The principle trend in recent years - a major step - has been the slow but sure move towards debranning and peeling in western hemisphere mills. This subject has been covered at some length in other articles and will continue to be debated by millers and engineers for many years to come.


The next most significant trend has been towards the use of double high rollermills on break and head reduction passages. The use of these machines has had a major impact on both flow sheet design and mill layout. They have also enabled a smaller floor area to be used and have reduced the number of pneumatic lifts needed for conveying mill stocks, as compared to the number required in a conventional mill diagram of say, fifteen to twenty years ago.

The two-high or superimposed rollermill is a much safer rollermill in terms of general welfare and fire prevention. Recent incidents in mills have received much attention and design engineers have spent much time addressing rollermills and the components used in both the fabric of the machine and the compressed air, hydraulic and electrical components. Today’s rollermills are a far cry from the much heavier cast machines of the 70s and early 80s and, as well as prices being lower in real terms, the capacities of these machines are much enhanced.


Greater individual machine capacity

The new generation of rollermills also throws open the door to millers who are seeking to remodel their existing mills and who now have the opportunity to increase capacity within their existing mill buildings. Greater individual machine capacity enables them to use the same number of rollermills, in terms of footprint, and achieve greater roll surface area with a more than corresponding increase in wheat throughput.

With the need to ensure that maintenance procedures are as efficient as possible, there has been a steady improvement to the design of rollermills. We are now familiar with the cartridge-type roll supports and the ease with which a roll change can be effected in the mill, leaving the engineers time to work on rolls and bearings at their leisure.

I will speak more about general servicing later, suffice for now that the need for speedy roll changes has greatly altered rollermill design of late.

Moving up the mill to the purifier floor, we have seen a much needed facelift of almost all the purifiers, with more efficient machines coming into use. Three decks rather than two have allowed better and more efficient separation and have enabled the semolina miller to be more precise in his purifier cover selection and to obtain a much improved particle size range.


Time saving

The access to purifiers has also greatly improved with mill spouting being fed through the centre of most machines, rather than blocking the aisles between them and making sample inspection almost impossible in the past. With dedicated air systems and better valve arrangements on the purifiers themselves, there is a much improved air flow through the product and the machines are easier to set and to operate. In my early milling days, it took hours to balance a purifier floor and the smallest change in moisture to first break or a minor adjustment to a break release meant you had to start again, with machines that were unresponsive. Today, the purifier can be set and left without much worry. I am pleased to see that these valuable machines, which contribute to product quality and mill performance, are returning to new mill installations.


Mill hygiene

Sifters have also seen some major developments, particularly in terms of mill hygiene. Both Satake and Buhler have introduced plastic sieves to the milling industry. These sieves are a major improvement and they are quickly being adopted throughout Europe. Before long, they will become the industry standard worldwide, at least in new mills. These sieves still need to be perfected and they do not suit every application. A greater range of sizes is required and until they can replace every type of sieve currently offered, there will still be room for the wood and melamine-lined versions.

Modular construction and the use of more than six sections in an individual machine are two key trends in sifter development, principally led by Buhler but now being followed by several other engineers. It takes a considerable amount of money and resources to bring a new sifter design to market and Buhler is probably best placed to do this, as it has the largest output of sifters among the engineering companies. The modular sifter combined with use of the superimposed rollermill leads to some novel flow diagrams and use of building space. Greater capacity can be installed in smaller space and thanks to the compact layout of the mill, with up to ten sections in one sifter, the spouting angles are improved and the need for relifts is reduced, giving a corresponding reduction in energy costs throughout the mill.


Pooling of engineering knowledge

Several engineers are now looking to combine their talents and resources. I believe there is a significant trend not towards amalgamation or takeovers but towards a pooling of engineering knowledge and better use of manufacturing facilities. It would be unfair of me to speculate which engineers are working together. But it is clear that if two engineers make 100 sifters a year each, it makes good sense to have only one factory produce 200 and spread the costs. This also makes it more viable to develop new products. Thee has already been a move towards using different manufacturing techniques to produce sifters.

The use of modular construction of sifters is ideal from the design engineer’s standpoint but it does make for a slightly more complex installation phase. Care must be taken to ensure that sifters are constructed properly and torque settings followed, to ensure that the sifter is solid and durable and not liable to become loosened during operation. Although I have not seen any evidence of post commissioning problems, I have noticed that great care is taken at the installation phase.

Sifter ventilation and the use of plastic sieves have greatly improved internal sifter conditions. Sifters have become more pleasant to work on. The machines should also last longer, although it is still too early to estimate the expected life of a modular machine or plastic sieve.


New designs

In the cleaning house, there have been new designs and the use of colour sorters has become a significant feature in new mills. Simultaneously, there has been a significant reduction in the use of trieur cylinders and other smaller ancillary machines, spiral seed separators and the like. Primarily driven by huge increases in the price of wheat, millers have decided that it is better to allow as much product through to first break as possible, rather than take out every weed seed and foreign grain. This seems a logical step and we can expect to see simpler wheat cleaning plant flow diagrams in the future. Colour sorters are replacing several machines, and although they may at first seem expensive, they require very little support steelwork or building containment. The new generation machines are very efficient and reliable, on condition that maintenance is adequate, with regular lamp and filter changes.

This brings me to the subject of maintenance and the pressing need to become more efficient. I have always believed that spares costs per annum should not exceed 2 percent of capital value for milling equipment and 0.2 percent for buildings. In older facilities especially, help is needed to achieve this goal but fortunately, help is available. Everyone is trying to sell us maintenance programmes to monitor operations. But when I look closely at most of these programmes, all I see is a paper chase. The Buhler package, usually supplied as an add-on to the Wincos mill control system, is however in a class of its own and really does provide the mill engineer with useful data, and assists him to schedule maintenance work and shutdowns.

The Satake system also offers many advantages and can be tailored to suit each and every need. Flexible and pertinent, it also provides desireable information and assists with scheduling. Satake also offers an on-site maintenance service which several millers are now using. From simple roll changes to sifter renovation, and even spouting changes and pneumatic filter work, they cover all the elements within a mill. Where mills are running to an eight, ten or twelve week shutdown frequency, the Satake maintenance regime can significantly reduce mill costs.


Packing equipment

Other trends in equipment concern packing equipment, where Dutch and Italian companies play a significant role. Buhler leads the field in Africa and countries where machinery gets heavy use, and abuse. Buhler’s new generation of packing machines are proving to be work horses. The carousel arrangement suits most sites and applications and takes up the minimum of space. Direct loading to vehicles reduces theft and fraud. Capacities can be achieved to enable a satisfactory turnaround time for loading vehicles direct from the mill without the need for double handling through the warehouse.


Automatic

Automatic online analyzers are becoming the norm in most mills with gluten loops and similar control features. Whilst calibration of some analyzers needs to be extensive, these systems are proving to be very useful and financial payback is swift. Measuring protein, colour, starch damage and a raft of other parameters is now relatively easy. This is causing the demise of several on-site laboratories as millers adopt a calibration service as back-up, instead of daily finished product quality testing. Certificates of analysis are now being replaced by proof of product quality and variance, and presented as real time data to the customer.


Acknowledgement

We greatly thank the kind collaboration of Perendale Publishers (UK), whose contribution of technical articles appeared on their magazines AQUAFEED and GRAIN & FEED MILLING TECHNOLOGY is deeply appreciated by Engormix.com and its community members.