Flow Computer Overview and Design
With Flow Computer Tags, Trihedral sought to develop an industry-specific solution with the following requirements in mind:
- Single SCADA platform for process data and compliance data collection, storage, and reporting with no reliance on 3rd party software.
- Compliance with Alberta Directive 17 requirements for custodial transfer data.
- Common configuration user interface for several RTU/Flow Computer hardware platforms.
- Common operator user interface for several RTU/Flow Computer hardware platforms.
- Leverage all existing VTScada functionality to allow SCADA system integrators and operators to quickly and easily build SCADA systems to meet their specific needs.
- Use standard VTScada drivers for efficient communication on limited bandwidth connections to field I/O devices.
The Flow Computer tag is the basic building block of the Oil & Gas Solutions approach to EFM devices. This tag allows a complete field I/O device (i.e. a flow computer) to be defined as a single tag. Every Flow Computer tag includes several child tags that perform the necessary device communication, data reading and logging for compliance data, as well as provide a means of defining the device-specific I/O tags used for process monitoring and control functions.
Which child tags are started and how they operate depends on the configuration of the Flow Computer tag.
The following figure shows how the Flow Computer meets these requirements.
Key points shown in this figure include:
- A common I/O driver is used within VTScada for both operational process values and compliance reporting data.
- For each I/O device (flow computer or RTU), the driver can use communication link options that include direct serial, TCP/IP, UDP/IP, cellular, TCP/IP to serial, etc.
Multiple field I/O devices can use the same link, or multiple links can be deployed easily in a single application. - Tags that collect compliance data are built automatically based on the field I/O device in use. These tags log all collected data to the VTScada Historian, automatically on data change, using the same format that it is received from the I/O device. No scaling calculations or other manipulations are performed on the received data values.
- SCADA system developers use standard VTScada tags to monitor process data. These tags are used to build the displays that operators use to interact with the process and can include standard VTScada tools for visualization and control, along with custom calculations to meet application specific needs.
- The VTScada reporting engine is used to generate reports from the Historian. These can be tailor-made to the end user’s requirements.
The Oil & Gas Solutions layer contains a number of reports specifically designed as industry compliance reports (CFX files for example) but all logged data, including process and compliance values, is readily available using a number of built-in VTScada report types.
All Historian data is also available via the VTScada ODBC driver for report generation using 3 rd party reporting tools.
Flow Computer Tag Structure
The following figure shows the general structure of Flow Computer Tags, built automatically whenever they are created. Note that the structure will vary depending on configuration choices made while creating the parent tag. Also, you may choose to add your own tags within this structure to collect extra information. In the following diagram, A&E stands for Alarm & Event.
Communications Driver Tags
Four independent Polling Driver tags in combination with four independent I/O driver tags are created, based on the field I/O device selected when configuring the Flow Computer tag. The four independent drivers are created to allow custom polling schedules for each of the major types of data that the SCADA system will need to read from the remote devices:
- Real-time process values
- Alarm and event logs
- Hourly history logs
- Daily history logs
VTScada allows all four drivers to communicate with the same field I/O device over the same communication medium. Note that the Flow Computer tag also reads configuration data, and that this is usually done using the real-time process value driver tag using an ad-hoc read.
Alarm and Event Handler Tag
The Alarm & Event Handler tag is a layer-specific tag that is automatically started by Flow Computer tags as a child tag. Its role is to capture inbound alarm and event information (aka Audit Log or Audit Trail data) from the field I/O device that is read by the I/O Driver tag and to convert these device-specific messages into a common format for storage in the VTScada Historian. Once logged in the historian in this format, the alarm and event data can be reported in a device-independent manner using the VTScada reporting tools.
Notebook Tags
The Flow Computer tag automatically starts one or more Notebook tags; one for the device as a whole and one for each flow meter run that is configured within the device. These are standard VTScada Notebook tags and can be accessed, read, and reported on in the same way as any Notebook tag.
Process Data Tag
The Process Data tag is a standard Context tag that is a direct child of the Flow Computer tag. It is used as a container for any process Analog Status or Digital Status tags that are not associated with a particular meter run (e.g. RTU battery life). Just by creating an Analog Status or digital Status tag as a child of the Process Data tag, that tag will automatically find the correct driver tag and will use the standard process polling cycle.
Meter Run #1 through Meter Run #11 tags
The Meter Run tags are Oil & Gas Solutions tags that provide three distinct functions:
- Provide a container to hold hourly logs, daily logs, and process values
- Provide a user interface to change commonly adjusted configuration settings for the flow meter run
- Provide the tools to accept and store the meter run configuration values from the field I/O device
The first of these is accomplished using the standard container features of VTScada – it treats all log tags and process tags as its children.
For the second function, user interface for configuration, a standard device configuration display is available to allow users to adjust several settings for the flow meter run, including the gas compositions.
For the third function, RTU configuration data, the Meter Run tags capture all details of the flow meter run from the RTU and log this data to the VTScada Historian. Reading and logging of this data may be triggered by three actions:
- Timed update interval (typically in days)
- User-initiated read of the data
- On events received from the field I/O device that may indicate changes in the field to the device’s configuration
Refer to RTU Configuration Log Format for details on the format of the meter run configuration logs produced by this tag. The format will need to be understood if you are using the ODBC interface to generate reports of device flow meter run configuration.
