Getting Metal Out of Processed Vegetables

Ideal Locations for Magnetic Separators and Metal Detectors in a Vegetable Processing Plant

Processed vegetables are a vital part of the food chain.  Tens of thousands of bags of pre-cut carrots and freshly prepared kale are bought in supermarkets daily.  Frozen vegetables have been very popular since Clarence Birdseye invented the quick freezing method in 1924.  Also,  often-unnoticed processed vegetables are present in many everyday food items such as tinned soup, baby food, sauces, and ready-made meals.

However, processing vegetables takes a great deal of care and attention as the products are often delicate and can be easily damaged.

BUNT-2286 4 8.5x11 plants

As with all processed foods, there is always the risk of metal contamination.  Metal can be introduced at various stages in the process.  The design and positioning of the Magnetic Separator or Metal Detector has to also respect the delicate nature of the product.

Untreated Vegetables Feedstock

During the collection and transportation of the raw vegetables, there is always a high risk of metal contamination.  This can be remove using a Plate Magnet.  To avoid contact with the vegetables and eliminate the risk of damage, the Plate Magnet is suspended above the incline conveyor feeding the washer.  Metal is attracted up onto the face of the Magnet and held until cleaned.  This is ideal to remove larger metal items such as screws and nails.

Post Washing

The vegetables washing process frees dirt and other detritus including metal particles.  Prior to the washed vegetables being fed into a drier, a Permanent Magnetic Pulley, replacing the standard head pulley of a conveyor, attracts and automatically removes any free metal before entering the drier.  Again, there is no physical content between the Magnetic Separator and the vegetables.  After drying, the vegetables are fed into a dicing machine.

Prior to Dicing

Plate Magnet Tapered Step-9545
Plate Magnet Tapered Step

The blades on a dicing machine are delicate and expensive.  Metal contamination can cause significant damage.  To ensure that no metal is present, the dried vegetables are fed over the surface of a Plate Magnet.  This enables higher levels of separation that when the Plate Magnet is suspended as the material is passing closer to the area of maximum magnetic strength.  Any potential damage to the vegetables as they flow over the surface of the Plate Magnet is limited.  Metal is captured and then held under the lip of a tapered step on the surface of the Magnet.

Undersized Vegetables

Smaller sized diced vegetables are often taken on a different route.  They can be mixed with water, for ease of transportation, before being reintroduced into the process.  Immediately after dicing, the smaller particles fall through a Quicktron Metal Detector to remove any small ferrous and non-ferrous metals (including any broken blades from the dicer).  Water from the external source is passed through a Magnetic Liquid Filter Magnet to ensure that any rust or other ferrous metal contamination is not introduced into the process.  The Undersized Vegetables are mixed with the water and then re-introduced into the process.

Final Packed Product

Metron 05C Metal Detector
Metron Metal Detector

The final stage of weighing and packing includes 3 steps of Metal Removal and Detection.  Prior to weighing, the processed vegetables are passed over the surface of a Plate Magnet to ensure that all ferrous metal contamination has been removed.  After weighing, the vegetables fall under gravity through a Quicktron Metal Detector where any non-ferrous metals are removed.  Finally, after packing, the finished packed batch of processed vegetables are passed through a tunnel-type Metron C02 Metal Detector as a final check prior to shipment.

This is a typical example of a Vegetable Processing Plant.  However, each plant is unique and often a site visit is required to assess and recommend the best ways to ensure a metal-free end product.

For further information on removing Metal from Processed Vegetables using Magnetic Separators and Metal Detectors, please contact the Bunting technical sales team on:

Phone: +44 (0) 1442 875081
Fax: +44 (0) 1442 875009
Email: sales@buntingeurope.com
Web: http://www.buntingeurope.com

Other Food Plant Reviews include:

Temperature Effect on Rare Earth Magnetic Separators

Neodymium Magnet Damage From High Temperatures

If a Neodymium Rare Earth Tube Magnet is put into a red-hot fire, then it would not be surprising if the magnetic properties are destroyed.  However, what if the same Tube Magnet is just exposed to steam being flushed through a pipeline system to clean the pipes?

Tube Magnets manufactured with high quality Neodymium Magnets are able to operate well in temperatures up to 100 degrees C.  There is a gradual drop in magnetic strength when the temperature rises above 80 degrees C, but this loss in magnetic strength recovers when the temperature falls back to normal levels.

