14.2 Checklists, Alarms & Time to Terminate

Checklists turn CAM/ASOG theory into a start gate

You can know Class 2 philosophy perfectly and still enter critical DP work with the wrong bus state, a thruster deselected, or a single PRS family online. Location and setup checklists exist to stop that. They are the operational bridge between planning (capability, ASOG, CAM/TAM) and the moment thrusters take the load near a hazard.

Induction and Simulator assessments reward candidates who treat checklists as verification, not as a tick-box race.

Location / setup checklists before DP

Exact company forms differ. Exam-stable families of checks before entering or continuing critical DP include:

[!IMPORTANT] A completed checklist is a snapshot. If the plant changes after the tick, re-verify. Checklists do not freeze the universe green forever.

Alarm prioritisation: critical vs advisory

DP bridges can generate many alarms. Safe operators prioritise:

Examples of critical-leaning alarms (context-dependent, but exam-recognisable):

• loss of multiple PRS / voting collapse toward single-reference control,
• thruster emergency stop or unexpected full thrust (drive-off suspicion),
• bus section blackout / generator cascade under critical load,
• DP process station failure without healthy changeover,
• consequence analysis residual inadequate during critical work,
• position excursion beyond agreed limits near a structure.

Examples of advisory-leaning alarms:

• one of three gyros disagreed and rejected,
• single generator high temperature with reserve still online,
• one laser target quality drop while two other PRS families remain healthy,
• weather approaching but still inside yellow band with actions defined.

Rules of prioritisation under stress:

1. Position and power first — is the vessel about to move dangerously, or is residual power collapsing?
2. Do not bury critical alarms under silent-acknowledge spam.
3. One root cause may spawn many secondary alarms — find the initiating failure.
4. Link alarms to ASOG rows — many “yellow/red” decisions are alarm-driven.
5. Never disable critical alarms to keep the screen quiet during client visits.

Time to terminate (TTT) — the core idea

Time to terminate (TTT) is the time required to safely conclude the external critical activity and place people, equipment, and the vessel in a safer condition. It is not merely “how long until we hit the platform if we drift now,” though drift/drive timing informs how much TTT margin you still have.

Think of TTT as a clock that starts when you decide to stop (or when conditions force a stop):

If divers need 35 minutes to recover safely, you cannot wait until weather or residual capability is already beyond limits and then start recovery. You must start termination early enough that recovery finishes while residual safety still exists.

Exam language: “Weather is rising; recovery takes 40 minutes; limits will be exceeded in 25 minutes if the trend continues — when do you start recovery?” Correct conceptual answer: now / immediately, not after the limit is crossed.

Drift-off, drive-off, and blackout TTT thinking

TTT interacts with failure scenarios you studied under drive-off / drift-off and blackout recovery:

Blackout TTT is conceptual on the exam:

• If blackout recovery typically needs several minutes and divers need much longer underwater recovery, diving is planned on residual capability and early abort, not on hoping blackout never happens mid-dive without margin.
• If the vessel is already at ASOG red plant status, do not start a long recovery activity that assumes perfect power.
• After blackout, priorities are safety of people, blackout recovery procedure, and avoiding structure — not finishing commercial task steps.

You are not expected to integrate differential equations of drift. You are expected to reason:

1. How long does safe termination take?
2. How fast are conditions or failures eating the remaining margin?
3. Is residual capability after WCF still enough for that duration?
4. If not → terminate earlier or do not start the critical phase.

Worked conceptual TTT examples

Example 1 — Rising weather. Wind still green but trend will reach abort limit in ~20 minutes. Divers need ~30 minutes to recover. Start controlled recovery now (or sooner). Waiting for the red weather number guarantees recovery finishes outside safe limits.

Example 2 — Advisory generator loss. Spinning reserve enters ASOG yellow. ROV can be recovered in 8 minutes; structure is 80 m away in light current. Notify worksite, start standby gen, consider early ROV recovery if residual after next failure would be inadequate — do not ignore yellow because position still looks pretty.

Example 3 — Blackout during close approach. Blackout occurs inside the 500 m zone. Immediate actions follow blackout/emergency procedures; worksite stops external critical tasks as planned. TTT for “finish the survey line” is zero — commercial completion is abandoned.

Example 4 — Checklist prevents TTT crisis. Pre-entry checklist catches taut wire not deployed and only GNSS online. Approach delayed. Better to spend ten minutes on the checklist than invent a TTT plan after common-mode GNSS failure mid-approach.

Linking checklists, alarms, and TTT in one loop

Pre-job: location/setup checklist → CAM/TAM true → ASOG active
    │
Watch: prioritise alarms → map to ASOG colour → reassess residual
    │
If margin shrinking: compare remaining safe time vs TTT
    │
    ├─ Margin > TTT + buffer → notify, restore, continue if ASOG allows
    └─ Margin ≤ TTT + buffer → start terminate / abort path now

Exam traps for checklists, alarms, and TTT

Operator habits

1. Run the right checklist for this location and activity — not last voyage’s standby list.
2. Rank alarms: position/power/critical first.
3. Know the worksite’s realistic TTT before the critical phase starts.
4. Start termination when remaining margin ≤ TTT plus buffer, not after red is already true.
5. After any critical alarm or blackout, drop commercial goals and run emergency/ASOG logic.

Bottom line: Setup checklists prove the plant and references match the job before DP critical work. Alarms must be prioritised — critical threats first, advisories managed, never silenced for convenience. Time to terminate is how long a safe stop takes; compare it to remaining weather/plant margin, including blackout/drift thinking, using conceptual judgment rather than heavy maths.