There are thousands of miles of oil and natural gas pipelines in the United States. Because these valuable pipelines are made of metal, they are vulnerable to rust and corrosion. To prevent leaks and other damage, energy companies use Cathodic Protection (CP) rectifiers on the lines, which impress electric current onto the metal pipe to prevent corrosion. The Chicago regional office of Enbridge Energy U.S. in Griffith, IN, currently has approximately 100 of these rectifiers spaced 10 to 25 miles apart on its natural gas and liquid petroleum pipelines in Wisconsin, Illinois, Michigan, Ohio, and New York. Federal regulations require that the rectifiers be checked periodically to make sure they are still operating properly, but because of their remote locations, field technicians only periodically inspected the units. If a rectifier failed in the meantime, the problem might go weeks without being detected. "We sent electricians into the field once a month to collect readings," says Jerry DeWitt, CP specialist at Enbridge. "Consequently, if something went down you wouldn't know until someone was out to check." Enbridge needed a way to remotely collect data on the performance of the rectifiers and to control the current interrupters used on these systems to turn the rectifiers on and off during scheduled surveys.
Enbridge selected the Pipeline Watchdog Remote Monitoring System from NTG to collect data from the rectifiers. The Watchdog system includes surge-protected remote monitoring hardware, satellite and cellular communications capabilities, and a Web-based monitoring system. Enbridge had already ordered approximately 25 of the Watchdog units when DeWitt arrived at the company in 2007. The company then ordered more units to expand the system's coverage and took delivery in January 2008.
REMOTE MONITORING ALLOWS AUTOMATION OF MANUAL TASK
Now, DeWitt and his team can monitor volts and amps on each rectifier and remotely interrupt the current prior to pipeline surveys (the interrupters on the line have to be shut on and off during the surveys). The company can also monitor bonds with other pipelines as well as AC potentials in corridors where the pipeline runs alongside electrical power lines. The monitor readings can then be imported into the company's Cathodic Protection data manager system. DeWitt also receives exception alarms if one of the rectifiers malfunctions.
The NTG monitoring systems use a proprietary short-range, low-power wireless technology from Coronis (which is similar to Zigbee mesh networking technology) to collect sensor data on voltage, current, interrupter status, and other information to the base unit. This protects the monitoring system from electrical surges. "The NTG system is less likely to sustain damage because of the current flow," DeWitt says. "You can sustain some fairly large voltages on the pipeline because of lightning strikes and AC faults, and a lot of remote monitoring units are susceptible to those events. I haven't had a single one of the Watchdog units burn up because of that."
DeWitt had to make a few physical modifications to the system so that it could operate safely on the pipelines. Because rectifiers could potentially damage the electronic components of the monitoring system, DeWitt housed the mesh sensors in fiberglass junction boxes connected to the rectifier using a six-lead cable. The enclosures not only protect the equipment, but also save time during installation in the field, since the nodes are prewired in the box. NTG has incorporated a wireless GSM (global system for mobile communication) modem from Multi-Tech Systems into the Watchdog system. Multi-Tech's modems are precertified for operation by the wireless carriers, saving NTG the time and hassle of obtaining those individual certifications on its own. Enbridge is able to swap out cellular and satellite radios in the units based on wireless coverage in the area where the rectifier is mounted. "That's another desirable feature," DeWitt says. "We haven't lost radio communication for any part of this system. It works flawlessly."
The primary benefit of the monitoring system has been time savings. "We estimate we've saved about 40 man-hours a month because we don't have to manually collect that data," DeWitt says. "We have instant access. We can also see if there are any maintenance issues, which helps us with scheduling." If a rectifier fails, the NTG system alerts Enbridge via the online system. "The system has pretty good alarm capabilities," DeWitt says. "I don't have the system set up to send me an email in case there's a problem, but I could do that pretty easily."
DeWitt says that he expects 100% of his rectifiers to be fitted with the NTG monitors within the next 12 months, bringing the total number of units to more than 150. The company is also commissioning a new pipeline that will include at least 10 of the monitoring units.