Monitoring Manual and Semi-Automatic Valves Wirelessly

I’ve seen a number of stories about applications for wireless transmitters, but not for wireless valve monitoring. That all changed earlier this week when I received a Twitter direct message “tweet” from a colleague. For those not yet on Twitter, it’s an option to send direct communications, unseen by others, when you have a reciprocal follow relationship with one another. It’s like instant messaging but comes with the stream of others’ short notes in your follow list. I have it set up where these direct messages come as text messages to my phone as well. I mention all this because it’s another way communications are rapidly evolving from the world of email in which we’ve lived over the past many years.

The Valve magazine article, The Reliability and Security of Wireless Valve Monitors, is written by Emerson’s Kurtis Jensen, an instruments product manager for Fisher and Valve Automation products.

One of Kurtis’ closing paragraphs provides the primary reasons process manufacturers may consider wireless monitoring on some of their valves:

Most operations have a large number of “blind valves” that are either manual or semi-automatic but provide no valve position feedback, normally because of cost or location. As such valves age, their performance can degrade to sluggish, slow operation. The true position of the valve may be questionable, and operators have to start visiting certain trouble-prone valves to verify their position. Where valve position monitoring does not currently exist, wireless monitoring is a great way to start using this technology with minimum risk.”

If you’ve ever come across the ModelingandControl.com blog, you’ll know that sluggish valve performance is a contributor of deadtime that impacts overall control performance and plant efficiency.

As with any newly introduced technology, its ease of use is critical in its adoption. Kurtis notes that an upcoming release of a wireless position monitor product is non-contact and does linkage-less position sensing. After attaching and calibrating the device, it sends valve position information wirelessly across the self-organizing network to the automation system or asset management software.

He discusses some of the reliability and security aspects that I’ve described in earlier posts. The reliability aspects are largely to do with the self-organizing nature of the WirelessHART field networks. Alternative communications paths are taken from the devices to the wireless gateway when permanent or temporary obstacles happen.

Security is addressed in the WirelessHART standard and described by Kurtis through its changing encryption, message authentication, data verification and frequency hopping.

An important point made is that, “…wireless should not be viewed as a direct replacement for wired instrumentation.” It’s well suited for:

…hard-to-reach locations, in areas hazardous to plant personnel, where power does not exist and where running wires is not allowed or prohibitively expensive, to name a few.

This certainly opens up opportunities in many facilities to reduce the number of blind spots the operations staff face that must be covered by periodic manual inspection. The opportunities for wireless monitoring may be with the valves were early notification of performance degradation can help avoid overall poor control performance.

Posted Wednesday, July 30th, 2008 under Final Control Element, Technologies, Wireless.

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