In-line inspection of a subsea crude-oil pipeline not designed for pigging took place last summer in Singapore.
In July, a 48-in., 5.2-km pipeline used to unload crude oil from tankers at Shell Eastern Petroleum (Pte) Ltd.'s Bukom refinery in Singapore was inspected by NKK's bidirectional, ultrasonic, in-line inspection tool.
The pipeline incorporates a pipeline end manifold (PLEM) that permits connection to tankers via a flexible hose. Final analysis of the inspection results has been submitted to Shell.
PROCEDURE
Under its inspection contract, NKK provided a package of services that included engineering work for temporary shore piping arrangements, mobilization of a launcher-receiver and pumps, fabrication of major piping components, and pipeline cleaning in addition to inspection.
NKK's ultrasonic inspection tool is equipped with special sells that permit it to travel both directions in a pipeline.
This capability allows deadend pipelines, such as those used for offshore loading and unloading to be inspected without, says NKK, the time and expense of modifying subsea installations (Fig. 1).
A profile pig and NKK's ultrasonic inspection tool were inserted and retrieved through the shore port of the pipeline.
Following are the steps taken in the operation:
- A 7,000-dwt tanker was connected to the PLEM.
- The ship received contaminated water from the line. The ship's pumps provided pressure to drive the pig back the way it had come.
- Two sets of pig detectors were located 100 m and 20 m from the PLEM so that the pig and tool could be detected before they entered the PLEM.
- The profile pig was run first to determine the piggability of the pipeline and to remove sludge and debris.
- The ultrasonic inspection pig was then passed through the line to collect data on the line's condition.
- An on-site data presentation was made to Shell and a final analysis was prepared in Japan and submitted.
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