TWI began by producing a dead-leg integrity management strategy, in consultation with the client, to define the different stages of the process and provide guidance on the required tasks for the implementation of this strategy.
This involved a risk-based approach to identify and register dead-legs using operational, physical and historic inspection data, before creating a mitigation plan which was implemented before further inspection determined whether further work was required.
The approach was based guidance provided by API 581 on the risk-based assessment of dead-legs. However, a more in-depth methodology was developed using additional parameters, such as; the type of system, the dead-leg design, dead-leg orientation, the length to diameter ratio, flow rate and the corrosion rate of the main line.
Suitable NDT techniques were highlighted for this work based on the type of equipment to be inspected, the surface condition, operating temperatures, the damage that was expected to have occurred and the size and accessibility of components.
This information was used to create the inspection/mitigation recommendations, with each dead-leg location receiving a unique identification number for reference in a dead-legs register.
The register allowed for risk assessment details to be compiled in consideration of damage mechanisms and the consequence of failure. This, in turn, allowed for the prioritisation of inspection based on risk categorisation for each item in the register.