Conventional pigging technology frequently carries inherent limitations in traversing difficult pipelines which contain such challenges as multi-diameters, tight bends, restrictive appurtenances (i.e. heavy wall fittings, reduced diameter valves), excessive bore restrictions, and operational constraints (i.e. low gas pressure/volume conditions).
Baker Hughes Pipeline Management Group (PMG) has engineered a new line of pigging technology that negotiates pipelines previously relegated to “˜unpiggable’ status. After starting with a “˜clean sheet of paper’, Baker Hughes’ new CPIGâ„¢ High Resolution ILI technology overcomes conventional mechanical and electronic limitations, resulting in minimising costly pipeline modifications and operating expense.
Mechanical Attributes
The current range of CPIG ILI tools (4 in. to 38 in.) will pass 1.5 D bends. Nearly all of the tools (as standard) will traverse bore restrictions of 25 per cent of OD (only the 6 in. and 8 in. tools are limited to 20 per cent capability). The tools are generally shorter to minimise costly trap modification and simplify handling.
Electronic Attributes
Across the full range of diameters, scan pitch (sampling rate) is established at 2.5 mm and sensor spacing is 6.5 mm. Expandable flash memory and the latest lithium batteries enable single-pass inspections of even the longest pipelines.
Real-Life Benefits/Case Histories
In three of the first pipelines that PMG inspected, the need for costly manifold and trap modifications (using other ILI tools) was eliminated by using a standard CPIG ILI 10 in. pig slightly less than 2 metres in length. Over $US150,000 was saved in facilities modifications alone.
The same 10 in. tool was then used in a pipeline containing “˜gorilla’ girthwelds with IDs of 226 mm, and its 12 in. cousin was used to negotiate a heavy wall natural gas riser consisting of 21.4 mm wall. The same 12 in. tool then negotiated (albeit, with damage) a 12 in. pipeline with a wrinkle in excess of 35 per cent diameter. No other existing MFL tools could have negotiated such restrictions, and costly cut-outs were avoided.
A CPIG ILI 16 in. tool was used in a low pressure/low volume gas pipeline containing nearly 200 1.5 D elbows (not to mention extensive dirt in the line). Other tools attempted, but failed to achieve good runs with speed excursions downstream of the elbows of up to 80 kph. The low-drag-coefficient CPIG tool negotiated and inspected the problem line in a single pass with a maximum velocity of 20 kph downstream of the elbows.
Considering a standard bore passing ability of more than twice that of conventional MFL tools, the CPIG tools’ ability to traverse multi-diameter lines has been made easier. A standard 20 in. tool has been used to successfully inspect both 18 in./20 in. and 20 in./22 in. dual diameter gas lines. Small inch dual diameter tools have been fabricated to inspect 6 in./8 in., 8 in./10 in., 10 in./12 in., and
12 in./14 in. dual diameters. The CPIG ILI 24 in. tool was slightly modified in order to successfully inspect a tri-diameter 20 in./22 in./24 in. gas line.
And in a 367 km section of 10 in. pipeline with heavily corroded, seamless pipe, a CPIG high resolution tool was able to complete the inspection with 30 per cent of its memory capacity remaining. Conventional tools would have required up to eight passes of the same line for full inspection.
Currently, Baker Hughes PMG is in the process of adding integrated high resolution caliper inspection capability to all MFL tools – for a metal loss/caliper inspection in a single pass and with a single data set. Inertial Mapping Units (IMUs) are also being added as an optional mapping device.
The CPIG ILI tools have been used to inspect pipelines moving crude oil, refined product, natural gas, LPG, ethylene, and propylene. For those pipelines that must be inspected out-of-service, Baker Hughes also supplies VERTILINE® Tethered MFL inspection.