FEATURE FOOD & BEVERAGE
How to get your conveyors under control
ABB’s Andrew Bould explains why variable speed drives are key to keeping your conveying systems in top condition
C
onveyor systems are one of the most common machines found in
food production, shifting vast volumes of materials from place to place throughout a facility. Belt conveyors, roller conveyors, overhead conveyors, spiral conveyors and others in addition make up the arterial routes along which ingredients, products and packaging travel through each stage of the production process. Whilst they come in a range of shapes and sizes, a common characteristic of almost all conveyors is the requirement for speed control. When we talk about variable speed
drives (VSDs), which are typically used to provide speed control for motors, the focus is very often on energy saving. Indeed, in variable torque applications such as fans and pumps they can reduce energy costs by up to 60 per cent. However, conveyors are a fixed torque application. In many food conveyor applications, throughput typically remains relatively constant with uniform quantities and batches providing little need for significant variations in torque requirement. Whilst energy savings are still very much achievable, they are often much smaller in scale compared to variable torque applications like centrifugal pumps and fans.
12 SEPTEMBER 2019 | FACTORY EQUIPMENT It can therefore be easy to fall into the
trap of thinking that VSDs have little to offer for conveyors. On the contrary, VSDs can offer significant productivity improvements. Modern VSDs now come packed with features, some of which are specific to conveyors and their particular characteristics, which can help food and beverage producers to improve productivity and profitability.
Modern VSDs now
come packed with features, some of which are specific to conveyors and their particular characteristics, which can help food and beverage producers to improve productivity and profitability”
OVERALL EQUIPMENT EFFECTIVENESS (OEE) In examining how VSDs can boost productivity, it is perhaps helpful to
/ FACTORYEQUIPMENT
Variable speed drives doubled the packing rate of a tomato handling machine built by OEM D&D Engineering
NEED FOR SPEED Sudden starts and stops, or jolts when transitioning between different speeds, can damage goods on a conveyor and lead to costly wastage. Any spillage may also require cleaning and disinfection of the line. It is therefore important that conveyor motion is managed smoothly.
Modern VSDs now come packed with features to help improve productivity and reliability in conveyor applications
frame the discussion within the context of overall equipment effectiveness (OEE). OEE is a lean production concept that determines manufacturing productivity. It calculates actual productivity as a percentage of theoretical productivity in three key areas: availability, performance and quality. To determine where the greatest potential for improvement is, these areas are then further subdivided into what are known as the ‘Six Big Losses’, grouped as follows: • Availability 1. Planned downtime 2. Breakdowns • Performance 3. Minor stops 4. Speed loss • Quality 5. Production rejects 6. Rejects on start up Conveyors are a common cause of
many of these losses on a typical food production line, yet VSDs can provide mitigation against all six metrics, helping in turn to increase OEE percentages in each area.
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