The avoidance method prevents explosions by utilising equipment or parts that do not produce arcs or sparks during normal operations.
This eliminates potential ignition sources.
Equipment can be designed to have increased safety (Ex e) or to be non-sparking (Ex n).
Increased Safety (Ex e)
- The increased safety method is one of the most commonly used protection techniques.
- The design and manufacturing of increased safety equipment prevent sparking components from being included.
Manufacturers design other components to greatly reduce the likelihood of ignition through fault conditions by:
- Managing and reducing working temperatures.
- Ensuring reliable electrical connections.
- Improving insulation effectiveness.
- Lowering contamination risks from dirt and moisture ingress.
- Common applications include terminal and connection boxes, control boxes, and light fittings.
Table: Type of protection schemes and protection designation
| Type of Protection | Symbol (Ex or EEx) |
|---|---|
| Explosion-proof enclosures | Ex d |
| Intrinsic safety in Zone 0 | Ex ia |
| Intrinsic safety in Zone 1 | Ex ib |
| Increased safety | Ex e |
| Non-sparking equipment | Ex n |
Table: Device and Zones
| Device | Zone 0 | Zone 1 | Zone 2 |
|---|---|---|---|
| Transmitter/Positioner | Ex i | Ex i (preferred) Ex d (alternative) | Ex i (preferred) Ex d, Ex e, Ex m (alternatives) |
| Switch/Push-Button | – | Ex de | Ex i (preferred) Ex e, Ex m (alternatives) |
| Temperature Sensor | – | Ex e | Ex e |
| Solenoid Valve | – | Ex d | Ex d |
| Junction Box | – | Ex e | Ex e |
| Fire and Gas Detector | – | Ex d | Ex d |
| Analyser | – | Ex I, Ex d | Ex i, Ex d |
| Local Panel | – | Ex d or Ex p | Ex d or Ex p |
