While 25kg sacks are ubiquitous across the bulk handling sector, efficient methods of emptying them are rare. Israeli company Ayal Robotics & Engineering is promoting its LaborSave sack emptying device which it bills as the most efficient and fully automated system on the market. Local distributor Equip (Aust) P/L of Queensland has orders and interest from the plastics, sugar and grain sectors.
Ayal, established in 1995, has developed numerous products including assembly robots, palletisers, de-palletisers, and conveying systems.
It introduced LaborSave in 2004 and Ayal reports installations in over 300 locations worldwide.
Closer to home, Equip (Aust) started distributing the system around 2011. Russell Fairey of Equip said that “We have installations in both Australia and New Zealand, primarily in the plastics area, debagging 25kg sacks of PE granules. We have also sold a unit into Malaysia for sugar debagging, and are currently working on areas in agriculture for grain and the like up to 40kg sacks.”
25kg sacks ubiquitous in bulk handling
Across all markets and industries receiving and processing raw materials, delivery options are essentially the same – 25k sack or a train/truck delivered silo.
When considering raw material processing, and sack delivery in particular, the obvious expense is manual labour, where multiple teams of workers lift and cut sacks over a hopper. Yet within this seemingly “simple” manual process, lie some of the largest risks and avoidable expenses facing bulk handling sites and factories today, including injury, contamination, raw material loss and overall factory efficiency.
According to safety data, the most common triggers of employee injury are manual handling, sprains, tears, pain and lacerations – accounting for well over 50% of on the job injuries. When considering the monotonous and repetitive task of lifting heavy sacks with a knife in hand, it is easy to understand how these employees are at a high-risk for injury. And the cost implications of employee injury, especially in Western countries, can quickly reach prohibitive sums in both direct and indirect costs.
Workers’ compensation, medical and legal expenses and factory downtime are just some of the direct expenses, while accident investigation, implementing new safety protocols, training new employees, lower employee morale and absenteeism are some of the indirect costs that will likely be encountered.
In fact, due to the high risk of employee injury, regulators in some countries have set guidelines for the maximum amount of weight that an employee may lift. It goes without saying that this limit is often times not followed, leaving the window open for the levy of significant fines on sites breaking the rules.
Contamination a headache
Keeping sack fragments from mixing with the raw material is crucial for quality control. Cutting the sack too roughly can shred the edge, mixing bits of paper, plastic or jute fibre into the product as it pours out. In addition to ingredient contamination, sack fragments can clog filters, block pumps or interfere with solubility.
And even in the traditional method of sack emptying, the risk of contamination from sack shavings, broken knives, cigarette butts and other waste is enough to result in product rejects and the occasional machine downtime for sterilisation.
Raw material loss
High-priced products like pigments, plastic granules or powdered chemicals are not free-flowing and can stick to the seams or corners of sacks. Industrial production lines must choose between sacrificing those valuable bits in the interest of speed, and taking valuable time to brush out each sack.
According to Ayal Robotics & Engineering, in a university study conducted on raw material loss at a plastics factory, the results pointed to a 3% loss on average. Assuming each sack of raw material cost $100, the company lost $3, and racked up an opportunity cost of around $12 by not producing more. And even if a factory is conscious of this issue, and manages to lower waste and spillage to 0.3%, multiply this number by several thousand sacks, and herein lies one of the well-known challenges of sack emptying.
To solve this problem, the industry has suggested a number of technological solutions for preventing raw material loss.
Some solutions come with drawbacks
One semi-automatic solution cuts the sack, while leaving the emptying to be performed on the run. With this device, employees load each sack onto the moving conveyor belt, demonstrating the first disadvantage: the process still requires manual labour.
The conveyor brings the sack to an automatic cutter blade, which slices the sack open as it passes. However, sack emptying time is limited to the time required for the torn sack to be pulled across a 1.5 metre gap with a hopper placed beneath. Any material still clinging to the interior of the sack after it crosses this opening is lost — an average of 1%-2%.
A second automatic solution resembles a giant blender. It destroys the sack to release the contents, inevitably mixing pieces of sack with the raw material. Whatever problem was solved by speed is replaced by a new problem: filtering the raw material from the shredded waste.
Using a “tumble dryer” method, the mixture is spun with force against a cylinder with holes similar to a sieve. Some of the holes become plugged by sack fragments or pockets of clumped material, while tiny sack bits escape through other holes to contaminate the sifted product.
Raw material waste still averages around 2%, making this fully automatic process a costly one. While increasing the processing speed will only increase that loss — to as much as 3%.
Site efficiency
Even in optimal working conditions and all safety measures being followed, there will always exist limits on human capacity. Under best case scenarios, a factory worker can be expected to lift and cut up to 60 sacks per hour. For large plants using manual labour, the reality is a lot of workers with a seemingly never-ending amount of sacks to be opened.
All of these factors ultimately effect a plant’s costs, product quality and time-to-delivery.
Rail and silo delivery
Due to the challenges presented by manual sack emptying, and the shortcomings of the automated solutions suggested by industry, various bulk transport innovations have appeared, including gigantic sacks delivered in 30-ton containers, and bulk storage in 200-ton silos which enable raw materials to be added to a production process at a controlled, uninterrupted rate.
However, these innovations have been a mixed blessing. While bulk packaging does reduce man hours, the potential savings are eroded by the cost of dedicated trucks or trains required to deliver the huge containers. These methods cannot haul anything on the return trip, and must therefore return to the supplier empty with the cost of wasted logistical resources passed on to the buyer.
Bulk storage, in addition to the considerable cost of each silo, runs the risk of disaster by mixing multiple deliveries of raw material: high-quality material topped by an “off spec” shipment can render the entire silo contents useless, triggering alarming losses in material and production time. For these reasons, it is estimated that only 8% of factories receive their raw materials in bulk transport.
The market trend: back to the sack
Companies which opted for bulk delivery have learned these lessons the hard way, and are returning to shipments of raw materials in small sacks of no more than 25kg each. The ease of quality control, cost-effective transport, and the simple storage requirements are further enhanced by the competitive pricing among a wider choice of suppliers.
According to Ayal, studies have shown that unit sacks of raw plastic materials are more cost-effective than bulk by 40 – 80 Euros per ton.
And for this reason, companies find themselves facing the same disadvantages that prompted the move toward bulk packaging in the first place.
Where LaborSave fits in
LaborSave is an automated sack cutting and emptying system. Ayal Robotics & Engineering says that it has proven itself at several hundred of the world’s largest and well-known plastic, food and chemical factories.
According to Ayal’s publicity “LaborSave handles up to 1,300 sacks per hour, empties more than 99.99% of sack contents and eliminates manual lifting, cutting or risk of contamination.
“Factories that have integrated LaborSave within their production line have experienced an increase in efficiency and profits, with a reduction in costs related to employee absenteeism, machine downtime and lost material.
“Short of using a forklift to place a pallet of sacks on a conveyor belt, LaborSave is a fully automated sack cutting and emptying solution. With a loaded pallet of sacks within the system’s unloading chamber, metal grips grab the top layer of sacks and carry them over a set of blades which neatly slice the sacks in parallel lines; without producing sack shavings. The slit sacks are then shaken above a loading hopper for several seconds, ensuring maximum material emptying before discarding the sack in a bin and starting the process again for the next level of sacks.
The Australian distributor, Equip (Aust), is at 55 Avon Ave, Banksia Beach , Qld 4507.
Contact: Russell Fairey, email: equip@equipplastics.com