SC-15 is a 15 kW horizontal paddle agitator for biogas digesters, secondary digesters and digestate storage tanks. A slow shaft and large paddles mix the substrate, break floating layers and help release trapped gas. The design accommodates constant or variable liquid levels within the approved operating range. The mixing diameter is 4.2 m. This price covers the configuration with an internal support for a shaft height of 6.5–9 m, external mounting and sealing. A different shaft height or mounting arrangement may change the price.

Low-speed mixing combines substrate circulation with gentle treatment of bacteria. With a suitable operating programme, it can favour the formation and preservation of bacterial colonies and their cooperation in biogas production. Excessively intense mixing and high shear can disrupt these colonies and impair bacterial interaction. The effect depends on paddle geometry, tip speed, substrate properties and mixing duration, not rpm alone. The aim is sufficient circulation without unnecessary mechanical stress.

The paddle layout works across changing levels within the mixing diameter. Operation below the shaft axis requires the specifically approved sealing, monitoring and coating configuration. The three-stage planetary gearbox transfers torque to the horizontal shaft, while the inner polymer bearing and outer flange bearing support the assembly. The reference paddle area is 1.9 m². Tank connections and support heights are specified before manufacture.

Selection considers tank geometry, working volume, minimum and maximum liquid levels, viscosity, dry matter content and fibre length. Suitability for dry matter content up to 15% depends on the feedstock. Sand, grit and other abrasive contaminants affect wear and the choice of seals and protective components. The number and position of agitators are determined for the tank, including columns, heating pipes, feed inlets and withdrawal points.

The complete configuration includes the electric motor, planetary gearbox, horizontal shaft, paddle arms and paddles, inner support and bearing, external mounting and bearing assembly, torque support, mechanical seal, wall connection and assembly fasteners. Steelwork, coating and any stainless steel parts are specified for the medium. Additional wear protection and monitoring equipment can be selected where required. Support loads and tank interfaces are coordinated with the tank designer.

The electrical installation is coordinated with the site supply and control system. Voltage, frequency, motor protection and hazardous-area requirements are confirmed for the selected configuration. A frequency converter and its starting and stopping ramps must meet the drive requirements. A control cabinet, converter and site cabling are specified separately when required.

Modular construction provides access to serviceable drive, bearing and sealing components. Inspection intervals, lubrication and replacement procedures follow the operating instructions. Permitted daily running time and liquid level are set during commissioning. Service without emptying the tank is possible only for the components and procedures provided for by the approved design; the complete machine is not maintenance-free.

The slow paddle action helps break floating layers, mobilise settled material and release gas trapped in the substrate. Regular circulation distributes fresh feedstock and supports contact with the active bacterial population. Mixing duration is matched to feeding and the consistency of the medium. Lower speed alone does not guarantee a higher gas yield.

For a new installation or replacement, provide a tank section with liquid levels, planned feedstocks and the positions of internal equipment. This allows the paddle sweep, wall connection and support clearances to be coordinated before ordering. Access for lifting equipment and assembly space are checked against the project drawing. Installation work, civil works and electrical integration are agreed separately. Final dimensions, permissible operating conditions and the complete supply schedule follow the approved project documentation.