Design decisions

It's a simple equation: there's a fair chance that a mixer will cost less if it is smaller and therefore made from less steel. Moreover, it may well do just as good as job, if not better, than a larger design — and prove to be far more economical to maintain because it has less moving parts.

 

Simple, maybe, but it's sound advice, and it should nonetheless be handed out by reputable mixer designers and manufacturers who have the wherewithal to tackle the considerable problems caused by the alarming rise in the price of steel.

 

Examining the cost of some of the key materials, 'alarming' is no exaggeration. The price of molybdenum has gone up by 96% in the past 10 months; nickel has increased by 20% in the same period; and chrome has risen by 40% in the past 12 months.

 

During the past year, the overall price hike in world steel has been so astronomical — a rise of almost 50% — that 316-grade stainless steel mixers, vital to food and chemical applications, may soon only become available to those willing to pay a very challenging asking price.

 

There is no doubt that the price rises caused by the phenomenal demand for steel in China are already creating headaches for mixer and agitator supply. Shortages and the subsequent increased costs are also being heightened by the fact that much of the world's scrap metal is now going to the new mills in the Middle East, which are not producing steel from ore.

 

In Chemineer's 50-plus years of mixer manufacture, the company has never experienced such a sudden and dramatic pressure on the price and availability of materials, which has a number of serious knock-on effects.

 

There are already some worrying examples of those tempted into buying cheaper imported steel, which sometimes has a very debatable quality.

 

This is all the more reason to work with an experienced and knowledgeable mixer firm which has reputable suppliers who understand the crucial practicalities of heat treated steel — and not just the theory.

 

With prices rising so quickly, Chemineer and other mixer manufacturers are also faced with very tricky price quotations for materials.

The norm of working with a quote valid for 28 days or more has largely shrunk to just 7 days.

 

Often the pricing is based only on stocked material and is no longer valid once existing stock is sold. For exotic alloys with corrosion resistant properties, many price quotes are now valid for just 24 hours, making it very difficult indeed for the mixer manufacturer to gain go ahead from its customers within such a tight turnaround.

 

Although there have been suggestions within the mixer market about changing over to 304 grade, this is not a palatable proposition to food and drugs companies who insist on 316 in order to adhere to their strict industry standards. It is easy to say that if you can't get what you are after, then you must opt for the next best thing. But end-users need to consider carefully whether the mixer they think they need is really the mixer they want. This can only be achieved by working closely with mixing specialists.

 

The cost, from whomever end-users contact, may look at first like a quantum leap from the previous installation, so the price rise may well force their hand to look at an alternative specification.

 

However, they shouldn't look to simply replace an existing mixer with one the same size but of a lesser quality alloy, or from a cheaper, perhaps questionable supplier.

 

Instead, they may find that a smaller mixer equipped with the latest technology high efficiency impellers, and designed using the most advanced shaft stress analysis software may be more economic: not just in this time of shortage, but in the long term too.

 

Bryan Moores is a buyer, and Nick Davies is operations manager, at mixing specialist Chemineer.