Calculate Intrinsic Safety - Intergraph Smart Instrumentation - Help

Intrinsic safety calculation in Smart Instrumentation allows you to calculate the maximum permissible cable length between the hazardous and non-hazardous areas based on three main criteria:

• Resistance

• Capacitance

• Inductance

The calculations are made at the domain level.

1. Start the Wiring module and select Actions > Intrinsic Safety .

2. On the Intrinsically Safe Circuit dialog, from the Circuit type list, select the appropriate circuit type.

   

   • The remaining fields on the dialog are filled in automatically with the data for the circuit type you select.

   • If the required circuit type is not on the list, create a new one or edit an existing circuit type. For more information, see Calculate Intrinsic Safety for a Loop.

3. Select OK.

4. On the Intrinsically Safe Data Input dialog, under Non-hazardous area loop components, enter the relevant data for the non-hazardous devices, such as barrier, isolator, and so forth. You must define the R1, C1, and L1 values.

5. Under Hazardous area loop components, enter the relevant data for the hazardous devices, such as transmitters, I/P converters, and so forth. You must define the R2, C2, and L2 values.

6. Define the cable parameters between the junction box and the marshaling rack.

7. Define the cable parameters between the device panel and the junction box (if the cable exists). If the field instrument is connected directly to the marshaling rack, specify the cable length (B) = 0.

8. Select Calculate to calculate the limit criteria (resistance, inductance, or capacitance) and the maximum permissible cable length between the junction box and the marshaling rack (Cable A) based on the values you entered.

   

   • The Intrinsically Safe Calculation Results dialog opens where you can view the calculation results, change the units of measure, and save the results with the different units.

   • The maximum permissible length must be less than the actual length of the cable used (Cable “A” – connecting the hazardous and non-hazardous areas).

9. Select OK to return to the Intrinsically Safe Data Input dialog.

10. If required, you can do any of the following:

    • View and enter revisions.

    • Enter intrinsic safety notes.

    • Select Print to generate and print a report that shows all the data that you entered and the calculation results.