Intrinsic Safety Use Shows Some Spark

Often Dismissed as “European” Technology, Use of Intrinsic Safety Devices Appears Ready for Substantial Growth in North America

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By Jim Taylor, Venture Development Corp., and Joe Feeley, Editor in Chief

Intrinsic safety is a method used to prevent equipment from causing fires and explosions in areas with hazardous atmospheres, such as explosive gas-air mixtures. Intrinsically safe equipment and wiring is incapable of releasing sufficient electrical or thermal energy to cause ignition of a hazardous atmosphere in its most ignitable concentration. Equipment going into hazardous areas for intrinsically safe applications is classified as either simple or non-simple.

Simple devices have limitations on voltage, current, and energy. These include products such as switches, thermocouples, RTDs, non-inductive potentiometers, and resistors.

Top criteria for selecting hazardous environment protection methods

Figure 1
Non-simple devices include field transmitters, solenoid valves, and many other types of equipment that can create and store energy levels high enough to create an explosion if not limited. For these applications, the devices have safety limits on the amount of inductance, capacitance, and temperature operating levels. For wireline devices and equipment, field wiring runs through intrinsic safety barriers (located outside the hazardous region). The barriers limit the voltage and current levels to the devices below those that could cause an explosion.

Simple devices connected to an approved intrinsic safety barrier do not have to be approved as being intrinsically safe. Certification for the design and installation of non-simple devices and equipment is required.

As we’ve done previously, Industrial Networking worked with Venture Development Corp. (www.vdc-corp.com) to invite readers to participate in a study on worldwide trends in the use of intrinsically safe devices. Users from our system integrator, industrial machine builder, and processing industry end user communities participated in the study. The following are some of the significant research findings.

Wireline Devices and Equipment

By using wireline networks/buses, field devices located in hazardous areas can be connected to controllers outside those areas. Alternatively, wireline networks/buses can connect to distributed/remote I/O located in the hazardous regions that are designed to be intrinsically safe. The field devices then interface with the distributed/remote I/O. Wireline networks/buses used in these applications must limit energy levels to ensure intrinsic safety, and incorporate isolators for this purpose. In addition to the energy-limiting requirements for intrinsically safe networks and buses, critical specifications for such systems include redundancy and a high level of determinism.

The use of wireline intrinsically safe networks/buses allows distributed intelligence in hazardous areas, which provides advantages such as elimination of long, hardwired, point-to-point signal connections; the capability for value-added features such as self-calibration, failure-prediction algorithms and self-generating work orders; and simplification of control system designs.

The use of wireline intrinsic safety is well established as a preferred hazardous protection method in the European/Middle East/Africa (EMEA) region, and the majority (55%) of 2006 worldwide shipments of these products were to this region. For the most part, the remainder was evenly split between shipments to markets in the Americas and Asia-Pacific regions.

Among the three regions, the highest growth rates for all these wireline products are foreseen for the Asia-Pacific region. A large portion of these shipments is projected to go to China and other developing countries in the region where new facility construction is expected to be high. Most of the EMEA market is in Western Europe, where wireline intrinsic safety is well established, and shipment growth expectations are more moderate. However, the growth rate for Eastern European countries is expected to be high as new facility construction there is foreseen to be relatively robust.

Of the three regions, the growth rates of all the products to the Americas are expected to be the lowest. While intrinsic safety is perceived as a better technology with lower operating cost/total cost of ownership, there is little movement in the U.S. toward this technology using wireline equipment and devices. Explosion-proofing still is the preferred and proven method in the U.S. However, light, portable, intrinsically safe wireless devices can address new uses. The explosion-proof protection methodology simply does not apply in this case, leaving more room for greater adoption of intrinsically safe wireless products in the Americas.

The geographic shipment distribution of these wireless, intrinsically safe products is considerably different than the findings for wireline products used in intrinsically safe applications. Of the wireless intrinsically safe devices and equipment studied, 67% of 2006 shipments were to markets in the Americas, 22% to markets in the EMEA region, and 11% to markets in the Asia-Pacific region. 

The market for wireless, intrinsically safe products has developed more rapidly in the Americas, following the general trend in adoption of wireless technology in industrial applications. For example, VDC just completed a worldwide study on wireless industrial networking infrastructure products (access points, antennas, bridges, console and device servers, gateways, modems, multiplexers, repeaters, switches, transceivers, and network management software). It found that, of the 2006 worldwide market for these products, about 60% of shipments were to markets in the Americas.

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