Intrinsic safety
1. Reference legislation
- ATEX Directive: 2014/34/EU for equipment and protective systems intended for use in explosive atmospheres.
- IEC/EN 60079 standards (e.g. IEC/EN 60079-11 for intrinsic safety).
2. Input Data
- Probe Features:
- Rated voltage
- Rated current
- Rated power
- Inductance
- Capacity
- ATEX Zone:
- Zone 0, 1 or 2.
- Type of gas or dust (e.g. IIC, IIB).
- Ambient and maximum temperature.
- Intrinsic barrier:
- Output voltage
- Output current
- Output inductance
- Output capacity
- Maximum power transferred.
3. Essential Calculations
- Compatibility between Probe and Barrier:
- Verify that the probe values are less than or equal to the barrier values:
- Ui≤Uo,Ii≤Io,Pi≤PoU_i \leq U_o, \quad I_i \leq I_o, \quad P_i \leq P_oUi≤Uo,Ii≤Io,Pi≤Po
- Maximum Transferable Energy Calculation:
- Determination of stored energy:
- E=12⋅Co⋅Uo2 12⋅Lo⋅Io2E = \frac{1}{2} \cdot C_o \cdot U_o^2 \frac{1}{2} \cdot L_o \cdot I_o^2E=21⋅Co⋅Uo2 21⋅Lo⋅Io2
- Compatibility with Explosive Atmospheres:
- Compare the barrier protection level with the gas/dust group and the ignition temperature.
- Checking Safety Limits:
- Comparison between:
- L<sub>i</sub> L<sub>cable</sub> ≤ L<sub>o</sub>.
- C<sub>i</sub> C<sub>cable</sub> ≤ C<sub>o</sub>.
4. Safety Margin
Make sure there is an adequate safety margin for each parameter, also considering the length and type of cables.
5. Documentation
- Complete technical specification of the probe and barrier.
- ATEX Declaration of Conformity.
- Installation diagrams.
