MTL 7700 Intrinsically Safe Barrier
DIN-rail zener barriers limit the amount of energy transferred across the barrier to a level that cannot ignite flammable atmospheres
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- Removable terminals for easy cabling
- Bussed power feed to other modules
- Relay and solid state switch modules
- Dual channel variants: 6.3mm per channel
- Barrier protection module
- Proximity detector inputs
- Electronic fusing
- Direct replacement for MTL700 Series barriers
- Compatible terminal numbering and safety descriptions
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.
Here's how some of our customers used this product.
Protecting Sensor Circuits in a Hazardous Location
The Background: Our customer is a ceramics manufacturer seeking a means to protect sensor circuits in a hazardous area location.
The Problem: The customer utilizes methanol during the annealing process. As a highly flammable substance, the storage area for the methanol is classified as a hazardous area. As such, they must have intrinsically safe barriers for all sensor circuits that pass into the methanol storage area.
The Solution: We recommended MTL7700 Intrinsically Safe Barriers. The 7700 is a shunt-diode barrier that limits the amount of energy allowed to pass between safe and hazardous areas to a level that cannot ignite flammable atmospheres. They are DIN-rail mounted which provides quick and easy installation without the need for special hardware.
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