So, what’s important when comparing high shear mixers? :
1. The shear performance – “Rotor to stator gap” – this offers the ‘cutting’ or ‘particle shattering’ performance of the machine. As with any emulsifier, the closer the high speed rotating element (Rotor) is to the static element (Stator) the greater the shear will be. Additional benefits in product consistency and quality will also be gained as particles will all be of the desired minimum size. The size of holes in the stator do also play a key role in particle size reduction.
2. The peripheral speed of the impeller – many high shear mixers operate at 1500 and up to 6000rpm, however, the small Rotor diameter fitted by other manufacturer’s means relatively low thrust compared to a Greaves, hence the flow and shear performance are not as intense.
3. The motor power does not dictate the flowrate, shear performance or intensity,
a. It’s amusing when I see vacuum cleaners for sale with graphics displaying say “3000 Watts”. We should be informed of the vacuum cleaners negative pressure BarG performance and the air intake flowrate!!! In a vacuum cleaner (or pump) it’s all about the fan size, peripheral speed, geometry, the rotating element, hosing bore and the seals. Certain makes of vacuum cleaner offer more suction with less power, as most of us know….
b. I recently purchased a new paint sprayer, but I suppose a powerwasher (right) is a similar comparison. I wasn’t interested in the motor power, just the pressure (psi) and the flowrate (litres/min) – shouldn’t mixers be the same? Higher installed horsepower does not mean high speed or flow it’s all about what the horsepower is connected to and peripheral output speed and geometry of impellers…….
c. As my ancestors told me – “It is critical the machine draws as close to its installed power as possible as the power is then being delivered to the fluid”. Again, many mixer companies install huge motor powers to convince the customers there’s it is more powerful, so better value. The reality is, when the amperes drawn through the motor are measured, the machine is only using 40-50% of the installed power – why the pointless larger motor? … it just looked good on the quote and probably cost more overall!!! Measure your amps and compare to the installed motor amp rating!
4. Flowrate – this may also dictate how quickly your process will take. The higher the flowrate, the more ‘turns in the vessel’ will occur. Clearly, if the flowrate is higher and the shear tolerances are higher, the quicker the process. In addition, a machine with high tolerances will deliver a better particle size reduction therefore requiring less ‘fluid passes’ or ‘cycles’ through the mixer head. All these elements combined will produce Minimum process time, High Flow & Maximum Shear, but without air entrainment.
Inline High Shear Mixers (Rotor Stator) Data:
Greaves PLMS 2 x 5 (4kW) :
- Nominal Shear rate: = 88,761.50 S?¹
- H20 Nominal Flowrate: 559 L/min = 33,540 Litres per hour
Closest competitor 2 x 10 (7.5kW) :
- Nominal Shear rate: = 69,120.00 S?¹
- H20 Nominal Flowrate: 417 L/min = 25,000 Litres per hour
Result: The Greaves machine:
- 28% more shear
- 34% more flow
- 87% less installed power
“Since 1947 Greaves have manufactured High Shear mixers with industry leading Rotor Stator gap tolerances, efficient motor selection and robust contact materials. Greaves offer the highest quality, high flow, and highest shear mixers available. Often copied over the past 68 years the design & manufacturing tolerances still keep Greaves ahead. Due to this unique design and manufacture procedure all machines are fully scalable, allowing a laboratory technician to produce say a 1 litre sample that can be upscaled to the production line without the need for taking these high output machines off-line for testing/trials and then further laboratory reformulation.”
Conclusions?:
Greaves are convinced you can improve your process time and achieve better results with less power consumption and probably with improved machine reliability, too.