However, as soon as the Neodymium Rare Earth Tube Magnets are exposed to temperatures exceeding 100 degrees C, the magnetic strength becomes compromised.  On returning to normal operating temperatures below 80 degrees C, there is an irreversible loss in magnetic strength and permanent damage.

Bunting Magnetic Liquid TrapIn a pipeline which is cleaned using steam, the temperature will be above 100 degrees C for a period of time.  This will certainly damage any standard Neodymium Rare Earth Tube Magnets or Magnetic Separators (e.g. the Magnetic Liquid Filter) installed in the pipeline.  However, most users are totally unaware of the potential loss in magnetic separation performance and that the ability of the Magnetic Separator to remove small pieces of metal contamination has been permanently compromised.

Magnetic Separators in High Temperature Environments

There are types of Neodymium Rare Earth Magnets that are designed to operate in high temperature environments.  These tend to be lower in magnetic strength at room temperature, but the magnetic field does not degrade as quickly as standard Neodymium Magnets at higher temperatures.  Also, on returning to normal temperatures, there is only a small irreversible loss in magnetic field, which is only experienced when first exposed to high temperatures.

This type of high temperature Neodymium Rare Earth Magnet should be used in pipelines which are being cleaned for prolonged periods with steam.

Tube_Magnet_FireFor applications where there are extreme high temperatures (exceeding 150 degrees C), then the best option is to use Samarium Cobalt Rare Earth Magnets (SmCo).  These retain their magnetic properties in temperatures up to 300 degrees C.  However, such applications are rare.

It is recommended that the magnetic properties and strength of any Magnetic Separator installed in a pipeline cleaned with steam or in an environment where there is constant exposure to high temperatures is checked on a regular basis (e.g. during an annual Magnetic Separation Audit).  The best way to do this is with a Magnetic Pull Test Kit.

For further details on Magnetic Separators designed for high temperature applications, please contact our technical sales team on:

HFS Drawer Magnet Removes Metal from Recycled Plastics

French Plastics Recycling Operation Installs Bunting Drawer Magnet

The latest HS Drawer Magnet has just been boxed ready for despatch to a Plastics Recycling company in France.  The Magnetic Separator was manufactured in the Bunting Magnetics European manufacturing facility in Berkhamsted, UK.

HSF_Drawer_Grate_Bunting-1864

The French Plastics Recycling operation will install the HS Drawer Magnet to capture and remove ferrous metal contamination from the reclaimed plastic.

HFS Drawer Magnets are commonly used in virgin and secondary plastic processing operations.  The Magnetic Separator is equipped with powerful Neodymium Rare Earth Tube Magnets which enable the capture of both very fine iron and also work-hardened Stainless Steel.

How the HFS Drawer Magnet Works

In operation, material falls under gravity into the opening of the HFS Drawer Magnet.  Inside the housing are two rows of Tube Magnets, staggered to ensure that all the product has to pass over the surface of a magnet.  The magnetically susceptible particles are attracted and held onto the surface of the Tube Magnet, whilst non-magnetic material passes through.

Bunting Grate Magnet

The HFS design of Drawer Magnet enables easy-cleaning of the Tube Magnets.  Unlike other designs of Easy-Clean Grate Magnet, the Tube Magnets are not positioned within an outer tube and are in direct contact with the product.  This ensures maximum magnetic particle capture.

When the Tube Magnets need to be cleaned (daily cleaning is a recommended minimum requirement), the extended Tube Magnets are manually pulled outside the housing using an external handle.  Any captured magnetic material is stopped from being pulled outside the housing by specially designed Grommets.  These Grommets are positioned in the side of the housing and fitted tightly around each Tube Magnet.  Each Tube Magnet has a non-magnetic tapered end which, on reaching the Grommet, allows the captured metal contamination to fall into a separate collection bin.  The Tube Magnets are then fully cleaned and ready to be re-introduced into the product stream.

Typical Features of the HFS Drawer Magnet

  • For Gravity Flow Applications in All Industries;
  • Configurable design to suit the flow of materials and separation required;
  • High duty construction, for long life;
  • Large range of sizes, magnet types and finishes available;
  • Easily fitted into existing systems, optional  top and bottom transitions available;

For further details on the Bunting range of Magnetic Separators and Metal Detectors used to remove metal from virgin and recycled plastic, please contact our technical sales team on:

Other Articles Related to Plastics Recycling

HFS_Grate_Magnet_Plastics-1866

 

Metal Found In Rice

Magnetic Separator Ensuring Food Safety

There are a lot of negative Food Safety reports about metal being found in food (e.g. Morrisons’ Green Beans, Sainsbury’s Bread), but there is also a great deal of good practice.

