Case Study

Design and Analysis of a Large Cavity Type B(U)F SAFKEG®

Croft Associates Ltd has recently completed the design and development of a new, large cavity (Ø400 mm x 700mm), Type B(U)F transport package. The design is typical of proven transport containers; however, several novel features are incorporated to provide enhanced performance under Normal and Accident Conditions of Transport (NCT & ACT). In particular, a large screw ring closure mechanism has been developed to provide the structural and containment performance of the Containment Vessel (CV) closure.

This paper focuses on the design, development, and substantiation of the new SAFKEG® design, with particular emphasis on the novel features utilised to enhance the package performance. The paper describes the design development from the initial preliminary design through to post-test reference design, regulatory impact testing and underpinning Finite Element Analyses (FEA).

The screw ring closure mechanism is key to the CV structural and containment performance. This paper discusses the benefits of this type of closure design along with the challenges faced during design development, not least with respect to preload, consistency of torque application and determination of the acceptable torque range for O-ring seal compression within the CV closure system.

As part of the new package performance substantiation, in-depth analyses of the impact performance were undertaken. A verification strategy was derived utilising a benchmarking/decision matrix approach, this considered experience gained upon the successful licensing of previous SAFKEG® designs.

The verification strategy prescribed a combination of physical testing and FEA to validate the impact performance of the package. High speed photography and Faro Arm metrology measurements were used to analyse the resulting deformations from the impact tests.

Once benchmarked, the detailed FEA model accurately demonstrated the performance of the package under impact conditions. Furthermore, the model was used to examine package behaviour under conditions not feasible to undertake within the physical test program, including further sensitivity studies, e.g., upon increased drop height to explore whether “cliff edges” existed in the impact performance verification.

This paper presents a summary of the packages’ design development, regulatory testing, and performance validation with an emphasis on modelling, test strategy, analysis, and evaluation.