Smart DP Flow Metering A summary of Established Technology and Latest Innovation. Gary Fish

Transcription

1 Smart DP Flow Metering A summary of Established Technology and Latest Innovation Gary Fish

2 DP Flow Measurement Established Technology Large range of line sizes, materials, connection interfaces, etc Customised solutions New innovations and improvements

3 Square Edged Orifice Plate ISO β range 0.1 to 0.75 Min Re D 5 x 10 3 Max Re D Permanent Pressure loss: β dependent between 42% and 98% of ΔP Uncalibrated Uncertainty C d 0.5% (for β between 0.2 & 0.6) General Flow metering applications- gas allocation and fiscal standard

4 Conical Entrance Orifice Plate ISO TR β range 0.1 to Min Re D 80 Max Re D 6.3 x 10 4 (for β 0.316) Uncalibrated Uncertainty C d 2% Application viscous fluids

5 Quarter-Circle Orifice Plate ISO TR β range to 0.6 Min Re D 245 (for β 0.245) Max Re D 6 x 10 4 (for β 0.6) Uncalibrated Uncertainty C d 2% to 2.5% Application viscous fluids

6 Eccentric Orifice Plate ISO TR β range 0.46 to 0.84 Min Re D 4.2 x 10 3 Max Re D 8.4 x 10 5 Uncalibrated Uncertainty C d 1% to 2% (can be calibrated to improve) Application entrained gas in liquid service, entrained liquid in gas service, sediments, etc

7 ISA 1932 Nozzle ISO β range 0.3 to 0.8 Min Re D 2 x 10 4 (for β 0.44 or greater) Max Re D 1 x 10 7 Uncalibrated Uncertainty C d 0.8% to 1.2% (β dependent) Permanent Pressure loss: between 25% and 80% of ΔP (typical) high velocity, steam flow.

8 Long Radius Nozzle ISO β range 0.2 to 0.8 Min Re D 1 x 10 4 Max Re D 1 x 10 7 Uncalibrated Uncertainty C d 2% Permanent Pressure loss: between 24% and 92% of ΔP (typical) high velocity, steam flow.

9 Venturi Nozzle ISO β range to Min Re D 1.5 x 10 5 Max Re D 2 x 10 6 Uncalibrated Uncertainty C d 1.2% to 1.7% Permanent Pressure loss: between 5% and 20% of ΔP (typical) high velocity, steam flow. Low permanent pressure loss

10 Machined Venturi ISO β range 0.4 to 0.75 Min Re D 2 x 10 5 Max Re D 1x 10 6 Uncalibrated Uncertainty C d 1% (for Re D limits shown) Re D limits increased according to Annex B with increased uncertainty Permanent Pressure loss: between 5% and 20% of ΔP General Flow metering applications- gas allocation, high velocity, low maintenance and intervention. Low permanent pressure loss.

11 Fabricated Venturi ISO β range 0.4 to 0.7 Min Re D 2 x 10 5 Max Re D 2 x 10 6 Uncalibrated Uncertainty C d 1.5% (for Re D limits shown) Re D limits increased according to Annex B with increased uncertainty Permanent Pressure loss: between 5% and 20% of ΔP General Flow metering applications- gas allocation, high velocity, low maintenance and intervention. Low permanent pressure loss.

12 As Cast Venturi ISO β range 0.3 to 0.75 Min Re D 2 x 10 5 Max Re D 2 x 10 6 Uncalibrated Uncertainty C d 0.7% (for Re D limits shown) Re D limits increased according to Annex B with increased uncertainty Permanent Pressure loss: between 5% and 20% of ΔP General Flow metering applications- gas allocation, high velocity, low maintenance and intervention. Low permanent pressure loss.

13 Cone Meter ISO β range 0.45 to 0.75 Min Re D 8 x 10 4 Max Re D 1.2 x 10 7 Uncalibrated Uncertainty C d 5% Permanent Pressure loss: between 48% and 72% of ΔP (typical) General Metering applications, allocation, shorter overall installation than Venturi meter

14 Wedge Meter ISO (not yet published) β range to Min Re D 1 x 10 4 note 1 Max Re D 9 x 10 6 Uncalibrated Uncertainty C d 4% Permanent Pressure loss: between 47% and 79% of ΔP (typical) Suspended solids, viscous fluids note 1 Note 1 : Standard will be based upon available data Wedge Meters have been known to operate at Re =500, but will require calibration- resulting in much lower uncertainty also.

