Fabricating Complex Multi Curve Profiles in SS 316Ln


As the Director and Head of Research & Development cell at KRR Engineering Pvt Ltd, we developed some indigenous fabrication techniques for the BHAVINI’s (Bharatiya Nabhikiya Vidyut Nigam Ltd) nuclear project. The project involved fabricating critical components for India’s first 500 MW Nuclear Power Plant’s Prototype Fast Breeder Reactor and later for the Commercial Fast Breeder Reactor.

The components were namely: Inner vessel, main vessel and safety vessel. These components had a thickness of 20-40 mm and were to be made out of nuclear grade stainless steel plates. This research was undertaken to develop a technique to cold form thick Stainless Steel sections with complex geometry and multi-curve profiles to close tolerance of ±5 mm.

The outcome was one of the major breakthroughs in fabrication technology. At every stage of the manufacturing process many indigenous innovative techniques were used to save time and form the complex geometry with close tolerances and material efficiency.

Each of these components were divided into smaller segments. The figure shows the exploded views of the complex geometrical profiles of the three components depicting their segmental assemblage. Each segment is referred to as a ‘petal’. Several dies and punches were designed and built for every type of petal to form the complex profile.

The components were made of modified stainless steel alloys 316LN and 304LN. Full size die and punch were deployed for crafting the petals incorporating the spring-back allowances. The pressing was carried out by cold-forming procedure in a 4000 tonnes hydraulic press in order to comply with the requirement of full-profile formation in a single stroke and no point-pressing to avoid imbalances in the stress formation in the material.

With proper R&D and implementation along with stringent quality control, it was possible to achieve the profile accuracy within the close tolerances as recommended by IGCAR (Indria Gandhi Centre for Atomic Research) and NPCIL (Nuclear Power Corporation India Ltd).

Publications:

Technical Papers

International Symposium on Advances in Stainless Steel – 2007
Stainless Steel Fabrication Techniques of Complex Double Curve Profiles for Critical Components of 500 MW Fast Breeder Reactor
Ramaswamy Sakthivel, K.R.Ramaswamy and S E Manoharan

Technical Posters

Forming and Trial Assembly of Stainless Steel Dished Ends for Fast Breeder Reactors
Ramaswamy Sakthivel, K.R.Ramaswamy and S.E. Manoharan at International Conference on Pressure Vessels and Piping , Le Meridian, Meenambakkam, Chennai

Exhibits

OPE – International Conference on Pressure Vessels and Piping – 2006
Fabrication Techniques of Complex Double Curve Profiles for Nuclear Applications at Chennai Convention Centre, Nandambakkam, Chennai