North American Oil & Gas Pipelines

SEP 2018

North American Oil & Gas Pipelines covers the news shaping the business of oil and gas pipeline construction and maintenance in North America, including pipeline installation methods, integrity management innovations and managerial strategies.

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napipelines.com SEPTEMBER 2 018 | North American Oil & Gas Pipelines 29 oxidation, arc burns, etc. The next step is inspecting the condition of the corrosion-inhibiting chemical surface coating. Magnetic particle testing (MT) and dye penetrant testing (PT) are standard inspection tools to detect surface abnormalities and identify lack of fusion in welds. Examining below the surface requires ultrasonic de- vices that use high-frequency sound. The energy loss reflected from areas with discontinuities causes ampli- tude decreases in the ultrasonic echo. Like a doctor us- ing sonography, ultrasonics enable the technician to "see" beneath the exterior to volumetrically size corro- sion, pitting, cracks, laminations, etc. Digital pit gauges and pencil probes use compres- sion-wave ultrasonic signals to acquire precise di- mensional measurements for mapping corrosion/ cracking and calculating pipe wall thickness. Auto- mated ultrasonic testing (AUT) automates ultrasonic mapping with a high-speed robotic sensor that gener- ate a 360-degree digital representation of the pipe at a resolution of 0.10 x 0.10 in. AUT data can be archived for time-lapsed comparisons. In addition to conventional compression-wave ul- trasonics, advanced ultrasonic inspection technolo- gies include: • Shear-wave ultrasonic testing (UTSW), which introduces sound signals into the pipe at a prede- termined angle (rather than a straight beam) to obtain a maximum acoustic response. Angled-beam transducers provide accurate wall depth/metal loss measurements, and detection of longitudinal fissures (including SCC) and weld defects. • Phased-array ultrasonic testing (PAUT), which is essentially the same technology as a sonogram, en- abling the ultrasonic beam to be "steered" at angles ranging from very sharp to very shallow. This is par- ticularly useful in examining linear discontinuities. • Mid-range ultrasonic testing (MRUT), which sends a guided-wave ultrasonic signal axially along the length of the pipe. It's not used for volumetric depth measurements, but to detect corrosion and provide go/no-go indications of pipe integrity. • Time-of-flight diffraction (TOFD), which is argu- ably the most accurate of all ultrasonic inspection methods. While limited in pipeline integrity testing applications, TOFD can map girth weld preferential corrosion that can be masked by external weld pro- files using other ultrasonic techniques. BUILDING BOOM The U.S. is undergoing a pipeline building boom. Enough pipeline construction projects were permitted in 2017 in only one state (Texas) to lay joints of pipe end-to- end from New York City to Los Angeles and back again. 4 The technologies being used to construct new lines are vastly superior to what was used in the past, but half of

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