Minimising risk Rob Judd, our Group Managing Director explains why we are leading the way and minimising risk by recommending heat soaked toughened glass in lieu of toughened glass. The potential for even toughened glass to break can’t be ignored as the potential for someone getting hurt is a risk that’s too painful to contemplate. Why does toughened glass break? There are many reasons why a toughened piece of glass might break including impact damage, damage to the edge of the sheet, poor installation or design and inclusions in the glass. These inclusions particularly nickel sulphide (NIS) are what create the most concern as they appear to be “spontaneous” breakages with no cause. Is nickel sulphide to blame? Nickel sulphide crystals have a high temperature and a low temperature form. The dense crystal formed at high temperature swells on cooling to make a less dense crystal form at low temperatures. In ordinary annealed glass nickel sulphide inclusions do not cause problems because the transformation occurs as the glass is cooled slowly during manufacture. However, the transformation is sluggish and when glass is rapidly cooled as part of the toughening process, the nickel sulphide remains trapped in its high temperature form. Therefore breakage can occur without any load being applied to the glass, at any time, even five or ten years after the glass has been tempered as the nickel sulphide transforms back to its more stable state. What does heat soaking do? The heat soaking process puts the glass through a heat cycle to encourage the glass to break under test if it is at risk of inclusions. The result is a pane with a much lower risk of fracture than ‘ordinary’ thermally toughened glass. Heat soaking significantly reduces the risk of spontaneous breakage ‘in situ’ of thermally toughened safety glass, and is estimated to eliminate up to 98% of toughened glass panels from production that have potential for spontaneous breakages. Why specify only heat soaked toughened glass? Toughened glass is commonly specified in the partitioning industry for its various benefits that include increased strength and improved safety performance. However as spontaneous failure of toughened glass can sometimes occur, We have taken the bold stand to offer heat soaked toughened glass in these situations. When it comes to specifying glass partitions, a ‘safety first’ approach must be a prerequisite because whatever the risk, it is surely not worth taking.
