A duty to discharge

27-Feb-2007 - Last updated on 14-Mar-2017 at 17:37 GMT

While the handling of raw materials has improved in recent years, hygiene and explosion hazards still exist, as Bob Brooks discovers

Raw materials arrive at food sites in a wide variety of ways, depending upon their nature, volume and origin. Sugar and flour, for example, can be delivered in anything from 1kg bags to a 20t road tanker.

Keith Simpson, marketing manager for Spiraflow, believes that for many a tanker-load is too much. "The one-tonne rigid intermediate bulk container (IBC) was a compromise, which allowed dust to be kept under control. However, empty IBCs use valuable space, so the flexible intermediate bulk container (FIBC), also known as the big bag, became popular because it's lightweight and folds up to make a compact return package."

The acceptance of these bags is down to the equipment that fills them and the dischargers that empty them, says Simpson. "Overall safe, hygienic, reliable discharge and containment can be achieved." However, he warns that users should beware of suppliers which offer FIBC dischargers as an accessory to other equipment. "Given the potential for problems with all but the most free flowing of materials, it is essential to use a supplier which regards dischargers as key products."

Recent developments have overcome the problems caused by loose liners, which can result in dust and spillage during discharge and disposal. A liner spout clamping system provides total containment preventing exposure of operator and environment to hazardous products while eliminating reverse flow, ie, contamination of product by operator and environment. During discharge the bag and its liner are kept in tension in order to promote a smooth flow of product and ensure that total emptying takes place. The tensioning also prevents the bag/liner becoming entangled with moving parts of the process or of any conveyor system.

Big bag filling

Machines have been developed that can effect a big bag filling in less than a minute, reports Simpson. "That is about the time that it takes to rig a new bag into position and to remove a filled bag at the end of a cycle. So, a dust-free and spillage-free filling rate of about 20 bags an hour can be achieved."

Quick-release hooks, pneumatically-powered support arms, bulk bag loop-releasing mechanisms, vibration equipment, and weight and measuring equipment can be included into the procedure and thus speed turn-round.

Any product or process that prevents the problems caused by dust and spillage must lead to an improvement in hygiene and safety as well as speeding delivery and production and eliminating waste.

There are, of course, other factors that must be overcome; for example, many food products are potentially explosive. "It is impossible to set fire to a pile of flour," says Simpson. "But sprinkle flour slowly over a lighted match and you have the potential for an explosion. Don't try this! Take my word for it!" Continually breathing in flour, sugar, or any other food product dust is another hazard to health, just as inhaling coal dust was to the miners of old.

Matthew Cork, Ex-Solutions - part of Pyroban - specialises in identifying potential explosion hazards and feels that specialist companies can help.

"In the past, a manufacturer might enlist the advice of an expert who would visit a company's premises and produce a lengthy report," says Cork. "This would detail the hazards, the likely sources of ignition, and provide recommendations. However, often no practical solutions were suggested and it was left to the company to resolve the problems and initiate whatever work needed to be done. In many situations nothing was done or, if it was, it was not done properly."

Matters have improved, however, he says. "Nowadays companies can be employed, which not only identify the problems and make the recommendations, but carry on through by appointing people to correct the faults, eliminate the hazards, and take the responsibility to ensure that necessary improvements are carried out."

Raw materials, stored in bags, drums and hoppers as powders, vapours, and gases, can all be potentially explosive. "Pyroban's role in managing the explosion risk is at the front end of classifying the areas of operation into zones and then engineering solutions for the equipment," says md Ian Ratcliff. "Handling equipment is widely used and is required to operate in hazardous areas, but it represents a risk of ignition. Pyroban converts this type of equipment so that it is safe."

Pyroban's sales and marketing director, Malcolm Davis, cites a new contract in a large flavours warehouse where 90 fork-lift trucks are operating in a potentially flammable atmosphere, which includes vapours and powders. Trucks will be adapted so that they cannot be the source of an ignition.

Unhygienic conveyors

Considerable progress has also been made in recent years to reduce the health and hygiene hazards posed by using unprotected equipment on handling systems such as conveyors.

In 2004 Chris Middleton, then md of BDL Drum Motors, told Food Manufacture that the majority of conveyor belt drives had external gearboxes that were almost inaccessible for cleaning purposes. Since then BDL Drum Motors has merged with Interroll, which Middleton now heads up as md.

"There is no doubt that the situation has improved with many conveyors in the food industry being manufactured from stainless steel and their parts sealed for life," he says. "However, there are still far too many external motors out there which are not sealed, allowing powder, fruit parts, onion juice, and similar to contaminate. The heads and the tails of conveyors are major areas for trapped food and they require a lot of washing."

Also, although lubricants used on such items may in themselves be harmless, they can attract dust-containing protein which, in turn, can encourage bacterial growth. This can accumulate and then break free due to normal processing vibration and end up in food being handled, he warns.

One of Middleton's biggest concerns is the increased use of external contractors to clean down and maintain equipment. "The vast majority of this work is done at weekends or at other times when the factory may not be operating. Because of this, the cleaning is carried out without those involved in the manufacturing processes being present."

While the introduction of anti-bacterial belting has helped improve hygiene, says Middleton, day-to-day cleaning and maintenance must be supervised. "In many cases it is not," he claims.

Developments in conveyor technology have led to "low maintenance and easy clean" systems, says Mike Read, sales director of Wright Machinery. "A weighing conveyor that is based on the vibratory principle has been developed as an alternative to systems that use belts to handle dry, free-flowing products. It has no moving parts and is built in stainless steel to IP65 standards for wash-down."

Filling lines in which ingredients are dosed separately, and the automatic control of continuous processes such as drum coating where flavours are added, are among the applications cited. "There are no belts, no motors, and no rollers to track, clean, or repair," says Reed.

Wright Machinery has also introduced conveyors that use only differential horizontal movement. "Compared with vibratory conveyors, the new technology offers longer conveyor lengths without any risk of product damage or the creation of dust," says Reed. "And compared with belt conveyors, build-up of sticky residue from oily or sugar-based products is resisted since the unit's sliding action is essentially self-cleaning thus reducing downtime for cleaning."

In another development, an anti-slip plastic pallet has been made by Allibert Buckhorn, which is claimed to improve safety across the entire pallet deck and runners. "Never before have the health and safety of workers and the hygiene considerations for the products being handled been more important," claims the company.

Allibert Buckhorn cites Health and Safety Executive figures which show that someone slips or trips at work every three minutes, and, on average, two instances a year are fatal. FM

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