Development path of the A26 replacement polymeric insulator for the WCML project

Early in 1999, Raychem began to work with a Railway maintenance company on the development of a polymeric replacement for the A26 porcelain insulator and electrification of the new WCML project, (West Coast Main Line). The interest in polymeric insulators initiated from the market trend towards the employment of polymeric insulators by the railway industry worldwide. The reason for this trend is because of the superior mechanical and electrical properties of the polymeric insulator. Through this paper the main advantages of the polymeric insulator will be addressed, including its mechanical and electrical advantages over porcelain, i.e. elimination of chipping, improved shock/impact resistance, high tear strength of sheds, and superior flashover performance. The specific advantages of employing Raychem proprietary EVA housing material (with more than 20 years worldwide experience) will be addressed. The low moisture vapour transmission rate of the EVA reduces the possibility of internal tracking and acid notching failures in the most aggressive environments. The superior mechanical performance will be illustrated through the comprehensive elastic limit testing of the core material, and in the work carried out on the end fitting design with a view to minimising deflection and internal crimp joint stresses and maximising strength. Also the paper describes the development path that the A26, (designed & optimised specifically for GTRM) has taken from conception through to the product. Details of the relevant standards, material selection & qualification, Finite Element Analysis of the assembly, and resultant design and type testing carried out through its development phase is discussed. Finally, Raychem's experience in the high speed railway industries in Japan, Taiwan, Scandinavia, France and the UK will be discussed and experience shared.


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  • Accession Number: 01011778
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-947644-43-1
  • Files: ITRD
  • Created Date: Dec 19 2005 3:31PM