An operational network of maintenance and safety

To increase production and meet competitive pressures, today’s plants run closer to operational limits, posing greater safety risks. Additionally, safety regulations can increase the scope of safety applications within operating units. Malware attacks on safety systems also have heightened cybersecurity concerns.

Once complex process safety systems are installed, the challenge is to maintain them. Operations and maintenance staff need to understand the system’s operating status, know when changes have been made, test them periodically to ensure they can handle trip conditions, and feel comfortable that they are properly trained to work on the systems. Effective maintenance programs can help plants avoid spurious trips and shutdowns.

Role of a safety-instrumented system

In process industry operations, the distributed control system (DCS) manages the normal operation of the plant, whereas the safety-instrumented system (SIS) protects life, the environment, and the equipment being monitored. The SIS is composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state, when predetermined conditions are exceeded. The objective is to avoid accidents in plants and surrounding areas, such as fires, explosions, and equipment damage.

A conventional SIS is a multi-faceted system requiring plant personnel to perform laborious work processes to maintain safety integrity throughout the plant lifecycle. These efforts are often hindered by:

• Difficulty of maintenance due to limited visibility of asset health
• Inability to analyze system performance during plant operation
• Need for extensive training to understand safety functionality
• Lack of understanding of SIS design objectives
• Difficulty in interpreting records of past events and alarms
• Problems in managing and storing historical safety data.

IEC 61511 is an important standard from a maintenance point of view as it prescribes regular safety system maintenance/validation and verification by trained personnel.

Strategy for protecting assets

Industrial organizations face rising costs for implementing effective safety solutions. They must also address a lack of expertise or fewer available human resources, so their safety systems need to be easy to understand and maintain, and flexible enough to use across a wide variety of safety applications.

The best industrial safety solution is one that prevents problems before they have a chance to occur. Unfortunately, the aging installed base of process safety systems are usually large, complex, and difficult to maintain by the very people they are designed for.

The SIS infrastructure requires careful preventive and corrective maintenance to ensure the expected level of safety is realized and maintained. To stay competitive and continue to retain regulatory compliance, plant operators must ensure safety equipment is still operating as required and at peak efficiency. It is important that a system designed for SIL 3 operation is actually providing a SIL 3 level of protection and has not degraded to a lesser level, unbeknownst to plant operations.

Various maintenance activities are required to prevent spurious trips in a safety system and guarantee its correct operation according to the defined safety requirement specification. Physical inspection of the safety solution can include standard maintenance of enclosures, including replacement of air inlet filters, verification of power and battery status, etc.

Corrective maintenance will be required when a fault is detected in the field or in the actual safety system. The fault might be related to hardware, software, or field equipment and cabling.

System support challenges

As safety system assets age and experienced personnel retire, knowledge about proper and safe maintenance procedures can be lost. In some cases, equipment may never have been replaced before, and new procedures must be fully understood to avoid unplanned delays or critical safety situations.

The challenges in safety system support include:

Advancements in safety technology

Industrial organizations realize the advantages of standardizing on a single safety system architecture and applying it in diverse applications across their plant or enterprise. They are also benefiting from integrated safety and distributed control solutions, and the simplicity of partnering with one supplier for all their needs.

A new breed of advanced safety solutions employing a modular, scalable design can function as a single platform for all enterprise safety applications, allowing plant owners-who are often using multiple different safety system platforms-to consolidate and reduce their training and engineering costs, and spare parts inventories.

The latest safety solutions employ universal I/O technology, allowing each channel to be configured individually to a different I/O type (AI, AO, DI, or DO). Also, the use of offline virtualization and cloud engineering enables physical design to be separated from functional design, allowing parallel workflows and standardized configurations, and enabling engineering and testing to be done from almost anywhere in the world.

Advanced safety solutions employing intelligent soft-ware and more robust hardware require less proof testing and verification of functionality. Testing requirements can be reduced to once every 10-20 years in some cases, dramatically lowering plant operational costs.

Advanced safety solutions also help replace the knowledge of a retiring workforce, and with self-diagnostics, are capable of telling the plant maintenance department when maintenance is required-and what type of service is needed. This may allow normally scheduled maintenance to be bypassed or put off until the best possible time.

With tight control and safety system integration, plants can realize benefits such as reduced number of databases, easy access to historical data, and comprehensive analysis reports. Information about safety issues or equipment failures can be shared with DCS operators and addressed without requiring trips to the field for troubleshooting and repair.

The latest streamlined SIS design relies on just a couple components, versus countless individual components and parts in legacy systems, which makes it easier to troubleshoot and maintain. The use of universal channel I/O ensures an optimal footprint and lower total installed costs. Engineers can now configure all system variations with the same I/O module, where previously they needed to have multiple I/O module types to achieve the same outcome. And, with less components, plants can keep fewer replacement spare-parts in stock.

In addition, seamless integration with the plant DCS, advanced applications and engineering tools provides operations and maintenance personnel with critical information about the system’s performance and status.

Modular and scalable SIS solutions are easily configured to meet small to large distributed safety applications requiring varying levels of redundancy. There are key advantages in the use of remote I/O and smart marshalling cabinets in hazardous locations. These include a simplified design where controllers and I/O are sized to the process area, and there are layers of redundancy with controllers and I/O on each piece of equipment.

Benefits to plant operators

Innovations in safety system technology, including Lean project execution methodology, universal I/O technology, advanced diagnostics, DCS integration, and reduced software tools/applications by using cloud engineering and validation, can help optimize the operations and safety of industrial process facilities.

These advancements have simplified system design, engineering, development, and testing, while reducing the time and money needed for training and engineering activities. They have also minimized maintenance requirements and the need for highly skilled support personnel. Lastly, the systems are protected against cyber threats as verified by ISA Secure certification.

With an integrated approach to control and safety, process plants can achieve:

• Reduced number of databases and engineering tools
• Integrated alarms and events
• Improved handling of process control and safety system alarms
• Automated tracking, recording and validation of safety systems and final elements throughout the safety lifecycle.
• Enhanced collection and storage of sequence of events (SOE) information
• Expanded view of system asset health data
• Secure integration with plant sub-systems such as fire and gas, security, etc.

By optimizing SIS lifecycle cost and performance, industrial organizations are able to:

• Minimize interruptions and upsets to increase process uptime
• Maximize effective and efficient utilization of safety assets
• Decrease testing and maintenance requirements
• Empower operators with actionable and reliable data and safety knowledge.

The ability to address a wide spectrum of safety applications with a common safety platform alleviates the demands on plant expertise and simplifies spare parts management. In the case of the latest SIS solutions, there are only a handful of components to manage to begin with, due to the use of universal I/O.

Industrial organizations that migrate their aging SIS platforms to advanced technology can take advantage of many features that simplify system diagnosis and maintenance. These safety solutions can share data with DCSs, advanced applications, and safety engineering tools, helping operations and maintenance understand the systems’ real-time operating conditions, historical performance, and maintenance requirements.

By implementing a modern safety solution with innovative features and capabilities, plant owners/operators can meet system maintenance challenges, address the loss of specialized skill sets, reduce the complexity of training and support, and drive down spare parts costs.

Johan School is safety systems product manager and is located at Honeywell’s Safety Centre of Excellence in ‘s-Hertogenbosch, the Netherlands.

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