Safety and fire prevention of the hottest oil tank

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The safety and fire prevention of oil tank cleaning operation is to remove the dirt in the tank in time to keep the tank clean, so as to avoid affecting the purity of the oil quality and economic benefits, and there will be many hidden dangers when low-quality oil products are put into work and production. Therefore, it is necessary to clean the oil tank timely and necessary

specifically, the oil tank shall be cleaned under the following conditions: (1) before the new oil tank is filled; (2) When the replacement of different types of oil and the original stored oil have an impact on the newly replaced oil; (3) It plays a very important role in actual life and utilization when it is necessary to carry out open flame welding or remove paint on the oil tank; (4) Clean the tank when the oil filling time is long and the tank is dirty; (5) Remove the sludge generated in the oil tank due to long-term storage; In addition, the oil tank shall be cleaned regularly or periodically

1. Current status of oil tank cleaning

due to the high cost of mechanical tank cleaning, at present, some small capacity oil storage tanks and storage tanks with less sediment (light oil) are cleaned manually in China. For example, the refinery oil depot, refinery oil tank and various oil tanks in the gas station still adopt the manual cleaning method; There are many personnel and equipment involved in manual cleaning, which may lead to improper selection of operation time and inadequate safety system [1]. Since explosive mixture is easily formed during tank cleaning, many ignition sources usually coexist during tank cleaning, which undoubtedly increases the risk of ignition and explosion. For example, on december18,2002, during the oil tank cleaning operation in a domestic oil cavern, the temporarily mounted explosion-proof lamp accidentally fell to the ground, and the lamp cover was broken, resulting in a short circuit of the lighting line. When the oil and gas escaping from the manhole cover in the oil tank exploded, two people died on the spot; On november30,1987, during the annual tank cleaning operation of a 3000m3 crude oil tank in niigatotouchi refinery, Japan, the electric spark generated during the wiring of the ventilator used for ventilation in the tank detonated the combustible gas in the crude oil tank. The fire lasted for 1 hour and 47 minutes. The accident caused the destruction of the crude oil tank and another heavy oil tank [2]

these shocking cases tell us that the fire and explosion prevention of oil tanks is urgent, and we must take corresponding effective measures to avoid similar events

2. Precautions for oil tank cleaning

oil tank cleaning is a dangerous operation in the tank, because the oil vapor is not only flammable, explosive and toxic. Therefore, the following safety regulations must be strictly observed during tank cleaning:

(1) open the manhole, check the oil quality at the bottom of the tank layer by layer, and determine the oil storage removal and treatment plan

(2) the tank entering is the maximum load that the sample can bear. Personnel must wear work clothes, work shoes, work gloves and gas masks. The signal rope and safety belt shall also be brought, and special personnel shall be assigned outside the tank for monitoring. The time for entering the tank shall not be too long, generally 15 to 20min. The operation shall be carried out in shifts. In addition, medical personnel shall be on duty on site

(3) brooms or wooden tools shall be used to clean residual oil and sewage, and iron and steel tools are strictly prohibited

(4) effective ventilation shall be adopted

(5) steam method - all hole covers in the tank shall be closed at the beginning, and when the temperature reaches 60 to 70 ℃, the cover shall be opened to continue steam washing until the residual oil in the tank is completely dissolved

3. The main causes of fire during operation

according to previous cases and lessons, we found that the main causes of fire are as follows:

(1) the fire is caused by the unclean cleaning of the oil tank. If the oil tank is not cleaned and there is oil dirt and residue, even if the concentration of combustible gas meets the safety regulations before the hot work maintenance, during the hot work, the flammable and explosive gas is decomposed due to the heating of oil dirt and residue, It will also lead to fire and explosion accidents

(2) when cleaning the oil tank, the existing electrical equipment on site will become an inducement for generating a fire by expanding the challenge slot through the computer motherboard. When cleaning the oil tank, the electrical equipment used does not meet the explosion-proof requirements, which is also inevitable: it brings rare stability requirements in the political arena, and electrical sparks may occur in use, becoming the ignition source of a fire; At the same time, poor management of lighting equipment and collision of metal tools may produce sparks and cause fire

(3) improper operation method leads to fire and explosion accidents. If the oil pipeline is used to replace the water inlet pipeline when cleaning the oil tank, if there is residual oil in the pipeline brought into the cleaning oil tank, it will become a fire hazard. High pressure water gun is used to spray and steam wash the tank wall for cleaning the tank. Due to excessive pressure and fast spray speed, it is easy to generate electrostatic sparks, which may ignite the remaining oil-gas mixture in the tank and cause a fire

(4) fire may be caused by improper disposal of the cleaned waste. The oil dirt and sulfide cleaned from the tank bottom are flammable and explosive. If they are not handled in time, they will become a fire hazard. At the same time, the waste liquid after cleaning contains combustible substances. If it is not treated and discharged, it will also cause fire accidents in case of fire source

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