Intrinsic Safety Barriers are devices which limit the power (energy) that can be delivered from a safe area into a hazardous area. Explosions are therefore prevented, not just contained, in explosion-proof conduit and heavy cast housings. Electrical energy (voltage and current) and total energy are held within safe limits, eliminating the possibility of an explosion due to excessive heat.
The Ronan Intrinsic Safety Barriers Series X57 are plug-in modules containing one to four channels. Up to 20 barrier modules can be installed on a surface mount chassis.
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 system 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 cost during initial installation.
◗ Calibration and maintenance can be performed with the system in operation.
◗ Special skill levels are not needed to open heavy housings, to test for gas, or to 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 or to remove ground bars.
◗ Barriers are manufactured and stocked in the U.S.A. in Woodland Hills, California. (Los Angeles area)
◗ Multiple channels in one barrier minimize the total number of barrier modules needed and space required.
The Ronan I.S. Barriers are plug-in modules containing one to four channels. Up to twenty barrier modules can be installed in a 20 position surface mounted chassis. Single barrier surface or DIN rail chassis are also available. Each module has eight screw terminals. The terminals are arranged in the chassis so that four are located in the safe area and four are located in a protected compartment for the wiring to the hazardous area. The safe area terminals are numbered 1 through 4 and the protected terminals are numbered 5 through 8. These 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. grounding connection for the barriers is provided by an integral, fixed, #8 stud with self-locking nuts. Optional ground bus bars and multi-pin cable connectors are also available.
Shunt Diode Zener (Passive) I.S. Barriers
Ronan's Zener Barriers, especially the multi- channel versions, are a logical choice when space and cost are the major considerations. They do not require their own power supply, but rather provide protection passively. Most likely, there is a barrier that will work, and a detailed analysis of the applica- tion will usually identify a zener barrier that is right for the application. However, zener barriers do require a high integrity I.S. ground. This may present a problem, especially in older plant installations. When the quality or availability of an I.S. ground is questionable, the designer should consider using active barriers.
◗ Lowest Cost Barrier Option
◗ 1, 2, 3, and 4 Channel Barriers
◗ Negative, Positive, or AC Voltage Versions
◗ Highly Reliable Fast Acting Fuses
◗ Power Supply is Not Required
◗ NO FAULT “Blown Fuse” Barrier Replacement Policy
◗ DIN Rail or Multi-Barrier Surface Mount Chassis
Galvanic Isolation (Active) Barriers
In numerous applications, zener diode barriers will either not work, or they impose constraints that complicate system design. The series resistance, fuse rating and maximum working voltage of a zener diode barrier, can cause the design engineer hours of frustrating analysis to confirm both safety and proper system operation. Ronan's line of active I.S. barriers eliminates much of the tedious analysis re- quired. In some cases, the active barrier can actually double as a signal conditioner and eliminate other devices from the loop. These considerations, along with the fact that no I.S. ground is required, and the fact that most circuits are short circuit proof, has caused the active barriers to gain popularity.
◗ Full Input, Output and Power Isolation (Eliminates ground loops)
◗ Short Circuit Proof (Most models) or Fuse Protected
◗ No I.S. Ground Required
◗ Less Critical Circuit Design Constraints
◗ Eliminates Other Signal Conditioning, thereby Lowering Installed Cost
◗ Discrete or Analog Input and Output Barrier Options
Entity Approvals vs. Loop Approval
The concept of "Intrinsic Safety" originated in the European markets but is gaining in popularity all over the world. Originally, and still the case with some equipment, manufacturers had their field instruments tested and approved with a specific I.S. barrier (Loop Approvals). This limited the user's choices of field instruments and
barriers. The Entity Approval concept is now becoming the standard because it allows the user to select field instruments and I.S. barriers from any approved supplier. The only stipulation is that the entity numbers of both devices are properly matched and that the equipment is properly installed per the approved installation drawings.
It is important to remember that an l.S. barrier does not make a field device safe. The field instrument must be either a "simple apparatus" or an l.S. device which was certified under the entity concept in order for it to be compatible with Ronan l.S. barriers. If you have a question or concern about your application, contact Ronan and Anderson-Bolds for assistance.