Anti-overflow Flame Trap Breather Valves for tanker semitrailers Anti-overflow Flame Trap Breather Valves for tanker semitrailersItem No.: HYGVL10371. Used to reequip the old type tank car. 2. It conbines the functions of anti-flow, breather, flam arrester vents for manholes. Anti-overflow Flame Trap Breather Valves for tanker semitrailers