Safety does not come out of a box
Creating effective alarms
The move from panel board control to DCSs created the problem of alarm management, which spawned a whole new industry. In the old days when adding an alarm was an expensive process and took up valuable real estate on the wall or console, users took a great deal of care choosing those that were most important. Such is not the case anymore, and as we know, too many alarms make conditions worse for the operators and the plant.
Concepts of human software engineering suggest that alarm system design should ensure prompt, reliable, and effective operator response. A poorly designed system will leave an operator failing to act at all, or selecting the wrong course of action.
Today we have standards such as ISA18.2 and EEMUA 191 to guide users through the alarm lifecycle process, and most systems have built-in features to support assessing the current situation in a plant and identifying nuisance alarms and bad actors as part of rationalizing alarms.
State-based control is another methodology available to assist engineers while working through the design phase. By managing the parameters across process states, optimized process conditions can be maintained during normal conditions and correct action can be taken automatically during abnormal conditions. In this scenario, state-based control provides an additional layer of protection for the plant.
Integrated control and safety
Integrating control and safety systems can provide an enabling technology to drive effective operations and minimize the sources of human error discussed earlier. Some of those benefits include:
- Analysis of potential common cause failures and designing those out of the system.
- Standard access control to prevent unauthorized access and secure the systems without introducing additional custom programming.
- Integrated testing at the product test lab rather than during a FAT (factory acceptance test) ensures all standard functions are working as the product was designed prior to market release. This reduces the scope of a FAT to project-specific requirements.
- Version control, compatibility, and interoperability are all considered prior to the release of the product, reducing maintenance- and product-lifecycle costs.
Prescribing a solution does not address the need for analysis that is behind the performance based functional safety standards. It is our responsibility as users to design a system that effectively provides the required risk reduction and to verify that we have reduced the risk to an acceptable and reasonable level.
There is no doubt that process safety and security are interconnected, and both should be given serious thought in the design process. Safety standards such as IEC 61511 do not restrict or prohibit combining control and safety; in fact, Part 2 indicates that “Physical separation between BPCS (basic process control system) and SIS may not be necessary provided independence is maintained, and the equipment arrangements and the procedures applied ensure the SIS will not be dangerously affected by failures of the BPCS or work carried out on the BPCS, for example, maintenance, operation or modification. Where procedures are necessary to ensure the SIS is not dangerously affected, the SIS designer will then need to specify the procedures to be applied.”
Having an integrated control and safety system with embedded access control not only provides security to the safety system and prevents unauthorized or unintended access, it also facilitates maintenance of the safety system with standard bypass or override methods.
These standard methods give the operator feedback of the condition in the safety system and are registered in the audit trail supporting best-in-class management of change.
Similar to safety systems, prescribing a security solution does not address the need for the analysis to ensure the automation infrastructure is free of known vulnerabilities and satisfies the needs of the industrial environment. Security deserves the same attention as safety as part of the cultural paradigm in manufacturing companies.
A two-sided effort
Reducing risk in a process manufacturing environment requires a technical and cultural effort. The most careful and conscientious people can be injured in a plant with faulty equipment, and the most sophisticated equipment can be defeated by careless people.
When careful people work with a safe attitude driven by a sound culture using well-maintained equipment and appropriate work practices, safe and reliable production will become a way of life.
Luis Durán is product marketing manager for safety systems, control technologies, and process automation for ABB.
For more information, visit: www.abb.com
Read more about process safety below.
- Creating a safe working environment requires technical and human elements.
- A corporate culture of safety has to be supported at all levels of a company.
- Design elements in a control room can help or hinder the ability of operators to react in a crisis situation.
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