Firing pattern UNIDET 4 - Top and bottom initation
U 500 detonators are used both in top and bottom of the hole. The top detonator is delayed in relation to the bottom detonator by connecting it to a connecting block in the next row. In this case the top detonator is delayed 67 ms in relation to the bottom detonator. This is to avoid top initiation as far as possible. To distinguish which detonator is in the top and which is in the bottom, the top detonator has yellow tube and the bottom detonator red tube. The firing pattern is suitable when the rock is fissured and when bulk explosives are used. Risk of overlapping: An unlimited number of rows and holes in the rows may be connected without exceeding the demands stated in Swedish Standard for overlapping.