Process control

Although I firmly believe in globalisation and modernisation, until a short while ago I have always considered tannery automation something for the big industry in highly industrialised countries, for top quality products. I thought that automation was an expensive, sophisticated and difficult to use toy, impossible to run and maintain in developing countries. Looking a little bit further, I must admit that this position is rather short-sighted, and I have changed my opinion. Let's look at a couple of facts. Most of the developing countries are in areas where there is a serious shortage of water, with water being one of the major ingredients of tanning formulae. Since water is precious and sometimes in short supply, tanneries should take care not to waste water. Very few of the developing countries produce tannery chemicals, which makes chemicals by definition expensive as long distance transport forms a big chunk of the price. Like everywhere in the world, pollution and tannery effluent are also major problems and particularly in developing countries, hence it is a priority to keep the polluting agents as low in quantity as possible. Human errors are normal everywhere and any time, hence a mistake in the weighing of chemicals or the wrong application of a formula negatively influences the quality of leather. How many times does it happen that a tanner discovers that a chemical mix is prepared badly and that it has to be thrown away? How many dyeing operations are performed and result in a wrong colour match, forcing tanners to redye the mismatched lot into black or dark brown? Process control can address each of these parameters. Automation can be taken from a very basic platform to a very sophisticated form, from a relatively low cost to a million plus investment. The tanners who want or, even better, need to invest should keep three basic factors in their minds: 1) Savings 2) Effluent and 3) Quality, where 'Quality' should probably be seen as the actual priority that should induce a tanner to invest in this sort of equipment. The simplest form of automation is a water management system. This can range from merely feeding a precise quantity of water (and/or chemicals) into a drum with or without temperature control, up to mixing recycled water with fresh water at a determined temperature. It is a known fact that normally tanners fill their drum with water up to a certain level, based on their experience, rarely with an eye on the litre counter. In a 3x3 metre drum, a mere 10cm in difference in loading (close to the axle) will add or reduce the water quantity by almost 1 cubic metre, or almost 1,000 litres. If your water load would have been some 7,000 litres, you talk about a bath that dilutes or concentrates by some 15%, which has obvious effects on the leathers that are being processed. Saving 'just' 1,000 litres of water per day means nothing less than 300,000 litres per year, loading and after processing, discharging! Similarly a precise water temperature for a bath means that the fibres of the treated leathers will be penetrated by the processing chemicals in the specific way as designed in the formula. If the next bath of the next batch has a different temperature, those skins will have a different outcome compared with the earlier batch. Therefore, good water management serves consistent quality in leathers from one batch to another, apart from savings in water supply, chemicals and effluent. Although the retanning and dyeing operations are the most sensitive to water temperature and chemical concentration, the importance of proper water management is for all tannery departments, and the same principles apply. One of the very important processes that depend on perfectly controlled chemical management is colour matching both in dyeing and in finishing. It is obvious that millimetric precision in the mixing of dyestuffs steered by computer offers a better chance to successfully match a colour to the same hue of a preceding lot of the same colour, than a man-made mix. Colour matching precision saves time and money. By using process control tanners are likely to avoid the need to adjust colours in already dyed skins, or even complete redyeing in case the colour is not properly matched and cannot be adjusted. The same consideration is also true for the finishing department, where pigment mixes need to be matched to colour swatches from which the buyers of finished leathers chose the colours of their orders. Simple water management systems can be found in about 50 countries, both developed and developing, whereas more than half that number have adopted a more advanced form of process control. Automation exists for a number of liquid products using automatic feed systems whereas other powder products, often, but not exclusively, may not follow exactly the process formula as operation interaction is involved. The more complete automation systems can be found in developed countries, although front-runner developing countries, specially markets like India, China, Namibia, Dominican Republic and Brazil seem to understand that process control helps them to off-set the lack of qualified technicians compared with countries such as Italy. Leather fashion leader Italy doesn't seem too keen on adopting process control wholesale and relies a lot on the experience of its technicians. Once these first generation leather magicians leave the field, process control will definitely take their places. A number of manufacturers offer a variety of systems, but only a few are state of the art, Swiss Hüni for instance. Tanners are not known for their readiness to open their pockets for the purchase of new technology, so price is a deciding factor, even if in reality they should know better and let themselves be led by quality. Many reason that you cannot do without a shaving or splitting machine, but 'you don't really need automation'. That's true, but then just after WWII tanners were still fleshing hides by hand as they were convinced that 'they didn't really need a fleshing machine'. Until recently the process control hardware was indeed expensive, but prices have come down to levels that also open the doors to small tanneries with smaller investment budgets. Technology and progress aim to make work easier, cheaper per production unit and better in quality. Buyers consider that a supplier of a standard quality product saves lots of problems when it comes to putting the leathers through their production of shoes, leathergoods or upholstery. Stable standard quality simply serves buyers better. That means that producers of good standard quality, including those of so-called 'cheap' leathers, will have an advantage over their colleagues and competitors who do not produce a consistent repeatable quality. Better quality fetches a better price in the market and thus a better profit. On top of a better price for the leather, process control saves money as there is no waste of water and chemicals, but also of energy, not to mention less effluent treatment costs. A win-win package. First stage standard water management equipment may cost somewhere around $35,000 depending on the number of drums that are being served, but will pay for itself in a very short period of time, certainly less than a year. Advanced equipment will cost much more and may not be suitable for small tanneries in terms of investment, unless high quality is required. Automation equipment is designed for use in the rather unfriendly tannery environment dominated by an atmospheric chemical saturation. Command modules are designed for use by workers who don't necessarily have a PhD in chemistry. Touchscreen pads are schematic for easy use, and any language can be programmed. It is worth tanners reflecting on the usefulness of automation for their factory whether they are in the US or Bangladesh. Sam Setter samsetter@limeblast.org