Process control systems

by World Grain Staff
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When it comes to blending raw materials in "the middle of the mill," it is quite normal and acceptable to use software that stands alone from the rest of the mill.

While the software controls weighing and blending operations within the plant, that’s not always its primary function. It may be tied to a number of other functions, including quality control and batch record maintenance, and production and batch tracking of micro-ingredients. It is also invariably linked to inventory packages and financial accounts packages to provide accurate cost of raw materials used for sales generation each month in combination with the cost of raw materials for those sales.

The software may also be used as a budgeting tool or to carry out financial modeling and to evaluate raw material price fluctuations during the month. And it will undoubtedly be used for preparing least-cost formulations and transferring that data to the mill for use by the mill operatives.

Invariably referred to as the "formulations" computer, the nutritionist will have a key role to play in the choice and maintenance of software programs for this function. However, though I say it with tongue in cheek, nutritionists over the years have not always curried favor with mill managers and they seem to have differing viewpoints when it comes to who controls which aspects of the blending operation. Often a compromise is reached and two programs run in parallel in order to satisfy the needs of both.

The financial accounts staff also has its say in what information is generated, when, and on what basis to meet the needs of the monthly accounts package on which so many mill managers and operatives depend for operational information and to make managerial decisions each month.

However, whatever way you choose to run your businesses and whatever information you choose to generate, you need to be sure the information is accurate and reliable and that you crosscheck your computer-generated figures against physical stocks each month so that you have confidence in the data you are receiving. Simple overall inventory reconciliations can tell you if a gross error exists, and it also tells you where to go to correct it. Usually simple addition tasks tell you all you need to know.


There are so many bespoke systems available these days, and nearly all millers use the programs they have grown up with and understand the best. Simplicity is a key word when it comes to having the confidence in any software system, and it is only when you have major changes to make in the mill or in your formulation system that you will consider anything that takes you out of your comfort zone.

The system you use does have a significant role within the mill, as it controls all the batch blending operations, which is no small feat, especially in a post-grind mill where the hammermills are also controlled. The machine speed, screen size, feed rate, air flow and other factors, all depending upon the sophistication of the hammermill or rollermill, are controlled at this point. When layer grists are made to an ever-increasing granularity, it is important that the grist spectrum matches the weight and size of the bird or consumption will be severely impaired and uptake will be reduced. Such parameters are input along with the formulae, generally monthly, and the software package then controls the screen change mechanisms at the hammermills.

There may also be a wide range of liquid additions that are controlled by this computer section, and most certainly routing from raw material bins, or silos, will be controlled through to pre-press bins and bulk mash outload bins. Where there are other facilities on the same site, such as a baby piglet feed plant or organic sections where whole diets or partially prepared diets are made up in the main mill, then these too are scheduled in with mainstream production, and it is important to allow for controlling the risks of cross-contamination. Flush sequencing is usually pre-programmed into the blending control sequence, and batch recording of both bulk and micro-ingredients is carried out here so that online records can be examined and scrutinized by inspection bodies at their will and convenience.

Such formulations may well be used for financial modeling purposes. This is a tool the sales manager will seek to use independently of other users, and the quality control staff will also wish to use the system independently to access true batch records.

Hence, there will be great frequency of use, and it is paramount to avoid software systems becoming easily corrupted. A good password system will prevent most problems, but this is not always easy when one individual is tasked with carrying out functions using the system that require him or her to operate at different security levels.

Good protocols are essential and good records of who has accessed which part of the program is also important in tracing any corruptions and errors that may occur. Having a system regularly updated and restored by someone qualified to maintain the system is imperative on a regular basis.


Calibration of the plant is vital to effective operation, and it is normal for the blending and mixing plant to remind the operative precisely when regular calibrations are due. Calibrating mixer uniformity using salt, for example, can easily be done, but it requires the operative to draw samples throughout an individual mix to subsequently test for salt. This is easily prompted on screen before the system allows the operative to proceed to the next task when a protocol needs to be followed.

Similarly, calibration of liquid addition pumps needs to be carried out regularly, often once per week. Again, a simple prompt and confirmation by the operative to say this has been done before the programs or production schedule can be continued is all part of a good operator-friendly program.

The thorny question of back-up is well debated and will no doubt be continued as a hot topic. I prefer to simply keep a back-up copy of all activities on a disk and archive it at the end of each month. But this obviously depends on who else needs access to batch records and records of raw material and finished feed movements.

In most mill locations, this is relatively simple. But in cases where a mill is operating on an island where raw materials are sourced from all over the world and where traceability needs to match legislation in anywhere up to 12 countries, it may not be so easy. When local laws require data to be available in three currencies and two languages, and quality control records need to show evidence of compliance in another three, it becomes more complex. Taking a hard line and simply making the data available in local language and currency may take some persuading of the authority, but it is often the easiest discussion you will have. It is very important in international locations to establish ground rules early in the inception process of a new facility.

Finally, there is the need to address corruption and theft. Feed millers operate in a high-value business compared to most local economies, and even though you may feel your feed is not worth stealing, you will be surprised how many people think it is worth diverting for their own use.

All the usual checks and balances need to be in place, and regular inspections and calibrations of scales, weighers, truck scales and other devices are important.

Do not allow drivers to develop working relationships with packing crews or warehousemen. Rotate staff regularly from one place to another so they do not have a chance to set up misleading paper trails, and always observe what is going on around you. A punctured truck tire being washed out may also be drained to allow for the equivalent weight of feed to be carried out from the mill in place of the water just brought in over the truck scale. Regarding these and other matters, it is important to be vigilant at all times.

Jonathan Bradshaw is a consultant to the agribusiness and food processing industries, specializing in project management and bespoke training programs through his company, J.B. Bradshaw Ltd. He has extensive experience in flour and feed milling in Africa, the Americas, Europe and the Caribbean. He may be contacted at: