OIL TANKER OPERATIONS (Loading) – Conventional Tanker Basics

Good planning is the hallmark of efficient tanker operations.

Before a tanker approaches port, there are several factors that must be considered:

1. Testing of cargo/ballast valves, sea valves, pipelines, pumps, inert gas systems, emergency stops.
2. Preparedness of fire-fighting, life-saving and anti-pollution equipment. A pollution drill held before a ship arrives in port will serve the purpose of checking ail equipment. Any response during an emergency will be good since a drill had been executed recently.
3. Preparation of tanks, including readiness of slop tanks.
4. Planning for proper distribution of cargo.
5. Checking of cranes/derricks, winches and other mooring gear.
6. Checking of all communication equipment.
7. Pumproom fans to be running for at least 24 hours prior arrival.
8. Ensuring that oil record book is filled in immediately after each operation.
9. Filling in the pre-arrival checklist.

Loading

There are several operations that must proceed side by side as soon as a tanker is tied up at the terminal. Each shipping company will have its own procedures as to who does what.

A ship-shore checklist must be filled out on arrival. The terminal as well as the vessel should be apprised of any special requirements, particular to that ship or to the port.

There should be a proper exchange of information. The terminal representative should be explained the plan for loading. Similarly the terminal should point out any peculiarities, shore tank to be used and its details, cargo specifications, ship-shore communication and emergency stop procedures. Loading rate and rate on starting and tapping off should be agreed upon.

The tanker must be securely moored at all times. It Is important for the deck watch to know the state of tides. There is pot much room for tankers to move once they are tied and the loading arms are connected, The loading arms should be properly aligned to the manifolds throughout the operation, as otherwise, there can be too much strain on the loading arm resulting in a catastrophe.

While taking rounds on deck, the watch keeper should ensure that:

1. accommodation doors/portholes are secured,
2. pumproom vents should be in operation,
3. no radio aerials should stick out from portholes,
4. radars should not be operational,
5. a sharp lookout for any signs of leakage through pipelines,
6. a watch overside,
7. a proper gangway watch,
8. no unauthorized visitors to board,
9. a proper manifold watch,
10. proper check on moorings,
11. scuppers to be efficiently plugged, rain water to be drained,
12. tank venting/vapour recovery system is properly lined up.

Safety precautions should be taken when connecting/disconnecting manifold and an officer should be in attendance. There have been many incidents of tankers having accidents due to improper operating procedures during connecting / disconnecting of manifolds.

In almost all cases the tanks will be gauged on arrival. For this purpose, it will be necessary to reduce the pressure of inert gas within the tanks when dipping empty tanks. The on board quantity (OBQ) and Slop calculations are a standard procedure before loading. It should be ensured that all the openings of the tanks are properly sealed off and IG valve set properly prior starting operations.

After going through the preliminary checklist and ensuring that everything is OK, the chief officer will proceed to line up for loading. He will then indicate to the terminal that he is ready to load. Loading should always be started at a very slow rate and into only 1 tank. Soundings/ullage should be monitored to ensure that the cargo is going only to the tank that is intended to be loaded. The gas will be vented through the mast riser or connected to the vapour recovery system, if fitted. It is prudent to avoid loading through the pumproom pipelines. After everything is checked he will then open up valves for additional tanks and then ask the terminal to increase the rate slowly upto the stipulated rate.

Deballasting of tanks will be done as per the cargo plan drawn up by the chief officer. The regulations now require that the ballast water be discharged via the high overboard discharge (if fitted). ODME should be used when discharging clean ballast. One person should monitor visually the discharge of ballast even though it is segregated ballast. A special watch to be maintained when the ballast is being drawn from the bottom of the tank. Some terminals may take objection even with the slightly rust-coloured water that inevitably appears during the end of ballast discharge. In conventional tankers the deballasting must be stopped as soon as the slightest sheen of oil is detected in the ballast even though the ODME records a permissible ppm. All the remaining ballast in the tank will then have to be transferred to the slop tank, to avoid ballast mixing with the cargo.

When the tank is approaching top off ullage, a close watch to be kept on gauging. A stand-by tank valve will be ideally kept crack open and change over to the new tank will be gradual. During final topping off the rate of loading should be suitably reduced.

After completion of loading the tanks will be gauged/sampled once again to ascertain the quantity of cargo loaded. After calculations and comparing with shore figures the vessel will be cleared for sailing.

LOADED VOYAGE

Some crudes tend to give off a lot of vapour in the first few days after they are loaded. It may be necessary to vent off the gas in such cases to avoid excessive pressure in the tanks. During the voyage the IG pressure should be checked very closely.

When heated cargoes are carried, it would be important to monitor the temperatures daily. The initial cargo calculations should allow for the requisite increase in temperature.

It may be necessary to top up tanks with IG periodically to maintain the tanks in an inert condition at all times. Crew should be alert to the smell of gas anywhere on deck. Gas leakage through PV valves and tank-opening gaskets is not entirely unknown.

Charter parties also require to take water dips when carrying crude oil since the water will take some time to settle and can be determined more accurately only once the vessel sails out from the loading port.

It would also be prudent to monitor ullages periodically and take immediate action if any major difference from loading condition is noticed.

SBTs and cofferdams adjacent to oil tanks should also be checked periodically.