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PIPELINE PIGGING TECHNOLOGY- P4

PIPELINE PIGGING TECHNOLOGY- P4: Why pig a pipeline? This paper introduces a number of reasons for doing so, together with a discussion of the advantages and alternatives. In general terms, however, pigging is not an operation to be undertaken lightly. There are often technical problems to be resolved and the operation requires careful control and co-ordination. | Pipeline Pigging Technology In order better to understand how to inspect or make a condition assessment for flexible pipe one must first make a comparison between the general properties and characteristics of flexible pipe with that of steel pipe. Some of these differences are illustrated in Table 1 Neffgen 1988 . As can be seen from Table 1 considerable differences exist between rigid and flexible pipe. Flexible pipe s complex behaviour in practice means bending moments and strains cannot be easily calculated some component materials exhibit non-linear behaviour differences exist between component elastic moduli which must be analytically explained strain distribution around the pipe is axi-symmetrical. DEFECTS AND MODES OF FAILURE To understand the structure of flexible a pipe is to appreciate the complexities of its behaviour and then to relate those to the presence and significance of defects. The purpose of any inspection programme is principally directed at Bea et OTC 1988 detection and documentation of defects which can lead to a significant reduction in serviceability characteristics defining what should be inspected when and how establishing a long-term database and feedback loop establishing the significance of a defect and or the need for remedial action. Such an inspection programme initially must focus on the identification and determination of .significant defects which can affect structural capability i.e. the ability of the structure to remain serviceable not to fail during its projected operational life Bea etaL 1988 . The importance of establishing a database for pipe defects and understanding how such defects can propagate are important in relating significance with regard to failure modes. Two modes of failure have been identified as having principal impacts on structural integrity those being wear and fatigue. Veritec Veritec joint industry report 1987 has defined wear as .the damage to a solid surface caused by the removal or displacement of .