51314-3810-Axial Wrinkling Behavior of Heat Shrinkable Sleeves / Tapes in Buried Pipelines

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Product Number: 51314-3810-SG

ISBN: 3810 2014 CP

Author: King Lo

Publication Date: 2014

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Heat shrinkable sleeves are often used for coating girth-weld joints in 3 layer polyolefin coated pipelines and tapes are sometimes used for repairing damaged pipeline coatings in the field. These field applied coating systems usually consist of at least two different layers – an outer polyolefin backing layer and an inner adhesive layer. For heat shrinkable sleeves an epoxy primer layer is also used with the coating. For some buried pipelines wrinkling of the polyolefin backing has been observed after the pipelines have been in service for some time. In an earlier paper the wrinkling behavior of polyolefin backing under backfill loads was examined. Simple models were presented to assess the wrinkling resistance of the backing to external pressure and shearing loads associated with the backfill. Wrinkling of the backing was assumed to be mainly along the circumference of the backing. The purpose of this paper is to provide further evaluation of the wrinkling resistance of the backing. Specifically wrinkling of the backing in the axial direction due to relative axial movement between the pipeline and soil will be investigated. To delineate the effect of backing / adhesive mechanical properties and layer thicknesses on the wrinkling resistance of the backing simple mechanics models are developed to describe the backing axial wrinkling behavior. Analytical formulae are derived which could be used to guide the development and selection of appropriate heat shrinkable sleeve and tape products to meet specific application requirements.