Gas Custody Transfer

Willowglen can meet your industrial automation needs by providing:

  • Redundant Remote and Master Stations
  • Comprehensive System Security
  • Communication Statistics
  • Operational and Historical Archiving
  • Compressor Station Control
  • Sampling
  • Automatic Pump-off Control
  • PID Closed Loop Control
  • Optional Integrated Pipeline Simulator
  • and more

For gas pipelines, Willowglen can provide the following:

  • AGA-3 Gas Orifice Flow Rate and Accumulation Calculations
  • AGA-7 Gas Turbine Flow Rate and Accumulation Calculations
  • AGA-8 Supercompressibility Correction
  • NX-19 Supercompressibility Correction
  • Redlich-Kwong Supercompressibility Correction
  • Gas Flow Control

Key Features

Large Scale Metering

The Unisen Flow Computer interfaces to standard liquids or gas flow meters, and functions in a variety of configurations – from a single flow meter up to 25 meters, even if distributed across multiple headers.

Metering Proving

The Unisen Flow Computer is able to calculate corrective meter factors through volumetric proving.

Electronic Ticketing

Through our 40 years of experience, Willowglen knows that each customer operates differently and as such can have different expectations – especially when it comes to Electronic Ticketing for accounting and auditing. For that reason the Unisen’s electronic ticketing can be easily adapted to the needs of your business.

QA Sampling

The Unisen flow computer has sophisticated user customizable algorithms to control the sampling apparatus, as well as logic to determine when to take samples (according to the batch size, current flow rate and current sample volumes.)

Audit Logs

Every maintenance, configuration, or operator action performed on a Willowglen Unisen flow computer is recorded in an audit log. Each entry contains a time stamp, the change issuer, along with the old and new value.

Intuitive User Interface

Standard web browser can be connected to the Ethernet port on the Unisen Flow Computer to configure or view its database. No special software, hardware, or licenses needed.

Configurable Reports

By using one of the four Ethernet ports on the Unisen, reports can be set to automatically print directly from the flow computer itself (no need for an intermediate PC to do the printing). Alternatively, reports can be saved as
files in PostScript or CSV file format.

Flexible I/O Card Arrangement

Unisen allows I/O cards to populate any chassis slot with no pre-defined limiting arrangement.

IEC Programming Environment

The Unisen Flow Computer allows customers to create their own programs. These programs can be written in any of the five IEC 61131-3 languages. The Unisen’s high performance CPU and large memory capacity allows these programs to be large and complex.

Dual Redundant

When system reliability is paramount, two Unisen flow computers can be connected to the same field I/O and operate together. Both units operate simultaneously yet record I/O and do calculations independently. They share relevant data through our dual sync software. This ensures a smooth transition when control switches between the main and backup units. The Willowglen Changeover Switch mediates which flow computer controls analog outputs. The dual sync software ensures both units have the same analog output set points in the event that control switches from one unit to the other.


Technical Specifications

Double precision floating point math; 400 MHz 32-bit processor; Linux operating system; power saving modes; 256 MB memory.


The Unisen Series 5 Flow Computer is compliant with API chapter 11 measurement standards, as well as AGA 3, AGA 7, and AGA 8.


The small HMI features full graphic displays and keyboard for data entry, viewing reports and tickets, and can be easily upgraded with a pre-installed Omni Software Modbus Map.

Some 10+ year flow computer installations may need upgrading. To simplify upgrades, Willowglen provides a faceplate to directly fit older flow computer panel cut-outs that fits the following cut out: 121mm width x 210mm height (4.75in width x 8.25in height)

Value-Added Services

  • Software Configuration
  • Panel Wiring
  • Factory Acceptance Testing
  • Supervise On-site Installation
  • On-site Configuration
  • Assist with On-site Commissioning
  • Ongoing Servicing and Support