Shear Fiction?

Larger is Better – and justifies a higher price tag

Could this be a Sales & Marketing Myth?

Is bigger always better?

Whether it’s an industrial mixer or a domestic vacuum cleaner you are looking to buy, specifying extra power and larger dimensions usually increases cost and space requirements. BUT, in our experience this approach often fails to deliver any improvement in performance or efficiency.

In many cases, including high viscosity mixtures, best results are achieved by a correctly specified mixer with a smaller, lower rated motor.

12x16 Portrait (02)What are we suggesting?:

Outwardly most new Rotor Stator-type or in-line high shear mixers seem very similar in design or appearance. This can result in too much emphasis on one obvious point of difference – the installed motor power.

Surely more power means better mixing? – Well No, that’s not always the case…..

Numbers do matter – but it’s deciding which numbers that is important.

There is a temptation to emphasise a large kW power rating as the ultimate “trump card” in a mixer’s capabilities.

IMG_1506

Class leading Rotor to Stator gap tolerances, even at this scale – a 500mm stator – The World’s Largest Rotor Stator head

Perhaps this is because kW is a widely recognised and understood unit of measurement? But when specifying a new mixer, it is not necessarily a particularly helpful one!

We could compare this with a display of vacuum cleaners at an electrical retailer – each proudly displaying ‘3,000 watts’** as a prime selling point. The James Dysons of this world might explain that a far more important number would be the machine’s negative pressure BarG performance and the air intake flowrate!

**Even the EU is getting in on the act with the recent ruling that vacuum cleaners can have motors no larger than 1600W (reducing further to 900W in coming years).

Clearly the word is out that there is more to these machines than motor power!

After all, a vacuum cleaner is essentially an Air Pump used to filter dust-laden air. So… its performance is down to the fan size, peripheral speed, geometry, the rotating element, hosing bore and the seals…..!

Admittedly, this is not everyday terminology but most of us are well aware that certain leading makes of vacuum cleaner achieve greater suction with less power (less bulk, less noise and less energy consumption) – and this is precisely what makes them so successful. (Hats off to Mr. Dyson!)

The same point is illustrated in the way some other categories of equipment are marketed – including paint sprayers and power washers. Both rated in terms of flowrate (litres/min) and pressure (psi) with little mention of motor power.

At Greaves, we know that effective mixing depends on Output Performance, NOT power consumption

Looking at the wide range of mixer designs in our market, we see far too many cases where large amounts of “over specified” power go to waste.

Greaves develop and manufacture mixing machines in the knowledge that it is critical the power being delivered to the fluid is matched as close to the motor power as possible.

However, when the current drawn through the motor in many machines is measured, it is revealed that the mixer is only utilising some 40-50% of the installed power. Measuring your amps and comparing to the installed motor amp rating can be a worthwhile exercise. Often the extra motor power some companies shout about (and may charge more for) is simply pointless.

In reality, more power does not mean better mixing, any more than it means better suction or performance in a vacuum cleaner. It is the diameter of the rotor, its size in relation to the stator, or the gap between them, and the dimensions of the holes in the stator, that makes the difference, and high flowrate figures that should be highlighted – all the truly significant factors that we will examine in detail next time in our follow-up article – Shear Fact

At Greaves, we don’t just sell mixers. We work with our customers to help deliver the best equipment for the job. We are always will to talk so please get in touch to discuss your upcoming requirements

greaveshear- (High Res) - Higher Blue Strap DIN Medium 175 R6 G85 B157

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