What is IEC 60079-25? Intrinsically Safe Systems (IS Systems)
Short answer: IEC 60079-25, Intrinsically Safe Systems (IS systems) They define safety features. They ensure the intrinsic safety of the entire system, not just a single device, including the field device, barrier, and cabling. 60079-11 covers a single device, while 60079-25 addresses the entire system.
Intrinsic safety (Ex i) doesn't end with a single device; true safety comes from the entire system. A transmitter might be 'Ex i' certified, and so might the barrier it's connected to — but if the two are incompatible, or if the cabling between them exceeds permitted limits, the system is no longer safe. IEC 60079-25 provides this holistic perspective and defines how the system should be correctly installed and documented.
The system consists of three parts.
| Component | Role |
|---|---|
| Field device (apparatus) | Sensor/transmitter within the zone |
| Associated device | Barrier/galvanic isolator in the safe zone |
| Interconnect cabling | The line connecting the two carries capacitance/inductance. |
Critical Concept: Entity Concept
The safety of the system is ensured by the compatibility of the electrical parameters of each component as specified by the manufacturer. The maximum voltage and current (Uo, Io) that the barrier can withstand must be less than the values (Ui, Ii) that the field device can withstand; the total capacitance and inductance (Ci + cable C, Li + cable L) of the field device and the cable must remain below the maximum allowed by the barrier (Co, Lo). This comparison... ‘'entity' account It is called and is the mathematical basis of IS system security.
Descriptive System Document
60079-25, one for each intrinsically safe system. descriptive system document It requires documentation. This document includes all devices comprising the system, their parameters, cabling limits, and compliance calculations; it proves why the system is safe. Without this document, it is impossible to verify that an IS circuit in the field is truly compliant. The AES inspection checks the consistency between the system documentation and the actual field installation.
Frequently Asked Questions
What is the difference between 60079-11 and 60079-25?
60079-11 refers to the intrinsic safety of a single device (apparatus); 60079-25 refers to the device + barrier + cable. system It defines the self-reliance of the whole.
Is it enough to connect two compatible Ex i devices?
No. Cable capacitance/inductance must also be taken into account and entity compatibility verified; otherwise, the system may not be secure.
Document the Compliance of Your Intrinsically Safe Systems.
Related service: Explosive Atmosphere (ATEX/Ex-Proof) Inspections.