8.1.2 The thruster and propulsion units should provide good position keeping capabilities
in the intact and the worst case failure conditions. For such conditions, the mean
tension required for working with the highest pipe tension load for which the unit
is designed is to be accounted for in the force vectors of the dynamic positioning
system.
8.1.3 The control system software for the dynamic positioning system should be provided
with a tension input for pipe-laying operations to ensure that pipe lay initiation,
lay down and recovery are included in the dynamic positioning control model. It is
essential that this tension input is accurate, redundant and reliable to ensure
position keeping performance and stability.
8.1.4 The systems and equipment on board should be such that no single failure of the pipe
lay or positioning system would result in the total loss of the tension in the pipe
or loss of position stability. The tensioners should be designed with the same level
of redundancy as the dynamic positioning system and a Failure Modes and Effects
Analysis (FMEA) should be performed on the pipe lay system and its interaction with
the dynamic positioning system.