Exploring the Possibilities of Using Ultrasonic Gas Flow Meters in Wet Gas Applications. Eric Bras - Elster-Instromet

Transcription

1 Exploring the Possibilities of Using Ultrasonic Gas Flow Meters in Wet Gas Applications Eric Bras - Elster-Instromet

2 Exploring the Possibilities of Ultrasonic Gas Flow Meters in Wet Gas Applications Eric Bras Product Manager Ultrasonic s Mo Zarkan Lead RnD Ultrasonics Jeff Tilden, Martin Novak, Mike Thackray E-I Essen R&D 19th March 2015

3 Contents Introduction Bridging The Gap The journey So Far CEESI 2010 In-House Testing DNV-GL 2014/15 Observations Further Work Conclusions 3

4 Introduction The Intention of the presentation is to review recent testing carried out on an Elster-Instromet Ultrasonic Gas Meter that has been placed in a wet gas environment. The review will look at experience gained from CEESI testing in 2010, ongoing In-house testing and DNV-GL testing in Finally we will look at the overall progress and consider if this type of meter can offer a robust solution in this type of environment in the future. 4

5 Bridging The Gap Multiphase flow experts Ultrasonic flow experts LMF GVF GLR Lockhart-Martinelli SLP Whole other ballgame SNR Gain PF VOS RTD Clearly Understood 5

6 What is wet gas? Wet gas =! Suitable for Do It Yourself 6

7 What is wet gas? It can be described as a gas with a small amount of liquid present. In most cases the main interest is in knowing the amount of gas flowing rather than liquid. Ranging from a humid gas (i.e. gas saturated with liquid vapour) to multiphase flows with a gas volume fraction (volume of gas to the total volume of gas+liquid) of 90% or higher. * Definition taken from NEL Wet Gas Basics 7

8 Our Journey 2010, welcome to CEESI The Sun is out, the equipment has arrived, what could possibly go wrong What a difference 48 hours can make. 8

9 Our Journey 2014, welcome to Elster-Instromet If you cannot get to a test facility you make one!! 9

10 Our Journey 2014, welcome to DNV-GL All Ready to go! 10

11 How wet was the tested gas? Meter s Watchdog 11

12 How wet was the tested gas? During the testing, various liquid loadings have been introduced to varying gas flows at varying pressures to determine how the ultrasonic meter will respond. 12

13 What does It Look Like? 13

14 Flow regimes Stratified flow mist flow ** 14

15 Feasibility boundaries Can we transmit a pulse through the medium? Penetrate the medium (can we overcome Attenuation, reflection, absorption) What Soundspeed will the medium support (causing reflections in the signal in two phase or complete different SOS if medium changes) Diffraction in the medium (Will the signal physically change shape making it unrecognisable) Assuming we can transmit through the medium Can we properly detect and amplify the received pulse? Signal detection and Gain stability (Signal amplitude fluctuations ) Signal shape stability (does it remain consistent?) Noise Amplification, (impact noise, short circuit noise ) We can only talk about a reliable, stable, robust measurement if we have a good signal to work with. Without a solid signal, discussions about accuracy & uncertainties cannot even begin to take place. 15

16 Signal Quality Ultrasonic signal DNV-GL 2014 Stratified flow and mist flow (in the Gaseous region) Ultrasonic signal DNV-GL 2014 (dry gas) 16

17 Signal Quality Ultrasonic signal DNV-GL 2014 Stratified flow (in the Liquid region) Ultrasonic signal DNV-GL 2014 dry gas 17

18 Signal Quality In liquids the signal is saturating as most ultrasonic meters in gas applications use a Low Noise Amplifier (LNA) and a Variable Gain Amplifier (VGA) (LNA is already enough to have signal saturation) (Gains vary drastically between liquid & gas) 1-10,000 (60dB) Need fast routine to check if in liquid domain or gas domain (soundspeed!) Gas/liquid boundary domain will not work because of short circuit 18

19 Signal Quality Droplet on transducer transmission/receiving face surprisingly not affecting signal quality!! BUT If there is a path formed between transducer and meter body=>acoustic short circuit and loss of signal occurs!! 19

20 Lost of performance CEESI 2010 Experience 0.00% % % % % % % % % % % testpoint # CEESI 2010 In 2010, Measurement was lost during certain test cases (GVF down to 95%) due to acoustic short circuit predominantly on low pressure & high liquid loading. 20

21 Error Error DNV-GL 2014 Experience 30.00% 30.00% 20.00% 20.00% 10.00% 10.00% 0.00% % % % % % % # testpoint % testpoint DNV-GL 2014 Error before any correction (no cross sectional area correction applied). DNV-GL 2014 Error after Elster basic cross sectional area correction Since 2010, Enhancements to the transducer and the mounting have been made and as a result, Measurement was never lost in 200+ tests!! (GVF down to 93%) 21

22 What did the diagnostics tell us? Dry Gas-> All paths working (Measurement & Diagnostic paths) Introduction of liquid Increased standard deviation of diagnostic path (0.01 to 0.05 X LM ) Eventual loss of diagnostic path (all measurement paths operational) Loss of lower measurement path (submersed in liquid) Basic correction implemented for loss in Cross Sectional Area. (May be improved with release of DNV-GL Wet Gas Algorithm) Awaiting high definition video from DNV-GL to clarify regimes 22

23 Further Work Measurement error that is due to the area occupied by the liquid can be quantified. Quantification of actual liquid volumes may now be developed. Incorporating liquid level measurement will further reduce the measurement error. 23

24 Conclusions The measurement robustness has been improved significantly over recent years. Now that a solid signal has been established in even the most demanding condition, this provides a solid foundation upon which we can move forward. Enhancements in transducer & mounting design have helped eliminate the acoustic short circuit caused by liquid accumulation and fast recovery. Utilisation of key diagnostics to detect when liquids are present and in initial concentrations. Analysis of HD Video s of tests from DNV-GL (once released) will help identify regimes & transitions during the testing. 24

25 Conclusions This is the beginning of a journey for USM s in wet gas. There is a long way to go to get to the same position as the orifice or venturi, if indeed that will be possible who knows? DP measurement has 30+ years head start on USM s in this application so hopefully we can build on their experience and start bridging the gap between dry gas and wet gas. Maintaining a solid signal is the first piece of the jigsaw so hopefully we can continue to piece the solution together. One day USM s may have an ISO correction algorithm, if we don t try we will never know. 25

26 Acknowledgements CEESI Inc. (Richard Steven & Josh Kinney) for the organisation of the 2010 Wet Gas JIP DNV-GL (Dennis van Putten & Rene Bahlmann) for the organisation of the 2014 Wet Gas JIP Elster R&D Team for making this happen & References TUVNEL GOOD PRACTICE GUIDE - AN INTRODUCTION TO WET-GAS FLOW METERING R. Steven, G. Stobie, A. Hall: Further Evaluation of the Performance of Horizontally Installed Orifice Plate and Cone Differential Pressure Meters with Wet Gas Flows, SEA 2008, Kuala Lumpur, February

27 Thank you Any Questions Please?