ENHANCED PIPELINE GRAPHICS GIVE GREATER CONTROL OVER SYSTEM

Warren R. True
Pipeline/Gas Processing Editor

With the presence of more powerful workstations has also come enhanced graphics packages which allow individual operators greater control over a pipeline system from a single operator station.

In fact, enhanced graphics packages are becoming a standard for new pipeline scada systems. Fig. I presents an example from a recently installed scada system for a U.K. products pipeline.

AMOCO GAS' SYSTEM

Andrew Richmond, senior engineer for Amoco Gas Co., Texas City, Tex., says that historically, the presentation of real time information on Amoco Gas Co.'s scada system consoles (typically numerical data and alarm information) had been limited to tabular listings, rows and columns of numbers, and text descriptions where appropriate. In real-time systems, he says, the trending of information and the says to observe alarm information quickly is critical to the control of system variables.

Implementation of the new Amocams/Modular Inc. (AMI) Adacs system with WinTerm software has given Amoco Gas Co. the capability of custom designing operator displays using images (bitmaps) created in the DOSbased PC environment and integrating them into the Adacs (DEC's VMS operating system) generated displays.

This allows Amoco Gas easily to create images of the natural-gas pipeline system with software such as Microsoft Windows Paintbrush (by Microsoft Corp.) on a PC, or scanned images, and overlay real-time data onto the images.

Prior to this innovation, Richmond says, images were created with a very tedious process using a grid system with very low resolution and limited graphics capabilities. In addition to the presentation of absolute values, the graphical trending capabilities of the new system are more easily configurable by an individual user.

Again, trends of data points historically were illustrated on graphs with fixed scales (both value of data point and time span) or on tabular trends--screens filled with rows of numbers. Changes in scaling required reprogramming of the display by a system administrator, says Richmond.

With the new system, operators can choose the scaling, which points they wish displayed, compare multiple points against each other over time, and chose several combinations of historical averages.

Also, system users have historically accessed information with keyboard entry and cursor movement. Because the new user stations operate in a Microsoft Windows environment, says Richmond, a mouse can now be used to "poke" icons (tag symbols or colored areas) on displays to move around in the system and obtain information.

This capability provides a faster, more visual means of accessing the data, Richmond says. This means that infrequent users do not require significant amounts of training or reference material to access data. The displays are created with a what-you-see-is-what-you-get philosophy.

In the past, he says, a series of menus, accessed by typing information or hitting numerous "PF" keys would display the data.

The ability graphically to present alarm information using flashing colored images, changes in the foreground color and background color of numerical values, and the attachment of "quality flags" as a suffix to the numbers has improved the operator's says to monitor the quality of the information as well as the numerical value.

By observing the number (in isolation), the operator can tell whether the value is in an alarm state, is an old datum, or is suspicious. The alarm state may also be presented in at least six different ways to tell an operator the type of alarm: high, low, out of instrument range, so forth.

VALERO'S SYSTEM

A similar system employing enhanced graphics is being installed by Valero Gas Transmission Co., San Antonio, and is complemented by sophisticated modeling programs for simulating pipeline conditions and planning for various operations scenarios.

Valero will by the end of this year complete installation of a gas-pipeline management system that will use a single, dynamic graphical user interface (GUI) to monitor events in real time, model future events, perform vital economic analysis, and directly control operations.

Stoner Associates Inc., Houston, installed its modeling system within Valero's environment, using DataViews, a GUI development toolkit with input and output capabilities made by VI Corp., Northampton, Mass.

The hardware that hosts the system includes DEC computers (Models 8530, 8350, and 6410) and DEC's VT1300 display terminals.

Bob Yaffe, Valero manager for gas control systems, and John Yurchevich, Stoner manager for the GUI project, described the system.

Valero sought a single system that would provide users with familiar graphics, the ease of "point and click" commands, and an easy-to-use Windows capability that would enable controllers to monitor as many as six screens at a time.

The Stoner system receives and processes real-time field data from Valero's pipeline through an interface with Valero's recently upgraded scada system, said Yaffe and Yurchevich.

