Fatigue - Hybrid Staged Operations - Operation & Outputs
The procedure adopted by the Hybrid Staged Operations approach is similar to the Staged Operations option up to the point of calculating the fatigue damage incurred by each tracked weld during a particular stage.
In the case of the Staged Operations the weld damage is calculated by scaling the identified damage rate by the overall duration of the stage. This differs to the hybrid method where the welds are moved along the pipe string over a number of pulls and for each new weld location the corresponding damage rate is scaled by the Cycle Time to obtain weld damage values per pull. The total weld damages for the stage are computed by adding together the various pull damages. This process is repeated for all stages in the analysis and then the stage damages for each weld are summed together to give overall damage values for the entire operation. This use of Pull Length and Cycle Time is consistent with the Normal Lay method discussed earlier. Please note that the remainder of the hybrid operations analysis is identical to that of the standard staged method, for example the maximum allowable standby time is determined for each stage etc.
It is worth noting that the generation of tracked weld stress histograms for the Hybrid Staged Operations is as per the Staged Operations but with the aforementioned differences in tracked weld position catered for at each stage.
The outputs from a Hybrid Staged Operations fatigue analysis are the same as those for a Staged Operations analysis.