Compensating plates shall be of mild steel and, before attachment, shall be closely to the plates to which they are to be connected. Any welds therein shall be on the transverse centre line.

The terms ‘fusion weld’ is, for the purpose of this chapter applicable to all welded seams made by the metal arc process with covered electrodes or by any other electric arc process in which the arc steam and the deposited weld metal are shielded from atmospheric contamination.

The relevant provisions of this Chapter shall also apply to the single run or heavy run welding process and that welded boilers manufactured by that process shall comply with all regulations of this Chapter excepting those in which divergence is necessary solely because of special requirements essential for the most efficient utilisation of that process. Thus all regulations governing quality of material construction, workmanship, and testing (both non-destructive and otherwise) are applicable.

Where welded shells conforming to the regulations of this Chapter are made by single or heavy run process it shall be understood that regulation 557, 558 and 559 do not apply in their entirety. The method of making the welds shall be approved by the Inspecting Authority.

Provided the requisite quality of welding is achieved the seams may be welded from both sides of the plates or from one side of the plate. Before the second side of the plate is welded, the weld metal at the bottom of the first side shall be removed by grinding, chipping, machining or other approved method.

Additional runs of metal shall be deposited at both surfaces of the welded seams to ensure that the weld metal at the level of the surface of the plate is refined as far as possible. The surfaces of the weld which are to be subsequently radiographed shall thereafter be machined or ground so as to provide smooth contours and to be flush with the respective surfaces of the plate. In the case of circumferential shell seams welded by submerged arc or any other approved automatic process producing a similar surface finish, such circumferential welds, need not be flush dressed, subject to their surface finish and shape being acceptable to the Inspecting Authority. There shall be no under-cutting of the junctions.

The positions of the welds shall be marked permanently to facilitate their location.

When affixing standpipes, branchpipes, seatings, compensation plates, doubling plates or manhole frames, not less than two runs of metal shall be deposited at each weld.

Each run of weld metal shall be thoroughly cleaned and freed from slag before the next run is deposited.