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AutoQuiz: What Is the Purpose of an Intrinsic Safety Barrier?

AutoQuiz is edited by Joel Don, ISA's social media community manager.

This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.

What is the purpose of an intrinsic safety barrier?

a) provide a physical obstruction between the hazardous and non-hazardous areas
b) establish a central grounding point in the hazardous area
c) prevent excess voltage and current from reaching the hazardous area
d) increase the resistance in the circuit to reduce the risk of explosion
e) none of the above

Answer A is incorrect because just providing a physical obstruction between the hazardous and non-hazardous area does not eliminate any of the three elements required for ignition.

Answer B is incorrect because a common ground does not guarantee that a voltage or current less than what is required for ignition will not be present.

Answer D is incorrect because resistance does not necessarily reduce the overall energy in the circuit.

The correct answer is C, prevent excess voltage and current from reaching the hazardous area. In order for ignition to occur, three elements are required: Fuel (something to burn-gas, vapor, or powder), an oxidizer (air or oxygen), and an ignition source (electrical or thermal). An intrinsic safety barrier is designed to remove the last element-an ignition source-from the equation. Without an ignition source, there can be no ignition or combustion.

Reference: ANSI/ISA-60079-0 (12.00.01)-2005 - Electrical Apparatus for Use in Class 1, Zones 0, 1 & 2 Hazardous (Classified) Locations

About the Editor
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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Joel Don
Joel Don
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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