...while located in the hazardous (explosive) atmosphere?
While maintenance/live-work on intrinsically safe field-wiring circuits is often confused with maintenance on intrinsically safe equipment, IEC/EN 60079-17 Electrical apparatus for explosive gas atmospheres – Part 17: Inspection and maintenance of electrical installations in hazardous areas (other than mines) provides some information on this topic that can be useful to the reader.
In North America, we do not have a standard dedicated solely to the topic of maintenance on intrinsically safe equipment. Any approved maintenance procedure would be listed on the control drawing, manual or other referenced installation document. As a result, the certification agency would be aware of the maintenance activity and would have reviewed the procedures for safety.
The following are some general guidelines from IEC/EN 60079-17. It is recommended that a thorough review of the document is done for additional information and understanding of global, hazardous location concepts.
According the IEC/EN 60079-17 maintenance on live equipment, if it is intrinsically safe, is permitted under certain conditions. These conditions are as follows, as stated in our Interface Technology Engineers Guide:
Working on live electrical systems and apparatus in hazardous areas is strictly prohibited. Working on intrinsically safe systems is an exception to this rule. Therefore special requirements exist for the intrinsic safety ignition protection class:
Maintenance work on live intrinsically safe systems may be carried out under certain conditions. The ground connections of safety barriers may not be removed before the circuits in the hazardous area are disconnected. Work in hazardous areas is to be limited to:
- Disconnecting, removing, or changing parts
- Adjusting all settings required for calibration
- Removing or changing pluggable components
- Using testing instruments as set out in the documentation
After testing, the intrinsically safe system/apparatus must fulfill all requirements of the system documentation. The documentation must contain the following:
- Proof of intrinsic safety
- Manufacturer, type of apparatus and certification number, category, apparatus group, temperature class
- Electrical parameters (inductance, capacitance, length, type and routing of cables, leads)
- Special requirements according to the component data sheet
- The installation location of each component within the system
In addition the following should be tested:
- Easily identifiable marking of intrinsically safe circuits
- The conformity of the actual installation with the documentation
- Separation of components between intrinsically safe and non-intrinsically safe circuits
- Cables and leads and their shielding
- Continuity of grounding of non-galvanically isolated circuits, ground connections to ensure intrinsic safety
- Grounding or isolation of intrinsically safe circuits
- Adhering to specified minimum distances