Peaking is when the Vertical shell weld or weld joint is not properly fit up and it makes a peak at the joint. Sometimes this is caused because the shell plate was not properly rolled. The radius of the tank in that area will not be correct. It is checked by cutting a 1 meter okay 900mm long board to the outside radius of the tank, holding the board against the weld, and measuring the distance between the board and the tank shell. If the weld or joint holds the board more than 13mm 1/2 away from the shell, then the joint has too much peaking.
Banding is when a Horizontal weld or joint between two shell courses is not properly fit-up or made. Usually caused by a bad fit-up or bad welding. The tank shell will not be acceptably vertical in that area. It is checked by taking a straight edge, either a 1 meter board or a standard 1 meter 3 foot construction level and holding it vertically against the shell and measuring the distance between the edge and the tank shell. If the weld or joint holds the board more than 13mm 1/2 away from the shell, then the joint has too much banding.