Trans Alaska Pipeline System: TAPS Update
New solutions keep oil flowing in aging pipeline
TAPS, also known as the trans-Alaska oil pipeline.
Courtesy of Alyeska Pipeline Service Co.
For more than thirty-five years, the Trans Alaska Pipeline System (TAPS) has sent North Slope crude to waiting tankers in Valdez via eight hundred miles of pipe and pump stations.
Today, the giant system operates with near-perfect reliability, but orchestrating the migration of hundreds of millions of barrels of oil is no simple task. Keeping TAPS in motion depends on careful preparation and planning.
“We spend a lot of time trying to be upfront and be proactive,” says Melanie Myles, oil movements director at Alyeska Pipeline Services Company.
The company that maintains TAPS on behalf of its owners performs regular maintenance shutdowns and constant system checks to monitor pipeline valves, schedule future work, and make sure problems are fixed before they occur. These days, there are several maintenance shutdowns that occur over the course of the summer, including two long-duration shutdowns that last longer than twelve hours and involve major maintenance activities, Myles says. The first took place without a hitch earlier this season, and the second was scheduled for August 21.
During the second major pipeline shutdown of the summer, crews were to replace Remote Gate Valve 40, part of Alyeska’s proactive approach to maintenance that aims to head off emergencies before they occur. Even proactive maintenance takes a lot of advance preparation, Myles says.
“It’s an amazing amount of upfront planning, because once you take the line down and you make that first cut, you’re at the point of no return,” Myles says.
Past improvements included installing new pumping units to reduce operational costs and automating the system to allow remote control of pipeline operations. An advanced supervisory control and data acquisition system allows TAPS technicians to monitor everything from pipeline valves and pressures to tank levels, temperatures, and flow rates. These days, Myles says, the company is working on different kinds of upgrades.
Right now, her top priority is to heat the line to keep the oil flowing.
Heat for Speed
As throughput declines, heat becomes increasingly important. According to data kept by Alyeska, the amount of oil moving through the pipeline fell from a daily high of more than 2.1 million barrels in January 1988 to today’s average of approximately 500,000 barrels per day. As that number falls, so does pipeline flow speed, which makes it easier for particles to separate, allowing water to freeze and wax to accumulate. At roughly 500,000 barrels per day, water begins to separate into a flowing layer at the bottom of the pipe, increasing the risk for internal corrosion damage, according to a 2011 low flow impact study published by Alyeska.
The company considered the possibility of turning to cold-dry flow—the process of removing water from crude oil before it enters the pipeline—but research has shown little near-term viability for the cold-dry flow method and TAPS. The crude oil delivered to the pipeline has a relatively low water content, and the system modifications necessary to remove it would be prohibitive. Instead, Alyeska is keeping its efforts focused on heating the pipeline to keep ice at bay and “conducting other tests to research methods for prudent future operations.”
In June, Alyeska submitted a lease amendment request to add approximately 2.14 acres of land next to Remote Gate Valve 65, according to the Alaska Department of Natural Resources. The extra space would allow room to expand the pad and install a crude oil heater unit and fuel tanks “to help mitigate the continued decrease in crude oil temperatures,” the department reported. The installation project is expected to be complete sometime later this year.
Besides adding point-source heat along the pipeline, Alyeska is working to keep the oil warm by recirculating it at Pump Stations 3, 4, and 9. The previously decommissioned Pump Station 7 was put back online specifically for recirculation.
A Russian Diakont self-propelled buried pipeline inspection robot.
Courtesy of Diakont
Pigs in the Pipeline
When it comes to wax buildup, Myles says, the likely solution involves pigs.
“Pigs” are devices that travel through the pipeline to clean and test the system, but low flow makes it difficult to move the pigs from one point to another. One promising solution involves robotic pig crawlers and hydraulically activated pigs, Myles says.
Because the forty-eight-inch trans-Alaska oil pipeline is much larger than other oil pipelines around the globe, and travels over hundreds of miles of unforgiving terrain, designing a self-propelled pig that will work for TAPS means investigating and modifying technologies created for smaller pipes.
