Safety Instrumented Systems / Emerson Exchange

Emerson ‘Charms’ Hazardous Areas

IS CHARMs Provides Significant Savings in the System Design, Installation Cost and Ease of Maintenance

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By Keith Larson, Group Publisher/Vice President of Content

Building on its innovative electronic marshalling and single-channel characterization module (CHARM) technology, this week at the Emerson Global Users Exchange, Emerson Process Management is showing its latest offering, intrinsically safe (IS) CHARMs. Electronic marshalling with CHARMs is a key component of Emerson's "I/O on Demand" strategy, which provides solutions for all types of I/O interconnection—point-to-point, bussed and wireless.

DeltaV electronic marshalling is designed to deliver a new level of control system I/O performance with unprecedented flexibility and ease of use. The addition of IS CHARMs provides significant savings in the system design, installation cost and ease of maintenance expected with electronic marshalling, with the added intrinsically safe circuitry for field wiring into hazardous areas, including Zone 1, Zone 0 or Class 1, Div1. 

I/O in hazardous areas traditionally requires explosion-proof mounting or isolation barriers. These approaches are costly, require space for additional barrier and termination cabinets, and need ongoing maintenance to ensure that safety requirements continue to be met. IS CHARMs deliver a reduced footprint and eliminate the need for separate barriers and the associated inter-cabinet wiring. A smaller footprint together with fewer connections improves the reliability of the installation and delivers significant cost savings.

The DeltaV CHARM I/O Card (CIOC) supports both conventional and IS CHARMs, providing unprecedented flexibility in control system I/O topology. I/O can be added anywhere it is needed using standard Ethernet infrastructure hardware. Each I/O channel has a dedicated CHARM that provides both signal characterization and galvanic isolation for intrinsically safe applications. IS barriers are integrated inside the CHARM to provide single-channel fault isolation, as well as electrical isolation and energy-limiting circuitry that meets IEC Ex ia ratings. IS CHARM's signal types include IS AI 4-20 mA HART, IS AO 4-20 mA HART, IS DI Namur and IS DO 24 VDC.

"Electronic marshalling allows process manufacturers to shorten project schedules, accommodate late project changes, eliminate equipment and cabinets, and dramatically simplify the I/O and marshalling design process," says Peter Zornio, Emerson Process Management's chief strategic officer. "With the addition of IS CHARMs, we bring that flexibility and savings to some of the most challenging process environments where, arguably, flexibility and reliability are needed most."

Electronic marshalling can eliminate two-thirds of the wiring and connections needed in conventional marshalling cabinets. Single-channel integrity improves plant uptime and makes projects simpler and easier to engineer and implement. The CHARMs technology greatly increases flexibility in assigning I/O types, whether for late project changes or during start-up, operation or temporary installations. Similarly, it adds flexibility in deciding the best location for I/O—whether in a rack room, remote locations, hazardous areas or harsh environments.