Wireless: New tools, strategies change how plants are monitored
The Clinton Utilities Board needed to control and monitor devices at two outage-prone sites at substations in the Cumberland Mountains of eastern Tennessee. Terrain and distance were barriers to the solution, but wireless technology extended the board’s monitoring reach into the substations more than an hour away. Being able to gather this information benefits the board and its 29,000 customers. Now, the board can get more flexibility from substation monitoring while moving data securely. Wireless technology enabled Clinton Utilities Board to save numerous man-hours by being able to remotely monitor and control devices that normally would take hours to reach.
Wireless has created a palpable buzz in the industry — some are even calling it revolutionary. But is it really new?
“Wireless-based technology has been used in the industry for decades — mostly licensed radio transmitters, which have been used in long-distance data communications applications: oil/gas pipelines, pumping stations, remote sites, etc.,” said Dr. Gene Yon, president of Accutech, a division of Adaptive Instruments Corp.
What makes today’s wireless technology different is the convergence of sensor miniaturization, the power and sophistication of microprocessors and electronics, industry requirements to measure and control processes beyond the practical and economical reach of wired systems and the anticipated consensus of industry professionals who are defining the standards. Although the underlying principles have been long established, wireless technology is poised to change plant operations in a revolutionary way — particularly in the area of wireless networks and wireless sensor networks.
Wireless networks are used primarily in applications where it is desirable to replace wires in LANs that connect to Ethernet systems. Wireless sensor networks ‘connect’ wireless sensors to the devices that route the measurement data to the rest of the system.
According to Jeremy Bryant, automation technology specialist at Siemens Energy & Automation, a wireless network system includes access points, client module, power supply, antennas and accessories.
“An access point is used for setting up a wireless network (infrastructure) and for attaching to the wired data network (Ethernet),” Bryant said. “In the industrial world, they are also used to create a wireless distribution system or wireless backbone connecting to hardwired systems. A client module is used for connecting a node (with Ethernet attachment) to an industrial wireless LAN. A power supply, typically 24 Vdc, provides power to the access points and client modules.”
Antennas can be directional or omni-directional. Accessories include lightning protectors, terminating impedance connectors and antenna extension cables.
Wireless sensor networks
Wireless sensors send signals to receiving devices, which take the signals to the rest of the measurement or control system. A wireless sensor network is made up of sensor nodes, which communicate among themselves. They can be configured into mesh, star or star-mesh networks.
It should be noted that wireless sensors can connect to networks, regardless of whether the networks are wireless or wired. Mesh networking pushes a network down to the sensor level. A mesh network is not a LAN, and it is not Ethernet. Mesh networks are said to be self configuring and self healing.
Utilities use wireless mesh networks to measure battery banks. Companies use wireless technology for energy management. Wireless sensors allow load shedding, light dimming, environmental control and other energy saving measures to be done remotely.
Wireless has not made its way into closed loop control per se. Although wireless sensors appear in closed loop applications with slowly changing process variables such as temperature or level, they are more widely applied in non-mission-critical control loops and monitoring scenarios.
“Someone who needs continuous flow monitoring from sensor networks probably has a wired network,” said Gary Ambrosino, CEO of Sensicast Systems. “Wireless mesh networks are not good for this use. But there are some very powerful applications for data collection.”
Wireless technology is suited for long-term monitoring, short-term data gathering and evaluating viability of process control strategies. Specific tasks include monitoring of steam traps, relief valves, rotating equipment, tank level, safety showers, on/off valves, flow and corrosion. Wireless can also be used in leak detection for gas pipelines, and refinery and petrochemical environments.
One company developed a wireless sensing system to monitor pressure on gas cylinders, cylinder banks, cradles, cylinder changeover manifolds and tube trailers. For this application, wireless sensing offers tremendous benefits in cost, installation, flexibility and scalability. The company also offers back-end software that can predict gas usage levels. This helps customers understand their gas usage, aiding in inventory management.
Benefits of wireless
The most compelling reason to adopt wireless technology is cost. Using wireless systems for applications that would otherwise require wires dramatically decreases installation time and the exponentially escalating cost of materials and labor.
Another very compelling reason to adopt wireless technology is reach. “Only 20% of what could or should be measured in a process is actually measured,” said Yon. “Wired installations provide 20% of the data ideally needed to optimally control a process. An industrial-strength wireless sensor network platform can deliver the other 80% with low cost, simple installation and nearly zero maintenance. Wireless sensor network platforms will enhance and extend — not displace — conventional instrumentation usage.”
Ambrosino contends that the amount of inaccessible data is closer to 90%. “Wired systems are too expensive to deploy,” he said. “It’s cost-prohibitive to monitor the data manually.”
