The valve body and the valve cover are sealed with o-ring and gasket seals. When the fire occurs, the o-ring burns out and the graphite wound gasket is kept sealed. The valve stem is sealed in o-ring + graphite packing. When the fire occurs, the o-ring burns out and the graphite packing is sealed to ensure that the shell is not leaking.
In case of fire, all nonmetallic seals are burnt out, seat support ring in contact with ball, realizes the seat and ball metal to metal seal, seat back and body seal is O ring + packing seal, When a fire occurs, the O-ring burns out and fails, but the braided graphite remains sealed, effectively ensuring that the medium will not leak in large quantities.