A. EDGAR KROLL1
AN DH . V. FAIRBANKS
R o se P o ly te c h n ic I n s t i t u t e , T erre H a u te , I n d .T h e conversion o f an ordinary co m m er cia l valve in to a flow m eter is described. T h e valve flow co efficien t, K i, from w h ic h th e r a te o f liq u id flow th r o u g h a valve m a y be ca lcu la ted , is defined in th e follow in g m odified form o f th e fu n d a m e n ta l flow eq u a tio n :
K , = 1.496 u> /\/pA P i
Valve flow coefficien ts for various valve s e ttin g s on different sizes o f Crane brass-globe b e v el-sea t brass- disk valves are p resen ted , to g eth er w ith d e ta ils o f t h e m e th o d by w h ic h th e y w ere o b ta in ed . T hese co efficien ts were d eterm in ed w ith R eynolds n u m bers, referred to th e p ip e, ra n g in g fro m 30,000 to 150,000. I t is sh ow n th a t th e u se o f a glob e valve as a flow m eter is practical. Valve flow coefficien ts for th ree different V2-, an d 1-in c h valves were fo u n d to have a m a x im u m d ev ia tio n o f 5%;
for 11/4-in c h valves, flow coefficien ts h ad o n ly a 3%
m a x im u m deviation . Use o f th e se valve flow co efficien ts for co m p u tin g rates o f flow th r o u g h oth er valves, o f th e sa m e type and m a k e, w ith o u t calibra
tio n is feasible w here th e above m a x im u m devia
tio n s are perm issible. T h e valve flow coefficien ts presented agree w ith in 3.0% w ith values ca lcu la ted from d ata ob tain ed by Corp and R u b le an d by th e Crane C om pany for loss o f h ead th r o u g h fu lly open, new Crane globe valves.
Pointer
G l o i t Vafoe
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A
VALVE m eter is an ordinary commercial valve conve into a flowm eter by attach in g pressure connec 10ns u p stream and dow nstream from th e valve to a m anom eter or any other suitable pressure m easuring device, as shown m igure T he difference betw een th e pressures upstream and dow nstream from th e valve, caused by th e sm aller valve opening, can be m easured by m eans of th e m anom eter.T he use of a valve as a flowm eter was recently suggested b y one of th e authors. D a ta were given on a single 2-inch globe valve which was calibrated and used successfully to determ ine a n d con
tro l th e ra te of flow in a pipe line (6). In continuation of this idea it seemed of in terest (a) to o b tain fu rth er inform ation re
garding th e use of valves for determ ining and controlling th e ra te of liquid flow in pipe lines, (6) to determ ine valve flow coefficients for valves of different sizes, and (c) to inv estig ate th e feasibility of using commercial valves as flowm eters w ith o u t calib ratio n by v irtu e of predeterm ined flow coefficients.
Investigations in this field ap p ear to be lacking, since a search of th e literatu re revealed no inform ation rela tiv e to th e use of valves as flowmeters. T his p ap er describes th e resu lts obtained w ith various sizes of brass globe v alves m an u fa ctu re d by th e Crane Com pany.
APPARATUS AND M ETH O D O F T E S T IN G
C rane brass-globe valves, N o. 1, w ith bevel seat, brass disk, and screwed ends were used; sizes were lA to l 1/« inches, inclu
sive. R uns were m ade on th ree different valves of each size.
All th e valves were new except one l'A -in c h and one 1-inch valve, w hich were used b u t in good condition. T he resu lts o b tained on th e used valves were in good agreem ent w ith th o se on th e new valves. W ater tem p eratu re was 60° F . in all cases, w ith th e flow upw ard th ro u g h th e valve orifice.
Figure 2 is a diagram an d F ig u re 3 is a photograph of th e ap p aratu s. In all tests th e valve was preceded by fifteen pipe diam
-■ Present address, E . I. du P o n t de Nemours & Com
pany, Inc., Childersburg, Ala.
Vahe iin dsr t e s t
1 *^ 16— 80 f ^
F igu re 1 (A b o ve). D iagram o f Valve M eter
F ig u re 2
(Right).