Whilst undertaking an annual Magnetic Separation Survey at a rice processing factory, we were able to see the importance of installing metal separation equipment.

Fine Iron on Bunting Grate MagnetThe Food Processor had installed Bunting FF Drawer Grate Magnets at the base of hoppers holding Basmati rice prior to packing.  For maximum fine iron removal, the Grate Magnets were constructed with high strength Rare Earth Magnets with magnetic fields of approximately 11,200 Gauss on the surface.

A schedule had been established for the Grate Magnets to be cleaned on a weekly basis.  During the Survey, the amount of fine iron captured and held onto the surface of each of the Tube Magnets was found to be  substantial.  Subsequently, one of the recommendations was to increase the cleaning frequency.  This would then ensure that the Magnetic Separators were working optimally as performance can drop if the Magnets are laden with captured metal.

Where Does the Metal Come From?

Fine Iron on Bunting Grate MagnetThe majority of rice processed in the UK is imported from South-East Asia.  The process of collection, storage and transportation results in fine iron being introduced.  Additionally, very small amounts of fine iron may be introduced during the handling of the rice at the UK plant.  This could be from the wear of processing equipment.

Does the Amount of Metal Vary?

The UK food processor has very little control on the amount of metal present in the delivered rice and even working closely with the rice grower to improve Food Safety standards does not ensure a metal-free product.  As with all food imports, there are many stages of handling and storage where metal contamination occurs.  The amount of metal can vary significantly and, subsequently, the frequency of cleaning the Magnetic Separators will alter.

Good Food Safety Practice

As demonstrated at this rice processing plant, Magnetic Separators will separate magnetically susceptible metal (including work-hardened stainless steel) prior to any product reaching the consumer.  Annual reviews with the suppliers of the equipment will provide assurance of metal-separation performance.

For more information on good Food Safety practices and removing metal contamination, or to request a Magnetic Separation Audit, please contact the Bunting team on:

Phone:  +44 (0) 1442 875081

Email:  sales@buntingeurope.com

Via the website

Fine Iron on Bunting Grate Magnet
Fine iron captured by a Bunting Magnetics Europe Rare Earth FF Drawer Grate Magnet

Bunting and Master Magnets Headline Sponsors of Waste 17

Metal Separation Technology Operating at Waste 17

Bunting Magnetics Europe and Master Magnets are the headline sponsors of this year’s Waste 17 recycling show being held at the Old Trafford Football Ground in Manchester on Thursday 8th June.  An operating Eddy Current Separator and Stainless Steel Separator will be separating metals on stand A40 and we welcome visitors to bring along a sample to test.

Bunting Magnetics Europe at RWM16The Waste and Skip Trade Exhibition is being held for the 4th year, with an annual growth in exhibitors and visitors.  Bunting and Master Magnets have both exhibited since 2015.

“With the acquisition of Master Magnets, this is a big year for both companies and Waste 17 is the first time that we will be exhibiting together,” said Dave Hills, Bunting’s Head of Sales.

The amalgamation of the two product portfolios provides an extended range of metal separation solutions for the recycling sector.

The Master Magnets Overband Magnet is used extensively in recycling operations such as MRFs and on mobile plants.  Suspended above a conveyor, the Overband attracts and lifts metal out from non-metallic materials.

Master Magnets Mobile Eddy Current Separator (1200)Being demonstrated at Waste 17 is the Master Magnets Eddy Current Separator, used to separate non-ferrous metals from non-metallic materials.  2017 has proved to be a very busy year for Eddy Current Separator projects.  Metal Separation Systems incorporating Eddy Current Separators have been exported across the world and projects include a Finnish Waste Processing Plant.  At Waste 17, they will be officially launching the Mobile Eddy Current Separator.

Working alongside the Eddy Current Separator is the Bunting Stainless Steel Separator.  The two metal separators work side-by-side in recovering or removing non-ferrous metals from non-metallic materials such as reclaimed plastic.

“Visitors will be able to see stainless steel and non-ferrous metals being separated on our stand, ” reported Dave.  “Seeing is believing and we wanted to demonstrate our expanded metal separation capabilities.  This is a very exciting time for us and our customers.”

For more information of the Waste 17 show or Metal Separation Equipment such as the Eddy Current Separator, Stainless Steel Separator, and Overband Magnets, please contact us on:

Phone:  +44 (0) 1442 875081

Email:  sales@buntingeurope.com

Via the website