A Challenging Situation

During the deployment of non-reeled bundles the structure of the piping is subjected to a series of dynamic loads.  Predicting these loads even under normal conditions is extremely difficult, and when problems occur identifying and resolving the consequences can be hazardous. 

Difficult Failure Scenarios

One of our customers specialises in developing and deploying complex bundle systems of immense value to production programmes.  Installing these systems is difficult, and following a problem on one system Frazer-Nash was called in to assess the damage and determine whether the internal pipes could still sustain the operational and fault load cycles.  This particular bundle contained four major pipes and 31 minor lines of different types.  Diving reports indicated a leak from the outer casing, but no details of the degree of internal damage could be obtained.

Assessing Cause and Consequence

Our first task was to study the type of failure observed, and to assess the likely internal damage.  Using advanced dynamic finite element analysis methods, we were able to recreate the incident that had caused the damage, and predict the likely nature of the disruption to the bundle’s production pipelines.  The damage was difficult to analyse, as the pipe had buckled and torn at one of the resulting creases. Fortunately we have invested considerably over the years in developing and validating methods for this type of failure.

Assured Repair Strategy

The second part of the problem was to model the repair strategy, and assure the customer that it would be both adequate to restore the integrity of the bundle, and feasible with manual underwater repair techniques.  The repair process used a pre-stressed steel jacket to remove the stresses from the outer skin and restore the undamaged shape.  Again, detailed analysis of the repair process was necessary.  The final element of the complex repair process involved a clean-up programme in which the bundle was purged with an agent to destroy corrosion-promoting microbes.  Flow modelling was used to calculate the process required to treat the entire twelve mile length of the bundle.