The number of Meter Run tags started is controlled by the configuration of the Flow Computer Tags.
Daily and Hourly Tags
These two children of the Meter Run tag are standard VTScada Context tags used to group together the individual hourly and daily Analog Status tags, which are used to capture compliance reporting data logs from the RTU or flow computer. Some of these Analog Status tags are started automatically as child tags of the Meter Run tags based on the configuration of the individual meter runs in the Flow Computer – refer to section Flow Computer properties History Logs tab for details on configuring the flow meter runs in the Flow Computer tag. An address entered in the relevant field in that configuration folder is what determines whether the associated daily/hourly history tag is started or not. Additional user-defined tags may be added to capture further historical data, as long as they are added under the ‘Hourly’ or the ‘Daily’ context.
Note that the daily and hourly log tags are not started unless required. For example, if meter runs #1 and #4 are configured in a Flow Computer tag then only the hourly and daily log tags for flow meter runs #1 and #4 will be started. This helps to reduce the tag count by not starting I/O tags for flow meter runs that are not used in the field I/O device.
Process Tag
The Process tag, a child of the Meter Run tag, is a device-specific “Driver Redirect” tag that provides the following two functions:
- Acts as a container tag for all process data tags related to the meter run – these are configured as child tags of the Process tag
- Performs the proper linking of the process data to the poll driver required for reading and writing of process tags
By default, several Analog Status tags are configured as child tags within the Process context. Users can add additional status tags that are associated with a particular flow meter run by adding them as children within the Process context.
As mentioned above, if additional status tags need to be added to the application that are not part of a specific meter run, these tags can be added directly as children of to the main Process Data tag instead.
Data Logging
Compliance Data Recording
All I/O tags configured as part of Flow Computer Tags are automatically logged to the VTScada Historian. The Compliance Data consists of several components that are recorded to the VTScada Historian in different ways:
| Information | Recording |
|---|---|
| Alarms & Events | Log all received alarms and events |
| RTU Configuration | Log whenever data received (manual, timed, or event driven) |
| Hourly/Daily History Readings | Log all received readings regardless of value change magnitude |
Process Data Recording
All process data tags configured automatically by the Flow Computer tag, as well as those configured by the user, are recorded to the VTScada Historian using the standard mechanisms for these tags. In short:
| Tag Type | Recording |
|---|---|
| I/O and Calculation | Recorded on change of value that exceeds the tag’s deadband amount |
| Analog Status | Recorded on change of value that exceeds the tag’s deadband amount |
| Digital Status | Recorded on change |
| Drivers Statistics | Recorded as per VTScada standards for driver data logging |
| Calculation | Recorded on change of value that exceeds the tag’s deadband amount |
| All Others | Recorded on a timed basis only when a Logger tag is attached to the calculation |
Compliance Reporting
The Oil & Gas Solutions layer records and reports data in a way that is compliant with major oil and gas industry specifications for custodial transfer data. The following sections demonstrate how the Oil & Gas Solutions layer meets these requirements.
AER Directive 017: Measurement Requirements for Oil and Gas Operations, section 14.11 Records, outlines a number of records that must be kept for all metering equipment. These reports include
| Section # | D017 Report Requirement | Addressed in Oil & Gas Solutions via |
|---|---|---|
| 14.11.1 | The Daily Report | Hourly Log Tags |
| 14.11.2 | The Monthly Report | Daily Log Tags |
| 14.11.3 | The Event Log | Alarm and Event Tag Log |
| 14.11.5 | The Daily Report (EFM specific) | Hourly Log Tags |
| 14.11.6 | The Meter Report (EFM Specific) | Daily Log Tags |
| 14.11.7 | The Alarm Log (EFM Specific) | Alarm and Event Tag Log |
PVR Reporting
Settings in the Flow Computer tag allow your site to be easily linked to a PVR Report for customized data reporting.
See Flow Computer properties PVR Report tab
RTU & Flow Computer Compatibility
Flow Computer Tags will work with Flow Computers and RTUs from several manufacturers using different communication protocols. The currently supported devices include
| Manufacturer | Device | Protocol |
|---|---|---|
| Fisher | FloBoss 103 | ROC* |
| Fisher | FloBoss 107 | ROC* |
| Fisher | FloBoss 407 | ROC |
| Fisher | ROC300 | ROC |
| Fisher | ROC800 | ROC/ROC+ |
| Schneider Electric | RealFlo on SCADAPack RTUs | Enron Modbus, TeleBUS |
| Semaphore | TFlo on TBox RTUs | Enron Modbus |
| CalScan | DCR-1000 | Enron Modbus |
| CalScan | Hawk 9500 | Enron Modbus |
| ABB | Totalflow | Totalflow** |
| Bristol | ControlWave | IBP |
| Bristol | 33XX Series | BSAP |
* Note that FloBoss 103 and 107 units also support ROCNOC and Emerson’s Well Optimization Manager/Surface Control Manager products.
**Note that the Totalflow driver will only work in conjunction with the QCSI VTScada Helper Service from Quintessential Computing Ltd. Please contact Quintessential or Trihedral for more information.
New devices can be added.
