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General Information:
An Intrinsically Safe Barrier is a device which limits the power (energy) which can be
delivered from a safe area into a hazardous area. Explosions are prevented; not just
contained in explosion-proof conduit and housings. Not only is electrical energy
(voltage and current) held within safe limits, but also total energy, eliminating the
possibility of an explosion due to excessive heat. Use of barriers and a total
intrinsically safe design philosophy offers considerable advantages from cost and safety
standpoints.
The following features indicate the clear benefits of choosing an intrinsically safe design instead of an explosion-proof design and reflect the unique features of the Series X57 family of barriers.
 | All components are immediately accessible - no time-consuming opening of explosion-proof housings. |
| Personnel safety is assured because of low voltage operation. |
| Standard wiring techniques in open cable trays or light gauge conduit save on material and labor costs during initial installation. |
| Calibration and maintenance can be performed with the system in an operational status as though it were located in a general purpose area. |
| Special skill levels are not needed to open heavy housings, test for gas, or shut down the process in order to service, or operate the instrumentation. |
| Barrier replacement is accomplished by simple exchange of plug-in modules. There is no need to disconnect wiring. |
| Color-coded housings give visual indication of the barrier type in use for a particular circuit. |
| Barriers are manufactured in the U.S.A. - in Woodland Hills (Los Angeles), California. |
The Ronan zener safety barriers are plug-in modules containing one to four channels. Up to twenty modules can be installed in the Model X57SM-20 surface mounted chassis. One, four, and ten module chassis are also available. Each module has up to eight associated, active screw terminals. The terminals are arranged in the chassis so that four (per plug-in module) are located in the safe area and four are located in a protected compartment where the wiring to the hazardous area is terminated.
The safe area terminals are numbered 1 through 4 and the protected terminals are numbered 5 through 8. All of the compression-type screw terminals accept up to 12 AWG wire. The safe area terminals are connected to equipment in a location where the sources of potential with respect to each other or to ground do not exceed 250 VDC or RMS.
The I.S. ground connection for the barriers is provided by an integral, fixed, screw stud with self-locking nuts. Optional bus bars with compression-type terminations are available with the chassis for additional grounding connections. The zener barriers are available in positive, negative, or AC (alternating) voltage configuration with respect to ground. When the "Vmax" rating of the barriers is exceeded, the barriers provide a low impedance path to ground and the internal protection fuse will blow.