There are two methods for large storage tank construction, the traditional method and the jacking method. The traditional method refers to the bottom of storage tank as the reference plane, the tank wall will be installed one by one from the first section of tank bottom to the top.
The traditional method features for storage tank construction
- The project scale of traditional method is often large, also the structure is complex, when choose the traditional method for the storage tank construction method, it requires full consideration on the sequence of the tank body and the floating plate, as well as the other lap-joint sequence of tank process.
- All of the tank walls welding adopt automatic welding, so that it has the advantages of high quality of welding seam, fast welding speed, smaller welding deformation, and low labor strength.
- As for steel plate pre-process of tank wall, using a CNC plate rolling machine can guarantee the arc degree of the tank wall.
- The application of suspension platform can greatly reduce the use of scaffolding.
Pre-process of tank wall
Typesetting: typeset of tank wall must be in accordance with the design drawing, standard requirement, and material specifications.
Lofting: Chord length of arc template can not be less than 2m; chord length of linear template can not be less than 1m; the template had better be made of the thick steel plate with thickness raging from 0.5mm to 0.7mm, and use a flat iron or wood board to reinforce.
Cutting: the surface of steel should be cleaned before cutting, the slag and spatter should be removed after cutting.
Beveling: the beveling process of steel plate should adopt a angle grinder.
Bottom plate laying
Sequence of bottom plate laying: Ⅰ→Ⅱ→Ⅲ→Ⅳ→Ⅴ
Sequence of each row of plate: ①→②→③→④→⑤→⑥→⑦→⑧ or 1→2→3→4→5→6→7→8.
Welding of bottom plate
Generally, the transverse joints are first, then the long joints, the tap-joint seam of central plate and sideboard should be left without welding, in order to shrink welding seam after the large circle of storage tank is sealed. Finally, do the nondestructive examination (NDE).
Storage tank construction sequence with the tradition method
Assemble sequence of the storage tank assemble the first section of the wall——spot welding for temporary support——welding——Install circle seam clamp——coaming——welding
Assemble of the first section of wall plate:
The assemble of tank is docking style, find out the central point on the laid bottom plate, draw the circle line of the tank wall, weld a temporary a baffle along the circumference at intervals of 50m. Set a bearing plate between the baffle and tank wall when assemble the tank wall, each tank wall is supported by adjustable oblique frame.
Through the support of adjustable oblique frame, the verticality, levelness, and misalignment degree of the first ring wall can be adjusted. After the tank wall is welded, the verticality should be ad adjusted secondly.
Assemble of the second section of wall plate
Adopt the method of suspending a scaffold inside the storage tank, construction is mainly carried out on the platform. Before lifting the second section of the wall, mark the position and number of the second section on the first section of the wall, according to the determined starting point hanging board, each board should be sited in the right place.
Assemble of more than the second section of wall plate
The method is similar to assemble of the second section of wall plate. Through the erection of second layers of operation platform, increase the staircase height to group the seam.
The assemble of floating roof
Assemble the floating roof after the first and second section of tank wall is assembled. The construction sequence of floating roof is:
Install the temporary support——single disc of floating roof——bottom plate of floating roof——Intermediate ring plate、external edge plate——baffle plate——floating roof frame、truss——welding from the center to the surrounding——top plate of the floating roof——support pipe、accessories.
Installation of other accessories
In accordance with the relevant technical requirements to install the floating ladders, track, sealing device, and other accessories.
Clean the storage tank and hand over the completed project:
After construct all of the accessories, inject water and observation the foundation settlement. After passing, discharge water、clean the storage tank、and hand over the completed project.