【Haichuan Illustrated Chemical Equipment】Series Posts – Internal Floating Roof Tanks

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Get to know equipment, understand it, and make good use of it. [Haichuan’s Illustrated Guide to Chemical Equipment] series posts: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5719196. Everyone is welcome to participate in the discussions. ----------------------------------------------------------- The internal floating roof tank is a key component in petrochemical storage and transportation systems. It represents the best solution for balancing safety, economy, and environmental protection, especially when storing volatile light petroleum products such as gasoline, aviation kerosene, and light diesel. If an external floating roof tank is one in which a cover is placed directly on top of the liquid, and a fixed-roof tank is one that has a bell-shaped structure over the liquid, then an internal floating roof tank represents a perfect combination of the two: inside a fixed-roof tank, there is another \"cover\" floating on the surface of the liquid. 1. Why is an internal floating roof needed? (Solving “breathing loss”) In traditional fixed-roof storage tanks, there is a large gas space (vapor space) above the liquid level. Large breathing loss: When liquid is pumped into the tank, the rising liquid level pushes the saturated vapor mixture already present in the tank, which is rich in VOCs (volatile organic compounds), out of the tank. Minor breathing loss: Even without any material entering or leaving the tank, the intense sunlight during the day causes the temperature inside the tank to rise, accelerating the evaporation of the oil; the resulting gas expands and is released into the atmosphere ； At night, the temperature drops, the gas contracts, fresh air is drawn in, and it evaporates and is expelled again the next day. This is not only a huge economic loss, but also serious environmental pollution and a risk of fires. The core mission of an internal floating roof is to completely eliminate the oil and gas space on the liquid surface. The floating disk is in direct contact with the liquid surface; as the liquid level rises or falls, it rises or falls as well, thereby reducing the evaporation surface to its lowest possible level. 2. The core “components” of a floating roof tank – By combining principles of fluid dynamics and mechanical structure, a standard floating roof tank consists of the following key parts: Fixed Roof: Usually in the form of an arch or a cone shape. Its main function is to \"protect from wind and rain,\" shielding the inner floating disk from the risk of sinking due to accumulated snow and rain, while also blocking direct sunlight to reduce the temperature of the oil. Internal Floating Deck: A structure that floats on the surface of a liquid, usually made of aluminum alloy or stainless steel, and available in configurations such as tube box type (supported by buoyants) or honeycomb panel type. It acts like a thin film that presses firmly on the surface of the liquid, preventing oil and gas from escaping. Peripheral Seal System: There is inevitably a gap between the floating disk and the tank wall. The sealing system (usually a tongue-shaped rubber strip, a polyurethane foam block, or a mechanical tubular seal) acts like piston rings, continuously sealing this annular gap as the floating disc moves up and down; it represents the final line of defense against leaks. Vents: Located at the fixed roof and the top of the tank wall. Since the inner floating disk completely blocks oil and gas, the space above the floating disk actually contains only clean air. Vent holes ensure that this space is connected to the atmosphere, maintaining constant pressure and preventing combustible gases from accumulating accidentally to reach their explosive limit. Guide Pole / Anti-rotation Cable: Prevents the floating pad from rotating horizontally or getting stuck at an inclined angle during lifting or when there is fluid turbulence. Support Legs: When the storage tank is completely emptied for maintenance, these legs hold the floating deck at a certain height above the bottom of the tank, providing space for manual operations and protecting the inlet and outlet pipes located at the bottom.