The SBI apparatus contains two identical sandbox burners, one in the bottom plate of the trolley, one fixed to a post of the frame, with the following specifications: ... - box made of 1,5 mm steel (stainless), filled with a 60 mm bottom layer of gravel (size 4 to 8 mm) and a 20 mm top layer of 'sand` (2 to 4 mm); metal gauzes shall stabilise the two layers and prevent the gravel from entering the gas pipe socket; thickness of layers ± 2 mm, ...
