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SUMMARY:Overtrawlability and Mechanical Damage of Pipe-in-pipe System - Ms
  Zheng Jiexin PhD candidate\, Department of Civil Engineering\, National U
 niversity of Singapore
DTSTART:20140423T160000Z
DTEND:20140423T170000Z
UID:TALK51502@talks.cam.ac.uk
CONTACT:Anama Lowday
DESCRIPTION:Trenching is an effective\, but often high cost\, method to pr
 otect a pipeline from external damage such as trawl gear impact. In the ea
 rly days of offshore field development\, all pipelines in the North Sea we
 re trenched. In order to avoid unnecessary trenching\, trenching guideline
 s were developed later. Nowadays\, an increasing number of pipe-in-pipe sy
 stems are used for transport of oil\, because of their significantly bette
 r thermal insulation than the single pipe system. This development raises 
 questions about the trenching decision for pipe-in-pipe\, because the prev
 ious research and guidelines are aimed at single wall pipe. If we apply th
 e approach of single wall pipes directly to pipe-in-pipes\, it is likely t
 o result in a conservative design\, as the outer pipe is not required to r
 esist internal pressure and can accommodate a greater level of indentation
  than a single\, pressure containing pipe. Eliminating conservatism in thi
 s aspect of design has the potential to eliminate the need  for  trenching
   in  areas  of  high  fishing  activity  and  can  therefore have conside
 rable economic benefits.\n\nTherefore\, a 3-year research project was set 
 up to study the overtrawlability of pipe-in-pipes and to develop a basis f
 or a rational trenching decision. When trawl gear interacts with a pipelin
 e\, it will impact the pipe first and then pull-over the pipe. Three diffe
 rent experimental programs were carried out to study the mechanical behavi
 or of pipe-in-pipe under trawl gear crossing\, including quasi-static inde
 ntation tests\, impact tests and pull-over tests. Finite element models we
 re built and verified against the test data. Semi-empirical models to esti
 mate the indentation response were built. Pull-over response of pipe-in-pi
 pes was studied and possible improvements of pull-over model test methodol
 ogy were proposed. \n
LOCATION: Cambridge University Engineering Department\, Lecture Room 4
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