Explosion-proof intercom phones are widely used in workplaces where explosive gases are present. They differ from civilian and conventional intercoms because of what can happen when an ordinary phone is used in an explosive atmosphere.
An explosion-proof intercom is not a phone that can resist an explosion. It is a phone designed to operate in an environment where an explosive atmosphere may be present, without becoming the ignition source.
Why an ordinary intercom is not enough
Intercom phones transmit signals through electromagnetic waves. That transmission relies on electric fields and the continuous conversion of the magnetic field, which can generate electric sparks during the process.
Explosion-proof intercoms use specially treated circuits so that every place where a spark could be produced is shielded. They must also use compatible explosion-proof batteries. A standard battery or an uncertified replacement can undo the protection.
Where explosion-proof intercoms are required
Explosion-proof intercom phones are needed in industries with large amounts of gas, vapor or dust:
- Gas stations, oil depots and oil fields
- Petrochemical plants and chemical works
- Coal mines and coal preparation plants
- Natural gas processing facilities
- Flour, flax and other dust-generating processing plants
- Fire-protection and hazardous-material storage areas
Reading an explosion-proof rating
An explosion-proof rating is more than the letters “Ex.” The marking combines several pieces of information that must all fit the installation:
- Protection type: Ex d (flameproof) contains an internal explosion in a strong enclosure; Ex ib or Ex ia (intrinsic safety) limits circuit energy so an atmosphere cannot be ignited.
- Area classification: Zone 0, 1 or 2 (and the corresponding dust zones) describes how often an explosive atmosphere is present.
- Gas or dust group and temperature class: The equipment must be suitable for the specific medium and must not exceed the ignition temperature of the surrounding atmosphere.
The certificate, the nameplate and the installation instructions belong together. If a replacement handset, battery or cable gland is not part of the approved configuration, the protection can be compromised.
Safecom explosion-proof telephones are built for these environments and can be configured to project requirements.