The edges of all plates shall be prepared and surfaced by machining or chipping or flame cutting.

Before welding is commenced, the grooves shall be thoroughly cleaned of rust, oil or other foreign matter.

Before welding of the joint is commenced (apart from tack welding) it shall be ascertained that the chamfered edges are in alignment and that the defects in alignment between the surface of the plates do not exceed the limits indicated in the following table:-

_____________Alignment tolerance of Sections to be butt-welded.__________

Section                                           Direction of joints in cylindrical shells

Thickness, mm                          Longitudinal                                Circumferential_

Up to  13 mm incl.                         1/4 t                                              1/4 t                       

Over 13 mm up to 19 mm           3 mm                                            1/4 t

Over 19 mm and up to 38 mm          3 mm                                       5 mm

Over 38 mm and up to 51 mm          3 mm                                       3 mm

Over 51 mm                             Lesser of 1/16 t or 9mm       Lesser of 1/8 t or 19mm_

If plate edges of unequal thickness are abutted and the difference between the surfaces exceeds the limit mentioned as above on either side, the thicker plate shall be thinned to a smooth taper for a distance not less than 4 times the offset including, if so desired, the width of the weld. In longitudinal joints, the middle line of the plates shall be in alignment within 10 per cent, of the thickness of the thicker plate with a maximum of 3 mm (1/8 inch).

Each drum shell plate shall be of cylindrical form to the extreme edges of the plate.  The bending shall be done entirely by machine and local heating or hammering is prohibited.  Where the plates are bent to an internal diameter less than 20 times the plate thickness, they shall be efficiently heat-treated after bending to relieve internal stresses unless during the last stages of bending they have been uniformly heated throughout.

Provided the requisite quality of welding is achieved, the seams may be welded from both sides of the plate or from one side of the plate with or without a backing strip. If a backing strip is used, it shall be removed and the surface so exposed shall be dressed.

Additional runs of metal shall be deposited at the surface of the welded seams so that the welded metal at the level of the surfaces of the plate is refined as far as possible. The surfaces of the weld shall thereafter be machined or ground so as to provide smooth contours and to be flush with the respective surfaces of the plate. There shall be no undercutting at the junctions.

When affixing standpipes, branch pipes, seatings, compensating plates, doubling plates or manhole frames, not less than two runs of metal shall be deposited at each weld. Each run of weld shall be thoroughly cleaned and freed from slag that may adversely affect the quality of the succeeding runs. Welds shall be marked permanently to facilitate their location.

The longitudinal circumferential seams shall be made with butt joints of the single or double U or Vee type.