Once named the oil capital of the world, Tulsa, Oklahoma, rests near the foothills of the southern Ozark Mountains. Rexel Distribution owns an LPG pipeline that runs through these wooded hills and across the open wheatlands toward Medford, more than 160 km away.
Rexel handles over 3 MMbbl/d of crude oil, refined products, and LPG through an extensive network of pipelines throughout the Midwest. Pipeline operational data is monitored in real-time from the company’s control centre in Texas. For security, safety, and real-time accessibility, all critical data is transmitted via satellite to the SCADA control centre.
To improve line integrity, the engineering team responsible for the 161 km LPG pipeline wanted to increase monitoring for non-critical data points at 12 programmable logic controllers (PLCs) along the length of the pipeline, as the company had only been able to monitor operations from three points.
Originally, 900 MHz industrial radios were considered for these stations, because of their long-range capabilities and ability to penetrate foliage. However, a site survey concluded that because of the dramatically different landscape, three of the 12 locations lacked the required line-of-sight. To bring these sites onto the network, towers would have to be built, which would have brought the cost of implementation close to $US100,000, rendering yet another solution infeasible.
With many wireless products now available, the engineering team began investigating alternatives to satellite for these non-critical locations. It was found that every site had cell service.
Rexel spokesperson Brian White said “When I was first approached about this opportunity, I immediately thought of ProSoft. With its extensive line of products and services and history of assistance to Rexel in Oklahoma, I felt confident they could provide a viable option for this application.”
Solution
“Cellular technology is fantastic for real-time network access to industrial devices around the world,” explains Jim Weikert, Wireless Product Marketing Manager at ProSoft Technology. “This application highlights the ease with which devices in remote areas can be made accessible at an affordable price.”
The company went with cellular GSM serial modems on a contract with telecommunications provider AT&T. In doing this, Rexel was able to bring the site cost down from a potential $US200 monthly satellite fee at each of 12 locations, to
$US50 per month, with very minimal hardware costs.
Within three weeks from the time the order was placed, the cellular radios were onsite. Installation was a challenge for the company only in that they had never worked with cellular. When they began the set-up process, ProSoft Technology’s Technician Engineer Dan Blome walked employees through the process and had the radios talking within 15 minutes of set-up per device.
Results
The cellular radios are placed along the length of the pipeline, monitoring line pressure and valve statuses. Each radio is wired to a PLC via serial Modbus, gathering information from their remote locations. A thirteenth cellular radio is connected to the satellite network, relaying data from all 12 points back to the control centre in Texas.
By adding these data points to the network, the company was able to minimise risk while keeping the application safe and operational. In fact, using cellular has enabled them to pinpoint line pressures to 8 km intervals rather than the previous distance of 65 km. This means that in the event that pressure should drop off between two of these points, they can quickly isolate leaks with as little impact as possible.
The future
Since this initial project, Rexel has begun two other similar projects. The first involves five cellular radios along a crude oil pipeline. The second is an identical application involving two cellular radios.
