Submittal Sheet

PRESSURE DROP TABLES
Series STVL & STV,
1/2” - 2”
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 1” valve is
required to be open 8 turns
for a Cv value of 7.5 at a
flow rate of 10 gpm and a
pressure drop of 4 ft.
Flow Measurement & Accuracy
The measuring instrument connects to the test ports of the valve and
is pre-programmed with Macon B alancing 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 i s 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.
Corr ection For Liquids
Applies to liquids other than water. Correct the m easured 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).
Cv Values for Valve Series STVL, STV
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
A
B
C
D
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
Flow coefficient values (Cv's) at various handwheel settings
Handwheel
Setting
1/2"
DN 15
3/4"
DN 20
1"
DN 25
1 1/4"
DN 32
1 1/2"
DN 40
2"
DN 50
1 0.21 0.39 0.56 0.92 1.39 2.32
1.5 0.29 0.56 0.75 1.28 1.97 3.25
2 0.37 0.7 0.89 1.53 2.38 4.18
2.5 0.44 0.82 1.04 1.8 2.78 5.1
3 0.52 0.96 1.19 2.09 3.25 6.03
3.2 0.56 1.02 1.28 2.26 3.48 6.5
3.4 0.59 1.09 1.39 2.44 3.71 6.96
3.6 0.63 1.16 1.51 2.67 4.06 7.54
3.8 0.67 1.23 1.62 2.9 4.41 8.12
4 0.72 1.31 1.74 3.13 4.76 8.82
4.2 0.77 1.39 1.91 3.42 5.1 9.74
4.4 0.81 1.48 2.09 3.71 5.57 10.7
4.6 0.87 1.58 2.26 4.06 6.03 11.7
4.8 0.93 1.68 2.44 4.41 6.61 12.8
5 1 1.8 2.67 4.76 7.19 13.8
5.2 1.07 1.91 2.9 5.16 7.77 15
5.4 1.14 2.03 3.19 5.57 8.35 16
5.6 1.21 2.16 3.48 5.97 8.93 17.2
5.8 1.28 2.3 3.83 6.38 9.63 18.3
6 1.36 2.44 4.18 6.84 10.3 19.4
6.2 1.44 2.6 4.47 7.25 11 20.4
6.4 1.52 2.76 4.76 7.66 11.8 21.5
6.6 1.62 2.96 5.1 8.12 12.5 22.5
6.8 1.74 3.16 5.54 8.58 13.2 23.5
7 1.88 3.36 5.8 9.05 13.9 24.6
7.2 2.06 3.6 6.15 9.51 14.6 25.5
7.4 2.26 3.83 6.5 9.98 15.3 26.4
7.6 2.49 4.06 6.84 10.4 15.9 27.4
7.8 2.73 4.27 7.19 10.8 16.5 28.2
8 2.96 4.47 7.54 11.3 17.1 29
8.2 3.13 4.63 7.89 11.7 17.6 29.9
8.4 3.29 4.78 8.24 12.2 18.2 30.7
8.6 3.42 4.93 8.58 12.6 18.8 31.6
8.8 3.54 5.08 8.87 13 19.4 32.4
9 3.65 5.22 9.16 13.3 19.8 33.2
9.2 3.77 5.36 9.4 13.7 20.3 33.9
9.4 3.87 5.5 9.63 14.2 20.9 34.6
9.6 3.98 5.64 9.86 14.5 21.5 35.3
9.8 4.06 5.78 10 14.8 22 36
10 4.12* 5.92* 10.2* 15.2* 22.6* 36.5*
Tunstall Corporation
118 Exchange Street Chicopee, MA 01013
Phone: [phone] Fax: [phone]
www.tunstall-inc.com
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