Contrec 515 – GN05

  • Net Oil Computer

Natural Gas Flow Computer (AGA - 8) - DP Meter (AGA - 3)

The 515 GN05 application is a natural gas flow computer. This application measures the volume, mass and gross heat content of natural gas. The instrument uses single or stacked differential pressure inputs, as well as temperature and pressure sensor inputs.

This natural gas flow computer calculates the flow according to AGA-3 differential pressure equations. The flow calculations incorporate the conditions at which the flowmeter was calibrated and accurately account for thermal expansion effect.

The AGA-8 Detail Characterization Method is used to obtain accurate values of density and compressibility factors for the flow calculations. For other gas properties, such as viscosity and isentropic exponent, the AGA-3 recommended values are used.


The gas density and compressibility factor calculations are based on the AGA-8 equations. The calculations are valid for the region:

-130°C < t < 400°C P < 280MPa

-200°F < t < 760°F P < 40000psia


volume flow =Mflow/ρflow

corrected flow = Mflow/ρ ref

Heat flow = Mflow•Hm


Mflow = mass flow

ρflow = density at flow conditions

ρ ref = density at reference conditions

Hm = mass gross heating value


Displayed Information

The front panel display shows the current values of the input variables and the results of the calculations. A list of the variables for this application and their type (total or rate) is shown at the end of this document.
The instrument can be supplied with a real-time clock for data logging of over 1000 entries of the variables as displayed on the main menu.

Isolated Outputs

The opto-isolated outputs can re-transmit any main menu variable. The type of output is determined by the nature of the assigned variable. Totals are output as pulses and rates are output as 4-20 mA signals. One output is standard, a second output is available as an option.

Relay Outputs

The relay alarms can be assigned to any of the main menu variables of a rate type. The alarms can be fully configured including hysteresis. Two relays are standard with additional two relays available as an option. All set-up parameters, totals and logged data are stored in non-volatile memory with at least 30 years retention.

Software Configuration The instrument can be further tailored to suit specific application needs including units of measurement, custom tags, second language or access levels. A distributor can configure these requirements before delivery.
Instrument parameters including units of measurement can be programmed in the field, according to the user access levels assigned to parameters by the distributor.

Temperature and Pressure Input Types

Temperature sensor input(s) can be either PT100, PT500, 4-20 mA, 0-5 V or 1-5V signals. Pressure sensor input(s) can be either 4-20 mA, 0-5 V or 1-5V signals

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