ARNWAY CASE STUDY

CEMENT KILN TYRE - IRISH CEMENT PLATIN WORKS.

This repair was carried out with the minimum of notice. Within 6 hours of the initial telephone call there were 6 welders, 2 vehicles and 4 tonnes of equipment assembled at Holyhead docks waiting for the ferry. As the job progressed, the number of welders increased to 10, working 5 days and 5 nights, with 12 hour shifts.  The same manning regime was applied, that is to have 1 more man than welding arcs per shift, to allow for breaks and keep welding more or less continuous.

The defects consisted of 2 cracks spaced some 1.5M apart in a tyre 1500mm x 610mm section, weighing 130 tonnes. The initial meeting with Jorgen Holteman from FL Smidth indicated 900 kg of weld metal, and his estimate was for 28 days and nights continuous welding, plus time to cut out and grind after welding. The weld preparations amounted to some 1200mm long x 450 deep, with side wall defects aggravating matters of clearing the preparation for welding. The gouging was completed in 2 days for the first defect, so preheat could be installed and welding commenced. The second defect followed in similar time. There were sub-surface defects found between the two main cracks which were attended to after completion of the main welds.

The entire operation took 17 days, including gouging and grinding, saving in excess of 11 days from an FL Smidth estimate. In fact a total of 920kg of electrodes were used, making Jorgen’s original estimate of weight extremely accurate.

The emphasis throughout the repair was of adherence to procedure, economy of weld preparation and application of welders. The welders eventually totalled 5 on days and 5 on nights, using 4 arcs. The weight of consumables used over just one weekend was nearly 180kg. A significant factor in the speed and reliability of the repair was the use of the company’s in-house electric preheat system, which is extremely quick to set up and accurate in control. All the usual worries about loss of preheat if welding stopped for a short time were eliminated, and chart recording was possible for quality control.