NDTnet 1998 Aug, Vol.3 No.8

Abstract

In-line-inspection using ,,intelligent pigs" has become quite common to detect corrosion in large diameter pipelines transporting oil and gas. Only since recently, this technology is available for pipelines as small as 4" diameter and can thus be applied in different industries. Since 6 years, 3P Services in Germany has developed an inspection system to serve the diameters from 4" to 12". It applies the magnetic flux leakage principle (MFL) and thus can detect metal loss at the internal and external pipe surface. This is a fully self-supported ,,intelligent pig" that does not require cable support and that is pumped through the pipeline by either the product or water. Several case histories are presented that demonstrate, that the in-line-inspection equipment is adapted to the as-built situation of the existing pipe systems and that, therefore, more and more pipe systems can be inspected although never designed to be ,,piggable". Main subjects of the case histories are:
• Smallest possible dimensions of piggable/inspectable pipe: 4"-DIN pipe, 108.0x5.0mm was inspected, having over 100 U- and omega-shaped expansion loops with bend radius of 4 to 5 times OD.
• Short radius bends: 1.5D/90° bends can be negotiated for 6" pipe and larger. Therefore, the intelligent pig is now an option for all standard plant pipework, be it difficult to access (pipe bridge etc.) and/or insulated.
• Internal coating no longer prohibits in-line-inspection. Even through an internal cement coating of 8mm thickness a metal loss inspection was successfully performed in a 6" pipeline (168.3x4.5mm).
• Bi-directional pig trains allow to inspect pipelines that can be operated from one end only, like e.g. platform to shore loading/unloading pipelines. This equipment measures in a pump-in/pump-out mode and does not need cable support.

The practical matters of these examples are discussed, in particular (1) what kind of preparation is required ahead of an inspection run and (2) what kind of information does the operator get from an in-line-inspection.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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