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Disposal for Spilled Oil and Prevention for Secondary Disaster

Half of all major oil pollution claims arise from incidents on ships not carrying oil cargoes. Although major spills receive international attention, they contribute to less than 5-10% of oil pollution reported. When oil spills into the aquatic environment, it can harmorganisms that live on or around the water surface or under the water. Spilled oil can also damage parts of the food chain, including human food resources.

Well maintained pipeline

Although many species are harmed or killed soon after contact with the oil, other effects are not noticed immediately and can be longer lasting:
  1. wildlife can be slowly poisoned by long term exposure to toxins
  2. predators can be exposed to oil by eating contaminated prey
  3. scientists have observed developmental effects in bird embryosthat were exposed to oil
50% of all major pollution claims involve ships which are not carrying oil cargoes. Routine operational activities are of greater concern:
  1. bilge water disposal
  2. tank washing
  3. ballasting
  4. fuel transfer
  5. loading / unloading cargo on tankers.

MARPOL 73/78 Annex I:
As part of the environmental policy, regulations in MARPOL Annex I have to be considered during ballast operations. This is to ensure that ballast water is not contaminated by oil products as a result of failures e.g. failure of bulkheads/joints between tanks or pipework systems that run through ballast tanks.

Ballast overboard discharge valves are to be kept closed and warning notices posted at the valves, engine and cargo control rooms before the vessel enters port or designated Special Areas.

Any discharge into the sea of oil or oily mixtures from the cargo area of an oil tanker shall be prohibited, except when all the following conditions are satisfied:
  1. the tanker is not in a Special Area
  2. the tanker is more than 50 nautical miles from the nearest land
  3. the tanker is proceeding en route
  4. the rate of discharge does not exceed 30 litres per nautical mile
  5. the total quantity of oil discharged does not exceed 1/30,000 of the total quantity of the cargo
  6. the tanker has an Oil Discharge Monitoring Equipment(ODME) in operation.
The discharged monitoring and control system should be used to discharge residue (Regulation 15).

Tanker Standard Equipment For Disposal Of Spilled Oil & Secondary Disaster Prevention

Slop Dump (Surface) Valve Arrangement (Emergency drains)

The slop dump valve arrangement is generally provided at the aftermost portion of the tank deck area. It connects the “On-Deck” accumulation to the slop tank(s) on either side of the ship (where fitted).

Opening of the drain valves in the case of an on deck oil spill must be authorized by the Chief Officer, or in his absence the duty deck officer. Close attention must be taken of positive pressure in the slop tank, correct draining procedures must be followed.

A warning sign, displayed well above such fish plate level, with the text “Not to be opened without authorization from the Chief Officer or the duty deck officer” should be posted by the drain valves.

Every Quarter, the function testing of the Slop Tank Dump (Surface) Valves is to be exercised using “Quarterly Testing Record for Miscellaneous Equipment”

The crew are to be properly instructed during drills, on the correct draining procedures to be followed, at each case of oil spill. Incorrect procedures could lead to serious aggravation of the case.

Equipment and Materials for on deck Oil Spill Clean up

Company designates Equipment and Materials for on deck Oil Spill Clean up in “Shipboard Oil Pollution Emergency Plan (SOPEP)”.

Vessel’s equipment for clean up of an ‘on deck’ oil spill shall be distributed correctly to prepare for Emergency Measures. Steel Drums should not be directly placed or moved on deck without suitable non-conductive insulation beneath.

The Portable Pneumatic Diaphragm Pump shall be ready to use at aft Main deck. And Stripper pump (during discharge operations only) should to be kept in state of readiness for the intended duration of operations.

Refer to on board SOPEP manual (or CFR 33 part 155.205 or 155.210 as applicable if in US navigable waters).

Emergency Procedures - Incident at Manifold/Tank Overflow

The cargo manifold constitutes a high risk area. Accidents occurring in this area may be divided into two types:

i) Spillage through a fractured pipe or other cause that has not resulted in a fire.

ii) A spillage that has resulted in a fire.

In either case the first consideration will be to cut off the supply to the area. If the ship is discharging, this can only be done by stopping the ship's pumps and closing a valve between the pump and the fracture. If the ship is loading it will obviously be necessary for the shore installation to stop the supply and the means of communication or special signals must be established before loading is commenced.

With regard to the emergency shutdown of operations before loading or discharging is commenced in the case of such incidents the appropriate contingency plan must be activated.

The large surface area created by a typical spillage will allow the oil to give off gas more rapidly than would normally be the case. If a source of ignition is present, the resulting fire could create a major conflagration that may be beyond the extinguishing ability of the emergency party.

The Chief Officer must ensure that all possible sources of ignition are isolated or removed. The spillage area is to be covered with foam to minimise the risk as soon as possible before cleaning up operations are commenced. Careful judgement must be exercised as this action could spread the oil further causing greater risk and serious environmental pollution.

Under these circumstances, a spillage of oil or tank overflow will be considered as an emergency situation, and the Emergency Organisation brought into operation.

Inert Gas System

Main purpose of Inert Gas System is:
Maintain Pressure in Cargo Oil Tanks in proper range
Maintain Atmosphere in Cargo Oil Tanks as Inflammable Condition

In principle all operations should be suspended, if an Oil Pollution Incident occurs during Oil Transfer Operation, however Inert Gas System may be operated continuously to prevent secondary disaster, Fire Accident.

How to Report an Emergency

The Master shall ensure that company’s internal and local emergency contact details are posted in public areas and in accordance with the “Shipboard Oil Pollution Emergency Plan”, the “Emergency Procedures for Oil pollution Accidents” and “Vessel Response Plan (VRP)” for the vessels to serve in U.S. water.

Static Electricity Precautions

Matter consists of equal numbers of positive and negative ions and under normal conditions is electrically neutral. This is true of oils, chemical products and other liquids. A redistribution of ions tends to occur when a liquid comes into contact with a solid, giving rise to the formation of an Electric Double Layer where the ions adjacent to a liquid/solid interface are redistributed to produce a layer of ions of the same electrical sign. Close to this layer but slightly further away from the interface a layer of ions of the opposite sign will be formed. Elsewhere the distribution of ions remains unchanged.

When the liquid and solid are separated, as in any pipe line flow, the ions in contact with the solid (pipe) tend to remain attached to the solid and the oil (or other liquid) loses some of its ions, thus becoming electrostatically charged. The separated charges will attempt to recombine, their success depending upon the electrical conductivity of the oil. Crude oils, which contain high levels of impurities, have high electrical conductivity and charge recombination is rapid. Water also has high electrical conductivity.

By comparison, most refined products (white oils) contain few impurities and charge recombination in such products is very slow. These products are known as STATIC ACCUMULATOR OILS.

The rate of flow through pipes will influence the build-up of charge separation - the faster the flow, the faster the charge separation. Charge separation will also occur:
  1. In the filling lines of tanks being loaded with white oils.
  2. When oil mixes with water.
  3. When air is allowed to "bubble" through white oils and splashing occurs at the surface.
  4. When oil is splashed or sprayed.
  5. When water droplets in a steam jet (or CO2 particles) leave a nozzle.
  6. When water passes through tank cleaning machines at high pressure electrostatic charging of fine sprays or mists may result. Click here for a list of Static Accumulator Cargoes.

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