Design
The PITOBAR Averaging Pitot Tube is constructed and designed with a diamond shaped strut with several ports spaced centrally within concentric rings of equal area pointing towards the upstream side. This is done in order to get the best averaging measurement of the dynamic pressure, resulting in a more
accurate flow reading. The pitot tube creates a differential pressure signal which is proportional to the flow rate: Differential Pressure = ( Pstatic + Pdynamic) – Pstatic.
Installation
For optimal installation, the pitot tube should be placed in a straight cylindrical pipe with consistent cross-sectional area and free from obstructions. The inner pipe diameter must not deviate by more than 0.3% for accurate differential pressure calculations. To ensure accurate measurements, it is recommended to use full bore valves upstream of the primary element. The inner pipe wall roughness should meet specific limits depending on the material used. For steam flow, a horizontal mounting with a 5-degree slope is advised to facilitate condensate flow. Purge connections are available for fluids with impurities, and regular maintenance is suggested to maintain accurate readings. For proper instrument connection, the differential pressure transmitter should be positioned below the pitot tube for liquid and steam flow, and above it for gas flow, with impulse lines sloped to allow air escape.
Download the installation guide above for more detailed information.
- Easy to install
- Simple construction
- Free choice for horizontal or vertical pipe ru
- Risk of leakage is minimized
- Very low pressure loss
- No moving parts
Construction
|
Design and calculation standards |
VDE/VDI 2640, ASME, DIN, EN 13480 |
|
Types |
DK251, DK251/3 with mounting flange, DK251/4 with 3 valve manifold, DK251/5 with 5 valve manifold |
|
Pipe sizes |
DN 100 – DN 2000, 4″ – 80″ |
|
Pressure rating |
PN 16 – 40, 150 – 300 lbs, ISO PN 20, 50 (for higher pressure ratings a welded construction will be offered instead of flanged) |
|
Temperature range |
-100°C – +450 °C |
|
Material PITOBAR |
Stainless steel AISI 316, other stainless grades on request |
|
Material mounting part |
Carbon steel, stainless steel AISI 316, other on request |
|
Process connection |
Flange according to pressure rating |
|
Flange standards |
DIN, ANSI |
|
Bottom support |
For larger pipe sizes and high velocities |
|
Instrument connection |
DK251: ½” BSP, NPT or BW |
|
Mounting |
Welding to the pipe |
|
Mounting neck |
Standard lengths, 130, 180, 250 mm, other lenghts available |
Technical Data
|
Accuracy |
± 1% accuracy of actual flow |
|
Repeatability |
± 0,1% |
|
Reynolds no. |
Minimum 100.000 at full flow |
|
Rangeability |
10:1 |
|
Max. fluid velocity |
80 m/s |
|
Probe size |
25 x 25 mm |
Accessories
|
Shut-off valves: needle or ball |
Required Straight Pipe Lengths
Certain installation requirements for straight pipe lines must be fulfilled in order to achieve the most accurate flow measurement. See table below.
|
Upstream (x D)
|
Downstream (x D)
|
|
|---|---|---|
|
Single 90° bend
|
9
|
3
|
|
Two or more 90° bends in the same plane
|
14
|
3
|
|
Two or more 90° bends in in different planes
|
24
|
4
|
Maximum Allowable Differential Pressure
Without bottom support, with reference to mechanical bend. Pressure is measured in bar. See table below.
|
Length
|
DK200 @ 20°C
|
DK200 @ 400°C
|
DK250 @ 20°C
|
DK250 @ 400°C
|
|---|---|---|---|---|
|
200
|
3,75
|
1,81
|
||
|
300
|
1,66
|
0,81
|
2,52
|
1,19
|
|
400
|
0,94
|
0,45
|
1,42
|
0,67
|
|
500
|
0,60
|
0,29
|
0,91
|
0,43
|
|
600
|
0,42
|
0,20
|
0,63
|
0,30
|
|
700
|
0,31
|
0,15
|
0,46
|
0,22
|
|
800
|
0,23
|
0,11
|
0,35
|
0,17
|
|
1000
|
0,15
|
0,07
|
0,23
|
0,11
|
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