Tunstall Macon STV Series Manual page 10

Pressure Drop Tables
Series STVA
2-1/2" - 6"
This diagram details the
relationship between flow,
pressure drop and valve
preset points. Use the dia-
gram to select the correct
valve size and corresponding
handwheel setting to fulfill
the application requirements.
Determine the required flow
in the circuit (A) and the
pressure drop (B). Draw a
line between these two val-
ues. Read off the corre-
sponding Cv value on the Cv
scale.
Determine the valve setting,
in handwheel turns, by draw-
ing a horizontal line (D)
from the intersection point
on the Cv scale to the corre-
sponding valve setting posi-
tion.
For the highest level of accu-
racy, it is recommended to
choose a valve that has at
least 3 open turns.
Example:
A 4" valve is
required to be open 7.5 turns
for a Cv value of 160 at a
flow rate of 150 gpm and a
pressure drop of 2ft.
Installation Recommendations
Install the valve in the correct flow direction accord-
ing to the arrow on the valve body and the distance
parameters detailed in Figure 1 (Note: D = pipe diam-
eter).
For Series STVA, cover the valve body with a wet
cloth when soldering to prevent premature deteriora-
tion of valve components.
When used with a pump, it is recommended to use a
straight length of pipe totaling 10 x D (instead of 5 x
D) upstream or downstream to avoid turbulence that
will affect the measuring accuracy. See Figure 2.
Turbulence can influence the measurements by up to
20% if this recommendation is not followed.
Optional features and accessories available for this
Macon product are an extra charge, and not included
in the standard model price.
www.maconbalancing.com
- Model STVA - 2-1/2" to 6"
Flow Measurement & Accuracy
The measuring instrument connects to the test ports of
the valve and is pre-programmed with Macon Balanc-
ing characteristics. The pressure drop and flow read-
ings can be read off the display. If access to a Macon
Balancing instrument is unavailable, other industry
models are compatible. In addition, the flow can be
determined using the pressure drop diagram that is
included in the operating instructions with each Ma-
con Balancing valve.
The accuracy is highest when the valve is fully open.
Therefore, it is recommended to choose a valve that
can be opened at least three turns at the calculated pre
-setting value. Figure 3 represents the flow measure-
ment deviation in relation to handwheel turns.
Correction for Liquids
Applies to liquids other than water. Correct the meas-
ured flow (q) by the density (γ) according to this for-
mula. See Figure 4
Sizing a Balancing Valve
When the differential pressure and design flow are
known, use this formula to calculate Cv value.
See Figure 5
Section: Components
10
Cv Values for Valve Series STVA
Flow coefficient values (CV's) at various handwheel settings
Handwheel 2-1/2" 3"
Setting DN 65 DN 80
1 3.20 6.40
1.5 4.60 8.70
2 5.90 11.00
2.5 8.50 13.30
3 11.10 15.70
3.2 13.10 16.60
3.4 15.10 17.50
3.6 17.40 18.60
3.8 20.30 19.70
4 23.20 21.50
4.2 26.80 23.20
4.4 30.40 24.90
4.6 34.00 27.30
4.8 37.60 30.70
5 41.20 34.20
5.2 44.80 38.30
5.4 48.40 42.90
5.6 52.00 47.60
5.8 55.60 52.20
6 59.20 56.80
6.2 62.60 61.50
6.4 66.10 66.10
6.6 69.60 70.80
6.8 73.10 75.40
7 76.60 79.50
7.2 80.00 83.50
7.4 82.90 87.60
7.6 85.80 91.60
7.8 88.70 95.10
8 91.10 98.60
8.2 93.40 102
8.4 95.70 105
8.6 97.40 108
8.8 99.20 111
9 101 114
9.2 103 116
9.4 104 119
9.6 106 123
9.8 107 125
10 108* 128*
* Valve is fully open
Tunstall Corporation
118 Exchange Street · Chicopee, MA 01013
Phone (413) 594-8695 · Fax (413) 598-8109
Bulletin-MB-STVA-1016
4" 5" 6"
DN 100 DN 125 DN 150
9.30 11.60 20.90
12.80 19.70 29.00
15.70 25.50 38.30
19.10 30.20 53.40
22.00 38.30 78.90
23.80 42.90 90.50
25.50 48.70 103
29.00 55.70 118
33.60 63.80 135
38.30 73.10 151
45.20 82.40 164
53.40 91.60 176
61.50 102 189
69.60 113 202
77.70 123 216
85.80 135 231
94.00 146 246
102 157 260
109 166 273
115 174 285
122 183 298
129 194 311
135 204 322
140 215 332
145 225 341
151 235 351
157 246 363
162 255 374
168 264 384
174 274 394
180 283 406
186 292 418
190 302 428
194 310 437
197 317 447
202 324 456
206 331 465
211 338 474
216 343 484
220* 349* 493*