The new GUI will translate these data into user-friendly color graphics that change, in lock-step, with real-time pipeline conditions (for example, flow, gas quality) and events (such as equipment malfunctions).

In addition, the system provides the tools for hydraulic and economic analysis of operations and the graphical representation of those data in a variety of formats (dials, contour graphs, bar graphs, pie charts, so forth).

The on-line modeling system projects conditions and performance into the future and simulates various operational scenarios, enabling operators to determine the least expensive transmission options.

As in the Amoco Gas system, Valero operators will be able to communicate with and control virtually all components of the network-including transport-exchange and gas-measurement areas-from the same computer terminal used for these monitoring and modeling functions.

Commands for all system functions will be executed by pointing and clicking a mouse on graphical representations of the pipeline systems. Currently, commands are typed at the keyboard. In addition to improving Valero's overall operational efficiency, Yaffe and Yurchevich said the new graphical command capability will allow operators to respond three times faster than at present.

COLONIAL'S SYSTEM

Colonial Pipeline Co., Atlanta, is installing a scada system that also takes advantage of new graphics capabilities now available for pipeline scada systems.

To provide the pipeline controllers with the optimum displays for operation of large diameter lines, said Steve Meller and M.C. Coke in a 1991 API Pipeline Conference presentation, the X-Windows graphical display standard was specified for all console devices.

This design decision resulted in two serious problems, however.

The first was network data traffic. X-Windows requires transmitting large amounts of data between the host computer and the X display. Inherent in the X-Windows specification is the intent to use Ethernet LANs as the data highways If Colonial tried to put all 60 of the central control center monitors on the scada LANS, very little transmission time would remain for the high-priority scada traffic.

Instead Colonial chose to implement console LANs using computers at the consoles for the gateway between the scada LANs and the console LANS. This allows Colonial to keep almost all of the X-display traffic away from the raw scada data.

The second issue with using standard X-terminals is that Colonial would have been required to use one keyboard and mouse for each of the CRTs. There will be six display monitors for each controller console. The controller would have been repeatedly switching between keyboards to change displays, said Meller and Coke.

Alternatively, Colonial could have required Valmet to create custom software, at the expense of maintaining it in all future software releases. Digital Equipment Corp. (DEC) came to the rescue here, Meller and Coke said.

DEC offers a product which is essentially an X-terminal with up to eight CRTs associated with a single mouse and keyboard. This item by itself would have determined the hardware vendor for the project.

The requirement for X-windows evolved from one detail in particular. Colonial pipeline controllers have a display tool for hydraulics displays which was developed within the company. The in-house software is a combination of some analytical hydraulics with extensive sophisticated graphical displays built to conform with the X-Windows standard.

Because these displays were considered important for pipeline operations, said Meller and Coke, the decision was made to require the scada vendors to provide an appropriate interface.

This software was designed to provide controllers with two kinds of hydraulic information.

The first is the line packing, that is, whether pressures on the line are gradually increasing or decreasing. This information is commonly presented in the form of strip-chart recorders displaying pressures. Of course, all scada software vendors provide strip chart recorder simulations, but none is able to provide the quantities specific to very long pipelines like the Colonial main lines.

The second display is the instantaneous pressure profile known as the "hydraulic grade line." This display calculates and displays every second the entire pipeline pressure profile.

When there are line transients traveling between stations, this type of display is invaluable to present accurate timing information for the controller to respond with the appropriate actions.

These two kinds of display have been implemented in the control center for about a year on the main lines. The design for the new control center consoles includes two CRTs dedicated to each of these two displays (four CRTs total). This feature specified the minimum number of CRTs required for the consoles as well.

Another bonus provided by X-Windows, according to Meller and Coke, is the capability called "point-and-shoot." This means that when a controller wishes to start or stop a pump, he can use the mouse to point at the desired pump, then click a "mouse button."

The scada software will then send out the appropriate command to the appropriate pump. At no time will there be a need for the controller to look elsewhere than to the information displays themselves in order to obtain information or transmit to commands.