Risk Detection How PLCs Help to Avoid Hazards and Increase Plant Safety

Author / Editor: Deepak Makhijani, Consultant / Dominik Stephan

In the present times, when strategies to ascertain workplace safety and environment conservation have become a necessity, fail-safe PLC systems can work wonders. These systems minimize the risks involved in critical applications where the possibility of hazards is high. The fault-tolerant architecture ensures that the failure of a component does not interrupt the process operation, thus ensuring safety.

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Fail-safe PLC system is used in critical safety applications in refineries, petrochemical/chemical plants
Fail-safe PLC system is used in critical safety applications in refineries, petrochemical/chemical plants
(Picture: ABB)

Today, workplace safety and protection of workers as well as the environment are top priorities while preparing a plant design, and are routinely incorporated into operating and maintenance procedures. In general, design engineers and plant operators can use four different approaches to reduce risks in a chemical process plant, namely:

  • Seek inherently safe designs
  • Devise passive design solutions
  • Install active (engineered) protection
  • Implement procedural or administrative controls

To improve both process operations and plant safety, many operators are turning to advanced analytical tools, diagnostic devices and smarter field instrumentation to monitor critical operating variables, such as the presence and concentration of combustible gases; oxygen concentration in potentially explosive environments; flow rates and temperatures in pipelines and vessels, etc.


Combined with today’s open digital communication protocols, expert software and advanced control systems, these diagnostic devices can improve the real-time monitoring and control of process operations; reduce the time needed for repair of various equipment components; simplify troubleshooting; minimize unscheduled downtime; and reduce the risk of dangerous conditions such as undetected equipment failures.

What is a Safety Integrated System?

The safety integrated system (SIS) is one of the latest systems being used in refineries and petrochemical sector to mitigate hazards and reduce the level of risk. TUV is a governing body that offers support during the complete lifecycle of a product from concept to development and testing to certification. The IEC 61508 safety standard defines safety as ‘freedom from unacceptable risk’.

Some layers of protection can be used to reduce unacceptable risk to an acceptable level. The amount of risk reduction for each layer is dependent on specific nature of the safety risk and the impact of the layer on the risk. Economic analysis should be used to determine the appropriate combination of layers for mitigating safety risks.