Analysis And Prevention of Oil And Gas Concentration on Tanker

Oil tanker are ships carrying dangerous goods, which are prone to fires and explosions and require a high safety factor. In addition to the strict requirements on the selection of construction materials, a series of fire and explosion prevention systems, such as inert gas protection systems, have to be installed. In addition, it is in the implementation of the general ship fire prevention system at the same time, there are special system requirements for fire prevention. In this paper, based on the characteristics of oil tanker to analyze the concentration of oil and gas prevention.

Main Characteristics of Oil Tanker

Adopt single-layer longitudinal deck. The bottom and inner bottom of the deck in the cargo tank area are of longitudinal skeleton type, and for the tanker with a length of more than 150 meters, the side and longitudinal bulkheads are also of longitudinal skeleton type, which is conducive to bearing the total longitudinal bending stress. In addition, in order to ensure the strength and rigidity of the oil tanker, the cargo tank skeleton usually adopts high cladding truss material.

From a safety point of view, the materials used in the areas facing the oil cargo area have special requirements in terms of fire and explosion protection. Access doors, air doors and openings are not oriented towards the oil cargo area, and windows and portholes on the superstructure and deckhouse sides are of the permanently closed (non-opening) type. Such windows and portholes on the first level of the main deck are also fitted with internal covers made of steel or other equivalent materials. In addition, the bottom of the cargo oil tank is usually a single-story structure, which is mainly due to the fact that the relative density of cargo oil is smaller than that of seawater. The corrosion of the hull structure of oil tanker is much more serious than that of dry cargo ships, so the structural materials, in addition to the use of thickening measures, should also be used for the cargo oil tanks with a special coating treatment.

Analysis of Oil and Gas Concentrations by Oil Tanker

When the mixture of oil and air is between the lower and upper flammable limits (i.e., between 1% and 10% of the volume fraction), it is in the flammable range. In this condition, once it touches an ignition source, it will burn or even explode. Beyond this range is too dilute or too concentrated state. No matter what state, we can not simply regard them as absolute safety. This is because, when the air into the original over-dense state of the chamber, the air will be diluted in the original over-dense state of the mixture, may make the mixture into the combustible range. Similarly, when the temperature rises for some reason, the oil is heated and volatilized, and the volatilized oil and gas will make the original mixture in an over-diluted state enter the combustible range due to the increase in oil and gas concentration.

Changes in oxygen content also have a significant effect on the flammable range. When the oxygen content in the mixture of oil and gas and air decreases, the flammable range decreases, and when the volume content of oxygen is less than 8%~10%, it will no longer burn. On the contrary, when the oxygen content in the mixture increases, the combustible upper limit will rise and the combustible range will become larger. Therefore, special attention should be paid to the danger posed by leaky oxygen equipment.

Prevention of Oil and Gas Concentrations on Oil Tanker

1. Concentration of oil and gas in the superstructure and its prevention

In areas where oil and gas may be present on board an oil tanker, the rules for closing doors, windows and portholes in the superstructure should be strictly observed, and the rules for ventilation and air-conditioning use should be strictly observed, except for closed-cycle air-conditioning, which may be used. Assuming that there is suspicion of seepage of oil and gas in the galley, electric stoves cannot be used. No seepage of oil and gas is allowed in the cabin. If it is not possible to ensure that there is no seepage of oil vapor in the superstructure, stop loading and unloading of cargo oil. In addition, be especially alert to the possibility of seepage of oil and gas on board and in the surrounding environment.

2. Oil and gas concentration and prevention in the cargo oil pump bilge

Since the cargo oil pump cabin is equipped with many tubes, valves, pumps and other equipment and facilities, if the repair and maintenance is not done properly, it may cause these equipment leakage or oil leakage, thus making the cargo oil pump cabin appear the mixture of oil and air, when the volume percentage of the two reaches the combustible range, the formation of a dangerous combustible oil and gas concentration. In addition, there may be a lack of oxygen in the cargo oil pump compartment.

3. Combustible oil and gas on the deck in the cargo tank area and prevention

Since oil and gas are heavier than air, they tend to accumulate as combustible oil and gas on the deck in the cargo tank area when they are continuously discharged through the deck openings or the exhaust system during the loading of oil. Similarly, when filling ballast water into the cargo tanks, washing the tanks, removing the oil and gas in the tanks, or when the oil pipe or valve on the deck leaks, dangerous concentrations of oil and gas often accumulate on the deck in the cargo tank area. In the absence of wind or with little wind, it is difficult to dissipate the accumulated oil and gas. This poses a fire hazard on the one hand, and may cause poisoning due to the toxic effects of the oil and gas on the other.

Conclude

The analysis and prevention of oil and gas concentration by oil tanker is of great significance for the protection of marine environment and the promotion of sustainable development. Qinhai Shipyard has taken a series of measures, including fully considering the possibility of oil and gas escape in the engineering design stage and formulating corresponding protective measures; operating in strict accordance with the design requirements during the construction process and strengthening the supervision and management of the construction site; strengthening the communication and cooperation with the relevant departments to promote the analysis and prevention of oil and gas concentration; reducing the pollution to the environment; and strengthening the training and education of the staff to enhance their safety awareness and environmental protection consciousness. their awareness of safety and environmental protection.