Getting it right!15 October 2003
While this, and what follows, is obvious to many, putting obvious principles into practice often seems to pose difficulties. Having a cookery book on your shelf does not turn you into a Cordon Bleu cook! But it says a lot about your intentions. There have been suggestions that a tannery and a packing plant or abattoir should never get too close because their interests are just too far apart. But take a closer look at that conventional wisdom: properly integrated, you can't escape the potential benefits to both hide supplier and tanner. Ensuring consistent quality raw material The enthusiasm with which hide dealers and consumers of wet-blue responded at the outset to the Future Beef project proves that there is demand for better quality hides, with less damage and a higher percentage of high grade selections, for which there is ample evidence that a price premium would have been paid. To achieve this higher price traceability is essential. To achieve proper tracking of the processes to which a hide has been subjected, each hide has to have an ID and a listing in a database and an incrementing Hide Stamper, as supplied by Gibson-Bass, is indispensable. This PLC controlled device stamps an individual number on each hide, which can be correlated with the origin, date, weight, thickness, area, grading/selection and even a .jpg digital image of the hide for planning future utilisation. By the same token, a newer, high-tech approach uses RFID Tags (paper-thin labels which act as receivers of information, and transmitters of data) which can be stuck on pallets of wet leather. Once the leather is dry, it can be stuck on the crust leather itself, remaining with the hide right into the end-user's cutting plant. The benefit is that production management knows exactly what production step a batch of leather has reached during manufacture because the RFID tags signal the nearby receiver. This in turns signals the control network and the SCADA system in the control room. On the other hand, with the complementary means of hide identification, from Gibson-Bass and the RFID Tag, any hides from an end-user which are subject to quality criticism, may be traced back through the actual production steps that hide was subjected to. Was it selected out for a correction dyeing? Was it re-fatliquored? Was too long spent in the pickle due to a breakdown, or did the temperature in bating not reach the required set-point? With the means available today, it is possible to track the process back to the conditions in the abattoir, to the lot of cattle delivered on a date by a particular feed-lot, and even the breeding and genetics of the animals in question. This is still the goal of the animal husbandry and meat packing visionaries, who are still striving to make this happen. Getting the hides into the tannery Most of the grain damage seen by graders in the tannery occurs in the abattoir - something that the Hide ID Log can be a major incentive in improving. But the dwell time in raceways, at elevated temperatures and in the presence of bacteria, can cause extensive loss in value due to putrefaction. A tool being applied increasingly in abattoirs is to send the hides to the tannery in 'real-time' as they are pulled from the carcase. Slaughtering Services Srl, of Modena in Italy, have developed the Hide Cannon for just this purpose. This may be seen in plants in Italy, where systems have been running for several years. The pneumatic tube principle is the same as formerly used in banks or airport check-in desks for sending documents to the accounts department, only the hides are loaded into the cannon directly without need for the 'capsule'. An air-blast 'shoots' the hide along the route of the transport pipe a distance of 100m or more, turning corners, gaining altitude where necessary with the aid of additional pneumatic 'kicks' appropriately timed by the PLC controller. Trimming & fleshing As the hides arrive in the tannery in the same 'takt time' as the hides are being pulled in the abattoir, there is no time for bacterial damage to occur before trimming and fleshing. It is, therefore, important to arrange a trimming conveyor, with the speed properly synchronised to the arrival of the hides. The number of operators in the team of trimmers is chosen to correspond with getting those hides trimmed by the time they reach the fleshing machine. The selection of tannery equipment involves a balance between the criteria of economy, reliability, production rate, availability and price of spares, as well as on-going maintenance contracts and emergency technical service. For example, in the earlier project, one Persico Persana through-feed fleshing machine was selected because the throughput capacity of 340 hides per hour considerably exceeded the expected production rate of the hide puller of 200 hides per hour. Therefore, one machine was clearly able to meet the production needs. But, what about the risk of mechanical breakdown? Would it have been better to have two cheaper machines - perhaps in a 'back-to-back' configuration? This question was answered as follows: * More than 50 tanneries in Arzignano/Chiampo run the Persico Flesher at full capacity and completely endorse its reliability and ease of maintenance * A single 8 hour shift was able to handle the production needs of the new plant * Two more shifts are available for regular preventive