2017 Western Regional Gas Conference Bayview Ballroom 2 8/29/2017 9:00 9:45 Presenter: Dan Whaley Company:
Natural gas distribution Transfer and measuring stations for municipal and regional gas suppliers Measuring stations of industrial and commercial applications Applications where continuous gas supply must be ensured
Operating Principle Crossing a river A boat crossing a river diagonally with the flow needs less time than a boat crossing the river against the flow The stronger the current the faster the crossing with the flow and the slower the crossing against it The difference between the two transit times depends directly on the flow velocity Exactly this effect is exploited by the ultrasonic flow meter Crossing a pipe by ultra sound The two diagonally opposed transducers function alternatively as transmitters and receivers The sound signal emitted from Transducer A is accelerated by the flow The sound signal emitted from Transducer B is slowed by the flow The difference between the two transit times (T1 & T2) is directly proportional to the gas velocity From the gas velocity, the volumetric flow can then be calculated using cross sectional area. Transducer B Transit time from B to A (T2) Flow direction Delta time T = T2 - T1 Transducer A Transit time from A to B (T1)
Operating Principle
Typical Ultrasonic Meter Designs Several meter designs are available today Many diagnostic parameters are similar for all designs Main difference in designs is analysis of velocity info
Typical Ultrasonic Meter Designs Path A Path B Path B Path C Path A
Flow Profile Good measurement is dependent on flow profile Typical requirements for upstream/downstream piping with flow conditioning. Internal Flow Conditioning = No Upstream/Downstream Piping Requirements U-turn Flow conditioning Metering section
Diagnostics Diagnostic parameters in USMs that are required by AGA 9: Average Gain Control (AGC) Levels Path Transit Times Average Axial Flow Speed of Sound (SOS) for each path Flow Velocities (VOG) for each path Average Speed of Sound Velocity Sampling Interval Averaging Time Interval Percentage of accepted pulses Status and/or measurement quality Alarm and failure Meter, indicators Valve & Control, Inc
Diagnostics - Gain Gain? Can anyone tell me what it is?
Diagnostics - Gain Automatic operation in USMs Manufactures fire transducers with a fixed energy Gain is a measure of how much amplification is needed Amount of gain depends on several variables including: Metering pressure Gas velocity Meter size (path length) May increase due to contamination Gas composition (i.e.; Hydrogen vs. Natural Gas) Readings vary by manufacturer Contamination seldom causes gain to reach the maximum
Diagnostics - SNR Signal to Noise? Can anyone tell me what it is?
Diagnostics - SNR SNR is a measure of signal strength to noise Generally SNR is not used as much as others SNR becomes important when control valves are near At very high gas velocities, SNR will decrease Different manufactures have different methods of presenting this information When the SNR gets low enough, performance will also decline
Diagnostics - SOS Speed of Sound? Can anyone tell me what it is?
Diagnostics - SOS Equation is similar to velocity calculation Health check for path velocities SOS by path is required by AGA 9 SOS affect by gas composition, P&T, but not gas velocity! Can be calculated with AGA 10 or other algorithms If they do not agree, possibility of liquids, contamination or poorly entered data. Can be checked versus theoretical values using GC
Diagnostics - Performance Performance? Can anyone tell me what it is?
Diagnostics - Performance Signal Quality Level of accepted pulses (displayed in percent) Reported by path 100% acceptance isn t required for accurate measurement Pulses are rejected if they fail certain criteria The most important part of pulse detection is to insure we don t pick the wrong waveform peak and thus have a bad transit time
Diagnostics - Performance
Diagnostics In Action Software will automatically compare diagnostic parameters. If within tolerance, meter will give an all good signal If not in tolerance will give an indication as well
Diagnostics In Action All diagnostic data for each path is stored and can be reviewed to determine the cause. Can account for accuracy changes.
Diagnostics In Action
Verification Self-Diagnostics SOS Verification Transfer Prover
Verification Questions? Comments?