Blast analysis study

Service company
Business Unit:
Drilling and Consultancy

Our client approached us with a requirement to examine the capacity of the temporary refuge (TR) wall of the accommodation quarters wall for blast to support approval of the safety case.

A finite element analysis (FEA) model was set up and analysed in ANSYS to demonstrate the wall reacting to a variety of pressures. The acceptable pressure was found to be more than the required at the location in the event of a blast from the well bay. This was supplemented with manual calculations as required including to demonstrate that windows and doors were also suitable.

The Problem

  • There was not documentation to demonstrate the temporary refuge allowable blast rating, however the safety case required analysis to demonstrate that the wall could withstand a blast pressure of 0.2bar.

The Solution

  • Apollo delivered a Basis of Analysis document to ensure the client was happy with how we were going to proceed with the assessment.
  • Results were presented in a summary presentation followed up with a brief analysis report detailing the findings of the analysis and calculations.
  • We gave our conclusion and recommendations where we found would survive the predicted maximum blast over-pressure.
  • We suggested that it may be possible to further increase the maximum blast pressure if required by creating a more complex model with more rigorous analysis. However, the approach used was both efficient and accurately demonstrated the required integrity of the wall in the event of a credible blast.

And for all you engineers who want more details:

The background

A model was created using drawings provided by the client and this was analysed in ANSYS to a variety of pressures affecting the wall surface. Using an FEA model allowed accurate stresses to be assessed around windows and doors and other stress concentrations. The dynamic response of the wall was considered and a modification factor applied to the static results. A representative section of the accommodation module was selected and analysed. The boundary conditions were also modelled in based on the drawings & information provided by the client. A pragmatic modelling approach and acceptance criteria were selected in line with industry guidance and codes of practice. This allowed a rapid turnaround of results, while robustly demonstrating the required capacity could be demonstrated.

The solution

The analysis identified areas of high stress at locations with welded connections. Manual calculations were done to evaluate the welded connections not explicitly modelled in the analysis and verify the approach taken by the finite element analysis. Manual methods were also used to confirm the windows and doors were suitably rated for the required over-pressure.

What did the client think?

The client couldn’t fault the support we provided,

“I was very happy with the report which has now been issued as part of the safety case. I thought that there was excellent communication throughout and that you guys have a great understanding of the project and what was expected. I couldn’t fault the work you put in. Thanks for your help and the effort you put in.”

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