We already discuss about Section 1: Scopes and Section 4: Materials on the previous sharing. So please click this LINK to read.
Before we continue, lets familiarize with the design below:
VERTICAL SHELL JOINTS
- Verticals hall be butts joints with complete penetration and fusion that will provide the same quality of deposited metal on both outside and inside weld surfaces.
- Vertical joints (in adjacent shell courses) shall not be in alignment. An offset from each other of “5t” (where ‘t’ is the thickest course at the point of offset.
HORIZONTAL SHELL JOINTS
- Same criteria as for verticals above except that top angles may be double lap welded.
LAP-WELDED BOTTOM JOINTS
- Three plate laps shall not be closer than 300 mm (12″) from each other, the tank shell, butt welded annular plate joints and from joints between annular plate bottom.
- Welded on topside only.
- on other than annular plates under the shell must have the outer end of the joint fitted and welded to form a smooth bearing for the shell plate. Note: Called a ‘Break-over’ or ‘Joggle Joint’.
- Note: When annular plates are used or required, butt welding is required with a minimum distance of 60 mm (2 in) between shell and any bottom lap seam.
BUTT WELD BOTTOM JOINTS (LIE NORMALLY ON THE ANNULAR RING)
- Parallel edges – either square or V groove beveled.
- If square, root opening not less than 6 mm (1/4″).
- Minimum 3 mm (1/8″) thick back-up strip required.
- A 300 mm (12″ n) minimum space from each other or tank shell also applies.
ANNULAR RING JOINTS
- Complete penetration and fusion.
- A 50 mm (2″) minimum projection beyond outside edge of shell (ie edge projection. See paragraph 5.4.2).
SHELL-TO-BOTTOM FILLET WELDS
- If shell is 12.5 mm (1/2″) thickness or less – fillets not more than 12.5 mm (1/2″) or less than the nominal ‘t’ of the thinner plate joined.
- Two (2) weld passes minimum are required.
ROOF AND TOP ANGLE JOINTS
- Welded top side only with continuous full-fillet (butt welds are also permitted).
- Top angle shall be attached with continuous fillet weld on the top side only.
BOTTOM PLATES
- A minimum nominal ‘t’ of 6 mm (1/4″) [14.8 kg / m2 (10.2 lbf/ft2)] exclusive of any corrosion allowance (CA).
- At least a 50 mm (2″) minimum width to project beyond outside edge of shell, on lap weld bottoms (ie edge projection).
ANNULAR BOTTOM PLATES
- 50 mm (2″) minimum width to project beyond outside edge of shell, on annular ring bottom (ie bottom extension).
To be continued….
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