A critical aspect of production. By Peter Dowell, managing director of Delta Neu
Throughout the converting industry, today’s ’round the clock’ production schedules are dependent upon a truly reliable process waste handling system. In terms of savings and safety, the advantages cannot be ignored. The efficient operation of most modern converting machinery means waste handling is an intrinsic part of the process. Automatic collection at source frees valuable production space, minimizes potential safety and fire hazards, and allows machines to be operated to their maximum capacity. Also, where conversion creates dust, the work environment and the product is improved, and maintenance and cleaning time reduced.
Reclaim value of the material can be maximized by separation of recyclable trim from contaminated waste. Fully auto- mated, sequenced systems result in substantial energy savings, operating only when required and, if filtered, recycling warm conveying air back into a building for space heating.
While the concept might appear simple, there is far more to an efficient waste handling system than first meets the eye. The industry converts a wide range of materials, with very differing physical characteristics. Equally, the markets served have diverse requirements, which also need to be met. Process waste handling systems have to be designed to cope with these varying demands, otherwise maximum efficiency:minimum cost ratios cannot be achieved. It is worth examining these differences.
Printing and Stationery: The size of print operations varies enormously, as does the size of waste handling system required. Systems for the largest printers are of a scale and complexity rarely seen elsewhere, automatically feeding any one of three or four compactors and with built-in ‘fail-safe’ procedures to ensure 24 hour production, seven days a week. In addition, segregation of contaminated and uncontaminated trim and/or different types/colour of paper is achieved to ensure optimum waste values.
On the other hand, what is available for the ‘go-ahead’ small converter with limited finishing facilities? One answer is the pre-assembled package, designed specifically for the purpose, which comprises an automatic waste compactor, chopper fan and balanced air/product separator. No longer need smaller converters think the benefits of automatic extraction are beyond their reach. Such a package can be purchased or leased, making this approach practical and affordable. It can also be used in similar situations in other sectors.
Knowledge of the complementary technologies of process waste handling and dust control can mean optimization in the system design as the two process requirements are integrated. Irrespective of scale, another important issue that sometimes must be considered is static, which can be a major problem. Quite often the type of substrate being used is the cause, but not always. Elimination of static build-up within a waste extraction system should be within the capability of any reputable system supplier.
Corrugated and Cartons: Comparatively large scale waste extraction systems are an integral part of a modern corrugated and cartonboard plant. A recent innovation where plant layout permits is the use of rotary feeders to meter trim from several converting machines into a single main waste extraction system running below. The feeder replaces air/belt conveyors or individual fans on each machine, and reduces the air volume extracted and the power consumption while increasing reliability.
Coated Papers and Film: How to efficiently dispose of a continuous stream of narrow, tough, stretchable edge trim generated at 300m/min is a problem faced by flexible packaging producers and film converters. In many cases, the solution is to introduce a trim cutter at each collection point within a waste system, and so greatly reduce the potential for problems. The cutter reduces the waste to small, easily managed pieces and permits linking of multiple extraction lines into a single system. For the smaller producer, systems can be simplified by replacing the trim cutters and chopper fan with venturi based systems. By segregation and preventing contamination, recycling of plastics waste is often possible.
Paper and Tissue: On the high speed rewinders used in this sector, automatic waste handling is essential and edge trim is extracted from the slitting knives as it is cut. At speeds up to 3,000m/min, special design precautions regarding the collection points and chopper fan are called for to maximize rewinder performance. Following rewinding, paper sheeters can automatically reject rates of up to 10t/hour. This presents the waste system and shredder with a high instantaneous load, albeit at a reasonable overall rate. Nubbin extraction from tissue log saws is another area of specialized knowledge.
Foil converters, label and tape producers, wallpaper manufacturers and other specialists also have particular requirements to suit machinery, products and operating speeds.
While, in principle, all process waste handling systems are designed with the same components, there can be major differences between one supplier and another. It is important to choose a supplier with qualified and trained engineers, quality products, and the expertise and experience to meet the needs of any project. Availability of after-sales support and service personnel are other essential factors.