ProSoftOil and Gas Application Solutions www.prosoft-technology.com

Custody Transfer

In the oil and gas industry, the most 

critical application of flow measurement 

is undertaken by companies involved 

in fiscal transactions associated with 

the transfer of hydrocarbon gas or 

liquid from a seller to a buyer. This 

transfer of liquids or gases may 

take place at some remote LACT 

location many miles away from the 

corporate headquarters of the two 

or more contracting parties. These 

transactions have to be recorded 

and the information made available 

to the right departments for 

accounting and record keeping. 

The function of a Flow Computer 

for Custody Transfer is four- fold:

1) Collect Raw Measurement Data

2) Calculate & Store Measured 

Quantities

3) Transmit Measurement Data to a 

SCADA Host

4) Execute Limited Monitoring and 

Alarming Functions

Flow Measurement

Using your PLC as a cost effective controller, RTU and 

Flow Computer

Product flow measurement is a basis for commerce between many oil and 

gas producers, transporters and distributors. Hydrocarbon processing 

plants, transmission pipelines, and many other facilities require quantitative 

monitoring of fluid flow. Almost all of these measurement requirements can be 

broadly classified under three main areas:

1) Custody transfer of product between two contracting parties

2) Process flow control in pump stations, process plants, etc.

3) Line balance for leak detection

The four main system components of a typical Gas or Liquid LACT site are:

1) Station Monitoring, Control, and Safety (PLC)

2) HCF Flow Measurement (Flow Computer)

3) Communications to a SCADA Host (RTU)

4) System & Measurement Data Access (PLC/Flow Computer/RTU)

ProSoft provides the solution: 

AFC – Flow Calculation Modules with 

Modbus RTU Capability 

Meeting Industry Standards Standard Measurements

Most petroleum fluids are measured and sold on a volumetric basis. To 

obtain consistent and accurate dynamic flow measurements, the flow 

measurement device must convert the measured volume to an equivalent 

volume referenced to a set of standard conditions acceptable to both parties. 

All custody transfer transactions have to comply with two distinct categories 

of enforced standards:

 • Standards that define the actual algorithms and process conditions for 

volumetric or mass measurement of fluids.

 • Standards that define other secondary aspects of dynamic fluid 

measurement like the process sampling rates, data archiving, data 

security, data reporting, etc.

Process Flow Control

Many metering sites require pressure or fl ow control or both with pressure 

override capabilities. For stable fl ow control applications, it is important 

that the sampling of the process and computation of the fl ow rate be 

accomplished at least twice as fast as the fastest change component of the 

process. With the fast scan time of ProSoft’s AFC Module providing the 

process variable to the PID block in the PLC ladder logic, stable closed 

loop fl ow control can be implemented

The precision measurement 

of calculations and process 

inputs available utilizing 

the AFC Module can more 

than meet the application 

requirements.

ProSoft Flow Computers

ProSoft AFC modules are in-rack Oil & Gas Flow Computers for Allen-Bradley’s 

ControlLogix, SLC 500, and PLC-5 processors and Schneider Electric’s Quantum 

processor. These modules support 8 or 16 meter runs for the measurement 

of hydrocarbon gases using the AGA 3, 7 and 8 measurement standards. For 

hydrocarbon liquid flow measurement, this solution uses API 2540 standard. 

To obtain process inputs for the calculations, the module uses the process data 

collected by processor’s analog I/O modules. 

ProSoft’s AFC module calculates flow rates, accumulated volumes and accumulated 

mass. The results of the calculations are transferred back to the processor for 

use in the application ladder logic, or for transfer to a SCADA host.

Key Features • Hardware reliability • Backplane compatibility • Transient, Surge, RFI, EMI protection • Proven track record • Expandable I/O and RAM • Battery-backed RAM • Frequency Densitometer Interface • Gas/Liquid Chromatograph Interface • Field programmable • Selectable multiple measurement standards • Multiple meter runs • PLC/FC/RTU Integrated Data Base MVI71-AFC for PLC with 8 meter runs MVI46-AFC for SLC with 8 meter runs MVI56-AFC for ControlLogix with 16 meter runs PTQ-AFC for Quantum with 16 meter runs ProSoft Flow Computers ProSoft AFC modules are in-rack Oil & Gas Flow Computers for Allen-Bradley’s ControlLogix, SLC 500, and PLC-5 processors and Schneider Electric’s Quantum processor. These modules support 8 or 16 meter runs for the measurement of hydrocarbon gases using the AGA 3, 7 and 8 measurement standards. For hydrocarbon liquid flow measurement, this solution uses API 2540 standard. To obtain process inputs for the calculations, the module uses the process data collected by processor’s analog I/O modules. ProSoft’s AFC module calculates flow rates, accumulated volumes and accumulated mass. The results of the calculations are transferred back to the processor for use in the application ladder logic, or for transfer to a SCADA host. • Double Precision Math • Selectable Meter Factor Characterization • Accessible Data & System Interoperability • Data Archiving • Event Logging • Dynamic Meter Audit Scan • Local Display • Data Security • Fast Scan Times • Good Error Detection • MS Windows Based System Configuration • Site Specific System Documentation and Reports