With a mix of magnets, metal detector and detector ancillaries, a leading supplier of building industry materials is achieving high quality, effective and safe processing of its marine aggregates

With the timely provision of a mix of magnets, metal detector and detector ancillaries, Eriez Magnetics Europe is assisting a leading supplier of building industry granular materials to achieve high quality, effective and safe processing of its marine aggregates. The customer, United Marine Aggregates (UMA), is one of the largest suppliers of marine dredged sand and gravel in the UK, where it operates a fleet of dredgers which aided by satellite-guided location and positioning technology, use both the anchor and trailer dredging techniques to extract marine sand and gravel from licensed areas of the sea bed. These operations are continually scrutinised for their impact on the environment, material quality and no less care and attention has to be paid once the material is delivered onshore, which is where Eriez comes in.

The majority of UMA wharves have plants that wash, screen and separate aggregates to meet European Specifications and its customers' needs.

The raw ballast can contain tramp iron that needs to be removed during processing but this material can also pose a further problem - the potential presence of Second World War munitions - the obvious danger of which emphasises the absolute requirement for accurate and complete detection.

UMA, which is a joint venture between Tarmac and Hanson PLC, first began working with Eriez back in 2001, when just after the Hillhead exhibition an order was placed for three suspended permanent magnets, one CP 20/100 SC2 model for installation at the company's Murphy's Wharf site in Greenwich, London and two CP 20/80 SC2 models for operation at Ridham and Erith sites in Kent.

These self-cleaning models were chosen as they are ideal for magnetic separation of bulk product, especially where positioned over moving conveyor belts and where larger volumes of tramp iron are anticipated.

While UMA was satisfied with the reliability and high performance of the CP 20/80 models at their Ridham and Erith facilities there was a requirement to upgrade the metal detection and extraction equipment at their larger flagship operation at Greenwich in South East London.

UMA liaised with the Eriez team last year over the supply and installation of additional equipment, ultimately placing orders for a powerful suspended electromagnet (Model SE 745 MC), a Metalarm 3500 Quarrymaster 2 metal detection unit and a further three CP Magnets fitted with manually operated stripper plates to remove ferrous contamination from the magnet face.

Like permanent magnets, suspended electromagnets (SE Magnets) can operate either with manual cleaning of the magnet face or with a self-cleaning unit.

Either way, the customer can be sure of the correct configuration, strength and belt position of this equipment as Eriez designs and builds its SE Magnets to suit specific applications.

The Quarrymaster 2 is just one in the Eriez Metalarm series of metal detectors in operation around the world protecting a wide range of processing machinery from metallic items, fragments and swarf.

These sensitive detectors are easily fitted to both belt and vibratory conveyors and feature signal monitoring and self-checking facilities with, typically, audible alarms as well as the optional addition of visual alarms.

Eriez manufactures a wide range of search coils for use with the 3000 range of control units and these can be fitted to virtually any type of conveyor in ducts, slides etc All coils are manufactured in high-density polyethylene and are fully screened to comply with European Union EMC regulations.

All the Metalarm control units employ the Eriez proven 'Pulse Induction' technology circuitry and are mounted on a single printed circuit board (PCB) to ensure high reliability while at the same time enabling easy access for servicing.

All controls other than the front door reset switch and 'on' lamp are PCB mounted for the same reason.

The Quarrymaster 2 3500 is housed in an IP65 stainless steel cabinet with integral anti-condensation heater and is fitted with high power electronics.

The equipment offers robust, high performance detection of both ferrous and non-ferrous metals - a perfect choice for the close monitoring of conveyor borne marine aggregate.

UMA has reported very good technical and sales back-up on this important project, one element of which has seen Eriez adding to the picture by addressing the question of possible 'missed' detections subsequent to belt stoppage and restart.

Eriez has recently supplied a Coast Counter which UMA is using in conjunction with the Metalarm detector, a piece of equipment which means that not only is an alarm activated the moment metal is detected, but the number of items detected is counted and displayed.

So, if for instance the metal detector detects some ferrous or non-ferrous material it will halt the conveyor so that the detected metal may be dealt with.

A counter displays the number of items that caused the detector to trip the belt thus enabling the operator to know exactly how many items need to be checked and removed from the belt prior to re-starting the belt.

On restart of the belt the counter is automatically reset to zero so that subsequent detectable items will always be identified and can then be dealt with effectively and safely.

This was obviously a crucial consideration at the UMA processing station, given that more than one object could be involved with each detection event and that marine dredged munitions could be involved at any stage.

The Coast Counter is already regarded by UMA as an extremely useful supplementary tool.

UMA has entered their metal/munition detection system and additional safety developments at its Greenwich operation - including the Eriez equipment - in the upcoming Quarry Products Association (QPA) Best Practice Health and Safety Awards Competition.

Eriez expects further successes in the near future with this technology, especially as UMA is recommending use of the Coast Counter in all of their operations and to the quarrying Industry in general.