New wireless technologies for power plant instrumentation offer significant cost savings when compared to traditional wired networks. The value of this cost savings is especially relevant in the highly competitive power industry, where aging facilities are common and upgrades are an expensive necessity. Modern wireless networks offer a reliable upgrade path that even provides some unexpected benefits when compared to traditional copper networks.
Self-Organizing Field Networks
Industrial wireless networks have matured since the early days of point-to-point systems. The WirelessHART (highway addressable remote transducer) protocol has emerged as the de facto standard for wireless communication in a plant environment. This digital protocol allows operators to benefit from all the control and diagnostic features currently available to wired HART transmitters. Because it is an open standard, early adopters need not worry about being locked in to a single supplier by a proprietary communications protocol. This means that wireless devices from a variety of manufacturers can happily coexist on the same network, provided each manufacturer has conformed to the WirelessHART standard.
In WirelessHART self-organizing networks, each device needs only to maintain radio line-of-sight to one other device on the network and does not need to have direct line-of-sight to the gateway (Figure 3). Because each device is typically in communication with several of its peers, it will have redundant transmission paths available to it. If an obstruction blocks one transmission path, the blocked device will automatically revert to a redundant link to pass traffic to the next-nearest neighbor. That neighbor then forwards this traffic on to the gateway.
3. Disciplined organization. WirelessHART field networks utilize a self-organizing topology in which each device serves as a router for the traffic of other devices within radio range. This enables a self-organizing network to be far more reliable and fault-tolerant than older point-to-point systems. Source: Emerson Process Management
Reduce Installation Cost
Perhaps the most attractive attribute of a wireless network is that installation cost is significantly reduced when compared with that of an equivalent wired system. A significant portion of the cost of a measurement loop is for the cable, conduit, and multiplexing hardware required to connect the sensor to the plant’s distributed control system (DCS). A wireless network requires none of these infrastructure improvements, and the resulting savings are significant.
For example, engineers at a Midwestern power plant sought additional temperature data for a feedwater heating system. Discouraged by the cost of installing traditional 4-20 mA wired sensors, engineers looked to a wireless alternative. A wireless self-organizing topology network offered reliability similar to that of a wired system, but at an estimated savings of 60%.
Consider also the case of pH control in a closed cooling system. Scaling of piping and tower fill material by calcium carbonate is a significant problem. It is desirable to convert relatively insoluble calcium carbonate to soluble bicarbonate by lowering the cooling water pH, typically by treating it with sulfuric acid. However, depressing pH too far may lead to corrosion of steel surfaces. It is often beneficial to measure pH at several points in the tower basin to ensure accuracy, and wireless transmitters allow these auxiliary measurements to be installed at a fraction of the cost of a wired setup.
Email
Comments
Print
Reuse
