796 Tek Drive, Crystal Lake, IL 60014 USA
+1 847 857 6076
+1 847 655 6147
www.tek-trol.com
Quick Start Guide
Table 2: Required Straight Lengths for Classical Venturi Tubes
Beta
Ratio
Upstream Primary Devices (U1)
Downstream
Primary
Devices (D1)
Single 90°
bend(*)
Two or
more 90°
bends in
the same
plane(*)
Two or
more 90°
bends in
different
plane(*)(**)
Reducer
3D to D
over a
Length of
3.5 D
Expander
0.75D to D
over a
Length of D
Full bore
ball valve
or gate valve
fully poen
Fitting
(All
mentioned
in Upstream
Side of
Primary
Devices
0.30
0.5!
1.5
(0.5)
(0.5)
(0.5)!
1.5
(0.5)
1.5
(0.5)
4
0.35
0.5!
1.5
(0.5)
(0.5)
1.5
(0.5)
1.5
(0.5)
2.5
(0.5)
4
0.40
0.5!
1.5
(0.5)
(0.5)
2.5
(0.5)
1.5
(0.5)
2.5
(1.5)
4
0.45
1
(0.5)
1.5
(0.5)
(0.5)
4.5
(0.5)
2.5
(1)
3.5
(1.5)
4
0.50
1.5
(0.5)
2.5
(1.5)
(8.5)
5.5
(0.5)
2.5
(1.5)
3.5
(1.5)
4
0.55
2.5
(0.5)
2.5
(1.5)
(12.5)
6.5
(0.5)
3.5
(1.5)
4.5
(2.5)
4
0.60
3
(1)
3.5
(2.5)
(17.5)
8.5
(0.5)
3.5
(1.5)
4.5
(2.5)
4
0.65
4
(1.5)
4.5
(2.5)
(23.5)
9.5
(1.5)
4.5
(2.5)
4.5
(2.5)
4
0.70
4
(2)
4.5
(2.5)
(27.5)
10.5
(2.5)
5.5
(3.5)
5.5
(3.5)
4
0.75
4.5
(3)
4.5
(3.5)
(29.5)
11.5
(3.5)
6.5
(4.5)
5.5
(3.5)
4
U2
14
18
31
7
15
10
*Note:
* The radius of curvature of the bend shall be greater than or equal to the pipe diameter.
** As the effect of these fittings may still be present after 40D, no values without parentheses can be
given.
! Since no fitting can be placed closer than 0.5D to the upstream pressure tapping in the Venturi Tube,
the “Zero Additional Uncertainty” values are only ones applicable in this case.
• All straight lengths are expressed in multiples of diameter D.
• Values without parentheses are “Zero additional Uncertainty” values.
• Values in parentheses are “0.5% additional Uncertainty” values.
