Unprecedented Growth
When the Trans-Alaska Pipeline and related infrastructure were initially constructed in the mid 1970s, there was not a single Alaskan-owned NDE company. Now, 25 years later, growth has spawned more than a dozen companies and Alaska is emerging as one of the premiere proving grounds for state-of-the-art NDE inspection technology. Since Alaska offers unique applications and conditions, many emerging technologies have been developed, beta tested and brought into full production through various Alaskan ties.

Fig. 2 -- Real-time radioscopy crew at work. A -- Automated real-time radioscopy (real-time imaging of internal corrosion) being moved by crew members over a VSM; B -- RTR analysis of pitting in pipe done by a crew member inside the control room of the truck.

What is the current state of NDE in Alaska? What does the future hold for NDE as new infrastructure comes on line and existing infrastructure ages? Before investigating these questions, it's important to understand how the environment, weather and geology affect construction and, inevitably, the inspections performed.

A Unique Environment
The geology and weather of the region are vitally important to understand because both factors greatly influence engineering designs. Prudhoe Bay is home to the largest oilfield in the United States. Often called "the North Slope" or, more commonly, "the Slope," the area is a flat, emergent subsea floor that stretches from the shore of the Barents Sea and reaches up to the foothills of the Brooks Range. The Brooks Range was formed when an isthmus, located near the Mackenzie River delta area in Canada, swung around and contacted the North American plate. The North American plate subsequently deformed and the Brooks Range was created. Ever since the last ice age, approximately 10,000 years ago, the Slope has been undergoing isostatic rebound. The uplifting of the sea floor is due to the removal of weight from melted glaciers that were present in the Brooks Range.

Fig. 3 -- Automated ultrasonic testing. A -- Automated ultrasonnic system acquiring corrosion data on a test separator; B -- close up of automated ultrasonic scanner acquiring corrosion data on a test separator.

The Slope is an area of continuous permafrost, whereas the Trans-Alaska Pipeline traverses areas of continuous and discontinuous permafrost. In discontinuous regions, permafrost exists on the northern sides of hills and slopes, but the ground may be relatively frost free on the more southern-exposed slopes. Extracting hot oil, then transporting it across permafrost on the surface is a challenge. If permafrost melts, the surrounding area becomes an impassible, muddy quagmire.

Corrosion and Inspection on Elevated Piping
The galvanized wrap can be a contributing source to external corrosion. On April 16, Phillips Alaska had a 92,400-gallon spill of a produced water and oil mixture from a flow line in the Kuparuk field. This spill is one of the largest the slope has ever had, and it covered an area of tundra approximately one acre in size with a produced water and crude mix. How are such lines inspected for corrosion? Since these pipelines are elevated, many different NDE techniques are utilized. Unlike buried counterparts that may undergo hydrostatic testing and pigging, these lines are also inspected from the exterior, often with proprietary technology. Automated digital radioscopy and automated ultrasonics (AUT) are two technologies that have stepped up and proven critical to the success of corrosion mitigation programs.

The digital systems are used to find areas of gross corrosion that can be either internal or external in nature. The areas with the greatest interest are highlighted and may be evaluated by another NDE method. For internal corrosion, the insulation will be stripped off the pipe and automated or manual ultrasonic follow-up inspections will be conducted. Depending on the extent of damage, the area may be inspected on a regular basis to establish corrosion trending rates. AUT is the predominant method used to provide highly accurate corrosion trending information. A magnetic scanner attached to the external surface of the pipe manipulates a transducer over the surface while a pulser initiates a sound wave that propagates into the steel. The returning wave is received by the transducer, converted to a digital signal and displayed in a plan view or C-scan image presentation. This image is then used to determine the amount of wall loss, extent of damage, etc. -- Fig. 3.

The University, Industry and Government Triumverate Develops New Technologies
Technicians using RTR and AUT have become highly proficient at their trade. Often, suggestions from field technicians have been the savior of an experimental project. An engineer 5000 miles away does not know firsthand what works, or does not work, in the Arctic. The technicians and companies using this equipment watch it perform and intimately know the strengths and weaknesses. This is the main reason the utilization and design of cutting edge technology has prospered in Alaska. Companies, state oversight agencies and the university have worked together to develop, implement and train technicians in new techniques.

University of Alaska Anchorage
The University of Alaska Anchorage Welding Technology Department was started in the late 1950s, well before Prudhoe Bay ever came into production. After the Good Friday Earthquake of 1964 (the most powerful earthquake ever to hit a populated area), the University received monies through the Manpower Training Act and purchased new equipment and funded new positions for the training of welders. In 1965, the department became the first large-scale welder training and certification center in the state.

In 1969, the department moved to its current location at the University. That same year, Howard Long wrote the first two- year degree program in materials technology. This program consisted of a variety of welding, materials, inspection and industrial science classes. This degree program eventually evolved and became an associate of applied science in welding technology. But this degree, too, evolved as time passed. As technologies have evolved and infrastructure ages, the need for highly trained NDE technicians has increased.

