Dense Phase

Vacuum Conveying - Dense Phase

Dense phase vacuum conveying systems use high capacity vacuum pumps (up to 99% vacuum) to convey materials from a feed hopper or silo to a receiving vessel or vacuum hopper where the air and product are separated by a filter.


When the vessel is full, the vacuum is isolated and the conveyed product is discharged into the destination silo. The product conveyed through the pipeline at a controlled low velocity, usually in a fluidized state to reduce friction and pressure drop.


Systems generally operate on a batch basis, as follows:

  • the vacuum pump draws powder to the vacuum hopper until full 
  • the vacuum isolation valve closes and the discharge valve opens 
  • conveyed powder is emptied from the vacuum hopper 
  • the discharge valve is closed and the cycle repeats.

Valves and sensors are used throughout the process to control the applied vacuum, product fluidization settings and system velocities to ensure trouble-free product conveyance.


Dense phase vacuum conveying is particularly suitable for conveying high capacity materials over short to medium distances, from multiple sources to a single or multiple destinations. The low velocities and vacuum make it ideal for food, dairy and pharmaceutical applications involving friable or fragile agglomerates.


  • Convey Rates: medium, up to 20 tonnes/h (higher with multiple vessels) 
  • Convey Velocities: 0.5–8 m/s 
  • Convey Distances: up to 100 m (longer with push–pull systems) 
  • Air mover: vacuum pump (dry vane, oil or water sealed) 
  • Operating Pressure: <99% vacuum 
  • Air Ratios: medium (up to 50 kg/kg)

NB: All values are approximate: please contact GEA for advice about how to convey your product.


To optimize the system, various techniques can be used and additional options for specialized applications are available: 

  • feedback velocity control systems to minimize product degradation 
  • pulsed air injection to break the product flow into discrete slugs 
  • inline sampling, de-lumping, metal detection and magnetic separation systems 
  • line boosters to assist conveying 
  • automatic unblocking systems using compressed air 
  • vibration to loosen cohesive powders prior to conveying 
  • twin receiving vessels to provide continuous conveying 
  • stainless steel construction for sanitation or corrosion resistance 
  • demountable and polished designs to USDA 3A standards for ease of cleaning 
  • multiple inlet/outlet networks for maximum flexibility.

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