Question 1

During pre-operation checks on a DP2 cable-lay vessel, one of three online generators trips offline and cannot be restarted immediately. The remaining two generators are running within normal load limits. The lead DPO must decide whether DP operations can continue.

What is the key question the DPO must answer before continuing DP2 operations?

Accepted Answer

Whether the two remaining generators are sufficient to power all thrusters at maximum demand after the WCF The core DP2 power question is always: after the WCF occurs, do the remaining generators have enough capacity to power the remaining thrusters with adequate margin? If two generators are running on the same bus section and the WCF removes one, you may be left with insufficient power for the remaining thrust demand. A consequence analysis test with the current generator configuration must confirm adequate margin — if not, the ASOG should require aborting or downgrading operations.

Question 2

A DP Class 2 vessel is operating on a subsea construction project. The chief engineer asks whether the vessel can continue operating in the event of a single active component failure.

What does DP Class 2 guarantee in this situation?

Accepted Answer

The vessel can maintain position after a single failure of any active component or system, provided redundant systems are in place and operational IMO MSC/Circ.645 and IMCA M103 define DP Class 2 as: no loss of position following any single failure of an active component or system. Redundancy in active components is required — thrusters, generators, UPS, switchboards. Fire/flood protection requires DP Class 3. Static components (cables, pipes) are not covered by the single failure criterion.

Question 3

A semi-submersible drilling rig is classed DP Class 3 and operates in deep water on a well with well control implications. A trainee DPO asks what the key distinction is between DP2 and DP3.

Which statement correctly describes the DP Class 3 requirement?

Accepted Answer

DP3 requires redundant systems to be located in separate watertight compartments with physical separation, such that a single fire or flood cannot affect both systems simultaneously DP Class 3 extends the single failure criterion to include fire and flooding in any one compartment. This demands physical separation — redundant power systems, DP control systems, and thrusters must be arranged in separate fire and watertight subdivisions. A cable fire that destroys one entire DP system must leave the other fully capable of maintaining position. This is the "worst credible failure" standard.