The Need for Wireless Monitoring

There is a real on-going need for monitoring of valve positions (actuated or manual) in the process line. Malfunctioning of a valve can result in danger to human health and safety, affect yields, and generate environmental risks. In some industries, regulation requires constant recording of valve position. Currently, such monitoring is done through wired “Switch Boxes”. Each such device requires data transmission and power cabling. Not only are these cables costly to manufacture and install, they are also one of the most frequent sources of failures in the process line, due to the fact that they are very often exposed to harsh environmental conditions. In fact, it is right here, at the field device level, where the majority of problems with wires really exist.

The various field buses that have been integrated into most applications over the past years ago have not really changed the situation. The Switch Boxes are still typically connected via wires, in a star topology, to bus concentrators.

Wireless monitoring of valves can revolutionize industrial processing and help industries meet the demands of increasing competitiveness. Intelligent wireless valve monitoring in industrial environments enables real-time data sharing throughout a facility and this, by definition, increases industrial safety, efficiency, and productivity. Wireless valve monitoring technology offers reliable, autonomous, and improved process control enhancing safety, ameliorating product quality, increasing yield, and reducing costs.

Lower Costs. The costs associated with installing, maintaining, troubleshooting, and upgrading wiring have escalated while costs of wireless technology maintenance continue to drop – particularly in the areas of installation and maintenance. A market study by the Venture Development Corporation found that users of wireless technology cite lower cost as a major reason for adoption.

Installation. Wireless valves monitoring systems could ultimately eliminate tens of thousands of feet of wiring in the average industrial site. Deploying such wiring can cost $50 to $200 per foot . Specialized wiring for harsh environments can cost as much as $2,000 per foot.

Maintenance. As wires age, they can crack and fail. Inspecting, testing, troubleshooting, repairing, and replacing wires requires time, labor, and materials. If wiring faults cause a production stoppage, costs escalate rapidly. Wireless valve monitoring systems obviate any costs associated with running new wires and eliminate associated downtime.

Improved Flexibility. Without the constraint of wires, plant managers can better track materials and more easily reconfigure assembly lines to meet changing customer demands. Freedom from wires also allows greater flexibility in valves placement – particularly in the case of mobile equipment (e.g., cranes and ladles).

Rapid Commissioning. Simple wireless valve monitoring systems can be rapidly and easily organized and configured into an effective communications network. Self-calibration and verification open the door to the deployment of ad hoc wireless valve monitoring systems and offer a broad range of production scenarios.

Existing Wireless Standards

The ISA organization has established the standards committee on wireless systems for automation (ISA-100) and recently released the first draft (ISA-S100.11a) of the Wireless Network Optimized for Industrial Monitoring. The Wireless Hart protocol was recently released, and related products have started to appear on the market. The ZigBee protocol, which is very close to the ISA100 and Wireless Hart standards, has been available for some time and is supported by many chip and solution vendors and has the added advantage of being very cost-effective. The ZigBee technology is broadly utilized in building automation and energy control devices which are also used in the process industry.

All three protocols are based on IEEE 802.15.4 standard and have a lot of common.

The Exploding Need for Wireless Monitoring of Valves

The worldwide value of the industrial valve market reached $60 billion in 2006. This corresponds to the annual sale of about 350 million industrial ball valves of various sizes. Most of the valves sold (80%) are manual, without any remote monitoring capabilities. About 40% of the actuated industrial valves sold have no monitoring capabilities. All the valve monitoring systems sold today are wired.

Industrial users (pharmaceutical, petroleum, water, etc.) have expressed the need for more monitoring capabilities on the manual and actuated industrial valves they operate in their process lines. This will increase line safety, ensure compliance to regulations, improve yield, decrease operating line costs, provide better compliance to environmental requirements, etc. The option of installing a wired monitoring device on the manual or actuated valve is not practical due to the cost of wiring installation ($50 to $200 per foot) which can exceed $5,000 per value, and a process plant can have thousands of industrial valves. A wireless valve monitoring solution can cost a fraction of this (10%). The cost of a wired valve monitoring system with 5,000 valves can reach the prohibitive amount of $25,000,000 while setting up a wireless system will run at about $2,500,000.

Wireless technology comes with its own set of challenges – propagation, interference, security, regulations, and other issues. Some control applications can afford the cost of adding a high-end wireless communication system such as cellular phones, WiFi, WiMax, and so on. Nevertheless, the required wireless application will benefit if the technology is relatively low cost, is reliable, and robust, and it is standards compliance in order to drive interoperability among manufacturers and provide direct benefit to the end users.

The ZigBee Technology

The ZigBee technology is widely available and can be found in very cost-attractive industrial monitoring and control solutions. Many end users are considering using the ZigBee technology in their process line for simple monitoring applications and for energy management and automated infrastructures. The ZigBee wireless network is robust and reliable, low-cost, with a very low power consumption. It allows utilizing a valve monitoring solution powered by two small ½ AA Lithium batteries which last for more than 5 years assuming a 30-minute update rate, and with less than 100 ms latency.

The relatively low data rate (0.25 Mbps) achieved with a ZigBee network is adequate for valve monitoring requirements. The ultra low power consumption and the low cost features of ZigBee make this technology the best choice for valve monitoring applications. To achieve the goal of low total product cost as well as long battery life, the ZigBee / 802.15.4 protocol provides reasonable trade-offs in several performance metrics. To control the administrative costs of both the implementer and the user, ZigBee devices employ unlicensed radio bands. The ZigBee device is designed to be relatively short range without infrastructure. When increased range is necessary, the ZigBee infrastructure utilizes Mesh network topology.