Monday, January 07, 2013

Surveyor Guide Notes for Weld Inspection and Repair.

Inspections are made during and after the manufacturing cycle to ensure that parts meet specifications. Types of inspection include nondestructive examination (NDE), in which no portion of the completed weld is destroyed, and destructive tests, in which the weld is destroyed.

Weld integrity inspections may also be required in addition to the nondestructive test requirements to verify the weld quality. NDE includes visual tests, penetrant tests, magnetic particle tests, ultrasonic tests, and radiographic tests. Destructive tests include bend tests, tensile tests, notch-toughness tests, cross section tests, and nick-break tests. Weld integrity inspections include pressure tests, hardness tests, corrosion tests, and ferrite tests.

Fillet welds size and crown gauge.

Intended weld repairs must be evaluated as to whether the discontinuity should be removed.
Repairing a completed weld could cause buckling, distortion, or misalignment of the reworked area.
In some cases, a discontinuity can be left in a weld without affecting the weld’s function.

Repairs can be made to correct dimensional problems, surface defects, and internal defects.
Common surface defects include longitudinal, transverse, or crater cracks; undercut at the edges of the weld; porosity; cold laps; and incomplete penetration. Internal defects are generally found by radiographic and ultrasonic testing.

Stringer beads should be used for welding repairs in order to minimize shrinkage of the joint.

This adjustable fillet and crown gauge is being used to check the height of the weld bead.
If the weld repair is deep, an X-ray should be made after two or three completed passes to confirm that the original crack has been fully repaired and new cracks have not formed. Where the grain size must be controlled throughout the repair, temper beads should be used to reduce the surface grain size.
All nondestructive testing required for final acceptance of the weld must be completed after the weld repair is done. Repairs can cause new problems in a weld.

Weld Inspection and Repair.

IACS Materials and Welding:

IACS Non-destructive testing of ship hull steel welds:

IACS Guidelines on welding procedure qualification tests of aluminium alloys for hull construction and marine structures: