Extrusion and tunneling is the process for laying pipes without trenches, or boring tunnels and large cross-sections of channels.

Machines with a broad contact to the excavation face are generally used. These boring machines fully engage the excavation face and generally convey the material out through bentonite slurry, where CAB (SEPREX) separation equipment again separates and processes it. This procedure can handle groundwater and almost all soils from clay to rock.

For extrusion and tunneling, the requirements for downstream separation equipment are determined by the geology, boring speed and diameter of the drill rig. The separation equipment has a modular design and specific configuration of tanks, centrifugal pumps, dewatering separators and hydrocyclones, possibly with the addition of equipment for preparing and dosing with a flocculant solution and with sedimentation tanks or chamber filter presses.

The separation equipment is adapted to the geological conditions, especially the projected granulometric composition of drilling muds, their density and viscosity. Installed aggregates are sized to separate individual fractions: coarse separators separate gravel from rock, sand fractions are separated by means of hydrocyclones, clay and loam (fine grain) by means of centrifuges or chamber filter presses.

Drilling muds are conveyed by centrifugal pumps from the tunnel drill to a coarse separator. The heavier fractions of the coarse separator fall into the tank and from there are sucked up by a second centrifugal pump and fed to the hydrocyclone unit.

The purified light fractions of the cyclone are fed back into the flushing loop unless further separation of fine fractions using flocculation and decantation equipment is required. Using a dewatering screen (linear vibrator), heavier fractions can be further dewatered until the separated solid eventually reaches a consistency suitable for storage.

The tunnel drill and separator form a circulatory system and should be mutually aligned as much as possible. The more effective the separator equipment removes solid content from the drilling fluid, the more economical the operation of the circuit. During the construction of the tunnel, the physical properties of the drilling fluid are continuously changing and the content of the solids and particle size distribution become an especially major challenge for the separating equipment.