Aspects of Flow Control in Metering Henry Gomes SGS Kuwait WLL

Transcription

1

2

3 Aspects of Flow Control in Metering Henry Gomes SGS Kuwait WLL

4 HENRY GOMES Metering Consultant SGS Kuwait Born on Aruba (Carribean) in 1963 School and College in the Netherlands Resident in Romania - Bucharest Mechanical Engineer (3 years) at Stork Instrument Engineer (7 years) at MW Kellogg Metering Engineer (17 years) at Polar Systems / Imtech Systems Metering Consultant at SGS Kuwait

5 Aspects of Flow Control in Metering Sharing experience regarding flow control: Valve capacity sizing Control valve type Characteristic / Rangeability Effects on metering applications

6 Theory Principle of Daniel Bernoulli: Liquid flowing through an orifice, the square of the fluid velocity is directly proportional to the pressure differential across the orifice and inversely proportional to the specific gravity of the fluid.

7 Calculation Calculation for liquid Q = Flow rate Cv = Valve sizing Coeff. ΔP = diff. pressure G = Specific gravity Cv: Valve sizing coefficient determined experimentally for each style and size of valve using water Beside the flow and differential pressure: Choking, Flashing and Cavitation for liquid applications Critical flow for gas applications

8 Rangeability / Characteristic Inherent rangeability Ratio of its maximum Cv to its minimum controllable Cv Property of the control valve alone Installed rangeability Ratio of its maximum controllable flow to its minimum controllable flow Product from hydraulic calculations Characteristic: Linear Equal percentage Quick opening

9 Effects on Flow metering Proper valve sizing can reduce cost and prevent inconvenience A control valve that is too small will not pass the required flow An oversized valve is expensive and could lead to instability Cavitation caused by the control valve: Lifetime expectancy control valve Vibrations on the metering skid (negative effect on flow meter, temperature elements, valves, actuators). Flow profile disturbance when upstream meter run Noise cause by the control valve: Ultra-sonic noise from control valve can disturb the measurement in ultra-sonic metering

10 Control Valve Types Globe Control Valve Eccentric Rotary Plug Valve Segmented Ball Valve Butterfly Valve

11 Application 1 24 stream butterfly control valves Designed for flow balancing during loading / proving Loading rate flow control by control valve to vessel

12 Application 2 Coriolis meter trial proposed by metering supplier Higher pressure drop across Coriolis meter: Coriolis meter pressure max. flow 33 psi Turbine meter pressure max. flow 1 psi Cavitation expected at turbine run control valves while proving Coriolis flow meter Poor rangeability of 24 butterfly control valves

13 Application 3 12 Ultra-Sonic Natural Gas Flow Meter High pressure natural gas: Noise predicted across control valve Noise dampening with additional 90 elbows Control valve equipped with low-noise trim Integrator, flow meter manufacturer and control valve supplier cooperation to prevent noise problems on metering.

14 Application 4 Allocation Flow Control with inlet block valve of orifice meter run Inlet gate valve was used for flow control Straight length upstream orifice not designed for partially closed gate valve High pressure drop across gate valve caused cavitation: high vibration on the meter run noise

15 Conclusion Control Valves in Metering Applications must be right sized for its specific application. Improper sizing, or just line size control valves will have negative effects on the metering application when not done properly. Close cooperation between integrator, flow meter manufacturer and control valve manufacturer to achieve the best performance, especially in new technology metering.

16 Questions?