According to international standards, safety implementation is organised under a series of protection layers, which include, at the base levels, plant design, process control systems, work procedures, alarm systems and mechanical protection systems.


The safety shutdown system is a prevention safety layer, which takes automatic and independent action to prevent a hazardous incident from occurring, and to protect personnel and plant equipment against potentially serious harm. Conversely, the fire and gas system is a mitigation safety layer tasked with taking action to reduce the consequences of a hazardous event after it has occurred. The fire and gas system is used for automating emergency actions with a high-integrity safety and control solution to mitigate further escalation.

A typical fire and gas safety system comprises detection, logic control and alarm and mitigation functions. Logic solver is the central control unit of the overall fire and gas detection and control system. The controller receives alarm and status or analog signals from field monitoring devices required for fire and gas detection. The controller handles the required actions to initiate alarms and mitigate the hazard.

In the past, proprietary fire and gas systems were standalone equipment or a hardwired mimic overview panel via relays. Mitigation of the risk would take place via manual activation of fire control measures. These methods are not considered best practice. Today, fire and gas detection systems are generally programmable electronic systems (PES) with high safety availability and mitigation effectiveness.

Challenges facing industrial manufacturers

Manufacturing plants must cope with business challenges ranging from increased accident, incident and insurance costs, to compliance with strict standards and codes such as NFPA, API and OSHA in the US and BS EN and SEVESO II in Europe. Also, issues related to corporate image and environmental stewardship have growing implications in the global market.

Plants must find ways to improve fire and gas system effectiveness through optimisation of fire and gas detector coverage, system safety availability and mitigation effectiveness, and at the same time, reduce the cost of ownership for safety equipment. Many facilities are also dealing with the cost of upgrading and refurbishing existing, non-integrated systems.

As more plant owners move toward “smart” plants, appropriate integration with other systems will play an important role in increasing safety as well as efficiency. As part of an overall plant safety strategy, end users need a unified platform for emergency shutdown and fire and gas detection to have a single window for operators and common tool for engineering and maintenance to drive down operational risk and costs.

Understanding safety performance standards

Industrial standards are playing a large role in developing, implementing and installing fire and gas systems. The IEC 61511 standard (ANSI/ISA S84.01 in the US) is a major step towards protecting industrial plants. The overall safety lifecycle model described in the IEC standard lists all of the necessary project activities, from the concept (definition) phase to the decommissioning phase, necessary to ensure the functional safety of equipment under control (EUC). These activities can be divided over a wide range of categories such as procedures, documentation, testing and validation, planning, hardware and software development, and risk assessment.


More recently, there have been discussions over whether fire and gas detection systems should contribute to risk reduction or be considered as a protection for the installation only. The implementation of the IEC 61511 and S84.01 standards is becoming increasingly prevalent for fire and gas detection systems. An ISA technical report TR84.00.07 to provide guidance on the evaluation of fire and gas system effectiveness is currently in draft review.
The IEC 61511 standard concerns the determination and development of risk reduction measures (RRMs) required as the outcome of the EUC risk assessment. The basic principle of risk assessment is that all potential risks to the EUC are identified and analysed. This includes calculating the probability of each potential EUC hazard and determining the risk reduction measures required to achieve an acceptable SIL (safety integrity level).


The potential risk of EUC hazards can be considered as the outcome of the probability that the hazard occurs, and the consequences of the hazard: risk = probability x consequences.


The prescribed reduction measures either decrease the risk probability (eg ESD systems), or mitigate their consequences (eg Fire and gas systems). The risk of EUC hazards can be reduced by a combination of several RRMs, where each measure takes care of a part of the total required risk reduction factor (RRF).


A good fire and gas system combines state-of-the-art fire and gas detectors, conventional and analog addressable fire panels, clean agent and inert gas fire suppression systems, and a SIL 3-certified fire and gas logic solver into a consistently designed and executed solution. An integrated system provides common tools, operating interface and networking, resulting in a common platform with independent systems (see Fig. 3).
Thanks to advancements in fire and gas detectors, fire and gas systems can detect early warnings of explosive and health hazards, including combustible and toxic gas releases, thermal radiation from fires and minute traces of smoke in sensitive equipment enclosures. They also provide audible and visual alarm indications helping to ensure operators and personnel are informed of potentially hazardous situations.


Integration at the controller level provides plant-wide safety instrumented system (SIS) point data, diagnostics and system information, as well as alarms and events, operator displays and sequence of event information to any station. This minimises intervention and shutdowns, reduces hardware costs, and allows plants to recover more easily from process upsets.


The new generation of fire and gas solutions provides alerts of abnormal situations in a fast, accurate and structured way, giving personnel time to decide upon the correct course of action. These solutions include new integration capabilities with process simulation tools, fire and gas detectors and control communication protocols, enabling safety engineers to design and build large integrated and distributed plant-wide safety strategies.
Overall SIS technology integrates safety measures dispersed throughout a plant to reduce risk to employees and assets, increase process availability, and improve regulatory compliance. SIS solutions can be integrated with fire and gas detectors for increased protection, and unified with third-party applications and systems to reduce validation and acceptance testing costs.