maintenance * A spare fleshing cylinder may be kept ready for emergencies. It takes only three hours to replace a damaged cylinder, assuming the usual infrastructure of working space, overhead gantry/crane, forklift and the availability of skilled maintenance staff Thus, there is almost no risk that this machine can become a bottleneck and interfere with production. A further consideration was that the machine 'footprint' required for the Persana, is approximately 30% of the floor area needed for two conventional fleshing machines - a consideration when building costs have to be controlled. Similar considerations and evaluation precede the selection of every piece of equipment in the tannery: samming machines, shaving and setting machines etc. The maximum planned productivity of the tannery, the minimal economic production, the recommended maintenance intervals, and the reliability ratings must all be taken into consideration - together with price and availability of spares. There was no difficulty getting endorsements from many of the 50 or more tanneries in Arzignano for the Persico through-feed flesher, or from several UK wet-blue producers and upholstery tanners who use this machine. Conveyor systems in the tannery Handling of hides by human operators often introduces opportunity for error, faults which reduce the value of the hides and wastage. After fleshing, an automated conveyor system, which may include 'bucket-lifts' (such as those designed by Feltre Srl of Chiampo in Italy), turns an otherwise cumbersome batch procedure with indeterminate 'wait states' at each work station, into a specific real-time process flow, with the opportunity of data collection, and monitoring of 'takt time'. Such a system may include automated weighing platforms (mini-conveyors on load-cells) so that hide weight and even accumulated processed weight (= pack weight for a drum load) can be logged. This eliminates human error, speeds the transfer of hides and reduces the work load on operators. It also provides management with the opportunity to capture data on productivity which helps production management identify 'constraint resources' and bottlenecks, and to employ the principles of synchronous management1. When a selecting and grading/measuring conveyor is placed in-line, the system can also capture information about individual hides. The data is signaled via the industrial network to the SCADA program (usually in the control room), which at the same time is collecting data from all the inputs and outputs at each production step and workstation. Tannery process vessels: new technology drums The goal of quality consistency requires a look at the latest developments in process vessels. Among these, Olcina's low key development of the Cangilones drum stands out as the correct approach to introducing new technology to the leather industry. This has been developed by Olcina for several years, while the company carefully studied the characteristics and advantages and was finally launched after an accurate R&D process. It helps to describe some key points of this interesting system: 1. Large drums (4.20m diameter x 4.5m wide) are extremely strongly built in bolondo wood, with over-engineered strength in the staves, and crown drives, gear-box and motor 2. Inspecting inside, one is struck by the size of the drum shelves: not the foot-wide (30cm) conventional shelves, but massive 4ft6 (1.20m - almost the width of two doors!) wide heavy planks intended to move the entire drum load of hides toward axle height 3. Watching the drum rotate, one has the impression it is slowing to a stop. Actually, it is running at its operating speed: 1.4rpm! There is a slow speed for special applications and positioning of drum, but that is half-speed, at 0.7rpm. 4. Those new to this processing vessel may puzzle 'how such a drum can work?' How do the chemicals get the energy to penetrate the hides? The secret lies in four factors inside the drum during a process: a. the low float (the drum allows, if so desired, working with only 20-30% of water on the weight of hides in important steps of the process) b. the correspondingly high concentration of chemicals (Donnan membrane effect) c. the high ionic strength of salts d. the mechanical action of those wide shelves: no picking up of the pack and dropping the load onto the staves below. Instead, the hides slither off the wide shelves in a continuous cascade of hides. This gentle mixing action promotes very rapid dispersal of chemicals inside the drum, avoids excessive heat build-up and keeps the pelt in contact with the concentrated liquor. The tanner who is new to these drums has to readjust to some aspects of leather processing. Low-float liming successfully removes interfibrillary matter, and splits up the fibre bundles. The degree of swelling is understandably reduced in comparison with conventional processing, thus avoiding the appearance of wrinkles and veins, giving the hide a smoother surface and increasing its yield. These drums protect the grain membrane with their gentle action, increase the efficiency of chemical utilisation and lead to savings in water consumption, and also to a lower output of effluent and consequent reduction in chemical wastage. The advantages of fast distribution and penetration of chemicals are now being applied by Olcina to a new version of the Cangilones drum for dyeing; this time available in