Session: 10-03: Advanced Manufacturing 3

Paper Number: 136240

136240 - Manufacturing Challenges for Hot Isostatic Pressing of Large-Scale Vessels 

Abstract: 

Hot Isostatic Pressing (HIPing) has been used by Rolls-Royce to successfully manufacture nuclear plant components such as: valves, piping, and pump casings, the majority of these components being manufactured from stainless steels, typically 316L. Rolls-Royce considers there to be significant potential benefits in applying the HIP process to the manufacture of large Low Alloy Steel (LAS) pressure vessels. These benefits would include cost savings, lead-time reductions, an increase in the material quality, and improved inspectability of the as‑manufactured material. Production cost and timescale reductions are of particular interest, with large vessel manufacture being a most significant contributor to the overall cost and manufacturing time of primary nuclear plant; this against a backdrop of the industry striving to drive down the cost of nuclear power generation in order to ensure viability with other forms of power generation. HIPing of large-scale LAS structures though presents specific challenges compared to HIPing smaller, stainless-steel components, and these challenges must be met to provide a viable alternative to traditional methods of manufacture, i.e. casting and forging. This paper presents the challenges Rolls-Royce has experienced in their HIP vessel development work and the means of addressing those challenges. It covers key steps of the HIP manufacturing process, from powder production, through can manufacture including leak detection, powder filling and sealing. A particular issue is the risk of powder oxidisation and this affecting the material properties of the HIP consolidated material, specifically the toughness of the material. The paper presents this issue and how Rolls-Royce has achieved material properties equivalent to the wrought form. Another specific powder issue is the risk of contamination. The paper discusses this threat which can have serious consequences if contaminated material enters service, as experienced in other industries, and presents the means of reducing the contamination risk. Can failure during the HIP cycle as a consequence of poor can design and/or fabrication is likely to result in the structure being scrapped, as the powder will not be fully consolidated, this wasting a significance amount of expensive powder and the time and effort that has gone into fabricating large HIP cans. The paper shows examples of the results of can failures, e.g. unconsolidated powder, and how such failures can be identified and prevented. As a vacuum has to be achieved in the HIP can in order for the powder to consolidate during the HIP cycle, the can has to have a high level of leak tightness. Although detecting the presence of a leak is fairly straightforward, identifying the exact positon of a leak so that it can be rectified is particularly challenging in a large structure with extensive weld material present. The paper presents some techniques that Rolls-Royce has considered and applied, but it is identified that further work is required in this area.

Presenting Author: John Sulley Rolls-Royce

Presenting Author Biography: John Sulley is a UK Chartered Engineer and European registered engineer. He is a Rolls-Royce Engineering Fellow having previously held the positions of Chief Engineer, Chief Design Engineer, and Chief of Engineering Capability at Rolls-Royce. He has 40 years of nuclear component design and manufacturing experience, and has been heavily involved in implementing advanced manufacturing techniques such as Hot Isostatic Pressing, Laser-Powder Bed Fusion, and Electron Beam Welding.

Authors:

John Sulley Rolls-Royce
David Stewart Rolls-Royce