Fasteners - hdgasa

Gold MiningAlthough several bunton replacement methods were discussed the above idea proved to b the most cost effective.A further view of the accepted bunton replacement method.In order to facilitate the use of the already galvanized stock of buntonswhich were to be fixed to the new hot dip galvanized bunton brackets,welding had to be carried out and the damaged coating re-instatedbefore transporting and installing underground.bracket is installed the existingbunton would be cut off at the shaftwall and the new bunton would bebolted to the bracket. In some casesonly the corroded part of the buntonis replaced and fixed to the existingbunton by means of a bolted spliceplate.Moiling of the bunton cast in pocketsis a very tedious process and it takesthe maintenance crew one shift tomoil one bunton pocket. Once bothends have been moiled out, the newbunton has to be properly alignedbefore it is grouted in position. Dueto the big opening, shuttering for theconcrete has to be put in place andonce the concrete is set, theshuttering has to be removed.The other method of drilling is also along and sometimes dangerousmethod of replacing buntons. Due toshaft space constraints drilling isoften a difficult process andclearance from high voltage cablesneeds to be provided to ensuresafety of maintenance personnel.The design of a much bigger buntonbracket is therefore required to clearthe cables.Description of new buntonbracket designThe new design is a much faster andefficient way of replacing buntons.The new design makes use of theremainder of hollow section buntonwhich is left in the shaft sidewallwhen the old bunton is cut off. Thenew bracket is designed in such away that it fits into the hollow partof the old bunton. When the newbunton is placed in position, noalignment is necessary as the systemis self aligning. Moreover no bulkyshuttering is required as well as theamount of grout required is muchless than the previous method. Anon shrink pourable grout is thenpoured into a slot provided in thenew bracket to fill all the cavitiesbetween the bunton bracket and thehollow section of the bunton in theshaft lining. AngloGold Ashanti’sCivil Engineering department wasconsulted to ensure that the groutused in the design conforms toAngloGold Ashanti specificationsand quality criteria. This method ofreplacing buntons has led to anefficiency improvement of 300%.Specialised input from theGalvanizers Association was soughtto assist the Engineering DesignServices Department with thecorrosion protection of the on site12 Hot Dip Galvanizing Today Volume 3 Issue 4 2006