Corrections related to operation and calibration of liquid flow meters NFOGM Temadag 2016 Morten Marstein, FMC Kongsberg Metering

Transcription

1 Corrections related to operation and calibration of liquid flow meters NFOGM Temadag 2016 Morten Marstein, FMC Kongsberg Metering FMC Kongsberg Metering

2 General formulas Volumetric flow meter qq vv,ssssss = qq vv CC tttttt CC pppppp CC tttttt CC pppppp qq vv = PPPPPPPPPPPP/hhhhhhhh KK_ffffffffffff q v,std q v C tlm C plm C tsm C psm = Standard volume flow rate from flow meter (Sm 3 /h) = Actual volume flow rate from flow meter (m 3 /h) = Correction for the temperature effect on liquid at the meter = Correction for the pressure effect on liquid at the meter = Correction for the temperature effect on steel of the meter = Correction for the pressure effect on steel of the meter K_ factor = Calibration factor for flow meter (pulses/m 3 ) 1

3 General formulas Mass flow meter qq vv,ssssss = qq mm ρρ ssssss = qq mm ρρ CC tttttt CCCC llll qq mm = PPPPPPPPPPPP/hhhhhhhh KK_ffffffffffff q v,std q m ρ std ρ C tlm C plm K_ factor = Standard volume flow rate from flow meter (Sm 3 /h) = Mass flow rate from flow meter (kg/h) = Density of liquid at standard conditions ( bara, 15 C) = Operating density = Correction for the temperature effect on liquid at the meter = Correction for the pressure effect on liquid at the meter = Calibration factor for flow meter (pulses/kg) 2

4 Correction factors for liquid USM flow measurement qq vv,ssssss = PPPPPPPPPPPP/hhhhhhhh KK_ffffffffffff CC tttttt CC pppppp CC tttttt CC pppppp C tlm C plm C tsm C psm = temperature effect on liquid at the meter = pressure effect on liquid at the meter = temperature effect on steel of the meter = pressure effect on steel of the meter K_ factor = Calibration factor for flow meter (p/m 3 ) 3

5 C tlm temperature effect on liquid at the meter API MPMS Ch : CC tttttt = ee αα TT 0.8αα2 TT 2 Hydrocarbon Liquid K 0 K 1 Crude Oils Fuel Oils αα = KK KK 1 ρρ rrrrrr ρρ rrrrrr Jet Fuel Gasoline

6 C tlm temperature effect on liquid at the meter For a typical crude oil, a temperature increase of 1 C generates an increased volume of approximately 0.1%. 5

7 C plm pressure effect on liquid at the meter API MPMS Ch M: The most common used equation for C plm valid for density from 638 to 1074 [kg/sm 3 ]. Name Description A B C D T = temperature ( C) ρ = reference density (kg/sm 3 ) 6

8 C plm pressure effect on liquid at the meter For a typical crude oil, a pressure increase of 10 bar generates a reduced volume of approximately 0.1%. 7

9 Data entry for C tlm and C plm 8

10 Parameter report for C tlm and C plm Correction parameters must be available on flow computer parameter report 9

11 C tsm temperature effect on steel at the meter 10

12 C tsm temperature effect on steel at the meter Linear thermal expansion coefficient (α) Material α (m/m/k) Example: A 100 m steel rail expands 12 mm when temperature increases 10 degrees m at 20 C Carbon steel 1.2 x 10-5 Stainless steel AISI x 10-5 Duplex 1.3 x m at 30 C 11

13 C tsm temperature effect on steel at the meter Ultrasonic flow meters ISO 12242: CC tttttt = 11 + αα TT 33 CC tttttt αα TT α = Linear thermal expansion coefficient (/K) References: ISO 12242: Measurement of fluid flow in closed conduits - Ultrasonic meters for liquid ISO refers to ISO method for pressure and temperature correction of flow meter body T = T Tcal (K) 12

14 C tsm temperature effect on steel at the meter Ultrasonic flow meters The relative volume correction for thermal expansion of the flow meter body is approximately 0.1% if the temperature is increased by 25 C. 13

15 C psm pressure effect on steel at the meter Low pressure High pressure r 1 r 2 R 1 R 2 14

16 C psm pressure effect on steel at the meter Ultrasonic flow meters ISO ISO : Open pipe «Barrel» General formula: K P 2 2 d l r r + d l = = (1 + ) r r K Pne > K Pce No ends Capped ends Average K Pne 2 2 R + r P = µ R r 2 2 E K Pce 2 2 R (1 + µ ) + r (1 2µ ) P 1+ 4 R r 2 E = 2 K Pav K Pne + K = 2 Pce µ (Poisson ratio) = 0.3 E (Modulus of elasticity or Young s modulus) = 2 x 10 6 bar (typical) 15

17 C psm pressure effect on steel at the meter Ultrasonic flow meters Example: The relative volume correction for pressure expansion of the 12-inch flow meter body is approximately 0.1% if the temperature is increased by 170 bar. 16

18 Summary C tlm, C plm, C tsm, C plm for USM What gives 0.1% volume correction? Ctlm Cplm Ctsm Cplm 1 C 10 bar 25 C 170 bar Example shown for typical crude oil (800 kg/m3) and 12-inch USM 17

19 C tsm and C psm for turbine flow meters VVVVVVVVVVVV = PPPPPPPPPPPP CCCCCCCC CCCCCCCC KK ffffffffffff Pressure correction (C psm ) Insertion tube for pressure compensation C psm = 1 (typically) Temperature correction (C tsm ) Rotor blades will be affected Temperature changes are related to viscosity changes which will influence on the turbine meter characteristics C tsm = 1 (typically) 18

