24,517 children underwent ultrasonic examination during the 13-year period.

In order to confirm the suitability of the welding technology and to prepare test blocks for ultrasonic examination, test coupons of 100 mm in length were welded separately for each weld type.

For manual-arc welding electrodes, SFA-5.5 E9018-G with diameters of 3.25 mm and 4 mm were used. For submerged-arc welding an agglomerated basic flux UV 420 TTR was used in combination with a wire UNION S3NiMo1, EF3 according to SFA A 5.23 with a diameter of 4 mm, produced by Thyssen, was used.Welding was followed by the control required, i.e. visual inspection, radiographic examination, magnetic particle examination, ultrasonic examination, and weld grinding.

Where a hose test is not practicable because of possible damage to machinery, electrical equipment insulation or out fitting items, it may be replaced by a careful visual examination of welded connections, supported where deemed necessary by means such as a dye penetrant test or ultrasonic leak test or an equivalent test.