African Fusion March 2015

station until a green sticker is applied,” he adds. A plate with a green sticker then proceeds to rolling: “Rolling is our critical operation as it relies heavily on the skill of the operator. We currently have two roller operators rolling five to six cans per shift, but we are operating our growing lines on a pull-based production system, so the rolling ratemust match the speed of the of the whole line. We are looking for at least two more plate rollers so that we can implement a second shift,” Jauka reveals. To avoid double handling, the can roller operator inserts some initial tacks as soon as the required shape has been established. Then a welder immediately inserts a root run along the seam using the solid wire GMAW process. The can is then moved across to a submerged arc welding station. The outside seam is completed from the top. Then the can is rotated by 180 ° and the remaining welding is done fromthe insideat a lower level. Immediately after welding, the can is then re-rolled to correct any distortion that may have been introduced. “The crane operator then takes this can and places it onto an orange block painted on the floor. “As soon as a qual- ity inspector sees a can on an orange block, he does a visual inspection of the welding and weld-bead profiles. Then an ultrasonic (UT) inspection is done on the seam – and this must pass. If any flaw is detected, the inspector marks it up and the can will be moved aside to a separate repair station. Once repaired, both magnetic particle (MT) and UT are repeated until that can passes all tests. “Once cleared by the inspector, the can is moved onto the next available greenblock. These greenblocks are used to feed the growing line. Completed cans are moved up towards Green Block 1, which is the placeholder for the next can required for the sectionbeing fabricated. Our production target is tohave two cans in the correct sequence ready to feed the growing line at all times,” Jauka explains, adding that, froma production perspec- tive, “the idea is that a green block is filled as soon as it become empty”. In this way, the rate that cans are joined to the tower sections will be matched to the rate that cans are being produced. On the growing line, ESAB roller beds with built in manipulators are used to support the growing section and the can to be added. A set of hydraulically driven transfer rollers lift the can clear of the

Rolling is the critical operation as it relies heavily on the skill of the operator. DCD Wind Towers currently has two roller operators rolling five to six cans per shift.

Following rolling, the outside seam is completed from the top. Then the can is rotated by 180° and the remaining welding is done from the inside at a lower level.

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March 2015

AFRICAN FUSION