Knife-gate valves for the biomass industry

Many organic materials are suitable as raw material for biogas, e.g. sludge from sewage treatment plants, food waste, manure, different growing materials from the agricultural industry, and waste from the pulp & paper industry. There are many variations and the process equipment has to meet high standards. Stafsjö’s product range consist of 16 different models of which WB and MV Knife gate vales are particularly suited for biomass.

Valve type WB for Biomass:

  • This knife gate valve can be installed into a pipe system independent of pressure direction, and integrated flange gaskets makes installation simple. WB has a full bore with no cavity which gives excellent flow characteristics.
  • The valve is modular designed consisting of an epoxy coated one or two piece valve body in cast iron or nodular iron. It is equipped with a gate in stainless steel and has a sealing profile in either EPDM or Nitril.
  • WB is as standard equipped with Stafsjö’s unique box packing, TwinPack™, which gives a tight sealing where the gate exits the valve body and assures that no media reaches surrounding environment.
  • The gland box can also be supplied with a box-bottom scraper that prolongs the box packing braids’ life-length. The valve can easily be equipped with different types of actuators and accessories.
  • WB is available with several flange connections. Most common is the semi-lugged version which is available in sizes from DN 50 up to DN 1600. For square-flange connection we are able to supply WB11k, which has additional tapped holes for this, or WB 12 which has a square fully-flanged valve body.

Valve type MV for Biomass:

  • This knife-gate valve is reliable and easy to customize and can therefore be used in a wide range of applications. The retainer ring system simplifies maintenance and offers several seat materials. It is uni-directional valve, but in some sizes it is also capable to handle certain differential pressure in reversed pressure direction.
  • MV is modular designed and consists of a one or a two piece valve body in stainless steel, nodular iron or carbon steel, but it can easily be customized in other valve body materials.
  • The gate is available in several alloys and surface treatment is optional. The top works consist of aluminum beams and stainless steel tie rods which gives good corrosion resistance and stability at manoeuvring.
  • Just like other Stafsjö valves MV is as standard equipped with Stafsjö’s unique box packing, TwinPack™, which gives a tight sealing and assures high operation reliability.
  • The gland box can also be supplied with a box-bottom scraper or with a double gland for the most demanding applications.
  • MV is available with many actuator types and accessories from DN 50 up to DN 1200. The valve comes in a semi-lugged version with several flange drilling patterns to choose from. MV can also be supplied with a V-port for control duties.

All Stafsjö Valves come with Twinpack™ Gland Packing:

The braid is built up of strands of graphite-filled Teflon with silicone lubricant. The braid is precisely plaited together with Teflon-impregnated Kevlar fibre strands which are positioned at the corners of the braid as reinforcement.

The rubber core is made of silicone. The design, with the rubber core, gives the packing a more flexible, elastic profile and function. The diameter of the core has been established through extensive laboratory tests and confirmed in countless installations. The disadvantage of a bigger rubber core, as used in some other manufacturers’ valves, is that the core separates from the braid when the packing is compressed and exposed to valve cycling.

Stafsjö developed this braid system together with a packing producer in combination with many running tests in their lab for verification of the performance of the sealing function.

Reliability: in cycle-testing the packing lasted 4 times longer than competitors’ products before a leak was detected. The design on the packing as well as the control on the surface finish of the gate ensure tight long-lasting sealing.

For further information on knife-gate valves contact Brian Foley or Zane Flaiani on Ireland: +353 21 4510900; UK: +44 1633 877505; or via the product enquiry form

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