Safety Glasses

Heat Soak Tested

Heat Soak Tested

Our company regulary do Heat Soak test to keep our glass production in the highest level of quality. The aim of this test is to control and reduce  the risk of spontaneous breakages of heat-treated glass caused by nickel sulfide (NiS) inclusions. A nickel sulfide inclusion is a rare imperfection that can occur if nickel-rich elements are present in the glass-manufacturing process. These elements, such as stainless steel, can combine with sulphur to form nickel sulfide inclusions. When glass is heat-treated to produce fully tempered glass, nickel sulfide inclusions change size from what is known as a low-temperature (LT) structure to a high-temperature (HT), crystalline structure. When cooled quickly, the NiS particle is unable to change completely back to its original form (LT). Over time, NiS may slowly convert to its (LT) form but with an increase in volume of about 2-4%. That increase in size can cause breakage. 

ALTEHS is cooperating with leading glass manufacturers which have taken action to reduce nickel sulfide contamination. 

Heat soak testing procedure requires that the glass is heated to a temperature as high as 320°C, and left for a time long enough to fracture a large proportion of the panes which may otherwise fracture in service. It is a process recommended for glass used in high risk areas where breakage may result in serious injury or is hard and costly to replace: sloping overhead canopies (inside pane only), bolt fixed structural glass assemblies and free standing balustrades. The risk is greatly reduced but due to the nature of glass it can never be completely eliminated.

In practise, NiS inclusions, which have caused breakage, have been measured with sizes between 0.04mm and 0.45mm in diameter. The size of inclusion will also affect the time needed to generate failure stress, since, in a larger inclusion.

Recommended for sloping overhead canopies (inside pane only), bolt fixed structural glass assemblies and free standing balustrades.

Specifications:

Standard: EN14179

Max size: 2200*4200mm

Min size: 100*250mm

Thickness: 4-19mm