SP-15 is a 15 kW horizontal circulation agitator for biogas digesters and digestate tanks. Its paddle arrangement draws substrate axially from the tank centre and discharges it radially near the wall. This circulation helps distribute incoming material, break floating layers and mobilise sediment. The standard mixing diameter is 4.2 m at 10 rpm. The agitator can work with constant or variable levels within its approved range, with mounting and sealing adapted to the project.

Low-speed mixing is intended to combine 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 the biological processes of 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; lower speed by itself does not guarantee a higher gas yield.

This priced configuration has a mixing diameter of 4.2 m and a shaft installation height of 6.5–9 m. The external three-stage planetary geared drive works with inner and outer bearings. Minimum liquid level and support loads follow the approved drawing. A different shaft height or mounting arrangement may change the price.

Selection considers the tank geometry, working volume, minimum and maximum liquid levels, viscosity, dry matter content and fibre length. The dry matter figures are application guidelines, not universal limits for every 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 internal columns, heating pipes, feed inlets and withdrawal points.

The complete price includes the mixer, mounting frame, inner and outer supports, bearings, sealing system and assembly fasteners. The equipment is configured with a drive, transmission, mixing shaft, working elements, bearings and a sealed tank connection. Steelwork, coating and any stainless steel parts are specified for the medium. A stainless steel version, additional wear protection and monitoring equipment are selected as separate options where required. The dimensions and loads of the support structures are coordinated with the tank designer before manufacture.

The electrical installation is coordinated with the site supply and control system. Voltage, frequency, motor protection and any hazardous-area requirements are confirmed for the selected configuration. A frequency converter and its starting and stopping ramps must meet the drive requirements. The catalogue designation does not imply that a control cabinet, converter or site cabling is included. These items are listed separately when required in the supply schedule.

Modular construction provides access to serviceable drive, bearing and sealing components. Inspection intervals, lubrication and replacement procedures follow the operating instructions for the supplied machine. The 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 described as maintenance-free.

The supply schedule states the selected motor rating, shaft arrangement, paddle geometry, material and connection details. Mounting height, access for lifting equipment and the space needed for assembly are checked against the project drawing. The customer can request a configuration for a concrete or steel tank, including the appropriate wall or roof interface. Installation work, civil works and electrical integration are agreed separately.