Loading gasoline without inerting: velocity, sampling and bonding under terminal pressure
MT Delta Star is a 12,000 dwt product tanker with no inert gas system. She is loading 6,000 m³ of unleaded gasoline (flash point about –43 °C) at a Lagos terminal through two 8-inch loading arms. The previous cargo was gasoil, and the tanks were not gas-freed before switch loading. At 02:10 the loading rate reaches 1.8 m/s within five minutes, before the shore line and ship line are fully packed. At 02:25 a deck cadet prepares to take a dip sample from No. 3 port tank with a metal sampling bucket while cargo continues to flow. The terminal representative says bonding is unnecessary because the berth is busy and the ship has sacrificial anodes; he asks the cadet to finish sampling quickly. Wind is light and there is no thunderstorm.
1. Identify the three highest-risk actions in this loading operation and state what should happen immediately.
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The three highest-risk actions are: (1) starting at 1.8 m/s before the line and tank bottom are packed, which permits splash filling and rapid electrostatic charging; (2) taking a dip sample with a metal bucket while cargo is flowing, which introduces a conductive object into a charged vapour space and can produce a spark; and (3) accepting switch loading from gasoil to gasoline without confirmed bonding and without controlling the initial velocity.
Immediately, loading should be stopped or reduced to a safe initial rate of not more than 1 m/s until the lines and tank bottom are covered and no splash occurs. The sampling must be cancelled. The ship/shore bonding connection and resistance must be verified before restarting, and the terminal must confirm the loading plan is amended. The cadet should not rely on sacrificial anodes for bonding; anodes protect against corrosion, not against static ignition. Because the tank is not inerted, no dipping, gauging or sampling should occur until at least 30 minutes after cargo flow has stopped, allowing static charge to dissipate. The master and terminal loading master should be informed before any restart.
2. Explain the velocity and sampling limits that should have been in the loading plan, and why they are not optional.
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The loading plan should have specified an initial filling velocity of no more than 1 m/s until the loading lines are fully packed and the cargo has covered the tank bottom and internal structures, avoiding a free fall or splash. After that, the velocity may be increased only within the limit agreed for the line size and cargo, commonly up to about 7 m/s, provided there is no splash and the ship/shore system is bonded. These limits reduce charge generation and give the charge time to relax.
The sampling rule is equally firm. On a non-inerted tanker, metal sampling equipment must not be used while cargo is flowing. Sampling should be done through a closed sampling point or after flow has stopped and the recommended settling period has elapsed, normally 30 minutes. These controls are not administrative preferences: they target the ignition triangle in a tank atmosphere that is normally above the lower flammable limit. A metal bucket lowered into a charged ullage can equalise potential across an imperfect bond and spark. The cadet should treat the plan as a permit condition under ISGOTT and the vessel's SMS, not as a suggestion from the terminal.
3. How should the cadet respond to the terminal representative, and what should be recorded?
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The cadet should politely but clearly refuse to continue sampling and should ask for loading to be slowed or stopped. The response should be factual: the vessel is not inerted, cargo is gasoline, the tank has not been gas-freed since gasoil, bonding is not confirmed, and sampling during flow creates an ignition source. The cadet should call the duty officer and master rather than argue alone, and should not allow the terminal's berth pressure to override the loading plan.
Recording matters because it shows the safety intervention and protects the vessel if events are later questioned. The deck log and cargo record should note the time, the observed flow rate, the sampling attempt, the terminal request, the stop/reduction, and the master's instruction. The ship/shore safety checklist should be revisited and the loading plan amended before restart. If the terminal insists, the master should escalate to the terminal representative and, if necessary, suspend loading. This is a safety-culture test: a near miss should be reported internally, not hidden, and the crew should be briefed so that the same shortcut is not repeated on the next watch.