Abstract: Device for prevention against explosion of an on load tap changer on an electrical transformer, the on load tap changer including a tank and a cover, the tank including a cooling liquid. The prevention device includes a rupture element provided with tearing zones and with folding zones upon rupture, said rupture element being able to break open when the pressure inside the tank exceeds a predetermined ceiling, at least a support member supporting the rupture element, said support member supporting a duct downstream the rupture element, the support element being distinct from the cover.