Terrain, number of required checkpoints and available communications technology play a role in choosing remote equipment monitoring for your next big job
Gas, oil and mining companies have long been turning tosophisticated monitoring devices designed to keep tabs on a host of information ranging from pipeline flow volumes and line integrity, to the smooth operation of automated mineral processing lines. How that collected information is transmitted to home base is a critical decision that impacts not only the cost, but also the reliability of the data being reported.
Typically, information is transmitted using private radio frequency (RF), or satellite relays, but worldwide industrial automation specialist ProSoft Technology of Bakersfield, Calif., is finding that industrial cellular technology is also filling a market niche between the two, wherever there’s cellular network coverage. The company was founded more than 20 years ago, at the time primarily serving the oil and gas industry.
“We now provide protocol and interface solutions to a range of industries, including oil, gas and mining,” says Jim Ralston, product strategy/wireless product manager with ProSoft at the company’s wireless division headquarters in Madison, Wis. “A lot of larger companies such as Rockwell Automation or Schneider Electric want to focus on their core networks, whether Ethernet Industrial Protocol (Ethernet IP), Modbus, or other protocols, but they don’t want to get locked out of a project because their system won’t talk natively to their clients’ supervisory control and data acquisition (SCADA) system.
“Our specialty is creating communications modules and their associated software, ensuring that monitoring technology of any type can communicate effectively with hundreds of networks and all of the major protocols.”
Ensuring pipeline integrity
To help customers design a pipeline monitoring project, Ralston must first take down details on the length of the pipeline and on how many monitoring stations the client wants to place along its length to ensure line integrity. The distance from the monitors to the company’s SCADA system – whether 200 miles or 500 – is also critical.
Next, engineers will determine how much reporting data is required, whether simple data, photographs or streaming video. How quickly the data is required and how often the monitors are polled is also a critical consideration, determining the maximum data throughput of the system.
Finally, the terrain of the area will be analyzed to determine what sort of communication system will be most reliable, given such potential impediments as hills, valleys, buildings and structures or foliage.
“Obviously, the more monitoring stations on the line the higher the quality of intelligence they’ll be receiving,” says Ralston. “If you place a monitor every five miles, instead of every 25 miles, you’ll be able to pinpoint a leak significantly faster because you’ll be investigating shorter lengths of pipe. However, the more monitoring devices you put into play, the more costly the system will be to either build or to operate, if third-party data transmission is required.”
ProSoft has no financial interest in promoting one wireless technology over another. The emphasis is on choosing the most cost-effective technology to provide the best connectivity.
Choosing a monitoring system
For a private RF monitoring system, the cost is limited almost entirely to purchasing and setting up the monitoring equipment, RF transmitter and receivers. Depending on the terrain, surrounding buildings and foliage, the system may also require the installation of transmission towers using bucket trucks, which would add to the capital cost. However, the cost of operating the RF equipment is negligible, largely because the client owns the system and there are no recurring charges or third-party transmission costs involved.
“Also, with complete ownership of the project, we would know exactly what to troubleshoot, and how to fix it,” says Ralston.
Satellite monitoring service, on the other hand, uses satellites to report monitoring data back to headquarters. The third-party satellite monitoring service, however, may be costly, ranging typically around $200 per month per data point. “When you add up a number of data points and multiply by $200, that can add up to a significant operating cost for the monitoring system,” says Ralston. “The annual costs may actually discourage the operator from adding additional monitors to the system.”
ProSoft recently began to introduce the concept of transmitting monitoring data through the use of industrial cellular technology where RF appeared unsuitable and unreliable, and satellite transmission proved too costly. A case-in-point – the 2009 installation of an industrial spread spectrum cellular monitoring system on a 120-mile length of liquefied petroleum gas pipeline owned by a midstream oil company. The pipeline stretches from Tulsa, Okla., near the foothills of the Southern Ozark Mountains, through woods, hills and wheat fields to Medford, Okla.
“We would deem that 120-mile stretch to be a remote site,” says Ralston. “The traditional way the company had been monitoring the integrity of the pipeline was through satellite links, which transmitted real-time pressure and flow data and valve status information along the length of the line back to its SCADA control center in Texas.”
Increasing monitor density
However, the company wanted to increase the density of monitors at some of the data transfer points along the pipeline. At the time, existing monitors were located 40 miles apart. Although leaks are extremely rare, any signal indicating a leak would require an inspector to drive the full 40-mile length of the affected pipeline between monitoring stations to find the leak. Adding any monitor between existing monitors could theoretically cut those distances in half.
At $200 a month per station, however, additional satellite monitoring would have added up to a hefty bill in the neighborhood of $25,000 per year. ProSoft initially considered installing additional monitors that would use RF technology, but the unforgiving terrain made that option cost-prohibitive.
“At that point, the typical solution would have been RF-based monitoring,” says Ralston. “We could have installed 900 MHz radios in nine of the locations, which would have had enough range and transmission power. However, the terrain for the remaining three locations would have required the construction of three transmission towers, which would have brought the cost of building the network infrastructure to over $100,000.”
ProSoft instead offered the client the option of employing industrial spread spectrum cellular monitoring. Cellular monitoring was a newer technology but the client agreed that it might be a good choice for that span of pipeline. Each of the monitoring stations was located within the Oklahoma cellular Global System for Mobile Communications (GSM) network, providing access to 3G cellular service.
“We used aluminum cellular radio serial modems small enough to fit into the palm of your hand with extended range provided by an additional antenna,” says Ralston. “The radios were powered by a 12-volt DC battery, and connected using DB9 serial ports to GE programmable logic controllers via Modbus. Although the SCADA system at the control center was Modbus based, the GE equipment was pretty generic and it was no trouble for us to establish connectivity between the cellular radios and all of the data points.”
Installation of the units was also straightforward. Gas company technicians installed the test modules under the direction of ProSoft engineer Dan Blome, who walked them through the process. Installation required about 15 minutes of setup per device, followed by the technician placing a test cellular call to ensure the device was properly connected.
A thirteenth cellular radio was installed to relay data from all 12 cellular monitoring points, into the existing satellite network and back to the control center. The SCADA network in Texas is instructed to poll each of the cellular locations, scanning the network every few seconds to provide real-time operations data. The entire system was up and running within three weeks of the order being placed and immediately reduced the emergency leak inspection length of each line segment between monitors to about five miles.
less expensive than satellite
Better yet, cellular service was available in the area for about $50 a month per monitoring station using the local AT&T network – about one-quarter the cost of a satellite rig. The system also allows the option of installing additional equipment, including motion detection cameras, although such a system would be more suitable for capturing significant image frames, than for streaming video.
Ralston notes, however, that cellular isn’t a catchall solution.
“Cellular isn’t necessarily as fast as a private RF network, but neither is satellite,” he says. “And RF is usually near 100 percent reliable, while cellular ranges to 99 percent-plus reliability. Currently, RF and cellular are our two top choices, with clients usually only going to satellite if those options are ruled out.”
Since the project was completed, the gas company has embarked on two similar projects. The first is an identical application involving two cellular radios. The second involves five cellular radios mounted along a crude oil pipeline that runs from a terminal to the refinery.
“Feedback on cellular technology from our oil and gas clients has been very positive,” says Ralston. “Once we supply the connectivity, cellular radio provides the transmission service at an attractive service price. We’re finding that clients are not only interested in saving money. At that price point, they’re encouraged to add more data points to their existing pipeline networks.”