Liquid extraction from internal floating roof tanks
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Gentlemen, we need to remove the oil at a level below 2 meters in our internal floating roof storage tanks. How should we proceed? What are the precautions?
Just keep pumping; once the floating disk reaches its support level, it will no longer drop. The edge seals are under stress and are at risk of damage, and there is also a risk when the liquid surface comes into contact with air.
What the original poster is saying is that it is necessary to continue extracting the oil within a range of 2m, such as to empty the storage tank; for this purpose, the vent holes on the floating disk need to be opened.
When it drops below 2 meters, the floating platform has generally already touched the ground; according to standard procedures, this is not allowed. Air getting in can lead to explosions if there is static electricity present. Nitrogen is usually introduced to reduce the amount of oil-gas mixture.
Just pay attention to the following points: 1. If there is no level gauge under the floating disk, it should be measured manually every hour to prevent the liquid level from dropping to zero. 2. In winter in the north, try to keep it above the floating disk; if there is water in the tank, the pillars of the floating disk will freeze. 3. When it is below the floating tank, external air will enter beneath the tank and come into contact with the oil. If possible, some nitrogen can be added; if that’s not possible, I don’t think it’s a problem, as safety accidents generally do not occur. There is a metal mesh fire protector at the breather valve of the storage tank. 4. Pay attention to measurement errors, take into account the weight of the floating disk, and try to avoid measurements in areas where the floating disk fluctuates.
The ones on the internal floating disk are automatic vent holes that don’t need to be opened by you. After the tank is placed on its base, use a pump to draw out the liquid; most internal floating roof tanks are designed with such features. When pumping, pay attention to changes in the liquid level. If the DCS is accurate, monitor it; it’s best to check the liquid level from time to time to ensure that it is decreasing. Use a diaphragm pump and keep the flow rate low – pump slowly to prevent the automatic vent holes from being damaged
Don’t use too high a flow rate; draw slowly to prevent the automatic ventilation hole from being damaged. What flow rate is safe to avoid damage? Are there any manuals or other references?
There is a standard of 1 m/s for the initial oil filling rate in internal floating roof tanks, and the same rate should be maintained during discharge. It’s not clear whether there are any regulations regarding the oil extraction rate
Inspect the ventilation holes in advance to prevent deflation; draw air in slowly and control the flow rate
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