IKA RW 28 digital, mechanical stirrer, 80 L, 0005040000

Macro-rheology and mechanical power transmission

The mixing of structurally viscous, non-Newtonian fluids on a macro scale (up to 80 litres) requires the application of substantial and absolutely constant torque. The IKA RW 28 digital is designed as a classic electromechanical overhead agitator and utilises a robust, two-stage spur gear transmission for power transmission. This kinematic architecture enables the high-performance motor to optimally convert its electrical output power into a mechanical torque of up to 900 Ncm across two defined speed ranges (60–400 rpm for maximum torque and 240–1,400 rpm for high turbulence), depending on the rheological requirements. This reduction ratio is absolutely essential from a process engineering perspective in order to overcome the enormous fluid dynamic resistance of the fluid when dispersing paste-like media with a dynamic viscosity of up to 50,000 mPa·s, without driving the drive’s stator into thermal lock-up.

Fluid mechanics and axial positioning of the shear zone

The transfer of rotational energy into viscous media generates specific axial and radial flow vectors, which depend significantly on the position of the mixing tool within the fluid. A key mechanical advantage of the RW 28 digital is the drive shaft, which is designed as a hollow shaft. This allows the user to physically push the shaft of the stirring tool right through the entire motor block. This enables stepless adjustment of the immersion depth and thus of the active shear zone relative to the fill level of the reaction vessel. The hydrodynamic vortex can thus be precisely positioned for varying batch sizes without having to adjust the vertical locking mechanism of the 7.5 kg motor block on the telescopic stand.

System dynamics and metrological reproducibility

The application of 900 Ncm in 80 litres of highly viscous media induces massive asymmetrical counterforces (torsion and bending moment). To prevent resonance-induced failures, the RW 28 digital is equipped with a solid, 16 mm diameter extension arm milled directly from the chassis, which transfers the shear forces that arise to a static cross-sleeve without any play. Metrological control of the process is ensured via the digital LED display. Even in the event of significant viscosity fluctuations (e.g. due to thermally induced polymerisation) during the stirring process, the user retains complete visual control over the actual rotational kinematics, which guarantees GLP-compliant reproducibility of scale-up processes in the pilot plant.

Technical details

Kinematics & Mechanics

• Maximum stirring volume (based on H₂O): 80 litres
• Maximum viscosity of the medium: 50,000 mPa·s
• Maximum torque at the stirring shaft: 900 Ncm
• Gearbox architecture: Two-stage mechanical spur gearbox
• Kinematics (Gear I, 50 Hz): 60 – 400 rpm (focus on maximum torque)
• Kinematic characteristics (Gear II, 50 Hz): 240 – 1,400 rpm (focus on hydrodynamic turbulence)
• Chuck clamping range: 1.0 – 10.0 mm
• Mechanical hollow shaft (through-shaft): Yes (internal diameter 10.5 mm when stationary)

Metrology & Control Technology

• Speed display: Digital LED display
• Speed control: Stepless mechanical friction wheel drive
• Adjustment resolution: Continuous (analogue)

Motor & Power Consumption

• Motor type: Capacitor motor with high starting torque
• Motor power input / output: 220 W / 90 W

System infrastructure & dimensions

• System dimensions (W x H x D): 123 x 364 x 252 mm
• Machine weight: 7.5 kg
• Tripod arm (diameter / length): 16 mm / 145 mm
• Housing material: Die-cast aluminium (powder-coated)

Safety & Environmental Conditions

• Thermal safety device: Integrated temperature sensor on the motor (shuts down in the event of overload)
• Permissible ambient temperature range: 5 – 40 °C
• Permissible relative humidity: max. 80 %
• Protection class (to DIN EN 60529): IP 40

Electrical & Connectivity

• Voltage: 220 – 240 V
• Frequency: 50/60 Hz
• Power consumption: max. 220 W

Contents of delivery

• 1 x IKA RW 28 digital mechanical stirrer (drive unit)
• 1 x chuck key
• 1 x power cable for IT equipment

(Important note: The stand, cross-sockets and flow-specific stirring tools are essential for operation and are not included in the scope of delivery!)

Individual requirements & accessories

The RW 28 digital converts electrical power into a substantial torsional torque via the gearbox, but is ineffective without the correct fluid dynamics peripherals. The choice of stirring tool is crucial: for 80 litres of medium-viscosity fluids, use the R 1385 propeller stirrer to generate an axial suction flow. For extremely high-viscosity, paste-like media, you must use the R 1331 wall-hugging anchor stirrer to apply radial shear forces to the vessel wall. Due to its own weight of 7.5 kg, plus the rotational forces generated, the motor must be securely mounted on a solid telescopic stand (e.g. R 2723) fitted with a heavy-duty cross-coupling. Please contact our procurement service for the tribologically correct configuration of your scale-up setup.