Digester Covers

Digester Covers

Digester Covers Overview:

WesTech anaerobic digester covers are ideal for new and retrofit installations. These custom covers are innovatively designed by WesTech engineers who have decades of experience meeting customer specifications for biogas and odor containment. Incorporating the most current structural standards, WesTech covers are economical and easy to install.

WesTech offers three major structural designs: Steel Truss, Radial Beam, and DuoSphere™. Our Steel Truss and Radial Beam structures can be configured to fixed or buoyant configurations. Our DuoSphere Membrane Digester Cover is the most versatile cover available. The tank mount design provides an innovative and cost-effective solution for new and replacement covers.

Structural Designs

Radial Beam Structure: Beam covers are a very economical choice for anaerobic digester covers, as they have no ceiling plates and 50% less field weld length than a truss cover.

Steel Truss Structure: Truss covers use welded steel plates on both the top and bottom of the trusses to form an attic space, that protects the structural members from corrosion and provides insulation for the sludge.

DuoSphere: The DuoSphere membrane digester cover is the most versatile cover available. The tank mount design provides an innovative and cost-effective solution for new and replacement covers.

Additional WesTech Options:

  • Geomembrane seal
  • Hinged ballast block platform design

Digester Cover Types

Fixed Covers: Innovative cover designs incorporate a water launder or more advanced seal materials that overcome liquid level variation limitations. A conventional annular seal design relies on sidesheets submerged in the sludge to achieve a pressure seal and prevent odors from escaping.

Buoyant Covers: Buoyant floating covers are in contact with the sludge, which reduces the exposed liquid surface area and prevents a large scum blanket.

Gasholder Covers: Gasholder covers can be constructed using radial beams, trusses, or engineered textiles as in the case of the DuoSphere dual membrane covers.

Slide Guides for Gasholder and Buoyant Covers

Slide guides allow the cover to travel above the tank wall, thus increasing gas storage at high liquid levels.

WesTech’s Ultra-High Molecular Weight (UHMW) polyethylene slide plates, used on three sides of the structural steel tube, prevent covers from tipping and binding as they move vertically within the tank. They resist wind, seismic, and unbalanced loads in both radial and tangential directions. The durable, low-friction UHMW surfaces remove the need for lubrication, enabling maintenance-free operation.

Advantages of WesTech Slide Guides:

  • Great for retrofits and upgrades with old cover in place
  • Eliminates tipping and binding
  • Corrosion-proof slide plates
  • No lubrication required
  • Loads re-distributed over several guides
  • Adjustable for easy installation and alignment
  • Minimal wear and maintenance

 

Steel Truss and Radial Beam Covers:

Features

  • Several options available for various process requirements
  • Available sizes range from 20 ft. to 125 ft. in diameter

Benefits

  • Prefabricated beam roof sections for faster field installation
  • Custom-designed for wide latitude of application
  • Beam covers cost less than other options
  • Biogas and odor containment

 

DuoSphere Digester Covers:

Features

  • Variable liquid level capabilities
  • Significant gas storage volume

Benefits

  • Lowest installed cost
  • Absolute odor containment

 

Fixed Covers:

Features

  • Prefabricated beam roof sections
  • Designed for tank diameters that range from 20 to 125 feet

Benefits

  • Complete gas and odor containment
  • No movement, they are attached to the tank
  • Most economical steel cover option
  • Faster installation
  • Best option for small liquid level variations

 

Buoyant Covers:

Features

  • Innovative truss design
  • Covers float on the surface of the liquid
  • Attic space

Benefits

  • Best option for high liquid level variability
  • Truss design increases stability of cover
  • Provides natural thermal insulation

 

Gasholder Covers:

Features

  • Covers float on digester gas that is held under the cover
  • Stores digester gas and maintains pressure
  • Pressurized gas storage for optimized downstream utilization
  • Slide guides allow the cover to travel above the tank wall, thus increasing gas storage at high liquid levels

Benefits

  • Side sheet height can be designed to optimize gas storage
  • Stored biogas can be used as a fuel source