Welding Inspection and TestingAn external inspection of all weld surfaces shall be carried out by the sub-contractor. Where welds are to be water retaining (vessel and/or pipework fabrication) the surface of all welds shall be inspected visually and then tested by either Dye Penetrant or Magnetic Particle Inspection, to detect surface breaking indications such as cracks and porosity.The results of any NDT failure shall be fully rectified by the most suitable method. Where there is any doubt concerning the suitability of rectification then the Company must be consulted.Acceptance levels for visual, Magnetic Particle and Dye Penetrant testing will be as follows:a)Weld reinforcement / profile of external surface:Weld metal shall be properly fused with the parent plate. Any intermittent undercutting must not exceed those levels given in h) below. Overlapping at the toes is to be avoided as the weld must blend smoothly with the parent plate. The weld must be substantially symmetrical about the centre line of the joint, being in all cases of smooth contour. The stoop / starts shall merge and shall show now pronounced hump or crater in the weld surface.b) Cracks or fissures: Not permitted.c) Lack of fusion: Not permitted.d) Lack of penetration: Not permitted.e) Surface breaking indications: Not permitted.f) Including porosity: Not permitted.g) Arc strikes / tool marks: Not permitted.h) Undercut: Intermittent and not greater than 10% of wall thickness.i) Excessive dressing: Not permitted.j) Excess penetration: 3 mm maximum. As an overall guide to the quality of welding selected welds may be subjected to an internal inspection of weld volume using Radiography and/or Ultrasonics. When required this form of inspection shall be carried out by a specialist contractor, nominated by the Company, and carried out at a regular period to be specified by the Company. The inspection contractor will select a random 200 mm to 300 mm length of butt weld to be tested in-situ. The records of each test shall be retained by the Company with a copy being issued to the fabricator for informationWhere internal inspection of welds is carried out the Acceptance Levels for Radiography and Ultrasonics shall be as described previously and, in addition, for internal defects the following guideline limitations shall apply:a) Isolated pores: t/3 ie. not greater than wall thickness. b) Uniformly distributed or localised porosity: 10% by area provided that individual pores do not exceed t/4 and individual pores in a group are separated by at least 3 times the distance of the larger pore. c) Linear porosity: Not permitted. Defect associated with lack of fusion. d) Wormholes, isolated: Maximum length 2t. Maximum width t4. e) Wormholes, aligned: As linear porosity. See c). f) Individual slag inclusions: As isolated wormholes. Individual inclusions along the major axis must be separated by at the least the length of the longer inclusion. The sum of the inclusions shall not exceed the total weld length being examined.