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What to consider when choosing the right product distribution line

Supplier: Heat and Control
08 April, 2014

Choosing the right kit is only half the story. It is not simply a question of buying the most suitable weighing equipment, or distribution system.

Yes, speed, accuracy and reliability are vital, but you also need to choose a supplier with the service and support people that understand your wants and needs, and provide the right solution if ever a problem or issue occurs, by responding quickly.

Every retailer is looking for something a little bit different in their product range – be that a different type of snack, flavour or pack presentation – so there is the need to be able to customise and deliver exact requirements.

These days, weighing and packaging systems have become compact with a smaller footprint compared to previous single multi-head weighers and bag-makers. As an example, they are able to deliver around 130 bags per minute for chips and as much as 220 bags per minute for extruded snacks, on small target weights. Compare this to the 80 and 90 bags respectively with equipment of the past, yet achieving accuracy within 1 per cent of the target weight.

Factors that one should consider when looking to upgrade, or looking at a new distribution line, include: consideration for system layouts with a view to future requirements; provision for accumulation and feed modulation; methods to divert product, sanitation, operator safety, cross-contamination, sustainability; and product quality control.

While price, delivery and other commercial considerations are important, technical performance should certainly be the primary factor when evaluating a line of your choice.

Conveying

Conveying (product delivery) has become an integral part of controlling the feed to the weighing and packing stations of any food product, and has become more sophisticated than simply moving product from point A to point B.

When selecting a distribution system a processor needs to ask: do I need a vibratory conveyor or a horizontal motion conveyor for my line?

Vibratory conveyors come in two drive types: electromagnetic drives which produce variable speed movements with short amplitude (lift); and high frequency (speed).

Electromagnetic drives are best suited for lightweight, easy flowing products, and for conveying limited bed depths, spreading product, and fines removal. The other is a more aggressive mechanical vibratory drive.

While vibratory conveying are very useful for breaking up product and keeping it separate, the constant bounce and impact of product on the pan is aggressive and often can reduce the quality of the finished product. Vibration can cause micro-cracks in some products, making them more susceptible to breakage later in the packaging or delivery process.

There is often coating build up on a vibratory conveyor pan but not on horizontal motion conveyor.

Rather than bouncing product, horizontal motion conveyors slide product along the pan. This has become the preferred means of conveying fragile and coated foods such as snacks, fresh produce, and frozen prepared foods.

The horizontal motion virtually eliminates product breakage, cracking and does not shake off coatings, breading or seasoning. At the same time as being gentle on the product an added advantage is that seasoning, oil and other coatings do not build up in the pan, which in turn increases downtime for cleaning.

Horizontal motion conveyors are available with direct and inertia drives. The horizontal motion allows gentle short term product accumulation, whilst uphill horizontal motion conveying reduces product damage in return loops.

While sliding product prevents breakage, coating loss and noise - it also has some limitations that become evident in horizontal motion conveyors:

  • Product spreading can only be achieved with specially shaped pans
  • Product travel rates are slower than aggressive mechanical drive vibratory conveyors, but may be faster than high frequency electromagnetic drive designs
  • Uphill conveying is usually limited to about 1.5 degrees, although in some special cases, it is possible to convey product up to 8 degrees
  • Does not level piles of product without pan modifications
  • Difficulty conveying limp or sticky products

Direct drives use long strokes, producing travel rates up to 40ft/min (12.5 m/min). In addition to greater throughput/pan size, direct drives can also stop and start instantly, offer modular expandability, provide fast travel rates to reduce stale product complaints and improve the efficiency of seasoning applicators, weighers, bag-makers, and overall packaging room performance.

(Inertia drives generally deliver slower product travel rates, have delayed stop and start operation, and do not work well in modular and packaging feed applications.)

Selecting the proper type of direct drive will greatly reduce maintenance and energy usage, as well as improving safety and packaging feed efficiency.

Weighing and packing

Tasks usually performed by manual labour – involving sorting, counting, weighing, bagging and case packing  – can be replaced with consistent, accurate and high-speed systems, drastically reducing operational costs while increasing output and productivity.

Modern weighing technology brings with it higher speed and more accurate weighments, increasing product yield – which in turn relates to less "giveaway" per bag. Computer combination weighers deliver the performance processors need to meet high production requirements for their products.

Modern stainless steel weighers provide more sanitary weighing systems, while new surface profiles and coatings virtually eliminate product sticking. High-amplitude feeder drives provide powerful control of product flow, while Pulse Width Modulation systems automatically tune dispersion and radial feeder drives for maximum operating efficiency.

Technological advances have resulted in further increases for packer profit with higher production rates, reduced product giveaway, and lower cleaning and maintenance costs.

Developments in weighing technology cam be summarised as follows:

  • Speeds up to 15 per cent faster than earlier models
  • Control unit with Windows XP operating system and email capabilities
  • Capability for full integration and monitoring of other equipment on the line through single panel operator interface
  • USB camera for real-time monitoring of product conditions on the dispersion and radial feeders
  • Automatic timing settings that optimise productivity and reduce operator inputs
  • Reduced energy consumption
  • Quick and easy set-ups and product changeovers

Finally, when designing / engineering your plant layout, packaging platforms also need to be taken into consideration. Modular packaging room platforms reduce installation and cleaning costs in meat and poultry, plants and sanitary production environments.

Packaging platforms need to provide a safe, stable support for product distribution and inspection conveyors, weighers, control panels and other equipment. Light-weight structural members could cause vibrations that are not easily detectable but can translate into errors on the load cells of computer weighers.

The end result will be weight fluctuations that can cause weighing errors reducing productivity and efficiency. Structural members need to be located correctly to eliminate flat surfaces where debris can accumulate. Conveyors can also be elevated above the non-slip decking to facilitate cleaning. Another feature to consider is to design open frameworks that take minimal floorspace, allowing complete access to bagmakers, cartoners and other ground-level equipment.

Platforms are normally custom-configured for each installation and can include wash racks for weigher hoppers, plumbing and pre-wiring for single-point connection to utilities, lighting, hose storage, catwalks, stairways, safety railing, floor drains and other features.  

Before you buy, consider testing your products. Some suppliers have equipment set up and ready for customer testing to help prove capabilities such as gentle handling, conveying uphill, or moving large quantities of product, as well as weighing and packaging demo centres. If this service is available, making use of it can be of value in the decision making process. During a product test or demo, you can also get firsthand experience with other features such as operator interface, ease of use, and possibly sanitation.

Choosing a supplier as with any equipment purchase, the buyer is not just purchasing a piece of equipment but also entering into a long term relationship with the vendor.

Choose a reliable supplier that understands your industry and offers up front assistance with such things as system layout, sanitation procedures, and avoidance of cross-contamination.

Be sure that you are comfortable with the vendor's ongoing assistance such as warranty, training, spare parts, and technical support capabilities.

Price should not be the only consideration. Choosing the wrong partner can be more costly than the price difference that is paid upfront.