Steven R. McManus Environmental Product Support Teledyne Isco

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Lynette Jefferson
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1 Steven R. McManus Environmental Product Support Teledyne Isco

3 Flow Measurement Applications and Technologies. Methods of flow measurement Technologies of flow measurement

4 Flow Rate Applications Channel Shape and Size Open vs Closed Channel Flow

5 Open Channel Flow Rate Measurement Methods Timed gravimetric Dye Dilution Slope-hydraulic radius (Manning) Hydraulic structures (Primary Devices / Weirs & Flumes) Area velocity

6 Timed Gravimetric The bucket and a stopwatch!

7 Dye Dilution Highly accurate but very expensive One Time method of flow measurement

8 Manning Formula Developed by Robert Manning in 1889 and recommended for international use in 1936

9 Typical Manning Formula Application Need 200 to 1000 ft. of consistent channel conditions for accuracies of ±10-20% Problem sites ±20-50% or more!

10 Roughness? Manning Formula channel?

11 Primary Devices (Hydraulic Structures) Weirs Flumes

12 Weirs

13 Side Profile of a Weir Not suitable for flows with solids Regular maintenance (cleaning) required

14 Compound Weir

15 Compound Weir

16 Insert Weirs

17 Advantages/Disadvantages of Weirs ± 3-5% accuracy. Lower cost Made out of wood or metal Easy to design Easy to install High head loss (backs up water) Periodic cleaning Not suitable for flows with solids Accuracy affected by excessive approach velocities Approach channel requires a minimum run of 20 times H-max.

18 3 components Converging section Throat section Diverging section Flumes

19 Common Types of Flumes Parshall Palmer-Bowlus H Series Trapezoidal Cutthroat Etc

20 Parshall Flumes Head measurement for flow is done here Sized by their throat width

21 Parshall Flumes

22 Palmer-Bowlus Flumes 0 Point

23 H Flumes

24 Trapezoidal Flumes

25 A Very Famous Flume!!

26 Beginning Stage of Submerged Condition

27 Fully Submerged Flume

28 Advantages/Disadvantages of Flumes ± 3-5% accuracy. Self cleaning Lower head loss (the flow is not backed up) Accuracy less affected by approach velocity Higher cost Installation can be difficult

29 Level to Flow Conversion Equation for a Parshall Flume: Q = KH n Q = Flow rate K= constant, dependent on throat width and units of measurement H = head, measured at the proper point n = constant power, dependent on throat width 1 Parshall Flume: Q GPM = 1795 H 1.522

30 Flow meters do this automatically

31 Secondary Measuring Devices (Open Channel Flow Meters) Measure level Convert level to flow rate

32 Ultrasonic Level Measurement Technologies Submerged Pressure Transducer Bubbler

33 Ultrasonic Level Ultrasonic transducer Transmits sound wave Reflects off water surface Detects echoes Level Function of time interval between Time transmitted Time Received Dead-band Required time for transducer to dampen Dead-band

34 Using a built-in stilling well Avoid the issues that can impact measurement

35 Excessive turbulence

36 Foam

37 Steam

38 Advantages/Disadvantages of Ultrasonic Non-contact sensing Easy to install Maintenance-free Dead band Beam angle Wind Steam Air temperature gradients Foam Turbulence

39 P=H Submerged Pressure Probe

40 Flume installation with cavity for submerged probe

41 Advantages/Disadvantages of Submerged Pressure Probe Suitable for small channels Not affected by wind, steam, foam, turbulence Senses pressure through silt and sand Flow stream chemicals Flowing debris Temperature Lightning

42 Bubbler

43 Advantages/Disadvantages Suitable for small channels Not affected by wind, steam, foam, turbulence, temperature, lightning Only bubble tube contacts flow Accuracy Inexpensive of Bubbler Plugging Note: There are design features that can mitigate this issue. Purge (frequency and duration settings) Super Bubble Greater power consumption

44 Impellor Point Velocity Spot measurement Electro-magnetic Types of Velocity Point velocity Requires profiling Uses a conversion factor Transit time measurement Multiple sensors Travel time Difficult to install Limited area of measurement Expensive!!! Surface Velocity (Doppler) Measures surface velocity Mounting alignment is critical Uses a conversion factor Peak Velocity (Doppler) point velocity Requires profiling Uses a conversion factor Pulse Doppler Segments and reads velocity profile in layers. The various layered measurements are averaged Mounting is critical Continuous Wave Doppler Reads Velocity Profile Calculates Average Velocity in one lump sum Laser Doppler Reads multiple points below surface The point measurements are averaged

Flow Measurement Q = A x V (continuity equation) To measure flow rate (Q), we need... 1.

45 Flow Measurement Q = A x V (continuity equation) To measure flow rate (Q), we need The pipe or channel geometry 2. The depth of the flow 3. The average velocity of the flow

46 Doppler Velocity Measurement Profile C B A C B A CROSS SECTION A-A C-C B-B

47 CWD Velocity Measurement Average Velocity read based upon ALL combined returned signal.

48 Pulse Doppler (PD) Technology Individual location specific velocity measurements......and the flow depth... Pipe Geometry...determine the flow rate.

49 Laser Doppler Technology

50 Theory of operation LaserFlow Sensor Return Doppler Signal Light V Below Surface Flowing Water Stream

51 Laser Velocity Measurement Ultrasonic Level Measurement Multipoint Multidepth Velocity Method

Advantages/Disadvantages of Area Velocity No weir or flume No need to estimate channel slope and roughness Some devices require no profiling, no conversion or compensation factor Measures open

52 Advantages/Disadvantages of Area Velocity No weir or flume No need to estimate channel slope and roughness Some devices require no profiling, no conversion or compensation factor Measures open channel, submerged, full pipe, surcharged and reverse flows Becoming more accepted for billing applications. Fouling, debris, or silting impeding the sensor s vision Turbulence or swirling (poor hydraulics) Some devices require profiling and a conversion or compensation factor

53 Rule #1:

54 Questions?

Flow Like An Egyptian: The Basics of Open channel flow

Flow Like An Egyptian: The Basics of Open channel flow Walt Boyes,as ISA Life Fellow, Fellow of InstMC, Chartered Measurement and Control Technologist, Editor of Control and ControlGlobal.com and principal