In order to enable work on instruments without a hot work permit, the spur and instrument connection must be installed intrinsically safe (Ex i) or with non-incendive field wiring. However, to fulfill demands for high device count and long cable runs, more power is required than is technically feasible with intrinsic safety.
The high-power trunk concept fulfills these demands. The trunk carries power to 31 V and 500 mA requiring a means of mechanical ignition protection similar to those of electrical lighting or motors. The device coupler is the intrinsic safety barrier installed in the fieldbus junction box near the instrument. Up to four device couplers per segment provide power and protection to the maximum number of 31 instruments as per the fieldbus standard.
- Installation and maintenance crews benefit from working on field instrumentation without requiring a hot work permit during normal operation.
- Engineers can utilize the maximum cable length permitted for fieldbus and a high device count per segment in any hazardous area.