Discussion on the plan for cleaning residual oil from removed storage tanks
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The company’s gasoline storage tanks need to be demolished. Before doing so, we will fill the tanks with water and transfer the contents of the tanks twice, in order to move as much of the remaining oil as possible into other tanks. After that, blind flanges will be installed on the inlet and outlet pipelines of the tanks to cut off the flow of liquid； Subsequently, any remaining small amount of oil at the bottom of the tank is thoroughly cleaned up. Previously, the company’s procedure for this step was to open the manhole and the cleaning holes, connect a water pipe, and have a person stand outside the manhole to flush the inside of the tank, with the wastewater being discharged through the cleaning holes. But I’ve seen many tutorials on tank demolition, and in many of them hand-pump connections are used to handle the residual oil. Which method is more appropriate? What are the advantages and disadvantages of each? I would appreciate expert guidance
If it is gasoline stored there, and since it is insoluble in water, it cannot be cleaned by rinsing with water; gasoline will remain on the walls and bottom of the tank. All you need to do is fill the tank with water several times, then transfer the contents to another tank. After that, open the manhole to allow natural convection for ventilation, and use a fan to enhance ventilation until the gasoline in the tank has evaporated.
Can steam be introduced into the tank? If so, after installing the blind flanges, it’s sufficient to allow steam to flow in for a few hours. If steam is not available, natural ventilation after washing with water is also an option ； As for the residual oil, your method will work; just ventilate after discharging the wastewater. However, it’s essential to conduct an analysis before carrying out any welding work. Also, your gasoline tanks should have internal floating roofs; make sure to check the compartments of the floating boats or floats to confirm whether there is any gasoline seeping in, as this can be quite problematic
Our storage tanks are external floating roof tanks; they are quite old, having been in use for 40 years now, and are scheduled for demolition； Is it safe to wash directly with high-pressure water? What are the things to keep in mind? Thank you
Can’t we introduce steam to steam the tank? This is the safest way. Otherwise, using high-pressure water directly is not appropriate, as there have been cases where static electricity generated during the flushing process caused ignition. If it is confirmed that there is no ferrous sulfide in the tank, the manhole can be opened and rinsed with water – not washed. After removing the residual oil, allow natural ventilation for some time. Sample and analyze the combustible gas in the tank; once it meets the standards, entry into the tank is permitted. Before carrying out demolition work involving open flames, it is essential to check and confirm whether there is any oil leakage from each floating tank – this must be given careful attention. In some floating tanks, oil leakage is not obvious, but over time, a considerable amount of oil can accumulate inside them. Testing may show satisfactory results due to the slow rate of leakage, but this can turn dangerous once welding or other hot work is carried out.
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