D iagram o f A p p aratu sVeifht
ï ïd n o m e t e r
588
I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 589
* Approximate. Different valves varied slightly in the num ber of turns to fully open.
eters of straig h t galvanized steel pipe and was followed by fifteen pipe diam eters of sim ilar pipe and a gooseneck (1) in which th e handles were used and were equipped w ith a narrow strip of m etal bent a t a right angle, pointed on one end and having a hole in th e two and a h alf pipe diam eters upstream and eight pipe diam eters downstream from th e valve. G reat care was tak en to remove all burrs from th e edges of th e holes on th e inside wall of th e pipe.
These openings were connected to calibrated Bourdon pressure gages for large differential pressures and to a m ercury m anom eter for sm all differential pressures. R eadings on th e pressure gages were taken to t i e n earest 0.5 pound p er square inch on th e up stream gage and to th e n earest 0.2 pound on th e dow nstream gage.
T he m anom eter readings were tak en to th e n earest 0.1 cm.
T he q u a n tity of w ater discharged was determ ined b y weight on Fairbanks platform scales of 1000-pound capacity. In determ in
ing th e ra te of discharge, th e tim e was m easured b y a K odak tim er. T he Reynolds num ber, referred to th e pipe, for all runs varied from 30,000 to 150,000. T he source of w ater supply for th e investigation was a blow case w hich furnished th e various pressures, ranging from 10 to 40 pounds per square inch. D uring any one run, constant pressure was m aintained. an d differential pressure a t various valve settings.
T able I sum m arizes th e calculated results an d shows th e aver
age and m aximum deviation from th e m ean value of th e flow coefficient. One valve reproduces th e results of another, u sually w ithin less th an 5 % on th e V*-, 3/ r , and 1-inch valves; resu lts on th e iy«-inch valves varied less th a n 3% . T he largest
devia-F igu re 4. P h o to g ra p h o f G lob e V alves
*/ J
-2. / Z 3 4
V A L V E S E T T I N G , A /
0
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/ " T U R N S O P E N F ig u re 5. G lob e-V alve F low C oefficien ts a t Various Valve S ettin g stions were obtained a t V* tu rn open, which were probably due to variations in th e valve settings o r flow characteristics a t close th ro ttlin g con
ditions. T he valve settings are less critical as th e opening increases. T here is also danger of wiredrawing th e seat when th e flow is throttled dow n to '/ « tu rn open. F or these reasons use of th e V* tu rn open setting is no t recommended.
E ven w ith the favorable agreem ent shown above, it should be pointed ou t th a t valve flow characteristics are influenced considerably by m anufacturing variations, design details such as ty p e of disk, contour of body, etc., and direction of flow through the valve orifice, so th a t use of th e flow coefficients given here should be re
stricted to th e ty p e and m ake tested, since their use w ith other types and m akes m ay lead to serious error. F or example, valve flow coefficients determ ined for a composition disk valve varied as m uch as 30% from th e brass-disk bevel-seat type. I t is felt, however, th a t w ith consistent design and m anufacture the average flow coef
ficients for th e commonly used globe valves could be determ ined; th is would m ake possible th eir use as flowmeters w ithout calibration, pro
vided th e deviation and accuracy are stipulated.
T he valve flow coefficient curves given in Figure 5 m ay be used for com puting rates of flow through these C rane valves w ithout calibration, where th e above m axim um deviations are per
missible. T he pressure tap s should be installed according to Figure 1, th e direction of flow is upw ard through th e orifice, and th e weight
ra te of flow, w, is calculated from E q u a t i o n ■
W hile it is know n th a t th ere is little variation in orifice flow coefficients w ith R eynolds nuro ®rs above 30,000 (7), it should be n oted th a t ^ valve flow coefficients presented here were term ined w ith R eynolds num bers, referred to e pipe, betw een 30,000 an d 150,000.
F igure 6 shows th e flow characteristics o globe valves used. T he values for percentage of to ta l flow an d percentage of to ta l turns PP®n were calculated from th e m ean values o t e flow coefficients given in T able I, assum ing a co n stan t pressure drop. T able I I com pares valve flow coefficients obtained in th is stu d y w it those calculated from d a ta obtained by C orp and R uble (3) an d th e C rane C om pany (4) f° r *oss of h ead thro u g h fully open C rane globe valves.
T he p resent d a ta com pare favorably for th e 3/<- an d 1-inch valves tested by C orp and R uble in 1919, being 0.5% higher and 2.9% lower, respec
tively. T he V i-inch valve is 20,5% higher. T his unfavorable agreem ent m ay be due to th e fact th a t th e Vi-inch valves were tested by C orp an d R uble w ith R eynolds num bers less th a n 20,000.
