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SCADA standardization drives third-party connectivity

Ever more data leads to alternative means for capturing it as oil and gas refineries upgrade or migrate legacy control systems.


Courtesy: Maverick TechnologiesAs oil & gas refineries upgrade or migrate legacy control systems to 21st century technologies, they face having to address past third-party interface methodologies.

Upstream, midstream, and downstream end users can rely on supervisory control and data acquisition (SCADA) systems. As a go-to solution, SCADA is a highly configurable application that streamlines operations. Yet it remains possible for end users to achieve even more, using SCADA and applications considered native to modern distributed control systems (DCSs) to make effective, data-driven decisions that fuel operational efficiencies.

Many oil & gas end refineries conversant in past migration methodologies tended to migrate like-technology for like, extending existing system problems into what should be simpler, more robust, and integrated solutions. Earlier methodologies called for use of separate, often proprietary, interface technologies, too often clumsily integrated into control systems, which led to rework. Moreover, applying site or even corporate standards, like alarm or high-performance human-machine interface (HP-HMI) philosophies, proved difficult.

In addition, other third-party interface methodologies placed large processing requirements on already expensive, technologically limited process controllers. End users had to pick and choose among the various integration technologies, but were limited by data requirements, speed, or compatibility issues. Careful consideration was given to deciding whether to poll third-party devices or build them out into a standalone control system; however, this latter approach made it difficult to manage multiple systems simultaneously.

For downstream facilities, common third-party interfaces include for compressors, safety systems, analyzer networks, and other ancillary systems. These systems are often packaged as standalone subsystems that must be integrated into 21st-century control architectures. In legacy environments, these subsystems would be interfaced via a few key process variables and a generic common trouble alarm. However, usable data in these systems was limited.

In recent years, in-depth diagnostic, troubleshooting, and maintenance data has become widely available and is configured as a standard option in these vendor-provided solutions. For oil & gas end users, extracting and leveraging this data is a hurdle that must be overcome to gain better insight into operations and assets.

The data hurdle

To meet the data challenge head-on, modern control systems today have SCADA applications built-in to the existing software, making it easier to leverage the interface to third-party devices and allowing real-time access to local and remote process data. Many data communications protocols exist, such as Modbus TCP/IP, serial, OPC and others, that are widely available and come standard on a variety of third-party systems.

In the past, process controllers faced limitations in communicating with the multitudes of end devices; however, with newer SCADA solutions, point limitations are essentially non-existent as communication can be migrated to SCADA instead of a peer-to-peer controller interface.

In terms of usability, third-party data sets can be manipulated easily into formats readily imported into the SCADA application's software. For instance, the effort required to configure 300 digital alarms is rarely different than that needed for 1,500 alarms. Non-critical process information, like a generic common trouble alarm on a compressor skid, now can be expanded to include whether a communication module is faulted or whether maintenance has forced a specific point for troubleshooting purposes, amongst many others.

The biggest challenge, however, is deciding what third-party data types are important enough to hardwire, i.e., decide whether the data is operationally critical and should reside in the main process controller or whether SCADA input is sufficient. Using SCADA, operations and maintenance are not at risk of exposing the process to unnecessary controller loads when acquiring diagnostic data.

In today's production environments, accessing data may be easier, but you still need to rationalize what data types are most important. Due to the sheer volume of data available from third parties, capturing all data can prove inefficient and costly. More effective is to make data a part of the front-end loading (FEL) and discovery process, and properly optimize the way it is collected, organized, and contextualized. This is key to overall operational efficiency. For instance, ask yourself: Are you capturing the right data at the right frequency and granularity to be analyzed effectively, and to improve asset performance and business outcomes?

It is important to capture what is mission-critical, such as process data and the calculated values generated within process systems. Extract what's most important via a process data historian into a secure repository. The historian is then the focal point for both local and remote access across a wide variety of hardware platforms and software applications.

Alarms and HMI

Once it has been determined what mission-critical data types are to be captured from third-party devices, it's possible to define a roadmap that highlights which critical alarm events to display via human-machine interfaces (HMI). If alarm and HMI philosophies already are in place, a SCADA implementation does not impact functional design. Let's find out why.

From an operational standpoint, compared to a full DCS and bearing in mind how operations interface, SCADA is nearly identical in shape and feel. Discrete controls, analog indications, and state-based alarming solutions easily can integrate SCADA points without losing expected functionality. This reduces training time for operators while adding the flexibility inherent in modern operational technology, which drives efficiencies.

High-performance HMI is not at risk when using a SCADA system counterpart to continuous-control DCS. For instance, regardless of whether a discrete pump's feedback status is hard wired or via a soft Modbus TCP/IP connection from the safety system, that feedback status can be displayed. Indistinguishable in form and feel, either can integrate flawlessly into the data historian or alarm banner. Trends on a PID controller can be visualized side-by-side with a safety-system SCADA digital alarm to pinpoint exactly what caused an upset or untimely shutdown.

Alarm roll-up also is identical in how operations receive alerts about abnormal process situations. It doesn't matter if the process variable resides in a SCADA third-party interface or is wired directly to the DCS. Both are configured similarly as both would be integrated fully into the same operational interface. Alarm rationalization methods needn't change to analyze a high-level, hard-wired DCS alarm versus a high-level SCADA alarm. Operational response is not impacted by the process variable's origination.

As the gap between SCADA capabilities in comparison to a modern standalone DCS closes, implementation standards for the two systems follow. With a proper functional specification and FEL strategy, leveraging the SCADA option for more operational data acquisition opens doors to more standardized approaches to third-party interfaces, which overall drives cost down.

A standardized solution

Integration via SCADA of third-party automation hardware and software applications delivers a host of benefits, including making data immediately accessible to relevant on- and off-site personnel in operations, maintenance, engineering, management, and elsewhere. Incorporating SCADA applications into existing automation processes, however, can be a daunting task.

Consider consulting a platform-independent automation solutions expert on existing SCADA solutions and strategies that are already standard in today's modern manufacturing. By leveraging those consultant skills while driving toward a more connected and standardized SCADA solution, more value can be gained from systems and best practices already in place. This will drive operational efficiencies, while preventing unit upsets and unplanned shutdowns.

For oil & gas facilities, a SCADA solution offers valuable benefits when leveraged to support better, data-driven decisions for overall operational efficiencies, such as improved process troubleshooting and abnormal situation handling.

Stephen Milton works in the oil & gas industry and engineer at MAVERICK Technologies, a CFE Media content partner. He has expertise in legacy platform migrations to 21st century solutions and specializes in third-party system integration into large-scale existing processes.

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