Digester Covers


Digester Covers Overview:

WesTech provides innovative designs for custom digester covers using the latest structural standards while integrating ease of erection and economical value. 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:

Steel Truss Structure

Truss covers include steel plates welded to both the top and bottom of the trusses to form an attic space, which protects the structural members from corrosion and provides insulation for the sludge.

Radial Beam Structure

With no ceiling plates and 50% less field weld length than a truss cover, beam covers are a very economical choice for anaerobic digester covers.


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.

Digester Cover Types:

Fixed Covers

Innovative designs incorporating a water launder or more advanced seal materials can overcome liquid level variation limitations. A conventional annular seal design relies on the sidesheets being 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.



Steel Truss and Radial Beam Covers

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

  • Prefabricated 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

  • Variable liquid level capabilities.
  • Significant gas storage volume.
  • Lowest installed cost.
  • Absolute odor containment.

Fixed Covers

  • Prefabricated beam roof sections.
  • Designed for tank diameters that range from 20 to 125 feet.
  • Complete gas and odor containment.
  • Most economical steel cover option.
  • Faster installation.
  • Best option for small liquid level variations.

Buoyant Covers

  • Innovative truss design.
  • Attic space.
  • Best option for high liquid level variability.
  • Increases stability of cover.
  • Provides natural thermal insulation.

Gasholder Covers

  • Cover travel makes liquid level variation possible.
  • Slide guides allow the cover to travel above the tank wall, thus increasing gas storage at high liquid levels.
  • Side sheet height can be designed to optimize gas storage.
  • Stored biogas can be used as a fuel source.