T he C rane C om pany’s value for th e l/ 2-inch valve flow coefficient w as calculated from k = 10.0 in th e equation H = k V 2/2 g given in th e ref
erence for globe valves (4). A greem ent w ithin 3.1% is show n here.
SUM M ARY AND C O NC LUSIO N
1. V alve flow coefficients h av e been given for various valve settin g s on C rane 1/ r , V«-, 1-, and 1 Vi-inch brass-globe valves N o. 1 w ith bevel seat and brass disk. T h e flow coefficients were determ ined w ith R eynolds num bers, referred to th e pipe, ranging from 30,000 to 150,000.
L E G E N D
VALVE SIZE TURNS OPEN
TOTAL EL OK
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/£>£>F igu re 6. F low C h a ra cteristics o f G lo b e V alves w ith F low th ro u g h th e O rifice a n d B ased u p o n a C o n s ta n t P ressu re Drop41
I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
, A C K N O W LE D G M EN T
591
T a b l e I I . V a l v e F l o w C o e f f i c i e n t s C a l c u l a t e d f r o m E q u a t i o n 3, U s i n g D a t a O b t a i n e d b y C o r p axit> R u b l e (o) a n d t h e C r a n e C o m p a n y (4) f o r L o s s o f H e a d t h r o u g h G l o b e V a l v e s a s C o m p a r e d t o C o e f f i c i e n t s O b t a i n e d i n
T h i s S t u d y
Fully Open JC« for Valve Size of:
i/j in. •/« in. 1 in.
0.083° 0.208 0.351
0.097»
0.100 0.209 0.341«
Corp and Ruble (1922) Crane Co.
Kroll and Fairbanks (1944)
° Used valves a t Reynolds numbers less th a n 20,000.
& Calculated from k “ 10.0 in H — kV*/2g.
0 One used valve.
2. T he ordinary commercial globe valves of th e ty p e and m ake used in this study m ay be used as flowmeters w ithout calibration by use of th e valve flow coefficient, K v, from w hich th e ra te of flow m ay be calculated, where a m axim um error of 5% is perm is
sible.
3. G reater precision w ith larger size valves is indicated by th e fact th a t the m axim um deviation for th e l l/«-inch valves was only 3 % .
4. The principal advantages of a valve m eter are: (a) I t m ay be used as an adjustable orifice for widely varying conditions of flow; (&) th e valve is already in th e pipe line and hence there is no increased resistance to flow; (c) little initial cost is incurred by converting a valve into a flowm eter; and (d) th e upkeep is small.
T h an k s are due to B. E . H u n t for th e draw ings a n d to F . M . L undgren who to o k th e p ictures of th e valves an d a p p a ra tu s used.
N O M EN CLA TU R E
A t = cross-sectional area of discharge opening, sq. ft.
D = d iam eter of pipe, ft.
g = acceleration due to grav ity , 32.17 (ft./se c .)/se c . H = loss of head, feet of fluid
k = coefficient, dim ensionless K = flow coefficient, dim ensionless K , = K A i = valve now coefficient, sq. ft.
Pi, Vi — pressures a t u p stream a n d d ow nstream pressure tap s, respectively, lb ./s q . ft.
AP i = = differential pressure, lb ./s q . in.
V = velocity of w ater, ft./se c.
w = w eight ra te of discharge, lb ./se c.
p = density, lb ./c u . ft.
LIT E R A T U R E C IT E D
(1) Am. Soc. Mech. Engrs., “Flow Measurement” , p. 45, par. 121 (1940).
(2) Am. Soc. Mech. Engrs., “Fluid M eters R eport” , 4th ed., p. 48, par. 155 (1937).
(3) Corp and Ruble, Univ. Wisconsin Eng. Expt. Sta., Bull. 9, No.
1 (1922).
(4) Crane Co., Catalog 41, p. 630 (1941).
(5) Gess, Louis, In s tr u m e n ta tio n , 1, No. 2, 26 (1944).
(6) Kroll, A. E., Chem. & Met. Eng., 51, No. 7, 114 (1944).
(7) Perry, J. H., Chemical Engineers Handbook, 2nd ed., p. 848, New York, McGraw-Hill Book Co., 1941.