![23
Model selection
In-line meters: 0.5, 1, 2 inch
Flow range leads direct to model,
Check the diameter to ensure quick mechanical installation.
Insertion probes: 2 inch and up
The (normalized) velocity range needs to be calculated from the flow
range to determine the right model.
Normalized velocity = mass flow [m3
n/hr] / [3600] / tuber area](https://image.slidesharecdn.com/introductionintoflowmeasurmenttechnology2021dec6-240508212601-70286cbd/85/Introduction-into-Flow-Measurment-Technology_2021_Dec6-pdf-23-320.jpg)
Introduction into Flow Measurment Technology_2021_Dec6.pdf
- 2. 2 Normal cubic meter (m3 n) Gases do have a certain mass, but the density of gases is strongly dependent on pressure and temperature Normal conditions: defines the mass of a gas at a fixed temperature and pressure.
- 3. 3 Normal cubic meter (m3 n) • Volume: 1m3 • Temperature: 0°C • Pressure: 1013,25 mbar • Relative humidity: 0% • Mass: 1293 gram m3 n
- 4. 4 The ideal gas law Pressure * Volume / Temperature = Constant P∗V T =nm∗R V ½ V P 2P
- 5. 5 Normal conditions may vary Other common normal conditions: • 20˚C reference (FAD): See ISO 1217 • 15˚ reference: See DIN 1533 • CAGI: 68 F, 14.5 PSIA, 0% water vapor pressure Nm3/hr = V ∗ (TN / T) ∗ (P / PN)
- 6. 6 From FAD to normal cubic meter 100 m3/hr FAD ∗ 273,16/(273,16+20) ∗ 1000/1013,25 = 91,95 Nm3/hr FAD/Nm3 factor = 1,0874 → 8,7% difference when comparing numbers 20 deg 1000 20 deg 1000 20 deg 1013,25 20 deg 1000 0 deg 1013,25 FAD Nm3
- 7. 7 Thermabridge™ technology Core technology of the VPFlowScope®
- 8. 8 ThermabridgeTM technology Vout = k ∗ λ ∗ ρ ∗ v ∗ (Ts−Tg) • Vout = output voltage • k = sensor (geometrical) constant • λ = thermal conductivity of the gas • ρ = density of the gas • v = actual velocity in in m / sec • Ts = sensor temperature • Tg = gas temperature
- 9. 9 Normal meter per second Thermal mass flow: velocity in Normal meter per second Rule of thumb: “Actual velocity times absolute pressure” (forget temperature) Example: 8 m/sec∗ 7 bar abs ~ 56 mn/sec
- 10. 10 Principles compared Thermal Vortex DP – Orifice plate DP – Cone meter Coriolis Turbine/ rotary displacement Clamp on ultrasonic Mass flow Yes Optional Optional Optional Yes Optional Optional Meter run 20D 15D 15D 5D 0D 10D 20D Pressure loss Low Medium/high high high Low Low Low Dirty air Fouling OK Clogging Clogging Internal fouling Faillure OK Wet Air Spikes OK, spikes OK OK, orientation Yes, but affects reading Faillure Spikes Range 1:250 1:10 1:10 1:10 1:100 1:100 1:100 Accuracy 2% 2% 2% 2% 0.5 .. 1% 0.5…1 % 1% Purchase price $ $ $ $ $$$$ $$ $$$ Maintenance Medium Low Medium Medium Low High Low
- 11. 11 Value of mass flow and 3-in-1 We believe in: Pressure ∗ Flow = Voltage ∗ Current – Energy! • Flow, Pressure, Temperature combined • ISO 11011 (e.g. must measure pressure on multiple locations) • Difference between supply and demand • How to detect cause of a pressure drop if you dont measure? • Internal accounting: 7 bar is more expensive than 6 bar • Flow & temperature to identify issues with compressed air driers and (water) cooled compressors
- 12. 12 Velocity to mass flow True diameter Measured error Measured diameter % of error 50 3 53 12.36 100 3 103 6.09 200 3 203 3.02 300 3 303 2.01 Check the inner pipe diameter Area A = π∗ 0.25 ∗ D2 Wrong entry of D → big deviation Example: V = 60mn/sec D: 50 mm → Q = 0,117 m3 n / sec D: 54 mm → Q = 0,137 m3 n / sec Difference: 17%
- 14. 14 Thermal mass flow = pressure independent Why? The sensor counts molecules: More pressure = denser air* = more molecules = more heat loss* * : linear with pressure 2 x P 1 x P 1Q 2Q
- 15. 15 Differential pressure technology Dynamic pressure port Positive side Dynamic pressure port Negative side Temperature FLOW VPFlowScope Transmitter housing - Absolute pressure sensor - Differential pressure sensor Locking ring
- 16. 16 Flow range is critical Thermal vs DP technology: 1:300 range vs 1:10 (1:5) range Thermal: • From leakages to high flow • Dry air only • Temp range up to ~60°C DP: • Only medium to high flow rates • Not suitable for leakage/low flows • Wet air and dry air • Temp range up to ~150°C (or higher)
- 17. 17 Bi-directional flow: air can go both ways!