15 Dall Tube No International Standard β range 0.3 to 0.8 Min Re D 5 x 10 4 Max Re D Uncalibrated Uncertainty C d 3% Permanent Pressure loss: between 2.5% and 8% of ΔP (typical) Clean process fluids, very low pressure loss requirements

16 Comparison table for DP Devices Limits of use Device Standard Line Size (mm) β Re D Min Max Min Max Min Max Uncertainty C d (UNCALIBRATED) Permanent Pressure loss (% of ΔP) SQUARE EDGED ORIFICE PLATE ISO x % NOTE 1 42% to 98% CONICAL ENTRANCE ORIFICE PLATE ISO TR x % 86% to 98% QUARTER-CIRCLE ORIFICE PLATE ISO TR x % to 2.5% 53% to 91% ECCENTRIC ORIFICE PLATE ISO TR x x % to 2% 36% to 77% ISA 1932 NOZZLE IS x x % to 1.2% 25% to 83% LONG RADIUS NOZZLE ISO x x % 24% to 92% VENTURI NOZZLE ISO x x % to 1.7% 5% to 20% MACHINED VENTURI ISO x x % 5% to 20% FABRICATED VENTURI ISO x x % 5% to 20% AS CAST' VENTURI ISO x x % 5% to 20% CONE METER ISO x x % 48% to 72% WEDGE METER ISO NOTE x x % 47% to 79% DALL TUBE NO STANDARD x % 2.5% to 8% Notes 1 For β between 0.2 and Not yet published All C d Uncertainties can be reduced with flow calibration over entire operating range

17 Upstream Straight Length requirements 1off 90 o bend Generic DP Device β lim L β lim L β L ORIFICE 0.1 6D D NOZZLE D D VENTURI 0.3 8D D CONE METER D D WEDGE METER D D DALL TUBE 0.3 3D D D D 0.5 9D 0.5 3D 0.5 7D 0.5 4D Upsteam lengths may be reduced with C d uncertainties increasing

18 Upstream Straight Length requirements 1off 90 o bend Generic DP Device Uncalibrated C d Uncertainty β L ORIFICE (Square edged) 0.50% D NOZZLE (ISA 1932) 0.80% D VENTURI (Machined) 1.00% 0.5 9D CONE METER 5% 0.5 3D WEDGE METER 4% 0.5 7D DALL TUBE 3% 0.5 4D

19 Upstream Straight Length requirements 1off 90 o bend Generic DP Device Uncalibrated C d Uncertainty β L ORIFICE (Square edged) 1.0% 0.5 9D NOZZLE (ISA 1932) 1.3% 0.5 7D VENTURI (Machined) 1.5% 0.5 3D CONE METER 5%* 0.5 3D* WEDGE METER 4%* 0.5 7D* DALL TUBE 3.5% 0.5 3D *No data published in ISO regarding shorter length uncertainty

20 Differential Pressure Transmitter Technology Largest contribution to enhanced DP meter uncertainty in recent years Example 1 : Yokogawa EJX130A, ref accuracy :+/-0.04% of span (3σ) Example 2: Rosemount 3051CD (ranges 2-4), ref accuracy :+/-0.04% of span (3σ) Full transparent uncertainty analysis can be carried out for DP meters

21 DP Meter Uncertainty Analysis

22 Myth : The Differential Pressure is limited to 500mbar for an orifice plate

23 Limits for Orifice Plate DP End User/Operator specifications stating for instance DP limited to 500mbar Why? There is no need providing : Permanent Pressure loss is acceptable Orifice Plate Elastic or Plastic Deformation is considered DP is within expansibility limits

24 Myth : The flow turndown for DP devices is only 3:1

25 Turndown / Rangeability Claim / belief: You only get 3:1 with an orifice Turndown/rangeability is the ratio of the largest to smallest flow rate that can be metered to the meter s stated flow rate prediction uncertainty at a stated confidence level. For mass flow uncertainty below 0.8% we need the DP uncertainty <1%. [200, 2000] = 10:1 on DP ~3.2:1 flow range With 1 DP Transmitter

