10. Vessels must be constructed and checked in accordance with the design and manufacturing schedule referred to in Schedule 3.
11. The preparation of the component parts (eg forming and chamfering) must not give rise to surface defects, cracks or changes in the mechanical properties of those parts likely to be detrimental to the safety of the vessels.
12. The characteristics of welds and adjacent zones must be similar to those of the welded materials and must be free of any surface or internal defects detrimental to the safety of the vessels.Welds must be made by appropriately qualified welders or operators in accordance with approved welding techniques. “Qualified” means qualified by means of tests carried out by an approved body; and “approved” means approved by such a body.The manufacturer must also, during manufacture, ensure consistent weld quality by conducting appropriate tests using adequate procedures. These tests must be the subject of a written report.