Pig crawlers that move by their own motor force have “been very successful” for the operation, Myles says. Last summer, a two hundred-pound robotic pig owned by Russian company Diakont successfully inspected around 850 feet of buried pipeline at Pump Station 3, resulting in reduced risk and cost for Alyeska, according to the company. Myles says Alyeska has now begun including the new tool in its corrosion detection processes. Another technology—a hydraulically activated pig—is undergoing testing and proof of concept now, the oil movements director says.
While new technologies and system modifications can help offset the effects of low throughput, there’s one unavoidable consequence.
“As the pipeline continues to operate, we do have more maintenance and renewal work, and a lot of that occurs during shutdowns,” Stakeholder Relations Manager Katie Pesznecker wrote in an email.
A series of strategic reconfiguration facilities—the first of which came online in 2007—initially reduced availability for the pipeline system, according to an annual report from the State Pipeline Coordinator’s Office (SPCO). The legacy equipment, optimized over three decades of improvements, had achieved a system availability rate of 99.997 percent in fiscal year 2006, according to the state, and when the first strategic reconfiguration facility began to work the next year, the SPCO tracked a sharp increase in shutdowns; a number that began to drop as more strategic reconfiguration facilities came online. The spike was temporary—by fiscal year 2014, the reconfigured pipeline system achieved the same availability as the legacy equipment.
In July 2015, it maintained 100 percent availability, with a 99.5 percent rate for the year.
Oversight and Inspections
Earlier this year, the pipeline service company discovered a spill at Pump Station 10, located along the Richardson Highway at Mile 219. While the pump station had been out of service since 1998, it was being used to support operations along the pipeline system.
The spill was found around a weeping isolation fitting just north of the pump station, according to a report from the Alaska Department of Environmental Conservation. Alyeska crews discovered the release while excavating to investigate “a corrosion inspection anomaly in a separate location along the main line” and reported the spill to the state fifteen minutes later.
The crude oil had gathered in the tar membrane and packing material covering the coupling, according to the Alaska Department of Environmental Conservation, and it dripped from the fitting when the soil around the pipe was dug out. The weep was slow—about one drip every second—and the pipeline service company estimated that only about ten gallons were spilled.
In response, Alyeska removed contaminated gravel around the site and monitored the area “on a twenty-four-hour basis” while it developed proper controls, the Alaska Department of Environmental Conservation reported. That spill was the first reported pipeline release since 2011, according to the Department.
The pipeline system is subject to oversight from a variety of organizations, including the Anchorage-based SPCO. There’s an SPCO safety liaison who conducts routine checks of TAPS facilities and work sites and an SPCO electrical inspector who tracks code violations and performs random on-site inspections.
In fiscal year 2014, the office’s safety liaison conducted eighteen annual safety inspections at TAPS pump stations, response bases, Fairbanks-area shops, and storage facilities. He conducted four work-site safety inspections similar to the annual inspections but with an added emphasis on safety programming and procedures, according to the SPCO.
In the same period of time, the SPCO’s electrical inspector performed seventy inspections, issued one notice of violation, and reviewed fifty certificates of fitness, according to state data.
The inspections, frequent preventative maintenance, and forward-looking system upgrades keep the pipeline in operation, propping up a multibillion-dollar industry and a huge chunk of Alaska’s economy.
A herd of caribou grazing alongside TAPS.
Courtesy of Alyeska Pipeline Service Co.
The Pipeline’s Future
According to the 2011 low flow study, oil temperatures at 350,000-barrel-per-day speeds could allow the soil around buried sections of pipeline to freeze, causing potential damage. At 300,000 barrels per day, the system could experience “unacceptable pipe displacement limits and possible overstress conditions.” Those kinds of conditions would raise new questions about TAPS operations and its long-term viability.
In early August, the 2015 daily average throughput hovered just below 508,000 barrels per day. In July, the system averaged around 486,600 barrels per day. Total annual throughput has decreased steadily since 2002, according to data published by Alyeska; but for now, heat helps keep TAPS moving.
Kirsten Swann is a freelance writer based in Anchorage.
This article first appeared in the October 2015 print edition of Alaska Business Monthly.