By Dan Hebert, PE, Senior Technical Editor
Wireless communications in industrial facilities have moved decisively to become a practical solution. Practicality for industry means saving money without taking undue chances, and wireless has advanced to the point where it delivers concrete benefits with manageable risk.
The most obvious cost savings for wireless are delivered in installation, especially for projects in existing plants. It takes lots of money and time to dig trenches, lay conduit and pull wires. Even for above ground installations, the costs of conduit and wiring are often substantial.
Savings over and above lower installation costs are realized during operations because of reduced maintenance costs and greater flexibility. Wireless is cheaper to maintain because there no wires or cables that can be damaged. Wire and cable damage can occur through accidents such as lightning strikes, contact with moving in-plant equipment and inadvertent cutting during unrelated construction activities.
Normal wear and tear of wire and cables is most prevalent with connected components that move such as those mounted on cranes, material handling equipment and robot arms. Wiring and cabling to both moving and stationary components also can suffer wear and tear through corrosion, insulation breakdown and degradation due to temperature changes.
Another key advantage of wireless is flexibility. Once a wireless network is installed, the cost of adding another device is very low. Need an extra I/O point 2,000 ft from the control room? No problem with wireless, but very expensive with a wired system.
Wireless saves costs during installation and throughout the operational life of the control and monitoring system, but these savings are accompanied by the risk of implementing what for many is a new technology. Many users get around these risks by limiting the scope of the wireless system in terms of bandwidth, criticality and other parameters.
Cheaper to Install
In most instances, it is cheaper to install a wireless system than its wired counterpart. "We were hired by a major steel producer in the Midwest U.S. to replace the DCS controls on four large boilers that supplied steam to its steel making process," says Timothy Stout, PE, manager process systems for system integrator Matrix Technologies (www.matrixti.com) in Maumee, Ohio. "Wireless saved money because it replaced very long conduit and cable runs of up to 2 miles. This saved miles of conduit and wire which equates to several hundred thousand dollars in installation costs."