Safety system platforms based on Quadruple Modular Redundant (QMR) diagnostic technology execute automated safety functions and provide the interfaces and input functions for standard connection of a wide range of fire and gas detection devices. Applications include emergency shutdown, process shutdown, fire and gas systems, and burner management. Thanks to this technology, end users can achieve 2oo4D (2 out of 4 with integrated diagnostic to a > 99.9% coverage) – providing a fully SIL 3 certified solution which allows continuous production.
With innovative simulation solutions, safety engineers can easily test the impact of safety strategies on the overall plant design and operations before implementation.
In addition, new field device configuration tools allow plant personnel to automatically configure intelligent safety devices and integrate them into the control system database. Facilities subsequently save money by using a single tool to manage all equipment assets.

Integrated approach improves plant safety
Industrial operations benefit from a holistic approach to safety that supports a secure process control network to the perimeter of the plant. A layered safety strategy encompasses process and system technology – and the people who interact with that technology – to help plants achieve their safety objectives (see Fig. 4).


A layered safety strategy unifies all plant protection required for achieving optimum functional safety. Plus, it provides the required functional safety with a high SIL. This includes superior visualization and logging facilities enabling optimal operator response and accurate evaluations. By integrating basic control, prevention and mitigation components, overall project costs and ongoing maintenance expenses can be vastly reduced.
A truly integrated safety system delivers:
• Integrated operational interface
• Integrated peer control
• Integrated diagnostics
• Integrated postmortem analysis
• Integrated fire and gas system
• Integrated power supplies
• Integrated modifications
• Integrated simulation and optimization

Operational integration allows plant personnel to have a seamless interface to the process under control, and at the same time, maintain safe separation. From an operational perspective, it makes no difference where the application is running. All required information is available to the operator. This allows applications ranging from rotating equipment and compressor protective systems, to emergency shutdown systems and large plant-wide fire and gas applications to be monitored from any operator console.
Integrated control and safety systems (ICSS) provide multiple benefits to process plants. For instance, they help operators to minimise intervention and shutdowns.


Plants implementing an ICSS platform for fire and gas, ESD and DCS systems can significantly lower their operation and maintenance costs, and in many cases, reduce overall wall-to-wall project costs by 25 per cent. Seamless integration with the ESD and DCS via a common network protocol also provides a safe landing in case of emergencies and eliminates the need for additional equipment or engineering. Integration of fire detection and security systems for off-sites and utilities with the plant automation infrastructure further improves operator efficiency through single-window access for alarm visualisation, diagnostics, and events.


At the core of a layered safety strategy is process design – the embodiment of the business, safety, and production considerations necessary for effective operations. At the next layer, this approach implements tools and procedures for managing abnormal situations and reducing incidents. When an abnormal situation occurs, alarm management, early event detection, and abnormal situation management (ASM)-designed displays ensure operators have the information available in the context they need it.
Next, properly designed emergency shutdown systems and automated procedures can move a plant to a safe state in the event an incident escalates beyond the inner sphere of protection. Should an incident occur, fire and gas detection solutions coupled with rapid location of individuals and a carefully designed emergency response procedure will help contain the impact.

Supplier support increases lifecycle sustainability
Industrial facilities can leverage the benefits of their fire and gas strategy by employing an integrated main automation contractor (I-MAC) to help them meet critical asset protection needs – and ensure operational and business readiness at project startup. With the I-MAC approach, plant management has a single point of contact throughout the entire system lifecycle. This results in optimised risk reduction and operational performance, better compliance with safety standards, and increased lifecycle sustainability.


An effective project strategy starts with an assessment of future or existing fire and gas performance according to functional safety standards. Based on this assessment, end users have a detailed roadmap for installing new equipment or updating obsolete infrastructure to an optimal level of safety. The main automation contractor can help to identify fire and gas hazard points and possible risks, and develop basic design packages and related acceptance test criterions to meet safety requirements.


By partnering with an experienced automation contractor, industrial plants can develop an IEC 61511/ISA S84-compliant fire and gas detection and suppression capability, as well as solutions meeting desired international standards, eg NFPA/EN.


In oil and gas terminal applications, operators need an integrated fire and life safety system allowing proactive response to alarms and events and a single real-time view to any potential threat. Industrial plants have procedures and safety systems designed to bring operations to a safe state in the event of equipment malfunctions and other operational problems.

In the case of a significant security incident, an integrated system can activate these same procedures and systems. An integrated system also leads to less expensive implementation and maintenance because all the pieces work together.
An integrated fire and life safety solution for terminals typically includes high-high tank alarms and loading system interlocks (compliant with IEC 61511) that prevent overflow through shutdown of pumps. Likewise, it incorporates the latest technology gas/vapor detectors, integrated with the overfill shutdown system, to detect incidents before they escalate. The system will mitigate safety incidents by ensuring all personnel are informed of hazardous situations in a clear and unambiguous manner, and providing fast and efficient response to associated risks.

Conclusion

For today’s manufacturers, the safety of their facilities, personnel, production processes and the environment is crucial to achieving on-time delivery and minimizing any potential losses. Plants must meet their safety needs while ensuring operational and business readiness at project start-up. Faced with this reality, they are seeking the lowest risk, and highest value protection, from their safety system and fire and gas technology.

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