Get Required Information on a Budget

One day, the order came down. “We’ve got to install high-level alarm switches on the tanks in our remote tank farm.” In terms of megabytes of information, this was really a small data requirement. But the physical task of installation was daunting—not to mention the cost involved. Because the company standard for instrumentation wiring is to run it in conduit, running a wire from each switch back to the base station would be very expensive.

Eric Brown is the instrument and controls supervisor at the American Refining Group Inc. plant in Bradford, Pa., and was charged with finding a way to implement the system. This plant stretches over two miles along a small river, so finding better networking was essential. Now, a good story has conflict, intrigue, seemingly insurmountable challenges. This story, though, follows an engineer and some instrumentation technicians installing a cutting-edge technology in part of a day following a short training class.

Try it out

布朗说他第一次安装了一个点对点的radio system from Honeywell Process Solutions, a Phoenix-based process automation supplier, a couple of years ago. The system installed well and offered no problems. The wireless solution was just the answer he needed to do the job without breaking the bank. But when he had to expand the system, he looked at the newer array of technologies and devices and decided to try a wireless mesh sensor network from Emerson Process Management, the Austin, Texas, process automation supplier.

In a mesh network, the transmitter attached to each sensor looks for its neighbors and self-organizes a network with multiple paths. This means that if something should happen to break one path, the transmitter automatically searches out an alternative path. While this may sound a little complicated to explain, Brown says, it was easy to install. “In fact, we did it ourselves after just a little training from our Emerson representative.” After they had set up the interface of the radio network to the the plant’s Emerson DeltaV distributed control system (DCS), “it was easy. We went from the gateway to a serial card in the DeltaV, and configured the software. We saved a lot of money and time.”
Installation may not be in the league with “so easy a cave man can do it.” But it does not require an electronics engineer with a specialization in radio frequency technology to get a wireless mesh network up-and-running.

Bill Uhl is the instrumentation technician at the refinery who installed the system. He reports that it was pretty simple. He had a base radio, a little communication module to the DeltaV DCS with an RS485 link and wireless transmitter on each tank. He says he just gave each transmitter a name and told the base to look for the name. The base radio can tell if the switch is open or closed. “You have to have their software and a laptop, then once it’s hooked up, you give tag and ID,” says Uhl. “Each head has two switches, so you can pick up two sensors off one transmitter. To set up each transmitter, you turn on and look at the display. It tells you if you have signal to another transmitter. So you just walk around where you want it and install where you have the signal.”

Still growing

American Refining has 24 wireless Emerson sensors right now, and its technicians are still adding and building network. “We’re about to do another 30,” says Brown.

And how has the system worked? “Not a blip,” says Uhl. “We have had hellacious snow storms and other extremes with no problems. Rarely do you put something in without a lot of extra work.”