Problems with floating roof tanks
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This post was last edited by kangyusai on 2018-9-8 at 10:47. It’s my first time dealing with a floating roof tank with a nominal capacity of 40 cubic meters. Is there anyone who has CAD drawings of floating roof tanks that I can use as a reference? If not, I have a few questions. For the floating roof, we will definitely purchase it externally. So, are the openings in the floating roof created after it has been installed? What does the core-equipped manhole on the tank wall look like? Is there a reference standard? Haven’t seen it
Manholes can be ordered from the manufacturer to be pre-made, and manholes with cores can be requested directly from the manufacturer
I just saw two examples: one involved cleaning an old tank and then installing an internal floating roof, while the other involved upgrading a tank by fitting an internal floating roof. I didn’t pay close attention to the exact dimensions of the manholes and access openings in those tanks; it seems they probably don’t exceed 600 mm. I also took a look at the structure of the internal floating roof; it’s made up of various pieces put together. I used to wonder just how large an entrance and exit the storage tank would need to have in order to install an internal floating roof The result is completely not.
Manholes with cores: In contrast to floating roof tanks, in conventional tanks the cylinder that connects the manhole to the tank wall runs through the tank wall itself; such manholes hinder the lifting and sealing of the floating roof. A core-manhole features an additional core plate inside the manhole cover, with a curvature equal to that of the tank wall, and it is level with the tank wall. To facilitate opening and closing, a rotating arm and lifting lugs are also installed on the hole cover in conjunction with the tank body, ensuring that the manhole cover remains attached to the oil tank during operation. Manholes for internal floating roof oil tanks are generally provided in at least 2 numbers: one is located about 700 mm above the tank bottom, and is used for cleaning the tank as well as allowing maintenance personnel to enter ； One is located about 2400 mm from the bottom of the oil tank, for operators to board the floating deck. Compared to floating roof tanks, the cylinder that connects the manhole of conventional tanks to the tank wall passes through the tank wall, and such manholes are not conducive to the lifting and sealing of the floating deck. A core-manhole features an additional core plate inside the manhole cover, with a curvature equal to that of the tank wall, and it is level with the tank wall. To facilitate opening and closing, a rotating arm and lifting lugs are also installed on the hole cover in conjunction with the tank body, ensuring that the manhole cover remains attached to the oil tank during operation. Manholes for internal floating roof oil tanks are generally provided in at least 2 numbers: one is located about 700 mm above the tank bottom, and is used for cleaning the tank as well as allowing maintenance personnel to enter ； One is located about 2400 mm from the bottom of the oil tank, for operators to board the floating deck.
Core-equipped manholes are also used in mixing equipment; at the location of the opening, an arc-shaped circular plate that matches the shape of the cylinder is installed (it is welded to the manhole cover using short cylinder sections, allowing it to be removed along with the manhole cover).
For floating roof tanks, a manhole with a core is essential; otherwise, the sealing effect will be lost for a short period of time when the tank is raised to the manhole position
Designing a manhole with a core usually involves one below the inner floating disk and one above it. The next one is for tank cleaning, the previous one is for checking the floating disc. That’s what the book says; the specific height is determined according to the design
This post was last edited by “Finding Direction While Walking” on August 11, 2018, at 16:19. First point: All openings on the floating deck are made in the skin; for internal floating decks, there are standard specifications set by manufacturers, and installation is usually carried out by the manufacturers themselves. Therefore, the anti-rotation devices, anti-static conductive ropes, manholes, and breathing holes are all drilled on-site by the installation personnel. The standards for second-type manholes can be found in the following specifications: HG/T 21514–21535-2014 for steel manholes and handholes, and HG 21594 for the classification and technical requirements of stainless steel manholes and handholes
Are there manhole openings on the inner floating disk? So is it still necessary to have a core-equipped manhole on the tank wall?
Tanks with internal floating disks generally have a manhole on each side of the floating disk, at the top and bottom.