Intrinsic Safety (Ex i) – EN 60079-11
ntrinsic Safety relies upon the equipment supplies being of low voltage and power and is suited to electronic devices. The operating current of the circuitry should be low enough to not be affected by series resistance, which may be required to limit energy.
The circuitry should contain low values of inductance and capacitance.
Supply values exceeding 30V and 1.3W are possible though increasingly more difficult to certify.
A detailed analysis of the circuit design will be undertaken. In short, your circuit design will probably need to be modified to achieve certification, so this protection concept is not suited to circuit boards that cannot be modified.
The strength and shape of the enclosure is not as important as full control and knowledge of the circuit design.
ia for Zone 0 and 20
ib for Zone 1 and 21
ic for Zone 2 and 22
Important Design Parameters
Use of certain components for electrical and electronic circuits
Lower permitted load on the components compared to ordinary industrial applications with regard to:
Voltage with regard to electric strength
Current with regard to heat
Voltage and current, including a safety margin, are kept so low that no impermissible temperatures can occur. Sparks and arcing (in the event of open circuit or short-circuit), possess so little energy that they are unable to ignite a potentially explosive atmosphere.
An impression of this protection type is provided by the fact that potentially explosive atmospheres of subgroup IIA require only a few hundred μW and those of subgroup IIC only 10 μW for ignition.
Applications
Instrumentation and control
Sensors working on physical, chemical, or mechanical principles
Actuators working on optical, acoustic, and, to a certain extent, mechanical principles
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Intrinsic Safety (Ex i) – EN 60079-11
OverviewIntrinsic Safety (Ex i) is a protection concept that ensures electrical and electronic equipment operates safely in potentially explosive atmospheres by limiting energy, voltage, and current to levels that cannot ignite hazardous environments. It is particularly suited for low-power electronic devices.
Core Principles of Intrinsic Safety- Energy Limitation: Equipment ensures that energy levels remain below ignition thresholds, even under fault conditions.
- Low Operating Power: Supply values exceeding 30V and 1.3W are possible but require rigorous analysis for certification.
- Circuit Design Requirements: A detailed circuit analysis is mandatory, and modifications are often needed to meet certification standards.
- Ignition Prevention: Voltage, current, and energy levels are kept low to prevent impermissible temperatures, sparks, or arcs from igniting hazardous atmospheres.
- Enclosure Role: The shape and strength of the enclosure are less critical; control over the circuit design is paramount.
Zones and CategoriesIntrinsic Safety applies based on hazardous area classifications:
- ia: For Zone 0 (gases) and Zone 20 (dust). Provides the highest level of protection under two independent faults.
- ib: For Zone 1 (gases) and Zone 21 (dust). Protects against ignition under a single fault condition.
- ic: For Zone 2 (gases) and Zone 22 (dust). Ensures safety during normal operation only.
Key Design Parameters- Permitted Load on Components:
- Voltage: Limited to avoid exceeding electric strength of components.
- Current: Restricted to prevent excessive heat generation.
- Inductance and Capacitance Limits: Stored energy is tightly controlled to prevent discharge capable of ignition.
- Safety Margins: Large safety factors account for tolerances, environmental variations, and faults.
- Hazardous Subgroups:
- Group IIA: Requires only a few hundred μW for ignition.
- Group IIC: Needs as little as 10 μW for ignition.
Applications of Intrinsic SafetyIntrinsic Safety is widely used in hazardous environments for:
- Instrumentation and Control Systems: Monitoring and automation in hazardous areas.
- Sensors: Operating on physical, chemical, or mechanical principles (e.g., pressure, temperature, gas sensors).
- Actuators: Based on optical, acoustic, or limited mechanical principles (e.g., alarms, displays).
Advantages of Intrinsic Safety- Simplified Maintenance: Equipment can be repaired or inspected in hazardous zones without shutdown.
- Flexibility in Design: Applicable to various low-power devices without compromising functionality.
- Cost-Effective: No need for heavy-duty explosion-proof enclosures or pressurization systems.
- Global Compliance: Aligns with international standards like EN 60079-11.
ConclusionIntrinsic Safety (Ex i) is a vital method for ensuring safe operation in hazardous environments. By controlling voltage, current, and energy levels, it prevents ignition while maintaining functionality. Its flexibility, cost-effectiveness, and adherence to global standards make it a preferred choice for low-power devices in hazardous zones.