How can you design a control system that is both reliable and safe for your plant?

I would like to add following points: 1-Consider the type of process application & equipment under control for which control system is being designed. 2-In process safety past experiences are "Gold". Take into account the operational experiences, control system failure/malfunction events on similar process applications worldwide. 3-Review HAZOP & LOPA sheets to understand the risk reduction both BPCS and SIS are expected to provide. 4-Define boundary of the process, the BPCS, SIS, other systems, operators, environment & external factors. 5-Finalize SIS safety requirements e.g. proof tests, response time, safe state, etc. 6-Form field devices to control system keep the BPCS and SIS separate. 7-For SIS, consider IEC61511 Safety Life Cycle.

Following are my personal experience based on multiple mega projects critical infra starts from concept up to complete lifecycle which I would like to share: - At 1st define the control system philosophy, associated protocol/technology to be implemented, control room (local/remote/manning/topology) operating concepts, reference architecture etc. - To finalize clear control system & philosophy specifications including BPCS & SIS - To define Functional Safety Management (FSM) plan for SIS starts from conception stage up to complete Life-cycle - To finalize well written Scope of Work (free from ambiguity) for Control System including specially quantified items in-line with control philosophy Framework. - Make sure independence in BPCS & SIS

Another critical piece of any DCS/SIS is the Plant Asset Management applications to collect warnings and alerts generated by field devices. When properly implemented and used, provide plant operators the tools to monitor the health status of sensors, analyzers and final control elements (valves).

- A Backup and Recovery system to ensure anytime the server crashes, the configuration can be restored with minimal effort - A separate system to push latest system updates in an automated way. And an anti virus system being updated.

? Risk Assessment: Identify potential hazards and assess the risks associated with the plant operation. ? Safety Measures: Implement safety measures such as fail-safe designs, redundancy, and safety instrumented systems (SIS) to mitigate identified risks. ? Control System Design: Design a control system that is robust, reliable, and capable of handling uncertainties and disturbances. This includes selecting appropriate control strategies, controllers, and instrumentation. ? Testing and Validation: Rigorously test the control system under various scenarios to ensure it performs as expected. ? Maintenance and Monitoring: Regularly maintain and monitor the control system to ensure its continued reliability and safety.

The experience shared here is subjective and is varies case to case. I would start with assessing the complexity and scale of the plant. And determine performance and reliability requirements. Once this is available next need to evaluate budget and time constraints. Once this has been completed, finalizing control architecture and choose amongst centralized, decentralized, and distributed. The last step would be to select the appropriate hardware and software components. When choosing the hardware - Compatibility, Functionality, Reliability, Availability and Maintainability needs to be considered as well.

A fault-tolerant system is one that can experience failure (or multiple failures) in its components, but still continue operating properly. A single point of failure is a component in the system that will bring down the entire system if it fails. When we're trying to make sure a system is fault tolerant, we look for single points of failure and find ways to add redundancy at those points. Redundancy involves duplicating critical elements of a system to provide alternatives and reduce the risk of failure.

Best way to go about this would be to refer ISA/IEC 62443 standards. Especially for OEM and System Integrations the following address the security and integrity aspects and what needs to be taken care of. IEC 62443-3-1, Security technologies for industrial automation and control systems (IAC). IEC 62443-3-2, Security risk assessment and system design. IEC 62443-3-3, System security requirements and security levels. And for Service providers, IEC 62443-2-4, Requirements for IACS service providers

In my humble opinion, Humans are always the weakest link. And only through awareness and training this can be prevented. And this is not just for folks who work with Cybersecurity, but everyone in the organization. Awareness of do's and dont's, policies, procedures and practices also go a long way. Finally using clear and concise labeling, color coding, feedback loop, minimizes the risk of operator error, ability to customize the system are vital as well

In my opinion or if I’m the key person to decide , I will consider 1. Manufacturers record and specialisation and inherent mission and vision. Take away the technical side of it. Most manufacturers have what is required. 2. Appropriate solution that they can offer based on available specifications and what it can do more. 3. Lifecycle strategy - total replacement or phased upgrades reusing what can be used with “Lower “cost and turnaround impact. 4. After sales support and continual improvement, looking at the company investments 5. And most importantly , the project team. And don’t forget the technical proposal guy! He’s is the key . ??

I would additionally consider the importance of Project team, project sponsors, management support in addition to cost, time, maintenance and support, future needs and requirements needs to be factored in.

Well, I think that a number of elements need to be taken into consideration when designing a control system for a plant that is both reliable and safe. Firstly, in order to identify possible risks and estimate their impact, a complete risk assessment must be carried out. The selection of suitable safety precautions, such as protective enclosures, safety interlocks, and emergency shutdown systems, will be impacted by this. Advanced diagnostic features should also be included in the control system to enable real-time fault monitoring and abnormal condition identification. Regular maintenance programs that include testing and inspections should be put in place to guarantee reliability.