Process safety: Managing process safety with flexible IO

Industrial facilities should approach safety and security holistically by addressing critical requirements from the process control network to the perimeter of the plant.

06/14/2013


Industrial organizations are paying closer attention to safety applications for a variety of reasons, including strict industry regulations and widespread reports of safety incidents around the world. Plants need robust safety applications, which encompass all instrumentation and controls responsible for bringing a process to a safe state in the event of an unacceptable process deviation or failure. 

To manage process safety challenges—including the role of defense-in-depth strategies for protecting critical plant assets—plant personnel must understand the application of current technologies in the marketplace, as well as new technologies for optimizing overall safety performance and reducing capital and operating costs throughout the project lifecycle.

Operational demands

Industrial facilities are under growing pressure to better manage their process and safety assets. Complying with legislation to safeguard personnel, communities, and the environment is a priority for both legal and ethical reasons. Effective safety applications are needed to enable proactive protection (versus responsive mitigation), help stop events before they happen, prevent injuries, and save lives. 

Plant projects around the world are becoming larger and more complex. Greenfield construction often involves multiple engineering procurement contractors, while brownfield projects must be completed with minimal downtime. Operations of all types seek on-time or early start-up, as well as earlier-than-planned production to accelerate returns. 

In the process industries, operations such as oil and gas platforms, liquefied natural gas carriers, and floating production, storage, and offloading units typically face space, weight, and power constraints for automation equipment such as I/O devices. In addition, these operations must ensure a sufficient number of spares for the lifecycle of the installed asset. 

At greenfield sites, building adequate control room infrastructure is a high priority. This makes moving control and safety functionality to the field—as well as necessary hardware—a desirable alternative to traditional approaches. At the same time, users must cope with burdens such as time-consuming hardware configuration and programming, late design changes, frequent maintenance, and the need to reduce copper wiring connecting sensors, transmitters, and other devices with the control room. 

Brownfield facilities also deal with issues related to spares availability, not to mention the need to install additional homerun cables as part of any expansion project. 

Today, there is now a clear paradigm shift in the process industries from safety system cost to total cost of ownership. Current system architectures can be either centralized, distributed, or a combination of both. Each approach has its advantages and challenges. 

Many operations continue to employ outdated safety solutions implemented in PLCs, control systems, or other legacy platforms. Due to the continuous improvement aspects of ISA-84: Standards for Use in Process Safety Management of Highly Hazardous Chemicals and IEC-61511: Functional safety: Safety instrumented systems for the process industry sector, plants are finding it necessary to replace these systems with a modern safety instrumented system (SIS). The need to execute safety instrumented functions that weren’t previously implemented or identified is also driving the implementation of SIS technology. 

Implementing layers of protection

Ensuring the safety and security of personnel, equipment, and the environment is a priority for every industrial facility. This effort goes far beyond simply installing fail-safe controllers or an advanced SIS solution. In fact, to mitigate the risk of serious incidents, it is important to consider safety and security from all aspects of a plant's operation.

Industrial facilities should take a holistic approach to industrial safety and security, addressing critical requirements from the process control network to the perimeter of the plant. This approach is intended to increase situational awareness of production processes and improve response to emergency situations arising from safety- or security-related incidents. When properly implemented, this approach helps protect people, assets, and the environment while sustaining a high level of operational and business performance.

Figure 1: Defense-in-depth is inherent in safety and security best practices, which integrate independent layers of protection. Courtesy: Honeywell Process SolutionsAt the core of best practices for integrated safety and security is defense-in-depth with independent layers of protection (see Figure 1). This strategy is included in the IEC 61511 standard, which stipulates that every layer of protection—including both control and safety systems—should be unambiguously independent. Some of the reasons for this basic requirement are to avoid common-cause faults, minimize systematic errors, and provide security against unintentional access. 

With a layered solution, some layers of protection are preventive in nature (e.g., emergency shutdown), and some are there to mitigate the impact of an incident if it occurs (e.g., fire and gas protective systems or emergency response systems). Other layers of protection can deter incidents in the first place, or provide detection, alerting, and associated guidance. 

Maintaining segregated systems

One of the major achievements of process control technology in recent years has been its integration of an increasing number of safety functions within the plant automation environment. The move toward sharing critical information with the process control system through an SIS has brought significant benefits. 

Industrial organizations are seeking a unified control and safety infrastructure integrated at the controller and HMI level. This solution must comply with key industrial safety regulations as well as applicable cyber security standards. It must also meet industry requirements for high reliability and availability, simplify field device maintenance, and adapt easily to last-minute project engineering changes. 

Experience has shown the most robust and reliable approach to control and safety integration maintains the well-established separation principle for the basic process control system and SIS. In this way, users can achieve complete operational integration through a single dashboard, using a fully separated safety network for greater protection. 

Empowering plant personnel

Plant safety requires a comprehensive program for managing operator effectiveness, constant monitoring of distress indicators, and ongoing monitoring and maintenance for asset health. This integrated approach demands not only an understanding of safety’s relationship to human error, but also the interrelationships among root causes and interventions by plant systems and site personnel. 

The layer of protection often missed in the plant safety architecture is the one requiring human intervention. It is essential to equip the operations group with technology and work practices to manage abnormal situations or the eventuality of an incident. In addition, as an experienced workforce transitions and domain knowledge is potentially lost, it becomes increasingly important to transform that knowledge into institutional procedures and practices. The operator should be properly equipped to recognize an event, as well as be capable of properly evaluating the situation and responding accordingly. 

Operator effectiveness afforded by common and consistent HMIs across the entire operation, knowledge capture through automation of procedural operations, and an advanced alarming capability allow people to better prevent and respond to abnormal situations. 


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