Ex i Intrinsically Safe Loop Calculator
This calculator validates the parameters of an intrinsically safe (Ex i) loop to ensure compliance with intrinsic safety standards. It checks voltage, current, power, capacitance, and inductance limits for safe operation in hazardous areas.
Intrinsic Safety Validation Results
Loop Status: N/A
Step-by-Step Calculation & Checks
| Parameter | Barrier (Source) | Field Device | Cable (Total) | Check Status |
|---|
Applicable Standards and Guidelines: Intrinsic safety is a protection concept governed by rigorous international standards to prevent ignition in hazardous areas.
- IEC 60079-11: Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i". This is the primary international standard for intrinsic safety. It defines the requirements for construction and testing of intrinsically safe apparatus and associated apparatus.
- ATEX Directive (2014/34/EU): For the European Union, the ATEX directive mandates compliance for equipment and protective systems intended for use in potentially explosive atmospheres. Intrinsic safety is one of the protection types covered.
- NEC Article 504 (NFPA 70): In North America, the National Electrical Code (NEC) provides guidelines for electrical installations in hazardous (classified) locations, including intrinsic safety.
- Entity Parameters: The core of intrinsic safety validation relies on comparing "entity parameters" from the certificates of the intrinsically safe barrier (associated apparatus) and the field device (intrinsically safe apparatus).
- Barrier Output Parameters (Uo, Io, Po, Ca, La): These define the maximum energy the barrier can deliver to the hazardous area.
- Field Device Input Parameters (Ui, Ii, Pi, Ci, Li): These define the maximum energy the field device can safely accept without causing ignition.
- Cable Parameters: The capacitance and inductance of the connecting cable add to the total energy storage in the hazardous area and must be accounted for.
- Safety Factors: It is common practice, and sometimes mandated by national standards or specific applications, to apply safety factors (e.g., 1.5) to cable capacitance and inductance to provide an additional margin of safety.
- Loop Validation Criteria: For a loop to be intrinsically safe, the following conditions must typically be met:
- Barrier Uo ≤ Device Ui
- Barrier Io ≤ Device Ii
- Barrier Po ≤ Device Pi
- Device Ci + Cable Ccable ≤ Barrier Ca (with safety factor for Ccable if applied)
- Device Li + Cable Lcable ≤ Barrier La (with safety factor for Lcable if applied)
- Documentation: Proper documentation of intrinsic safety calculations and loop diagrams is essential for compliance and auditing.
This tool provides a practical calculation aid for intrinsic safety loop validation. However, it does not replace the need for thorough understanding of the relevant standards, manufacturer's instructions, and, for critical installations, review by certified intrinsic safety experts.