Malcom Ranson, Deputy CEO, Spiroflow Systems Inc.
The growth of bulk bag usage as a packaging form has increased dramatically over the past 20 years, with over 100 million now produced each year worldwide.
The benefits of bulk bags have also contributed to their growing use for the distribution of materials, previously only handled in 50 lb. small bags. Benefits include cost savings, worker safety and warehousing efficiency.
The migration to bulk bags goes across many industries including food, chemical, plastics and pharmaceutical production. Each industry has specific requirements in terms of hygiene, equipment size and options needed. Bulk bag handling equipment manufacturers must meet the challenges that may include achieving dust-free operation, varying material contact surfaces and size/footprint limitations.
Fifteen years ago, bulk bags were only used for high tonnages of relatively low value products. Now they are also employed for small amounts of valuable materials, including organic food ingredients, many of which have difficult flow characteristics and are inherently dusty.
Bulk bag discharge equipment manufacturers have also improved their designs and options to meet specific installation requirements and interface efficiently with other facility processes. The result is modern bulk bag discharge equipment that is almost universally applicable and flexible to operate.
In selecting an ingredients handling system, the main concern for the food industry is the need to meet stringent sanitary standards. Industry hygiene standards must be addressed and used in the specification of equipment. Agencies such as the USDA and 3A Sanitary regularly review equipment for exacting standards they have in place.
Other concerns or requirements include precise methods of product dosing and health related questions of reducing dust emissions and heavy lifting.
Clean in place technology, a staple in the food industry, assures the avoidance of spillage and waste. Safe, clean and efficient handling methods are therefore required for bulk bag usage to be viable.
Equipment manufacturers' contribution has been to create a range of discharge equipment that is almost universally applicable. Through research and development, these manufacturers are able to develop a bulk bag handling strategy. By offering a wide array of equipment designs and options, even the toughest powder can be discharged.
Companies receiving product in bulk bags for the first time often underestimate the task involved and buy a simple hanging rig in which a bag is suspended over a receiving hopper. These are often 'home-made' by a local fabricator without careful thought for safety implications and practical problems. This basic design may meet some requirements, such as for sugar and salt where flow problems of flow or dust are not an issue, but serious safety issues can be raised if the bag is not properly supported underneath as is often the case. Product waste through spillage and incomplete bag emptying are other problems.
Common Options in Bulk Bag Discharging
Height restrictions and hoists
A low-loading version is available to be used in height-restricted areas or where only a low lift fork truck is available. Where fork trucks are not used, equipment manufacturers can supply a discharger with an integral hoist designed to lift bulk bags into place. Also, a low level hoist may be provided.
Batching from bulk bags
A loss-in-weight discharger can be used where automatic batch emptying of bulk bags is required. This comprises a bag support dish mounted on load cells and attached to a batch controller, allowing for both 'bulk' and 'trickle' feed.
A pause and resume feature then retains in memory the amount dispensed when one bag is empty. When a new bag is placed in position, the controller recalls the remaining weight needed and resumes discharging.
Batch recipe operations often call for partly filled bags to be retied and removed from the discharger. This is facilitated by circular 'yoke' closure bars. Centralized computer inventory control is also possible as the amount of material remaining in a bulk bag can quickly be seen on the discharger's control panel.
A bag dump door allows the discharger to continue accepting minor quantities of additive products in 50 lb. bags.
Integral transfer conveyors
Food ingredients must be handled within an airless and totally enclosed environment to maintain the most hygienic conditions. Common flexible screw or other mechanical conveyors are inherently sanitary as they may be completely sealed all the way from where material is accepted to the point of processing.
All metal contact parts are stainless steel, and the plastic tube is a polymer approved for food use. Ambient air or moisture cannot enter the conveying tube, protecting the product against contamination. Material with particles of different sizes is conveyed without separation, size reduction or thermal degradation.
Delivery of material at the outlet is at a continuous and consistent rate, enabling precise weighing when batching a number of materials for mixing. Precision is normally to 1%, but 0.1% can be attained for more demanding applications.
Another optional model is the USDA/3A accepted discharger. Any foreign matter on the base of the bag is trapped in the outer chamber, while clean product passes through an inner tube directly into an integral transfer conveyor. Quick release clamps and self-draining surfaces allow for routine cleaning.
A glove-box arrangement for clean rooms and hazardous environments requiring indirect bag spout access and no contact with bag contents by the operator or environment can give high containment levels (up to 0.025 micrograms per cubic meter).
Tieing it all Together
Every batching project requires a separate set up specifications and options. As bulk bag handling equipment manufacturers become more savvy in their product offerings, innovative and cost-efficient methods become industry standards. Reviewing initial needs of a project, assigning priorities to each need, reviewing equiTipment offerings and budgeting accordingly is the groundwork to a successful integration of bulk bag handling equipment.