Regardless of where the numbers fall exactly, there is significant growth potential for the industrial wireless market. Lower TCO, the promise of self-managing systems and faster and simpler deployment make wireless a game-changing technology.
“Fundamentally, wireless networks deliver the same basic business benefits as wired networks: they connect data point A to data point B, enabling timely information sharing for a wide range of application and reporting functions,” said Hesh Kagan, director of technology marketing at Invensys Process Systems. “But because of the low cost of wireless sensors, and the no-cost of running wires, more points can be connected far more cost effectively than wired networks, raising the possibility of enabling way more detailed measure of process variables, including measures of things that could not even be measured before. Freed from the restrictions of wires, it is possible to set up measures for virtually any point of the enterprise and receive this information in real time.”
“The benefits of tomorrow’s wireless technology stretch far beyond saving installation and wiring costs,” said Jack Bolick, president of Honeywell Process Solutions, which is one of a number of suppliers announcing expanded wireless offerings recently. “These new advancements will help plant operators gather field data more easily, increase asset life through continuous monitoring and improve the safety of their most important assets — their people.”
Security is at the top of the list of end-user concerns regarding the use of wireless technology in industrial applications, followed by reliability and battery life.
Yon suggest that there are three primary areas of security concerns: blocking, spoofing and hacking. Blocking involves interfering or preventing data transmission. Data spoofing involves someone intentionally sending incorrect data in place of correct data. Hacking obviously involves illegal entry into other secure systems — is someone reading your data?
To reduce or eliminate the risk of these three intrusions, Yon suggests the following actions:
Use Frequency Hopping Spread Spectrum (FHSS)-based protocols to provide agile communication security
Use a deterministic communication protocol
Provide secure attachment procedures, error checking and encryption
Avoid the use of an IP address to the extent possible
Reduce the node radiated power to limit the range of transmission. If a node can’t be ‘heard,’ it can’t be jammed.
“First, ensure that all wireless sensor network devices have received the appropriate agency certifications,” said Yon. “Secondly, the performance of a site survey should be mandatory and should identify the presence of any interfering signal as well as ensure that the required link margin for transmitted signal strength will be met.”
Avoiding a wireless site survey is one of the biggest mistakes that engineers make with wireless technology according to Bryant. Taking this necessary step to have your site analyzed for RF penetration, coverage and dead zones and combining that knowledge with the goals you wish to achieve from a wireless system will circumvent most of the issues that people perceive as reliability problems.
The perception of short battery life on myriad wireless sensors and the inherent maintenance headaches of battery replacement present obvious barriers to widespread adoption of wireless sensor technology. However, these power-related problems seem to be improving.
“If you want to make batteries last a long time, you can’t just randomly send,” said Ambrosino. “You have to listen to see if there is anything else there. The trick is to not turn on the radio unless you absolutely have to because sending the signal takes all the current in the circuit.”
Improvements in battery technology and the configuration of network topology have dramatically improved how long batteries last. Some companies claim that their wireless sensors can have battery life of up to five years.
Groups from ISA and HART are each working toward the adoption of industrial wireless standards. Part of the problem is that different wireless types have to operate in and share the same RF spectrum. In wired systems, separate standards groups can operate independently, just as the technologies they represent can coexist in the same wire tray without interference.
ISA’s SP100 committee, Wireless Systems for Automation, was formed in 2005 to establish standards, recommend practices and deliver technical reports and related information that will define procedures for implementing wireless systems in the automation and control environment. The SP100 committee defined six distinct application classes for in-plant wireless systems (see “SP100 wireless application classes”). It also formed two working groups to address the adoption of wireless standards.
As first reported in PLANT ENGINEERING ’s HotWire on Automation newsletter, SP100.14 will define wireless connectivity standards optimized for the unique performance and cost needs of a wide range of industrial monitoring, logging and alerting applications. SP100.11 will define wireless connectivity standards that address a wide range of applications optimized for, but not restricted to, the unique performance needs of control applications, ranging from closed-loop regulatory control through open-loop manual control.
The HART Communication Foundation is pursuing standards as well. HART devices account for the lion’s share of the existing installed base. The HART standards working group seeks to leverage wireless connection to the diagnostics and intelligence available in currently installed HART smart devices.
The Wireless HART Working Group plans for a draft standard to be ready for balloting this summer, with anticipated adoption by mid-2008. It is also coordinating activities with the ISA SP100 Wireless Committee to ensure continuity and uniformity with wireless standardization efforts.
Wireless sensor networks can be configured as mesh, point-to-point, star or star-mesh (redundant star). There are also combinations of these configurations. There is considerable debate about which architecture is best. Like most technologies, it usually depends on the application.
