter and t h e valve diameter such a s t h e tunnel o u t l e t , the
e x i t v e l o c i t y i s usually so laow t h a t very l i t t l e spray e x i s t s a t t h e
exit.

Much of t h e energy of t h e j e t i s absorbed within the tunnel.

For

o u t l e t s of t h e l a t t e r category, the use of r a d i a l o r Taintor gates a s
r e g u l a t i n g devices has been planned.for & t . l e a s t one i n s t a l l a t i o n and
s e v e r a l more a r e contemplated.

The c h a r a c t e r i s t i c s of a r a d i a l gate

adapt themselves very w e l l t o such an i n s t a l l a t i o n and except f o r t h e
s e a l i n g problem seem t o be i d e a l l y s u i t e d f o r use a s a r e g u l a t i n g or
c o n t r o l gate.
F U W DEVELOPMENTS
Future dsvelopments i n t h e f i e l d of high-head o u t l e t valves will
probably take t h e form of f u r t h e r improvements i n t h e types now being used.
The problems of j e t shape and s t a b i l i t y , pressure conditions not conducive

t o c a v i t a t i o n erosion, and vibratioil-free operation have been q u i t e
s a t i s f a c t o r i l y met.

There does remain, however, a f e r t i l e field f o r

reducing c o s t s by improvements in mechanical design.
Same study has been given t o t h e p o s s i b i l i t i e s of adapting t h e
hollow-jet valve t o welded f a b r i c a t i o n from r o l l e d p l a t e s .

A completely

balanced design has been worked out by t h e Bureau of Reclamation, but
t h e present design i s appreciably l a r g e r i n diameter than t h e c a s t
design previously discussed.

The n e c e s s i t y of using sharp i n t e r s e c -

t i o n s f o r welded f a b r i c a t i o n imposes l i m i t a t i o n s on t h e angles with
which t h e f l u i d j e t impinges on t h e shell and r e s u l t s i n a l a r g e r size.
Fcrther developnent work t o increase the discharge capacity i s expected

expensive than t h e c a s t type.
Model experiments with t h e jet-flow valve have indicated t h a t t h e
j e t whose cross-section i s roughly rectangular can be adapted t o f r e e
discharge conditions,

For those i n s t a l l a t i o n s requiring a reasonably

smooth j e t f o r f r e e discharge conditions t h e jet-flow valve appears t o
o f f e r advantages as an inexpensive regulating device,

Simplification

of construction and reduction i n t h e amount nf machining may be expected
t o f u r t h e r reduce t h e cost.
The p o s s i b i l i t i e s of improving t h e s e a l s on r a d i a l g a t e s have
already been mentioned.

The p~oblemi s being studied a c t i v e l y by

sevepal organizations and a s a t i s f a c t o r y design i s i n t h e offing.
When such z design materializes t h e use of r a d i a l gates as o u t l e t
regulating devices w i l l undoubtedly be extended appreciably,

.

-

1 "I-Iigh-Pressure Heservoir Outlets," by J, M. Gaylord and J. L. Savage,
U. S. Government Printing Office, 1923

2 I1Handbook cf Applied I l y d r a ~ l i c,I1s by C. V. l)avls, IcGraw H i l l Book
-Coo, Inc., 1942

3

tlDevelopxnents i n Regulating Outlet Valves,It by G. J. Hornsby,
Transactions A.S.M.E., February 1942

4

Hydraulic Laboratory Reports, Hyd. 3.48 I1Model Studies f o r the Development of t h e Hollow-jet ValveN and Hyd. 189 I1Tests on 24-inch Hollowj e t Valve a t Boulder Dam, " Bureau of Reclamation, Denver, Colo.

5

Hydraulic Laboratory Reports, Hyd. 156 "Laboratory Study of a 6-inch
Howell-Bunger Valveu and Hyd. 168 ffInvestigations of the Hydraulic
Properties of the Revised Howell-Bunger Valve,Il Bureau of Reclamation,
Denver, Colo

e

.

6 Hydraulic Laboratory Report, Hyd. 171 "Model Tests f o r the Proposed
High Head &dial Gates f o r Davis Dani Outlets," Bureau of RzclamaIiLon,
Denver, Cola

.

7 Iiydraulic Laboratory Report, Hyd. 201 T h e Hydraulic Uesign of a
Control Gate f o r the 102-inch Outlets i n Shasta Dam,'' Bureau of
Reclamation, Denver, Colo.
8

Hydraulic Laboratory Report, Hyd. 160 IIHydraulic Studies f o r the
Design of the Tube Valves i n the Outlets i n the Shasta Dam,t1
Bureau of Reclamation, Denver, Colo.

DETAIL A
VALVC IN CWLCD

mIRm

8. PROPOSED REDESIGN WITH NEW STREAMLINED NEEDLE AND AIR VENT

0. RESISTANCE

C.

SLEEVE CONTROL

FIG. 1 ENSIGN B A L A N C E D V A L V E

TUBE CONTROL

FIG. 2

CAVITATIOII-EROSION OF ENSIGN VALVE AM) CONDUIT,
SHOSHONE DAM, WYOMING.

FIG. 3

CAVITATION-EROSION OF 84-INCHNEEDLE VAL'33,

rn

SECTION T H R U VALVE

FIG. 6 REVISED NEEDLE VALVE

FlG.7 REVISED TUBE VALVE

DETAIL Y
,

..

t e r s -::
-..- .--.-'';P/ezorne
.
: Approx. inner i
: noppe o f jet,'

-tole -:
L ...;3855
- . . .-...-3758

SECTlON THRU VALVE

mu^ VANES
Oh' VERT: r HORIZ. 6s

FOUR VANES
45. FROM VERT. Q

VANE SECTIONS

\

FIG. 8 HOLLOW

-JET

VALVE

8: VALVE
A.

SECTION THRU VALVE

-'+u--..-.--..A
.---.-..-. .

FIG. 9 HOWELL- BUNGLR VALVE

EXIT DETAIL

FIG. 13

DISCHARGE FROM SHASTA DAM OUTLET AT

FULL CAPAC2.i.