- 18. 18 Importance of bi-directional flow measurement Demand side (reverse flow) Tank Production line +1002 mn 3 +941 mn 3 - 61 mn 3 ____________ +880 mn 3 Flow Flow POU tank Production line Production line
- 19. 19 Bi-directional flow examples • Ring networks • Multiple compressor rooms • Complex (old) compressed air networks • Large receiver tanks • Non return valves in compressors • Leaking drains and seals Extremely useful information for audits and permanent installations.
- 20. 20 Turbulent vs laminar flow Reynolds number ρ∗v∗D η = density∗velocity∗tubediameter dynamic viscosity Air dynamic viscosity = 17,1 ∗ 10 −6, which is very small compared to water or syrup • Compressed air lines: Flow is always turbulent! • Turbulent: Velocity profile is nearly flat: Less sensitive for insertion depth
- 22. 22 Know the basics: Process data Key to correct measurements and to prevent damage to your flow meter • Type of gas • Flow range • Humidity (dry/saturated) • (Inner) Diameter • Pressure • Temperature range
- 23. 23 Model selection In-line meters: 0.5, 1, 2 inch Flow range leads direct to model, Check the diameter to ensure quick mechanical installation. Insertion probes: 2 inch and up The (normalized) velocity range needs to be calculated from the flow range to determine the right model. Normalized velocity = mass flow [m3 n/hr] / [3600] / tuber area
- 24. 24 ½” 1” 2” > 2” Insertion probes In-line meters Size (inch) Min flow m3 n/hr Max flow m3 n/hr Min flow SCFM Max flow SCFM ½ inch 0,32 80 0.19 50 1 inch 0,88 250 0,52 150 2 inch 3,53 1000 2,06 600 Flow ranges
- 25. 25 Flow ranges Thermal: Schedule 40 Standard Seamless Carbon Steel Pipe Size (inch) DN ID (inch) ID (mm) Min flow SCFM Max flow SCFM Min flow m3 n/hr Max flow m3 n/hr 2 50 2,1 52,5 2,3 688 3,9 1,169 4 100 4,0 102,3 8,7 2,610 15 4,435 6 150 6,1 154,1 20 5,924 34 10,065 12 300 11,9 303,2 77 22,953 130 38,995 20 500 18,8 477,8 190 56,996 323 96,832 ½” 1” 2” > 2” Insertion probes In-line meters
- 26. 26 Not sure? Use VPCalculator Use our calculator to determine which flow sensor you need. See online Velocity Calculator https://www.vpinstruments.com/selection- guide/velocity/
- 27. 27 When creating a project quote Gather enough information to be prepared • P&ID (Process and Instrumentation Diagram) • Plant map, to scale • Pictures of installation points • Use the on-line demand side table or Excel form • Use bi-directional as default option
- 29. 29 Read the manual… • User manual • VP Academy • Instruction video • This training • Helpdesk “how to” articles
- 30. 30 Check the direct environment • Avoiding excessive external heat • Protect against external water damage (IP) • Eliminating excessive system condensate • When having condensation in gas (100% condensation → VPS DP) • Avoid corrosive atmosphere where possible • Use the right cables and cable locations • Eliminate mechanical vibration and potential danger
- 31. 31 Check air quality • Water • Oil • Drains • Particles • (Cone strainer)
- 32. 32 Check temperature • Thermal mass: limited range: high temperature will cause sensor signal → 0 • Temperature fluctuations: lagging temperature compensation • Coming from cold outside → inside (audits) : allow 1 hour acclimatization for best results. • DP: high range, and reasonably fast response
- 33. 33 Installation location: Avoid excess water Piping not in scale
- 34. 34 2. Find a straight pipe General minimum rule: • 20*D upstream length (even 40*D preferred) • 5*D downstream length (10*D preferred) The longer the better Without conditioners: All other claimed shorter lengths are B.S. It’s based on physics, not technology
- 35. 35 3. Use the best orientation Take into account: • Ease of wiring, maintenance, read out of and access to display • Install at least at an angle of 15° upwards. ALWAYS if possible • Piping table! Minimum up- and downstream length. Longer = better • In case of doubt: Communicate with the end user 30o
- 36. 36 Recap • Thermal mass : dry air • Differential pressure : wet air • In Line : 0,5, 1 and 2 inch • Probes : > 2 inch • Always check : Temperature, Pressure diameter and range • Ring network : Bi – directional • General : Use the checklist! Things to avoid: • Large and fast temperature swings • Excessive condensate in the pipe • Short meter runs