28 Sep 2018
Hewitt Robins have recently replaced two Grading Screens for Hanson Bullslodge.
Bullslodge itself has had a varied history; once a WW2 airfield operating Buccaneer bombers, this was followed by a period after the war with motor racing which was organised by the West Essex Car Club until 1955 when the Ford Motor Company used the old airstrip for truck testing. The old airstrip was then dismantled by Pioneer Aggregates in the 1990s to get at the valuable gravel reserves below, with Hanson taking over in 2000.
Since operations commenced the plant has processed a minimum of 650,000 tonnes per annum and with a 4 million tonne extension, there is approximately 15 years of reserves to process. Today the plant supplies product primarily to local concrete plants as well as supplying its own concrete plant, asphalt plant and an on-site bagging plant.
With such a high profile plant it is essential that any downtime is kept to the absolute minimum and having suffered on-going issues with the existing grading screens.
Hewitt Robins supplied Grading Screen 1 which was a 2.4 x 6.6 Double Deck Screen which used a QV14 single shaft, 4 bearing unit. The screen was to handle 425tph of -100mm Sand & Gravel. The screen is separating at 40mm top deck and 20mm bottom deck using SCS85 Polyurethane modules. Grading screen 2 was 2.4 x 8.2 Double Deck Grading Screen which used the same unit (for commonality of parts) and this screen followed on and handles 275tph of -25mm Sand & Gravel. The screen is separating at 10mm top deck and 5mm bottom deck using SCS85 Polyurethane modules.
Both screens were bespoke screens and constructed to fit into the existing application. The screens incorporated 40mm thick rubber wear liners, direct cardan shaft drives, 37kw sea protected IE3 drive motors, 6mm thick 40 shore rubber cross member protection. Our Screen offers the benefit of friction checks which are built into the screen supports and efficiently retard the screen during shut-down, thus reducing forces transmitted to surrounding structures. The screen also has improved height between the decks to allow for easier screening media changes. The screens are circular motion with increased bearing life and improved wear protection. They are coated with a three-layer polyurethane paint protection to ensure it withstands water, sand and gravel. The screen support frames were completely bolted with no welds so all components are interchangeable. All surfaces that come within contact with material are rubber lined to increase the life of the equipment in this tough environment.
Richard Page, Essex Quarry Manager, commented, “We had serious issues with the original grading screens for a considerable time and although several attempts were made to resolve the problems the proposed changes were too expensive, so we decided the best way forward was to replace the screens. The tender was also offered to several other screen manufacturers but after a site visit and subsequent consultations Hewitt Robins proposed a viable solution with a 5-year guarantee and were successfully awarded the order for a replacement for two double deck gradings screens. Hewitt Robins carried out the installed the screens in the agreed timescale. Hewitt Robins also carry out monthly inspections on the screens and they have now been in for over 5 months with no issues so the job has been a complete success’’
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