MTL 7700 Intrinsically Safe Barrier

The MTL7700 Intrinsically Safe Barriers are 1- or 2-channel DIN-rail mounted shunt-diode safety barriers that use intrinsically safe explosion-protection techniques to pass electrical signals between safe and hazardous areas, while limiting transferred energy to a level that cannot ignite flammable atmospheres. Connected in series with wiring entering any hazardous area on process plant, MTL7700 Series barriers prevent explosions in all normally occurring explosive atmospheres – including mixtures of air with flammable gases, vapors, dusts and fibers – if a fault or faults develop in the safe area.

The MTL7700 is a DIN rail mounting barrier providing quick and easy installation without the need for special hardware. Removable terminals are used for ease of installation, maintenance and for providing a loop disconnect by simply unplugging the terminals from the side of the module. Wire entry is also angled to assist wiring within limited space enclosures. MTL7700 barriers clamp simply and securely onto standard T-section DIN rail, simultaneously making a reliable IS earth connection. For applications where field power is required for switch inputs or 2-wire transmitters, the MTL7700 range provides a bussed power feed facility. When used in conjunction with the MTL7798 power feed module the user has a fully protected, electronically fused supply to many barriers with no additional wiring required.

All MTL7700 Series barriers are based on the same simple principle. Each channel contains two stages of pulse-tested Zener or forward connected diodes and an ‘infallible' terminating resistor. In the event of an electrical fault in the safe area, the diodes limit the voltage that can reach the hazardous area and the resistor limits the current. A fuse protects the diodes, and the two stages of voltage limitation ensure continued safety if either stage should fail. No active output current limiting circuits are employed. All models (except MTL7707P+ and MTL7729P+, 'ia' 'IIB') are certified ‘ia' for all zones and ‘IIC' for all explosive atmospheres.