General System Configuration
Metering
System consists of flow meter, flow calculator panel, G/C and HMI
application softwares. Flow calculator panel has flow computer, PLC,
G/C Controller.
Flow compuer performs calculation of flowing density, volume
correction, mass flowrate, corrected volume flowrate and energy
flowrate by refering to gas component, pressure, temperature in case
of natural gas. PLC performs automatic meter run switching or manual
valve operation. Also PLC communicates with upper control system like
MCS or RTU. HMI application enables user to easlily operate system.
Please refer to Metering Software part for more details.
Metering System Panel
Metering
Panel (or Flow Calculator Panel) is different as system configuration
or user requirements. However basically includes flow computer, G/C
controller and PLC.
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Flow Computer Panel
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Gas Chromatograph
The
gas chromatograph is used to obtain on-line composition information of
selected process streams for current process operation. The gas
chromatograph must operate automatically with a high degree of
reliability, require a minimum of maintenance, and perform the desired
analysis within the required time. Gas composition is used for density
calculation and energy calculation.
The analyzer includes a
chromatographic column(s), sample injection and switching valves, a
detector, a temperature controller, flow controls for the carrier and
detector medium(s), and the necessary electronics. The controller
function may be separate or may be in the field with the analyzer,
which thereby becomes a stand-alone gas chromatograph. Both systems
provide analog outputs for concentration data and digital outputs for
alarms, external stream select, and other external functions.
The thermal conductivity detector (TCD) is the most widely used
because of its universal response to all components and its simplicity.
The detector measures the thermal conductivity of the gas passing
through it. The carrier gas is selected to have a thermal conductivity
different from the components being measured. Helium or hydrogen is
normally used for this reason.
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Gas Chromatograph Panel
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- Orifice Meter : AGA 3, ISO 5167
- Turbine Meter : AGA 7
- Ultrasonic Meter : AGA 9
- Density & Compressibility Calculation : AGA 8
- Energy Calculation : ISO 6976
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