What better way to convey Bulk Products than on a cushion of air?
Air Supported Belt Conveyor
Money does not grow on trees, but there is money to be made from trees. However in today’s fragile economy even a booming industry like bioenergy needs to watch the pennies. Mechanical faults, loss of product and hazards such as explosion and fires all mean extra costs for down-time and maintenance.
These are considerations to bear in mind when selecting a conveyor system, a range of which is supplied by the likes of UK-based
Robson Handling Technology Ltd. Chain, belt and screw conveyors are the most well-known methods but they are not without their imperfections and seem second to the air assisted options on the market.
Belt and chain conveyors are most common because of their reliability. Chain conveyors can operate at steeper slopes and are suitable for shorter or complicated runs but should avoid concave vertical curves.
The message echoed throughout the biomass handling system’s industry is that chain conveyors are used as a supporting unit and not a central transporter.
‘We prefer not to offer chain conveyors because of the dust generated increases the risk of possible explosion if the speed of the conveyor is too fast or contaminants such as tramp steel enter the system,’ Jon Skidmore, Marketing Manager at Robson, says. ‘We find it is better to carry material than the material to carry itself. If biomass is carried on a metal bed plate by the scraping of a chain it can generate heat unlike on an air supported belt conveyor which has no contact and no subsequent heat generation.’
In enclosed areas biomass material is combustible, and the dust that comes off the material is explosive. Biomass operators need to ensure fuel turn-around is as quick as possible. Robson’s conveyors can transport material in access of 1,000 tonnes per hour over distances beyond 300 metres.
The dust generated is potentially Explosive for which, there are Atex regulations, that rate explosive zones.
The DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002) describes the areas, which have potentially explosive atmospheres as zones, each zone is rated as to the time a potential risk is present:
Zone 20 (Dust) A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently (typically >1000 hr/year)
Zone 21 (Dust) A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally (typically 10-1000 hr/year)
Zone 22 (Dust) A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does, will persist for a short period only (typically <10 hr/year max 1 hour release)
Equipment manufactured for these zones have to meet stringent regulatory criteria, the equipment is rated by category as defined in the ATEX Regulations: Category 1: for Zone 20 - Category 2: for Zone 21 - Category 3: for Zone 22
A breath of fresh air
To avoid these difficulties, remove moving parts and just add air. Less moving parts and less hardware means a lower risk of contact and subsequent explosion or fires. When material sits on a conventional belt conveyor it undulates when moving over rollers meaning the angle of repose of the product can change resulting in spillage off the belt. With its clients in the Sugar Industry needing a new approach Robson did away with traditional rollers and sat the belt on a steel bed plate, within a sealed enclosure. Low pressure air is released from under the bed plate lifting the conveyor belt off the metal bed plate allowing it to float.
The Robson Airglide Belt Conveyor comprises of a drive head drum and tail drum in an enclosed casing with no other moving parts just the floating belt, this causes very little frictional resistance and allows a considerable drop in motor power. The entrained material on the belt does not pass over rollers, so the angle of repose is never altered therefore spillage is not a problem. For the project within the Sugar industry the conveyor was fully enclosed and certified to meet the stringent ATEX regulations, as sugar dust is potentially explosive.
With the success shown in the sugar industry, Robson supplied Airglide Conveyors to the power industry for use with Biomass. This proved very successful, as the material and dust is contained within the conveyor. Dust extraction points are provided to minimise dust in the system. Other safe guards such as heat detection and suppression or deluge systems can be incorporated.
Visit http://www.robson.co.uk/airglide.html for more insights in to the Airglide conveyor.
Robson Handling Technology Ltd
Coleford Road Sheffield, S9 5PA
Tel. 0114 2444221
Fax. 0114 2433066
Published on LinkedIn September 2015
"Robson is one of the leading UK Conveyor Manufacturers, offering service and value through its Conveyor products and services".