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.

12/09/2009


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, PWelander@cfemedia.com
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...
The true cost of lubrication: Three keys to consider when evaluating oils; Plant Engineering Lubrication Guide; 11 ways to protect bearing assets; Is lubrication part of your KPIs?
Contract maintenance: 5 ways to keep things humming while keeping an eye on costs; Pneumatic systems; Energy monitoring; The sixth 'S' is safety
Transport your data: Supply chain information critical to operational excellence; High-voltage faults; Portable cooling; Safety automation isn't automatic
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Synchronizing industrial Ethernet networks; Selecting protocol conversion gateways; Integrating HMIs with PLCs and PACs
Why manufacturers need to see energy in a different light: Current approaches to energy management yield quick savings, but leave plant managers searching for ways of improving on those early gains.

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

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.