The Flowserve Valtek Mark Six is a globe-style, single-seat, top-entry automatic control valve with a fabricated extension for cold box cryogenic applications to -425°F /-218°C.

Mark Six bodies are constructed of bronze or austenitic stainless steel for high impact strength at low temperature and minimum heat transfer. Mark Six is designed for high flow capacity with a minimum of mass to reduce boil-off on valve cool-down.

The Mark Six extension design permits easy access and removal of the valve trim without breaking down the cold box. During operation, a small amount of liquefied gas passes into the extension bonnet area where it vaporizes and insulates the packing from the liquefied gas temperature. The pressure resulting from the vaporization of the liquid prevents additional liquid from passing into the bonnet area.

The Mark Six is equipped with a standard, high-performance Valtek cylinder actuator, providing high thrust for tight shutoff and exceptionally accurate control.

Mark Six Low Flow is designed with the same features as the Mark Six, but is designed for low flow applications.

Mark Six is now available with CavStream trim. CavStream is used in moderatly cavitating services to control cavitation damage.


  • Temperatures down to -425F (-218C)
  • Top Entry, Without Removing Insulation
  • Low Mass Construction
  • Vapor Barrier to Keep High Packing Temperatures