Conventional sight glasses (DIN 7080, 7081, 8903) are sensitive to stress, bending and mechanical overloading; they might suddenly burst. If this occurs during installation, this results in little cost and inconvenience. If the glass cracks when a plant is fully operational, it may lead to major cost and safety faillures.
Metal fused sight glasses consist – in accordance with DIN 7079 standard – of a round sight glass sealed in a metal ring. The different thermal expansion coefficients of glass and metal result in a homogeneous state of compressive stress in the entire glass body. Therefore metal fused sight glass is a very tough material, based on the principle of “first leak before break”.
This glass is resistant to temperatures of (-60° C) -30° C to + 280° C (+ 300° C) depending on the materials.