Each wireless sensor in a mesh network behaves as a repeater or router. It sends and receives data from other sensors or the gateway. Mesh networks are self-configuring; they automatically determine the best path between the sensors and the gateway. If the signal path is blocked or a repeater fails, the signal is automatically routed around failed or blocked repeaters.
“In a ‘true mesh’ network, data flows through the mesh and flows through many, many mesh points %%MDASSML%% even if they are not directly involved with the sensor that is originating the data,” Ambrosino said. “These networks have some shortcomings having to do with data bottlenecks, scalability and battery life.”
“There is a mesh network that I would call a ‘star,’ which has sensors talking to mesh repeaters,” Ambrosino added. “The sensors transmit data from the sensor nodes to the mesh repeaters. The mesh repeaters organize themselves into a mesh fabric that relays the data around. This is much more efficient and results in much higher scalability of the network and much better performance.
“’Redundant star’ is the more interesting one,” Ambrosino said. “There is redundancy built in if the mesh repeaters can be made redundant in a way that they can reorganize the mesh fabric and communications with the sensor nodes if one of the mesh repeaters fails.”
Table 1 – SP100 wireless application classes
Category Class Application Description Safety 0 Emergency action Always critical to plant operation Control 1 Closed loop regulatory control Often Critical 2 Closed loop supervisory control Usually non-critical 3 Open loop control Human in the loop Monitoring 4 Alerting Short-term consequence 5 Monitoring No immediate consequence
Whether you use wireless sensors, networks, mesh, star or a combination, wireless technology has many benefits for industrial manufacturing facilities. But one size does not fit all.
“Poorly thought-out approaches for new applications will result in user dissatisfaction and retard the utilization of wireless sensor networks and realization of its benefits,” said Yon. “Wireless sensor network implementations will not replace conventional wired solutions but enhance the user’s capability to manage the process using both wired and wireless implementations.”
Yon suggests that users “focus on the best practices of your industry in defining applications requirements and performance expectations rather than the underlying fundamentals of the communication technology.”
Wireless sensors should provide visibility into plant operations. They should be easy to install and maintain. Engineers should not have to worry about spending all their time engineering, configuring, programming and integrating wireless systems. They should be spending time figuring out how to use the data %%MDASSML%% not how to get the data from one place to another.
More at www.plantengineering.com…
There are a number of white papers and case studies that discuss how wireless is successfully being deployed in manufacturing. For example, Apprion has a white paper, “The Wireless Plant of the Future: From Roadmap to Reality” which discusses the steps needed to effectively implement the latest ideas in wireless technology.
There are more than 20 such studies that are now available at www.plantengineering.com , from experts such as ISA, Intermec, Siemens, ProSoft Technologies and Cirronet that supply cutting-edge information on how to introduce wireless technology in a manufacturing facility.
Go to www.plantengineering.com and click on the Wireless logo at the top of the page to access these white papers.
Wireless network boosts Dasani plant efficiency
The Coca-Cola Co. purchased a plant in southern Missouri to bottle its Dasani brand drinking water. The plant pumps water from the nearby Roubidoux Formation, which is the source of some of the purest water in North America.
The recently redesigned control system uses a wireless Ethernet network to communicate with the operator terminal, I/O controller and various devices that control equipment in the plant. The Ethernet-enabled touch screen is the primary interface for plant workers to monitor the control system. The terminal is linked to an I/O controller, which is the central control device for the entire system. This system controls the three wells that pump the water into the plant.
A VFD controls the motor of each pump. The VFDs are programmed and coordinated to work together to ensure that the three wells are constantly pumping the exact amount of water that Coca-Cola needs to meet the current demand for Dasani water. Any of the pumps can be designated as the lead, which will maintain pressure at a preset level. If the lead pump reaches maximum speed of the VFD, the system brings more pumps online to maintain volume demand while maintaining system pressure.
The reactions to water flow happen in a fraction of a second. The Ethernet-based system operating over a wireless network ensures that all of the communication takes place very quickly and efficiently. When the I/O controller sends out a request for information, it is estimated that the response arrives within 3 milliseconds, as opposed to 5 to 10 seconds with traditional radio telemetry equipment.
The system allowed Dasani to eliminate a 30,000-gallon tank that was used to store water before it was bottled. Removing the storage tank has freed up 3,000 square feet of floor space in the plant and also eliminated the need for a 100-hp pump that moved water from the tank to the bottling process. Eliminating the storage tank also removes the possibility of bacteria forming in the water sitting idly in the tank.
Wireless technology Webcast in October
For more information on how wireless technology can benefit your plant, go to
PLANT ENGINEERING magazine will present a free Webcast titled “Advancements in Wireless Ethernet” on Thursday, Oct. 12 at 1 p.m. CDT. Learn about the advantages and challenges of applying wireless networking to your plant. Visit