Induction bends - or more commonly referred to by pipeliners as “hot bends” - are factorymanufactured bends formed from straight motherpipe using a pipe bending machine and the electricinduction heating process. Pipe bends produced from this process find application in the pipeline,mining, power, process and construction industries.
Induction bending is simultaneously a shaping and heat treatment process. During bending, the pipe is curved and changes section (wall thinning/thickening and ovality) and the material properties are modified by the induction heating and cooling cycle. Induction bending is a dynamic process and requires close control and monitoring to ensure that dimensional effects and impartedmaterial properties meet agreed values. Different pipe sizes and material types will respond in avarious ways to the induction bending process – and it is a requirement that the relationship between the motherpipe and the induction process be well mapped-out prior to manufacture of the production bends. The experience of the bending company, the size of the induction bendingmachine(s) and the sophistication of the induction bending process controls become increasinglyimportant as the grade and process limits are approached.
For pipeliners, induction bending allows the production of piggable bends directly from bareuncoated linepipe; generally from pipe produced directly for the project with due consideration for the advantages and limitations of the process. Physical properties of induction bends can bedemonstrated through the manufacture of qualification test bends and subsequent mechanical testing.
Suitable Standard references for the inspection and testing of pipeline induction bends are: ISO15590-1, ASME B16.49, DNV OS F101.
Some archaic methods of “hot bending” use gas furnaces or torches to heat the pipe to enable bending – “hot bends” formed in this manner are not applicable to the pipeline industry.
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