Peaking and banding refer to the roundness and straightness of shell plates around vertical and horizontal joints in storage tanks. Peaking is measured using a horizontal sweep board along vertical joints, while banding is measured using a vertical sweep board along horizontal joints. Acceptance criteria per API standards allow for peaking deviations of up to 13 mm and banding deviations of up to 13 or 25 mm depending on the standard. Proper measurement procedures involve visually inspecting the tank, positioning the sweep board accurately, and taking measurements at a minimum of 8 locations around the tank circumference.

2. PEAKING
• The peaking is the adjustment and checking for the roundness and the curvature of the shell plates around the
vertical joints.
• Peaking as an inspection point of view we check before & after the welding of Vertical joint to find the extend of
distortion happened after welding. It has a tolerance of +/- mm
• It is mainly initiated by material rolling and/or welding stresses during new construction. Occasionally it can get
worse in service.
Peaking Measurement
The peaking of each tank shell shall be measured by a horizontal sweep board made of either solid wood/plywood or
may be made of any metal sheet; however the sweep board shall be stiff enough so that it will not bend or sag
otherwise the results will be erroneous.
The sweep board shall be true to the radius of the tank, either inside radius or outside radius. For measuring from

3. inside the tank, the sweep board shall be convex shaped in one side and straight on the other side. For measuring
from outside the tank, the sweep board shall be concave shaped in one side and straight on the other side. The length
of the sweep board shall be 36 inches (915mm) minimum. See sketch below:

4. BANDING
• Banding is the adjustment and checking the straightness and verticality for the shell plates around horizontal
joint (between shell courses) and it is also done before and after welding .
• Banding as an inspection point of view we check after the welding of Banding joint to find the extend of
distortion happened after welding. It has a tolerance of +/- mm
• It is less common and almost always the result of construction (or repair/alteration/reconstruction)
inaccuracies.
Banding Measurement
The banding of each tank shell shall be measured by a vertical sweep board made of either solid wood/plywood or
may be made of any metal sheet; however the sweep board shall be stiff enough so that it will not bend or buckle
otherwise the results will be erroneous.
The sweep board shall be truly straight. Measurements can be taken either from inside or from outside of the tank.
The length of the sweep board shall be 36 inches (915mm) minimum.

5. Procedure for Peaking survey:
• Visually inspect the tank circumference either from inside or from outside for any visible signs of deformation.
A high-power search light may be used and held parallel to the surface with the torch touching the surface may aid
in finding the deformations easily from inside the tank.
• Mark the geographical direction (north/ south etc.) or mark location in degrees to identify each measured location.
• Put the horizontal sweep board truly horizontal on the inside or outside surface as applicable on the tank shell
course. Check the gap between the sweep board and the tank shell and note down the value if there is
considerable gap (beyond inches or 13mm). For a more accurate positioning of the sweep board, slide the board
horizontally to fit it properly to the tank shell. A torch light & scale/measuring tape may be used to assess the gap
between the sweep board and the tank shell.
• The peaking shall preferably be measured on the vertical welds of the tank shells; however it can be measured on
any portions of the tank shell if there are visible signs of deformation.
• Minimum number of locations is not specified in the applicable codes/standards however as a good practice it
shall be 8 nos.

6. Procedure for Banding survey:
• Visually inspect the tank circumference either from inside or from outside for any visible signs of deformation. A high-
power search light may be used and held parallel to the surface with the torch touching the surface may aid in finding
the deformations easily from inside the tank.
• Mark the geographical direction (north/ south etc.) or mark location in degrees to identify each measured location.
• Put the vertical sweep board truly vertical on the inside or outside surface as applicable on the tank shell course.
Check the gap between the sweep board and the tank shell and note down the value if there is considerable gap
(beyond 1 inch or 25.4mm). For a more accurate positioning of the sweep board, slide the board vertically to fit it
properly to the tank shell. A torch light & scale/measuring tape may be used to assess the gap between the sweep
board and the tank shell.
• The banding shall preferably be measured on the horizontal/circumferential welds of the tank shells; however it can
be measured on any portions of the tank shell if there are visible signs of deformation.
• Minimum number of locations is not specified in the applicable codes/standards however as a good practice it shall
be 8 nos.

7. ACCEPTANCE CRITERIA AS PER API 650
• Deviations (Peaking) at vertical weld joints shall not exceed 13 mm (1/2 in.).
• Deviations (Banding) at horizontal weld joints shall not exceed 13 mm (1/2 in.)
ACCEPTANCE CRITERIA AS PER API 653
• Deviations (Peaking) at vertical weld joints shall not exceed 13 mm (1/2 in.).
• Deviations (Banding) at horizontal weld joints shall not exceed 25 mm (1 in.)