In 2000, the University held its first Welding and Nondestructive Evaluation Symposium. The keynote speaker was ASNT chairman Robert Doggart. Highlights of the UAA program were acknowledged and areas earmarked for future growth identified. Then, in January 2001, the program advisory committee unanimously advised a name change to Welding and Nondestructive Evaluation (NDE) to further describe the proper educational emphasis of the program. Besides a name change, two certificates are being finalized; one in NDE, the other in welding.

CMOS Digital Radioscopy
Envision Product Design was founded in 1993 to develop real-time radiography systems. Its first client was CTI Alaska, Inc. As an early manufacturer of digital radioscopy systems, Envision has developed real-time radiography and tangential digital radioscopy systems based on intensified CCD and amorphous silicone technologies. Its biggest asset, however, has been the successful development of complementary metal oxide silicone (CMOS) radioscopy. CMOS technology provides a dramatic improvement over CCD digital systems now prevalent throughout the NDE industry --Fig. 6.

CMOS technology differs from current digital systems for several reasons. First, the pixels that constitute the detection panels have a larger detection surface compared to a CCD pixel. Because of the way the pixels are wired, the pixel has more available area to be hit by photons. Another major advantage over CCD technology is the fact each pixel on the thin film detector has its own amplifier, whereas CCD panels have amplifiers connected to multiple pixels in series. Resolution and clarity with CMOS arrays now exceed traditional film radiography. There is also the added benefit from the elimination of processing chemicals and waste manifesting. Additionally, since the panels are so sensitive, the radiation exposure levels are considerably reduced, thus ensuring a safer work environment. Interestingly, for some materials and applications, the exposure time is so short it is difficult for a typical exposure meter to detect the radiation.

The first purchaser of Envision CMOS technology was Boeing Commercial Aircraft. Additional clients include NASA's Langley Research Center and Lockheed Martin Space Systems. With each potential sale to a client, customers commonly send samples with defects to evaluate. On many occasions, John Cope, Envisions lead product engineer, and UAA student technicians have performed the initial shots on these products. Items viewed have included Titan missile fuel tubing, aluminum circumferential welds from the center tank of the space shuttle and coiled tubing drill pipe.

The time savings of digital radioscopy over traditional radiography is significant. For example, a student had a 6-in. API pipe certification requiring radiography. Depending on the film and kV chosen, the shot could take approximately 11Ž2 min. The film then would be manually or automatically processed and placed in a drier. The whole process would take approximately 25 min for a shot that may, or may not, meet the requirements of the code.

However, with the CMOS system, the same shot will only take 1 to 3 s. The crawler used on the pipe is no larger than the palm of a hand. The track the crawler follows may be either magnetically attached or taped in place on the pipe. The penetrameters, as well as lead coordinate numbers, are an integral part of the track. The crawler moves sequentially about the pipe, taking snapshots of no more than 3-s exposure time. The sequential images can be viewed individually, adjacent to each other, or linked together through software. The complete process requires no more than 90 s to complete a circumferential weld.

AUT/Phased Array Ultrasonics
Utilized for pressure vessel certification, corrosion mapping and volumetric weld inspection, AUT technology has proven itself in the Arctic as a highly accurate inspection technique. On a typical day, at least two different AUT crews are mobilized performing inspections throughout the state. During the busy summer months when projects such as API tank farm inspections, TAPS dead-leg inspections and new construction require inspection, the number of deployed systems swells to four to ten crews.

Recently, a 32-mile-long pipeline on the Slope failed when a fatigue crack propagated around a circumferential weld. Joel Degner, a UAA graduate, was instrumental in initiating the use of state-of-the-art technology using phased array ultrasonics. Technicians for Management Integrity Services (MIS) conducted the first volumetric weld inspections in the state utilizing a sixteen-element, linear-phased array. Using time of flight tip defraction (TOFD) sizing techniques, the system is capable of resolving and sizing a 0.5-mm-deep EDM notch. With manual ultrasonics, the reference standard couldn't even be detected, never mind sized.

During initial proving of the test system, four technicians and a professor from the University of Alaska attended a crash course on the intricacies of phased array ultrasonics. Representatives from the Joint Pipeline Office, a consortium of seven state and six federal agencies with oversight responsibilities for TAPS and other Alaskan oil and gas pipelines, were also present to observe and approve the use of the system based on test runs on manufactured mock-up pipeline segments. Technicians then went out to the field and inspected more than 150 suspect welds for fatigue cracking.

Both industry and the university are realizing the significance of working together, not only for the development of new equipment and techniques but also for the training of technicians that will graduate and find themselves in a workplace using the same technologies they saw in development. Jointly investigating applications and developing procedures from development to implementation can save time. By working hand in hand, educational institutions and industry can help each other bring new technologies to the field with a high rate of success.

Still More to Explore
Far away from the lower 48, Alaska's distance, weather and applications have forced the development of highly sophisticated inspection techniques. The development and application of these techniques are dependent upon the availability of technicians trained to understand the technology and its proper application and limitations. As development in Alaska matures, so will the NDE industry. By working together, industry, state agencies and the University will continue to keep Alaska on the map as a place where new frontiers in NDE are explored.