In 2001, the Office of Pipeline Safety (OPS) introduced new rules and regulations requiring liquid pipeline owners and operators to inspect their lines for defects which could cause failures in high consequence areas.
For more information about the OPS regulations, visit http://ops.dot.gov/.
Because of the specific nature of the OPS rules, pipeline inspection companies either are developing or already have developed technologies to provide owners and operators with the tools necessary to meet these requirements.
Some of the first internal inspection pigs were designed to find dents in pipelines. In fact, it was the result of a northern crude oil company's request of an industry pig provider that the first geometry inspection tool called a Caliper ( KALIPER® ) pig was designed and developed in late 1969 by T.D. Williamson, Inc. This tool was designed to find large dents or buckles in big-inch pipeline that are often the result of poorly laid pipe during construction.
These early geometry tools utilized mechanical sensors and analog charts. The distance measurements were recorded at a scale of one-thousandths of an inch. Therefore, it was very difficult to precisely locate and determine the true geometry of dents and buckles.
It was not uncommon to find buckles in the lower quadrant of large diameter pipe that measured 3- to 4-inches in depth. Usually, these were found in the 6 o'clock position and were the result of poor ditch padding, failure to remove support skids or inadequate sand bag support. This simple tool, at the time, eventually resulted in improved methods to lay new pipelines. In fact, most newly constructed pipelines today use geometry inspection tools as an internal assessment method to confirm proper pipeline construction.
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KALIPER® Survey Tool
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Clock-KALIPER™ Geometry Inspection Tool
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Through time and technology development, the industry has seen the benefit to precisely size and locate much smaller reductions as well as identify the o'clock positioning of these small dents. This was necessitated by the fact that small dents with metal loss are more apt to fail over larger dents 2 percent or greater without associated metal loss, causing environmental damage and even loss of life. So with the need to be more exact in finding anomalies comes the need to develop new or improved technology.
The KALIPER tool has evolved from being a buckle detection tool to being a tool that locates and describes dents as small as 1/4-inch in response to operators' requests that bend detection and bend sizing become a part of the assessment process.
Recently designed deformation tools find small anomalies in pipelines by using multiple sensors, spaced no more than 1-inch apart, which ride directly on the internal pipe wall as opposed to the fingers of the caliper riding on the inside of a cup. These sensors detect and record movement to the hundredths (.01) of an inch while tracking the o'clock positioning and direction changes at all times.
MAGPIE™ Deformation Tool
In addition to deformation tools, the Magnetic Flux Leakage (MFL) Principle is another technology that has been greatly improved over the last 10 years. Advancements include the use of "hall-effect" versus "coil" sensors. Further improvements include upgraded electronics to handle the numerous additional sensor inputs.
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MAGPIE™ MFL Tool
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Because identifying dents with metal loss is a critical portion of the OPS requirements, additional tool development is continuing. In years past, multiple tool runs with KALIPER and deformation tools were needed to fully identify dents with metal loss. The data from each run was compared or overlaid to determine the location of dents with metal loss. With the development of combination tools capable of gathering both sets of data in a single run, pipeline owners and operators eliminate the need to track two pig runs, reduce lost revenue and minimize complex operational procedures.
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While some of the updates to the technologies discussed were initiated prior to implementation of the Federal Regulations, others are a direct result of the Gas and Liquid Rules. The implications are that in-line inspection companies have been and will continue being dedicated to improving technologies that assist pipeline operators and owners with their task of maintaining pipeline integrity.
For more information about TDW's inspection tools, visit TDWilliamson.com or contact your TDW representative.
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