Chemical Engineering

Wireless Sensors for Environmental Compliance

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Courtesy of Chemical Engineering

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When no wires are required for power or signal transmission, monitoring devices not only become less costly to own and operate, but they can also be installed more quickly and relocated easily. This is especially helpful for tracking fugitive emissions

Over the past few years, many operating companies throughout the chemical process industries (CPI) have begun to implement wireless devices –– those based on radio-frequency signals –– to convey data from sensors and instruments used throughout the process plant to the central process control system.

Compared to instrumentation schemes that rely on conventional hard-wired connections, wireless communications schemes boast greater ease of use and substantially lower installation costs.1 One area of plant operation that is particularly well-suited for wireless applications is environmental compliance.

In a typical chemical or petrochemical plant or petroleum refinery, there are hundreds if not thousands of sensors and controllers in place to track potential sources of regulated, dangerous and often toxic emissions. For instance, plant operators must install, operate and maintain sensors and monitoring systems to analyze the composition of anticipated fluegas streams (such as those coming from flares and other process operations) and vapor streams from cooling towers, and to monitor fugitive emissions (such as intermittent leaks that might escape from valves, seals and couplings).

While sensors, monitoring systems, analyzers and other types of diagnostic devices are an essential part of operating any modern, highly regulated process plant, these systems are also costly to install, operate and maintain. So any opportunity to reduce the costs associated with them can help the company to improve profitability. In this article, we offer some recommendations on how to use wireless monitoring devices and systems to improve overall environmental performance and regulatory compliance. We also share some examples that show how wireless schemes can be offer a practical, affordable alternative to traditional hard-wired connections and have a fast return on investment (ROI) for a broad range of monitoring and control applications.

Sentry duty

There are literally thousands of potential sources of organics-laden emissions in a large-scale chemical process plant, and the task of monitoring each of them continuously can become quite costly when conventional, hard-wired sensing sensors are the only option. The installation cost alone for monitoring devices often exceeds the actual equipment cost by several multiples — in fact, it’s not uncommon to find that the cost of the actual measurement device represents just 10% of the overall project cost. This is particularly true in existing facilities, where the cost to design and install additional conduit, pull wires, and test and start up all devices must be done around existing equipment, structures and access points. Such work must also be managed to meet site-specific and regulated safety procedures, and often calls for permits and extensive oversight and administration.

By comparison, wireless sensors do away with the need for all of the infrastructure and administration associated with running signal wires, and in some cases, the use of battery-powered devices also eliminates the need for a hard-wired electricity source. When no wires are required for power or signal transmission, such tether-free monitoring devices not only become less costly to own and operate, but they can also be installed more quickly.

The portability of wireless monitoring instruments makes them particularly useful and economical for identifying the source of the leak, because a given analytical device can be easily redeployed for the periodic inspection of many potential sources. Wireless sensors are particularly ideal for providing either temporary (diagnostic) or permanent monitoring of sources that are remote, inaccessible or not designed for instrumentation, and those that produce intermittent emissions that could be missed by reliance on periodic inspections.

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