26 DP H: mbar DP M: 0-300mbar DP L: 0-50mbar Turndown / Rangeability Example, stacked transmitters Example : 30m/s, 25kg/m 3, 12 pipe ~260,000 Sm 3 /h Beta = 0.6, DP = ~2000mbar

27 Turndown / Rangeability Example, stacked transmitters 30m/s, 25kg/m 3, 12 pipe 260,000Sm 3 /h Beta = 0.6, DP = ~2000mbar DP H: mbar DP M: 0-300mbar DP L: 0-50mbar min: 30% of max flow -> 3.3:1 min: 11% of max flow -> 9.1:1 min: 4.5% of max flow -> 22:1

28 Turndown / Rangeability Claim / belief: You only get 3:1 with an orifice 0 m/s? 3.3% of flow rate (1 m/s) +/-0.8% 100%/3.3% = 30 i.e. turndown = 30:1 e.g. USM 100% of flow rate (30 m/s) 0 m/s 4.5% of flow rate (1.35 m/s) +/-0.8% 100%/4.5% = 22 i.e. turndown = 22:1 e.g. Orifice 100% of flow rate (30 m/s)

29 Turndown / Rangeability Similar Claim Turndown / belief: to USM in practice You only get 3:1 with an orifice 0 m/s 3.3% of flow rate (1 m/s) +/-0.8% 100%/3.3% = 30 i.e. turndown = 30:1 e.g. USM 100% of flow rate (30 m/s) 0 m/s 4.5% of flow rate (1.35 m/s) +/-0.8% 100%/4.5% = 22 i.e. turndown = 22:1 e.g. Orifice 100% of flow rate (30 m/s) Difference? 30:1 from 22:1 is an increase in flow range of (1.2/95.5) 1.26%

30 Turndown / Rangeability Later life example. Reduced Pressure and Flow E.g. Max flow: 3 m/s, (i.e. 15,500 Sm 3 /h) USM fixed at 30 m/s > U (m/s) > 1 m/s, (10% of USM full scale flow). 0.6β orifice meter produces 12mbar, (8% of orifice meter full scale flow). Easy improvement :change the beta 0.2β orifice meter produces 1150mbar 1150 DP mbar 5 gives 3 U (m/s) :1

31 Myth : The permanent pressure loss is always too high with DP devices

32 Permanent Pressure Loss Higher PPL may sometimes be significant, but meter PPL should be seen in context.

33 Permanent Pressure Loss 12, sch 40 gas (ordinary) pipe 40 Bar, 15 0 C, 31.8 kg/m 3, 15 m/s, 140 MMSCFD Components in pipe: Globe valve (3/4 open) for control Open butterfly valve (emergency shut off) 4 elbows, T-junction, sample probe, 2 thermowells A flow conditioner & flow meter What is the PPL across the system? What relative impact on overall PPL does the meter system have?

34 Permanent Pressure Loss P loss K loss V * 2 2 av

35 Permanent Pressure Loss P loss K loss V * 2 2 av

36 Permanent Pressure Loss The PPL is dependent on the length of pipe. P loss K loss V * 2 2 av Most pipe systems are long, that s why it s convention to call pipe loss the major loss!

37 Permanent Pressure Loss Often pipe losses dwarf any meter PPL. (Gas transmission compressor stations are > 40 miles apart, platform to shore is miles long etc.) Other calibrated DP devices can offer the measurement accuracy requirements and low pressure losses eg Venturi, Dall tube, etc

38 Myth : DP devices don t have diagnostic capabilities

39 Incorrect Metrology Data Excessive Flow Disturbance Contamination Build Up Saturated DP Tx Drifting DP Tx Incorrectly Spanned DP Tx DP Below Tx Range Two Phase Flow Electrical Loop Integrity Plugged Lines Process Leakage Improved Overall Safety Integrity Etc,Etc.. Validation / Diagnostics Combination of advancement in transmitter technology and specialised innovative developments the following diagnostics are available for DP meters

40 Validation / Diagnostics - Orifice Excellent diagnostics No calibration required. 3 x Flow Rate Comparisons 3 x DP Ratio Comparisons Reasonably objective 1 x DP Integrity Check DP Synchronisation / turbulence checks

41 Thankyou! : Questions?