CSA/ATEX Intrinsically Safe: Meaning & Requirements

CSA/ATEX INTRINSICALLY SAFE: MEANING & REQUIREMENTS

In the many industrial processes where flammable materials are handled, any leak or spillage may give rise to an explosive atmosphere. To protect both personnel and the plant, precautions must be taken to ensure that this atmosphere cannot be ignited. The areas at risk are known as “hazardous areas” and the materials that are commonly involved include crude oil and its derivatives, natural and man-made process gases, alcohols, metal dust, carbon dust, flour, starch, grain, and fibers.

Intrinsic Safety (IS) is based on the principle that the electrical energy in hazardous-area circuits is deliberately restricted such that any electrical sparks or hot spots that may occur are too weak to cause ignition. This is achieved by inserting an energy-limiting interface in the wiring between safe and hazardous areas. The interface passes signals in either direction as required but limits the voltage and current that can reach the hazardous area under fault conditions.

Guidelines for Use & Installation:

• A barrier is required for the installation of IS sensors. The barrier is required for the installation of IS sensors. The barrier passes signals in either direction as required, but limits the voltage and current that can reach the hazardous area under fault conditions. The barrier is put in series and is installed in a safe area.
• Proper IS barrier must be used with this sensor to ensure compliance with entity parameters.
• Approved cabling must be used to bring the signal from the sensor to the Zener diode barrier or galvanic isolator, which is the energy-limiting interface. 
• Sensors must be grounded to a grounded structure by stud mounting the sensor directly to the machine surface, ensuring metal (of the sensor) to metal (of the machine surface) contact.