AML Virtual Flow Computer & Supervisory

The vfcHint AML Virtual Flow Computer & Supervisory  (VFCS) is the perfect companion to integrate in flow metering systems for the calculation of flow related values or quantities of any kind. The FSC provides multi-stream processing  capabilities in a redundant hardware configuration. The application is currently for single phase measurements and can be used for:

  1. Custody transfer (Class I)
  2. Fiscal metering (Class II)
  3. Allocation (Class III)
  4. Environmental (Class IV)

The PC based flow computer is flexible, easy and convenient. E.g. it can run multiple (up to 50) streams on the same computer, which reduces costs. All the fluid properties can be acquired and calculated automatically online by the same computer and can be updated as often as required. So the fluid properties come directly with the most accurate measurement with less input errors. Therefore, it saves not only time and cost, but also produces more accurate and reliable results, which are the salient features of the PC based flow computer. As novel developments only require a software update, the flow computer is easily kept up to date at minimal costs. The VFCS is a collection of software modules configured based on the requirements of the metering system and capable to run on any platform, featuring added real time functionality, compared to ordinary flow computer. This means that the VFCS is hardware
independent, providing the option of selecting qualified robust, reliable or even redundant hardware (e.g. industrial PC).
Preselected, tested and certified hardware can be advised by Hint.

More Detail

Software Concept
The flow calculations are based on international standards like AHA, ISO, AGA, IEC. Software function modules have been developed for the current metering principles:

  1. Differential pressure flow meters (orifice, Venturi incl. multi-range, V-cone, Wedge, etc).
  2. Turbine meters
  3. Ultrasonic flow meters
  4. Coriolis & Vortex
    The function modules use NMI certified calculation methods.

Accurate flow calculation requires detailed knowledge of fluid properties. These can either be entered manually in the PFC or calculated by dedicated calculation blocks based on internationally accepted ISO standards using fluid composition values obtained from a Gas Chromatograph. The following properties can be calculated:

  1. Density
  2. Viscosity
  3. Compressibility under standard & meter conditions
  4. Gross Heat Value & Wobbe index
  5. Isentropic exponents (CP/CV)
  6. Velocity of sound (speed of sound)

Additional calculation blocks are available to calculate the compressibility under live conditions. These blocks cover the following calculation according to the latest version of AGA, S-GERG and NX methods.

Online Predictive Maintenance
By using diagnostic information from smart instruments we are able to visualize the health status of the instruments. The data will be extract  directly from the instrument itself and made available via a dedicated maintenance network in AML.

Online Validation
For all types of smart instruments, like pressure temperature, flow ect. online validations can be executed and be stored in a central AML database.

Online Uncertainty Calculation
During the engineering phase the total and calibration uncertainty per instrument will be determinates. Based on the operating envelope and real-time measured pressure, temperature, flow and composition the total measurement uncertainty will be calculated per meterrun/location.

User Interfaces
The following user interfaces are available for the PFC:

  1. Keyboard monitor and mouse directly connected to the PFC for local system configuration
  2. Remote Desktop for service / maintenance
  3. Laptop, notebook (service) or Control system (monitoring) connected through LAN
  4. Remote connection using web technology for data gathering initiated from the office domain
  5. Liquid-Crystal Display (LCD) display showing the most relevant inputs values and calculation results for operational purposes
  6. Speed of soundAvailable user interfaces are:
    – Windows-based
    – Web-based or others

Process Interfaces
To interface with the process, remote I/O hardware modules are used, connected to the PFC, using standard (wireless) PC interfaces (Ethernet (TCP/IP), Analogue, Digital , RS 232, RS 422, RS 485 via COM ports). The selected interface hardware is based on proven technology. The interfaces use digital data transfer from the transmitters and other remote equipment to exclude any negative effects to the accuracy. Protocols the VFSC can handle are: ModBus, Hart modules, Profibus, Ind. Fieldbus and OPC.

Software Configuration
The modules for the calculation methods are composed of function blocks. The same function blocks can be incorporated in different function modules depending on the nature of the calculation method. This includes function blocks created to determine fluid properties. The development basis for the software modules and blocks is the AML Framework. To run the VPFC application a runtime license for the AML Framework is required. Running multiple streams (up to 50) on the same computer or even a redundant computer still requires only one license.

Data Storage
Measured values, calculated results and events and alarms are logged in a database compatible with Microsoft SQL and other servers. Facilities for remote data collection from the office domain for hydrocarbon accounting and production reallocation are available via protected network connections.

Latest Developments
The software can be extended to wet gas using the best correlations from the literature. This will only require an extra module which can easily be added to the software on request.