This is the question with which we were recently faced in the context of a Shellvoy 6 Form Charterparty providing that “time shall not count … when … b) spent in carrying out vessel operations, including but not limited to bunkering, discharging slops and tank washings, and handling ballast, except to the extent that cargo operations are carried out concurrently and are not delayed thereby…”.
As is often the case, this led to an interesting debate concerning the construction of such a clause, and whether it should be construed in isolation, or in the context of the general laytime and demurrage regime.
Views vary, but The Stolt Spur  1 Lloyd’s Rep 786 indicates that the true approach is to construe such clauses within the laytime/demurrage context and to ensure that demurrage is only payable where there has been some “breach” of the charterparty by charterers. Accordingly, if the vessel is not always available to load the cargo, a condition precedent to a claim for demurrage being that the ship-owners should be ready to perform their duty under the contract, then time cannot count.
This means that in practice this will always be a question of fact and degree. Did the vessel move from the anchorage? Could she have continued into the berth at a moment’s notice to carry on her cargo operations?
As is often the case, this illustrates the difficulties with construing even standard form terms in the fact of practical realities. However, it is relatively clear that if the vessel is waiting for berthing instructions and there is no delay, time will count as long as the vessel was at charterers’ disposal and ready to load at all times. This will obviously depend on the precise circumstances of the exercise conducted, and whether this means that the vessel was unavailable for cargo operations at any time.