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The Mark 708 with bellows stem seals that eliminate fugitive emissions by surrounding the valve stem with a pressure-tight barrier, isolating the stem from the process fluid and preventing leakage to the atmosphere.
Mark 708DP Series – The Mark 708 with double packing is an alternative to a bellows stem seal and is used when standard packing will not adequately contain the controlled media. The optional bonnet features a double packing arrangement separated by a lantern ring. With a double packed bonnet, lubricant is pumped into the packing sets, supplying a tight seal similar to that provided by a bellows stem seal. The double packed bonnet is an excellent choice when service conditions could cause damage to a bellows assembly.
The 8000 Series the bellow stem seals eliminates fugitive emissions by surrounding the valve with a pressure-tight barrier, isolating the stem from the process fluid and preventing leakage to the atmosphere. For an extra measure of protection, the bellows stem seal option provides a back-up seal of Teflon, braided or Graphite/Grafoil packing.