stainless steel as well as in wood. These incorporate similar structure and geometry with float recirculation, heating and testing of solutions during the process and all the features of process control seen in other modern dyeing vessels. This new development brings with it the Cangilones advantages of higher load, high chemical uptake, fast distribution and penetration of chemicals and the gentle mechanical action that notably increases the quality of the leather grain, compared with dyeing processes in traditional drums. Process control Quality consistency implies the elimination of human error. This means applying stringent means of process control: automated monitoring of process parameters, and remote/automatic actuation of most of the process steps. The chief tool used is distributed, networked PLC control, with SCADA (supervisory control and data acquisition). SCADA has the advantage of gathering together all the process data during all the steps of production and comparing it with the specified 'set-points'. It gives a view of the process and the equipment as it runs, in a visualisation not only in the present, but also past production runs. If the hide has been suitably marked and its history kept - including the selection procedures, and the batch numbers of the processes it endured - then traceability is provided by the process history kept in computer memory. A working demo of such a SCADA system can be seen at [http://www.swystemlogic.com] This is based on the state-of-the-art SCADA package 'Reliance' from Geovap spol., and is an illustration of the ease and speed of development of a practical application, and especially the immediate overview and intuitive control available to technicians and production management. The merits of automating process control, as designed for the wider industrial field, including tanneries, by Innovative Controls Corp, (ICON) of Toledo, Ohio, are: * performing the technicians decisions related to 'control points' * ensuring the accuracy of set-points (to ensure they are with acceptable tolerance) * rigorously monitored, and documented in the manner which all quality assurance systems demand. Unfortunately, systems which rely on operators noting their own actions in a 'paper-trail', are not known for their reliability. Sometimes, with manual systems, process sheets have been seen completed in advance of the steps being carried out! * A process history exists in minute detail, stored in computer memory. Every actuation of a switch, a motor-started, a pneumatic valve, liquid addition valve etc is noted and compared with the original values specified in the Recipe. If the process goes well, much of this data may never be needed. But it is available, if needed, for diagnosing the source of non-conformance and the cause of equipment failure * An automated tannery process is never in a totally automatic mode! But it is being monitored automatically and signals the technician when process parameters stray outside the permitted maximum/minimum range of tolerance. Consequently, ICON were asked to do something not often seen in other industries: if an error is detected, the technician must be able to change the running process to adapt the process parameters or correct the set points at the Drum's control panel; those changes must be automatically logged in the official process for that batch of leather * Identical PLC control panels, using the same PLC's and touch-screen colour displays, are installed to control each of the elements of control in the tannery. For example: the weigh stations, the water control system and systems to control the recycling of lime-liquor and exhaust chrome liquor * In the case of the Reliance software used in the demo, and widely applied throughout industry, the diagnostic history can be played back in a re-run of the 'process visualisation' so that the equipment status and process conditions can be reviewed, as they relate to a batch of leather produced at some time ago, weeks, months, or years in the past. Wet-blue lab testing Bearing in mind the importance of knowing the exact quality of the finished product (the wet-blue) and knowing the volume of material being produced by the modern tannery, it is essential that a fast and reliable analytical technique is available which allows the tanner to conduct an unlimited number of sample analyses. Such a system as developed by AMTEC, of Leipzig in Germany, employs the principles of x-ray fluorescence to accurately calculate the chrome oxide concentration of a piece of wet-blue leather. This is a tremendous advantage over the traditional wet-chemistry using concentrated mixtures of oxidising agents, and mixtures of sulfuric and nitric acids at high temperatures. The AMTEC system is quicker and easier for a technician to learn, does not endanger laboratory staff. But above all, it allows each batch of leather to be quickly evaluated to give a much more reliable average figure. A further interesting and useful piece of equipment supplied by AMTEC is the Chromline S. When installed on a by-pass line from the lab-box or float recirculation pipe, it can continuously monitor chrome exhaustion in the tanning bath usual optical density measurements. Thus it avoids the use of traditional analytical chemistry. Wet-blue grading, palletising and packing Along with the conveyor handling methods that have been developed by Feltre, is the high