20 C tsp and C psp for pipe volume prover API MPMS Ch : CC tttttt = αα TT CC ppsspp = 11 + PP DD EE WWWW T bar Temperature increase from reference α m/m/k Linear thermal expansion coefficient P bar Pressure increase from reference D m Internal diameter of prover pipe E bar Prover steel elasticity module WT m Wall thickness of prover pipe 19

21 C tsp and C psp for compact provers Separate C tsp for area (squared) and for rod (linear) as piston and rod may have different thermal expansion coefficients C psp as for pipe volume prover RRRRRR PPPPPPPPPPPP 20

22 Data entry for C tsm and C psm parameters Required parameters in the flow computer. 21

23 Data entry for C tsm and C psm parameters For some flow meters the corrections may be done in the flow meter itself. But then flow meter needs to know the operating pressure and temperature! 22

24 C tsm and C psm during flow calibration New method: Three-stage calculation for corrections in accordance with ISO , Annex E Pressure and temperature correction for body expansion must be turned off in the USM during flow calibration Keep pressure and temperature correction turned off in the USM during operation in the field Step VCF = Ctsm*Cpsm Calculation of correction 1 VCF 1 Static to dynamic calibration 2 VCF 2 Static to field conditions 3 VVVVVV 3 = VVVVVV 2 VVVVVV 1 Dynamic calibration to field conditions 23

25 C tsm and C psm - ISO vs. MPU

26 Parameter report for C tsm and C psm Correction parameters must be available for inspections and audits on flow meter parameter report or on flow meter configuration print-out. 25

27 ISO detailed vs. simplified method Correction Detailed Simplified Temperature correction Yes Yes Radial pressure correction no ends condition Yes Yes Radial pressure correction capped ends conditions Yes Yes Axial pressure correction Yes No Body style effect, Ks (proximity to flanges) Yes No Transducer port temperature correction Yes No Transducer port pressure correction Yes No 26

28 K-factor qq vv,ssssss = PPPPPPPPPPPP/hhhhhhhh KK_ffffffffffff CC tttttt CC pppppp CC tttttt CC pppppp KK ffffffffffff = pppppppppppp mm 33 27

29 K-factor Calibration Curve - Example Linearity % K-factor (-) Avg. Lim.+0.08% Lim.-0.08% Lim.+0.15% Lim.-0.15% Flow Rate (m 3 /h) 28

30 Calibration Flow meter correction factors K-factor Determined for each flow rate Number of pulses per volume or mass unit (pulses/kg or pulses/m 3 ) VVVVVVVVVVVV = NNNNNNNNNNNN oooo pppppppppppp AAAAAAAAAAAA KK_ffffffffffff Meter factor (MF) Determined for each flow rate Correction factor (-) for multiplication with flow meter output Must know nominal K-factor! VVVVVVVVVVVV = MMMM NNNNNNNNNNNN oooo pppppppppppp NNNNNNNNNNNNNN KK_ffffffffffff 29

31 Meter Factor Calibration Curve - Example Linearity % K-factor (nominal): p/m 3 Meter factor (-) Avg. Lim.+0.08% Lim.-0.08% Lim.+0.15% Lim.-0.15% Flow Rate (m 3 /h) 30

32 Flow Calibration Certificate Example Turbine Deviation (%) = IIIIIIIIIIIIIIIIII ffffffff RRRRRRRRRRRRRRRRRR ffffffff RRRRRRRRRRRRRRRRRR ffffffff Nominal KF Meter factor = [ dddddddddddddddddd % 100 ] Flow Rate (m3/h) K-factor = NNNNNNNNNNNNNN KKKKKKKKKKKKKK MMMMMMMMMM ffffffffffff Meter Factor Error K-factor 31

33 Calibration Linearizing 0,50 0,40 0,30 Flow meter calibration curve (Gas USM example) Table entered into flow computer: Avg. Flow rate (m3/h) Meter factor (-) ,20 Measurement error (%) 0,10 0,00-0,10-0, Av. Error (%) Corrected (%) -0,30-0,40-0,50 Flow Rate (m3/h) 32

34 K-factor offset Linearizing curve established at accredited flow laboratory Proving No. 1 K-factor changed from to (offset +0.23) Linearity % The curve (shape) is kept unchanged for the flow meter Single point onsite proving generates a K-factor offset which shifts the curve up or down K-factor (-) Flow Rate (m 3 /h) Proving No. 2 K-factor changed from to (offset -0.15) Avg. K-factor offset 0.23 K-factor offset

35 Calibration Linearizing options Flow computer data entry options: 1. K-factor (p/m 3 ) against indicated flow rate (m 3 /h) 2. Meter factor (-) against indicated flow rate (m 3 /h) 3. Deviation (%) against indicated flow rate (m 3 /h) NEW! 4. K-factor (p/m 3 ) against Reynolds number (-) 5. Meter factor (-) against Reynolds number (-) 6. Deviation (%) against Reynolds number (-) NEW! 34

36 Calibration Linearizing w.r.t. Reynolds number 35

37 Coriolis meters Pressure and temperature correction for Coriolis flow meters? No standardized method Built-in temperature sensor and correction Sensitive to pressure Fixed pressure input? Online pressure correction? Coriolis flow meter MicroMotion CMF400 (6-inch) E+H Promass 84F DN150 (6-inch) Pressure effect on mass flow rate (%/bar)

38 Questions or comments 37