This post was authored by Joel Don, ISA's social media community manager.

This automation industry quiz question comes from the ISA Certified Automation Professional (CAP) certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

In the ISA84 standard, the concept of multiple independent protection layers refers to:

a) multiple layers in a control system architecture, which provide redundant data pathways from sensors and plant-floor level devices to servers, historians, and business networks, in order to ensure reliable data capture.
b) independent layers of protection for which each layer helps to reduce the overall level of risk of the process. The inner layers help to prevent a hazardous event (explosion, fire, etc.) from ever occurring, and the outer layers are designed to help lessen the consequences of an event once it has occurred.
c) independent software modules where each successive layer monitors each layer below to ensure the integrity of the sensor signals processed and the transfer of data to the next-higher software module.
d) independent layers of project management decision-making, which help ensure project execution is performed to meet schedule and budget constraints.
e) none of the above

Click Here to Reveal the Answer

Answer A is not correct since ISA84 does not directly address data flow on the plant floor. The stated concepts in this answer choice are covered in other standards, such as ISA95.

Answer C is not correct. This answer choice describes supervisory process control functionality, which is not covered in ISA84.

Answer D is not correct.  ISA84 is not a standard that addresses project management or project execution techniques.

The correct answer is B, “Independent layers of protection for which each layer helps to reduce the overall level of risk”. ISA84 addresses functional safety and safety instrumented systems. A consequence of the concept of multiple independent protection suggests minimization of risk occurs when safety instrumented systems are completely independent from process control systems.

Reference: ANSI/ISA84.00.01-2004 Part 1, Functional Safety-Safety Instrumented Systems for the Process Industry Sector – Part 1: Framework, Definitions, System, Hardware and Software Requirements.

About the Author
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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