The Temperatures Fuse Cap are mounted on the FOX nitrogen valve to discharge the accumulator from the gas inside it in the event of a fire. This TFC must be selected based on the maximum pre-charge pressure presenThe Temperatures Fuse Cap are mounted on the FOX nitrogen valve to discharge the accumulator from the gas inside it in the event of a fire. This TFC must be selected based on the maximum pre-charge pressure present inside the accumulator.t inside the accumulator.