Reader writes: Real semi-wireless installation

Instrumentation devices that communicate wirelessly may still need power supplied the old-fashioned way. Here's one reader's experience installing a radar level sensor.


Scott A. Somers, process control engineer for Katahdin Paper Co. in East Millinocket, ME sent an email recounting one of his experiences trying to solve a nagging problem. He writes, "Thank you for your article‘ Using Semi-Wireless Instrumentation .' I had recently completed the design of a semi-wireless installation and my research had revealed exactly what you discussed in your column. I was hoping to find a total wireless solution for a radar level transmitter mounted on a remote fuel oil storage tank. The engineering request included displaying the tank level on a DCS operator display in our steam plant control room. The control room is located roughly 600 feet from the storage tank across a roadway with no existing tray systems to connect the two locations.

"Because of the power requirements of radar level transmitters, a complete wireless solution was not economically feasible, considering the cost of a solar panel and rechargeable battery setup. Fortunately, an existing 120 Vac circuit ran underground past the tank to power receptacles at the unloading platform. This circuit was accessed via a manhole located in close proximity to the tank. As for the wireless part of the installation a third party single-point wireless system was purchased which allowed for up to 1,000 foot reception through obstructions. The wireless signal was converted to 4-20 mA within the steam plant, with a short cable run to the DCS termination rack. The cost savings came in not having to run cable and cable tray, complete with supporting structures to bridge the roadway, the full 600' between the tank and the control room."

The third-party transmitter in this case is an integrated radio and I/O module for one 4-20 mA current loop device from Phoenix Contact . This type of approach is appropriate if you plan to use wireless one device at a time, rather than a larger network with more nodes.

Given that the article cautioned about using plain lighting and power circuits for instrumentation, I had to ask Scott if he had thought about someone tripping or turning off that branch. He replied, "I'm not really concerned about the reliability of the power source, which originates from an unmanned pump house located about 200 feet from the tank. This is an indication-only loop, not a closed loop. This project was prompted by a safety concern for the steam plant operators who had to trudge out to the tank once a shift, often through knee-deep or higher snow, climb the stairs to the top and‘stick' it. We would have hours between measurement checks to reset the circuit if it should trip."


-Peter Welander, process industries editor,
Control Engineering Process Instrumentation & Sensors Monthly eNewsletter
Register here to select your choice of free eNewsletters .

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
A cool solution: Collaboration, chemistry leads to foundry coat product development; See the 2015 Product of the Year Finalists
Raising the standard: What's new with NFPA 70E; A global view of manufacturing; Maintenance data; Fit bearings properly
Sister act: Building on their father's legacy, a new generation moves Bales Metal Surface Solutions forward; Meet the 2015 Engineering Leaders Under 40
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Pipeline vulnerabilities? Securing hydrocarbon transit; Predictive analytics hit the mainstream; Dirty pipelines decrease flow, production—pig your line; Ensuring pipeline physical and cyber security
Upgrading secondary control systems; Keeping enclosures conditioned; Diagnostics increase equipment uptime; Mechatronics simplifies machine design
Designing positive-energy buildings; Ensuring power quality; Complying with NFPA 110; Minimizing arc flash hazards
Building high availability into industrial computers; Of key metrics and myth busting; The truth about five common VFD myths

Annual Salary Survey

After almost a decade of uncertainty, the confidence of plant floor managers is soaring. Even with a number of challenges and while implementing new technologies, there is a renewed sense of optimism among plant managers about their business and their future.

The respondents to the 2014 Plant Engineering Salary Survey come from throughout the U.S. and serve a variety of industries, but they are uniform in their optimism about manufacturing. This year’s survey found 79% consider manufacturing a secure career. That’s up from 75% in 2013 and significantly higher than the 63% figure when Plant Engineering first started asking that question a decade ago.

Read more: 2014 Salary Survey: Confidence rises amid the challenges

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.