Submittal Sheet

PRESSURE DROP TABLES
Series STVA,
2 1/2” - 6”
This diagram details the
relationship between flow,
pressure drop and valve
preset points. Use the
diagram 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 values. Read off the
corresponding Cv value on
the Cv scale (C).
Determine the valve
setting, in handwheel turns,
by drawing a horizontal line
(D) from the intersection
point on the Cv scale to the
corresponding valve setting
position.
For the highest level of
accuracy, it is recom-
mended 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 2 ft.
Flow Measurement & Accuracy
The measuring instrument connects to the test ports of the valve and is
pre-programmed with Macon Balancing characteristics. The pressure
drop and flow readings can be read off the display. If access to a Macon
Balancing instrument is unavailable, other industry standard models are
compatible. In addition, the flow can be determined using the pressure
drop diagram that is included in the operating instructions with each
Macon 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
measurement deviation in relation to handwheel turns.
Correction For Liquids
Applies to liquids other than water. Correct the measured flow (q) by the
density (γ) according to this formula.
Sizing a Balancing Valve
When the differential pressure and design flow are known, use this
formula to calculate Cv value.
Installation Recommendations
Install the valve in the correct flow direction according to the
arrow on the valve body and the distance parameters detailed in
Figure 1 (Note: D = pipe diameter).
Flow coefficient values (Cv's) at various handwheel settings
Handwheel
Setting
2 1/2"
DN 65
3"
DN 80
4"
DN 100
5"
DN 125
6"
DN 150
1 3.2 6.4 9.3 11.6 20.9
1.5 4.6 8.7 12.8 19.7 29
2 5.9 11 15.7 25.5 38.3
2.5 8.5 13.3 19.1 30.2 53.4
3 11.1 15.7 22 38.3 78.9
3.2 13.1 16.6 23.8 42.9 90.5
3.4 15.1 17.5 25.5 48.7 103
3.6 17.4 18.6 29 55.7 118
3.8 20.3 19.7 33.6 63.8 135
4 23.2 21.5 38.3 73.1 151
4.2 26.8 23.2 45.2 82.4 164
4.4 30.4 24.9 53.4 91.6 176
4.6 34 27.3 61.5 102 189
4.8 37.6 30.7 69.6 113 202
5 41.2 34.2 77.7 123 216
5.2 44.8 38.3 85.8 135 231
5.4 48.4 42.9 94 146 246
5.6 52 47.6 102 157 260
5.8 55.6 52.2 109 166 273
6 59.2 56.8 115 174 285
6.2 62.6 61.5 122 183 298
6.4 66.1 66.1 129 194 311
6.6 69.6 70.8 135 204 322
6.8 73.1 75.4 140 215 332
7 76.6 79.5 145 225 341
7.2 80 83.5 151 235 351
7.4 82.9 87.6 157 246 363
7.6 85.8 91.6 162 255 374
7.8 88.7 95.1 168 264 384
8 91.1 98.6 174 274 394
8.2 93.4 102 180 283 406
8.4 95.7 105 186 292 418
8.6 97.4 108 190 302 428
8.8 99.2 111 194 310 437
9 101 114 197 317 447
9.2 103 116 202 324 456
9.4 104 119 206 331 465
9.6 106 123 211 338 474
9.8 107 125 126 343 484
10 108* 128* 220* 349* 493*
Cv Values for Valve Series STVA
Figure 1
Figure 2
D
D
D1
D1
5 x
D
10 x D
2 x
D
2 x
D
For Series STVL, cover the valve body with a wet cloth when
soldering to prevent premature deterioration 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.
* Valve is fully open
Deviation +/%
Figure 3
Pre setting
Actual Flow =
qCBI
C
v
= 1.52
q
q in GPM, p in Ft. of H2O
C
v
=
q
q in GPM, p in PSI
1
2
3
4
5
6 7
8
9 10
2
4
6
8
10
12
14
16
√
γ
Δ
√
p
√
p
√
Δ
Δ
10/11
A
B
C
D
Tunstall Corporation
118 Exchange Street Chicopee, MA 01013
Phone: [phone] Fax: [phone]
www.tunstall-inc.com
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