Dome Roof with Internal Floating Roof October 23, 2009 by ferrysibarani
Pictures below are sequential procedure of tank erection in one of my project. This project titled Installation and Erection of Knock Down Tank in Brunei Methanol Project, Negara Brunei Darussalam. Project owner is Brunei Methanol Company Sdn. Bhd., with Mitsubishi Heavy Industries Ltd. as Main Contractor and PT. Rekayasa Industri is the Sub-Contractor. Consortium of PT. Bangun Bejana Baja and Adinin Works and Engineering is the manufacturer of 15 units Knock Down in this project. One of the biggest tank that built in the project is Product Methanol Tank with type Dome Roof with Internal Floating Roof, shell size 63 metres inside diameter and 18 metres height, dome roof radius is 50.4 metres, and internal floating roof diameter is 62.6 metres. Tank construction was done from September 2008 to October 2009.
Bottom plate consist of annular, rectangular, and sketches plate. The annular plate is the outer plate which on top of it the shell plate will be installed. Butt joint type welding connection used for annular to annular plate, and shall be 50% radiographic test. Rectangular and sketches plate was welded using fillet weld and all joint shall be
100% vacuum box tested.
Fit-up of bottom plate usually using temporary welding to plate using nut and u-bar, then bullpen used to make the overlap plate flat to each other.
After plate fit-up finished, the work continue with fillet welding. Welder classification for this welding is welder 1G.
The first installation of shell plate. Rigging using 2 automatic clamps (vertical clamp) with spreader bar.
Nozzle connection installation to shell plate. After welding completed, the welding shall be Post Weld Heat Treatment (PWHT).
Finished installation shell course #1 and #2 completed with vertical weld butt-joint.
Horizontal weld between shell course #1 and #2 and so on will be done by Automatic Girth Welding (AGW) Machine.
Dome roof ground assembly. Install the rafter and continue with roof plate welding. There are 24 block of roof will be assembly, 12 of them will be ground assembly and block in between section will install inside tank.
Some part of shell plate #1 and #2 was removed as entry access for crane and material, it is call door sheet.
Centre column support installation. This part will support the centre rafter of the dome roof which is the part that all roof block will be connected into.
Finish assembly of centre support and installation centre rafter on the top.
First installation of dome roof block. Roof block lifted by 300 Ton Crane.
Adjusted lower part of the roof block into the outer support.
Adjusted upper part of the roof block into the centre rafter.
Finished installation of the first 4 numbers of roof block (beautiful, isn’t it). It is important to keep the balance between installations section by section.
Overtime work for catch-up schedule, but only welding work without any rigging or fit-up.
In between roof block assembly. Manlift basket used to install and weld rafter. Rafters erected by crane from outside tank.
Roof plate installation in between roof block. The first 3 section roof plate were install from inside tank before finished rafter in between block. The 4th and 5th roof plate installed from outside tank.
Last shell course (#8) installation with tension bar. Last shell course and tension bars were assembled on workshop to decrease welding work on height.
Installation of roof plate in between block was remaining in the door sheet area. This part welded the last due to entry access for crane only available through door sheet.
Finished dome roof assembly viewed from inside tank. Dome roof now ready to be lifted up to the tension bar by air raising method.
The roof will float due to air pressure inside tank increased by blower through shell nozzle.
This picture showing the completion of air raising process of dome roof, and dome roof completely fixed to the tension bar.
Single deck internal floating roof assembly on process. This floating roof consists of general part and pontoon compartment. Floating roof supported by permanent pipe support with height approximately 2 metres. During construction the floating roof temporary supported then will be raised up by water to the correct elevation.
Pontoon compartments work as the buoy of the floating roof. These compartments shall be fully tested by oil leak test to ensure 100% leak proof.
Floating roof assembly finished and ready to be raised up. Next preparation will be closing all the shell manhole and nozzles and fill up the tank with water.
Water raising finished and the floating roof already setup on the permanent pipe support, locked with stud bolt.
Accessories of tank such as roof periphery platform, spiral and roof stairway, piping for fire fighting, etc. continue assembled prior to hydrostatic test.
Hydrostatic test was to fill the tank with water to the design pressure to ensure there is no leaking in the tank as well as to check the stability of the tank foundation. After all inspection finished, the water inside tank discharged.
Touch-up primer coat for welding area to be finished prior to applying final coat.
The tank installation finished. Awesome, isn’t it? Well, that’s it! I hope all of the reader enjoyed to read it