efficiency product quality and grading station linked to Feltre's own automatic hide folding, staking and palletising system. After samming, the hides are taken by conveyor via a system with multiple thickness measuring wheels, and an optical area scanner. At this point, an overhead digital camera can also record the grain characteristics (brands, holes etc) of each individual hide. In addition, the hide then pauses before a human selector, who gives a subjective assessment of each hide, which may include a decision on end-use. Depending upon the number of grades the tannery or the selector has to work with, the Feltre Palletiser takes the recorded grade number (corresponding to the pallet number) and automatically delivers that hide to the correct pallet, folding it to conform to the shape of the pallet. As the hides are delivered to the pallets at a consistent rate, there is minimal drying and they are stacked on the pallets with a consistent moisture content. The only other factor to control is ensuring that the wet-blue leather reaches the client-tanner with the same moisture content as when it was stacked. This means preventing the drying out of the wet-blue during storage and transport on trucks, in containers or by sea-freight. The system developed by VSI Ahrendt of Germany, and their engineer colleagues at Formzeug, places a shrink-wrap shroud around the hides stacked on the pallet. The pallet stands on a motor driven turntable, while hot-air guns direct heat at the shroud. This produces a tightly packed and stable package of wet-blue hides from which most air has been excluded, reducing the opportunity for mould or other contamination, and maintaining the moisture content. Implementation Quality of implementation However complete the design, the installation work must be monitored to ensure that contractors perform their work with an eye on the future reliability, and low maintenance costs of the operational plant. Assembling the project team: Lean, Mean and Motivated: * Project manager (planning, scheduling and coordinating) * Leather technologist * *Production/QA manager * Engineer(s) for the construction phase: civil/mechanical/electrical/hydraulic/water and effluent treatment * *Engineer for the operational phase - tannery maintenance and process controls * Process controls/systems integrator * Health and safety * Finance and administration * Team members marked to be future members of the operational team Review meetings Meetings will be held to develop the flow diagrams and proposed layouts (see diagrams). As discussed, the impact of cost is always a major consideration. But functionality and financial return during the operational working-life of the installation, must take precedence as the deciding factors. For example, a feature which ensures that the leather shade (colour, saturation and tone) is always correct after dyeing - if such a device would exist - would eliminate the operational costs of re-processing and re-dyeing. Such functionality might be seen by some as 'nice-to-have' but a technical luxury; an exercise in calculating the operational benefits should be able to prove that it will quickly pay for itself with operational cost-savings, and continue to earn income for the tannery - because re-processing is an activity where tanneries incur vast waste and heavy additional costs. The tannery's technical production team has the responsibility for deciding which features of control are needed and which can safely be excluded. This should not be in the hands of building contractors looking to save costs on a fixed price building contract. It is at this stage that many tanners will come to see the complexity of the development into which they are embarking and may well wish to turn to an experienced 'moderator' to help guide the meetings. In this case, the moderator should have a track record in similar tannery modernisation projects, and could be an in-house specialist, an external consultant or 'systems integrator' familiar with a wide range of industrial projects (preferably including liquid and powder batch-processing in the chemicals, food or petroleum industries). After final decisions, and final definition, the 'principle flow diagram' and the 'floor plan' layout of the equipment will have been agreed, and 'signed off' by all the participants at the review meetings, committing them to an agreed agenda for the implementation. Conclusion The goal of this article is to show how such a project should be implemented and to ensure a profitable outcome. I also believe that tanners intent on building a new, or upgraded, facility will want to understand the thought processes that went into the decision making. It should not be assumed that the participants in any proposal are strongly motivated for the well-being of the project. Individual team members may well have their own agendas, which lead to a myopic view of the project vision, causing some to lose sight of the future profitability and reliable low-maintenance of the plant. Repeating what was said at the beginning, implementing obvious principles often seems to pose difficulties when the time comes to put them into practice. The need for leadership, authority to decide, proper delegation to qualified support members, good communication and a spirit of empathetic team-work are critical for a successful and profitable outcome. Good project management is the key!