G4Z / G4EZ / MG4Z / G4EZB Fire Safe Plug Valves
In the event of a fire on site the fluoropolymer stem seals used on the majority of ball, plug and butterfly valves are very susceptible to damage allowing the process fluid to leak past the seals into the atmosphere. To help counteract this Durco have developed multiple metallic secondary seals for the G4 range of plug valves.
All the Durco G4, G4E and Mach 1 series plug valves can be supplied with special grafoil packing, stainless steel or monel secondary diaphragms and additional grafoil stem seal gasket. The valves have been subjected to the vigorous type approval tests to API 607 fourth edition, they surpasses the external sealing requirements of section 4 paragraph 4.2. Under normal use the valve uses the same PTFE sleeve as its primary seal, backed up with the live loaded PFA diaphragm as on standard G4 plug valves, in the ev 
ent of a fire as these seals decompose the grafoil and metal diaphragm reduce any atmospheric leakage to a minimum. The plug is supplied with a drilled vent hole in the side to prevent pressure build up within the plug bore safely venting to the upstream pipe line in the case of a fire where the elevated temperatures could cause significant expansion of the media.