Noisy conveyors may not in the past have been viewed as much of a health hazard, but that could be set to change as new controls come into force.
Draft regulations for the control of noise at work were published by the Health and Safety Executive (HSE) in April. These have caused something of a stir among suppliers and users of conveyors in the food industry.
The proposals are in response to the European Commission's 'Physical Agents (Noise) Directive (2003/10/EC). This, says the HSE, "tightens the legal requirements in relation to noise by lowering exposure values by five decibels from the present UK levels of 90dB(A), although the use of hearing protection equipment will be taken into account". The directive was introduced in February 2003 and gave European Union member states three years to incorporate it into their national legislation. But already suppliers are taking the changes on board.
Food conveyor manufacturer Cox and Plant, for example, claims to have made "revolutionary changes to noise levels". Following two years of research it has launched a new controller which is said to reduce noise of vibratory conveyors to 44dB(A). "This is about the same level as is found in a normal office environment," says md Andy Cox. "Ear defenders no longer need to be worn and the controller helps to dispel the traditional concept of conveyors being loud, oily, and dirty."
The Lanerveyor, introduced by Cox and Plant last year, is also being promoted for its lack of noise. It is used to align seafood, cereal and chocolate bars, bread rolls, fish fingers, sliced vegetables, etc, and operates at "below 58dB(A)", says Cox. "Already, 15 systems have been installed across Europe."
Those supplying conveyor components are also working on noise reducing products. Igus, for example, has developed two new items: a family of linear guides for its bearings used in packaging machinery, and an enclosed tube energy chain which "substantially reduces noise as well as vibration which could affect machine performance", says marketing manager Nikki Groom.
In a move to cut conveyor noise, people are also starting to specify different construction materials. Pennine Industrial Equipment, for example, which traditionally used steel chain and belt guides for food and beverage processing and packaging lines, now provides them in plastic. "In addition to being wear-resistant, self-lubricating and water-repellent, the range of plastic guides for conveyors reduces factory noise and chain vibration as well as improving hygiene standards," says Pennine sales manager Graham Womersley.
But, while the use of plastics can help to reduce noise, Brian Harbison, sales manager of Belt Technologies Europe, warns that cleanliness problems can arise. "It is essential that non-corrosive materials be used which are easy to clean and are free from crevices which are potential dirt traps," he says. "Traditional conveyors employing plastic belts are still employed and have led to food products being recalled due to contamination from chain lubricant, for example."
He claims that steel belts are becoming more popular because they overcome the problems of cleanliness common with conventional food industry belts. "They can be cleaned easily, are anti-corrosive, need no lubrication in order to transmit power, and are totally free from particulate," he says. Despite claims to the contrary, he warns that there are very few systems on the market which are totally stainless. "This is rarely the case," he says. "The system frames may be, but often the belts are plastic."
Chris Middleton, md of BDL Drum Motors, also warns against the use of conventional conveyor belt drives. He cites a study conducted by the Frauenhofer Institute in Stuttgart which found that 52% of food manufacturers had problems with hygiene.
"The main cause was belt drives, many of which had external gearboxes that were almost inaccessible for cleaning purposes," he reports. "Although lubricants are themselves harmless they can accumulate dust-containing protein which leads to germs, bacteria, salmonella, etc. These can break free due to normal process vibration and end up in the food."
Middleton believes the use of drum motor drives can eliminate the risk of contamination since their entire mechanism is located in a sealed unit which is easy to get at and clean.
Isoma, which specialises in the conveying of unstable and difficult-to-handle containers, also focuses on the promotion of conveyor hygiene. Isoma's md Tim Starkey says: "Hygiene is always the number one consideration, particularly when there is a need to update equipment and machinery to meet the requirements of new legislation."
Starkey believes that after 30 years of unchanged designs, specifiers are now making ease of cleaning a feature of their purchasing decisions. This is increasing demand for Isoma's conveyors, he claims. Isoma's water-tight, stainless steel trough conveyor, for example, ensures that spillages of product, lubrication, cleaning fluids, etc, are contained throughout its length. In addition, integral pipes allow internal cleaning.
"Hygiene was the key consideration in the design and installation by Isoma of a number of bottling lines at Robert Wiseman Dairies in Droitwich Spa, West Midlands," explains the company's operations director Martyn Mulcahy. "The trough conveyors ensured that product spillage could be trapped and that integrated washing and cleaning could be carried out."
"There are many crevices in which bugs can grow and smells develop, particularly in dairies," says Starkey. "Enclosed conveyors and clean-in-place systems can eliminate these; in addition, the lack of spillage means that floors can be kept dry, thus not only increasing hygiene standards but also reducing the risk of personnel slipping accidentally."
At the Wrexham facility of Dairy Crest, Vanriet has installed automated conveyor systems for feeding cartons of individually wrapped cheese portions on to six identical belt conveyor lines.
"Each conveyor was built without box sections which could harbour dirt and debris," says Vanriet's general manager Paul Farmery. "Wherever possible flanges and surfaces were angled in order to make it more difficult for dust and dirt to adhere than to a flat surface. All motors were equipped with separately sealed bearings and placed well clear of any food products to avoid possible oil contamination."
Hygiene problems have also been tackled by adopting completely different approaches to conveying. For example, Pneumatic Conveying Systems has developed and refined the concept of dense phase vacuum conveying of powders. "We believe that we have overcome the distance limitations and have produced a system that is effective when moving high tonnages of product over short distances," claims sales director Roger Burgess.
At National Starch's Goole factory, where liquid starches are made for the food industry, a dense phase vacuum conveying system has been installed to reduce the manual loading of a starch slurry mixer. Sean Wright, National Starch's chief engineer, reports that throughputs of up to 10-times the conventional conveying rates have been achieved with some products -- for virtually the same power consumption. "Moreover, it is user-friendly and guarantees a dust-free environment essential to our hygiene requirements and the well-being of our operatives," he adds.
Burgess also refers to other successful applications, including conveying spray-dried milk powder, freeze-dried coffee and baby foods. "We believe that we are making significant breakthroughs in dense phase vacuum conveying system technology which offers the benefits of low power consumption for high tonnage throughput, practically no product aggregation, and minimal or no damage to fragile products."
Starkey believes that specifiers will have a wider range of conveyors from which to choose in the future as factories get larger, speeds are raised, and greater emphasis is placed on design in order to release floor space.
"Design improvements will become very important --- especially as demand for on-line rejection systems increases," he says.FM