Emerson ControlWave GFC Manuel d'instructions télécharger pdf (Page 12)

ControlWave Gas Flow Computer (GFC) Instruction Manual (CI-ControlWave GFC)

1-8 Introduction Revised Nov-2011

1.7 Overview of the Gas Flow Measurement Application

Note: For detailed information on the gas flow measurement

application and web pages refer to the ControlWave Flow

Measurement Applications Guide (D5137).

You can purchase the ControlWave GFC with a pre-programmed flow

measurement application already loaded.

The ControlWave standard gas flow measurement application collects

static pressure, differential pressure and temperature data and computes

flow, energy, and volume for a station.

A station typically refers to a single flow computer and all its

associated meter runs. Each meter run refers to measurement of natural

gas through a single pipeline.

1.7.1 Data Acquisition – Static Pressure, Differential Pressure,

Temperature Variables

The application requires these process inputs for orifice measurement:

 static pressure (SP) collected once per second

 differential pressure (DP) collected once per second

 flowing temperature (T) collected once per second

The application requires these process inputs for measurement using a

positive displacement (PD), turbine, or ultrasonic meter:

 static pressure (SP) collected once per second

 frequency input collected once per second

 flowing temperature (T) collected once per second

The application also collects self-test and compensation variables at

intervals of four seconds or less.

Pressure data can come from any of the following sources:

 Analog pressure transmitters connected to analog input points on a

process I/O module in the ControlWave flow computer.

 Built-in multivariable transducer.

 External multivariable transmitters (Bristol or Rosemount) using

BSAP or Modbus communications through an RS-485

communication port.

1.7.2 Flow and Volume Calculations

Flow and volume calculations conform to American Petroleum Institute

(API) and American Gas Association (AGA) standards.

Supported flow calculations include:

 AGA3-1985/NX-19

 AGA3-1992 with selectable AGA8 Gross or AGA8 Detail

 AGA7/NX-19

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Emerson ControlWave GFC Manuel d'instructions Page 12