Home

E-mail: Sales

News

£3.2 MILLION SURFACE FINISHING FACILITY COMES ON STREAM

The biggest surface preparation and finishing facility built in the UK for several years is now in operation at the Defence Aviation Repair AgencyÕs new aircraft maintenance centre at St Athan, South Wales. The surface finishing facility, which cost £3.2 million, was designed and installed as a joint project by Sheffield-based Hodge Clemco Ltd and the US company Global Finishing Solutions, with Hodge Clemco providing project management. It consists of a plastic media paint stripping booth and four paint spray booths, all of them measuring 22.5 metres long x 20 metres wide x 8.5 metres high to accommodate military jets such as the Tornado and Eurofighter. All the booths have an energy-saving Ôtop-hatÕdesign with a narrower roof section running the length of each building to accommodate the tail-planes, which has reduced air volumes and heating costs. The paint stripping booth has automated abrasive recovery, air handling, dust extraction and media grading for size, density and ferrous particles. Six plastic media stripping machines have been fitted in the booth, each with sufficient capacity for 30 minutes continuous work without recharging. A remote valve controls media flow rates between 115 and 270 kg per hour, and operators can switch media supply and air on and off at the nozzle. A dust extraction system rated at 128,000m3/hr gives an air-flow down the length of the room to maintain good visibility at the work-face. A magnahelic gauge monitors pressure drop across the cartridges, and an alarm indicates when filters are blocked. Clean air enters the room through a plenum in the ceiling and can be heated to maintain a temperature in the room of 18¡C to 20¡C. The plastic media reclamation system is designed to match the output from the six PMS nozzles working together and consists of a partial floor scraper, intermediate hopper, rotary valve, magnetic separator, vibratory screen, three bucket elevators and a dense particle separator. The scraper system is designed to maximise abrasive recovery and takes into account the shape of the aircraft, and the dense particle separator is included to remove dense particles from recovered plastic media of the same mesh size. The bulk hopper where clean media is stored has enough capacity for six operators to work continuously for four hours without having to activate the abrasive recovery system. The six outlets are independently valved, so each can be serviced while the others continue in use. The spray booths have a pressurised cross-draught design and include inlet plenum filters to ensure first-class air-flow through the booth, indoor-mounted indirect gas-fired air-handling units, three-stage exhaust filtration and three 1250mm diameter exhaust fans with variable frequency drives. The whole system has PLC controls to maintain optimum booth pressure at all times, irrespective of filter loading, and the lighting system provides 1000 lux at the work-face. The air inlet and exhaust systems have been designed to maximise dust particle capture and minimise turbulence under wings, fuselage and tail sections while providing sufficient extract volume to maintain safe levels of flammable substances. The three-stage exhaust filtration was supplied by A J Dralle Inc and consists of CPA multi-layered multi-density polyester, ME/PT tackified polyester panels and XFP 6000 polyester-fibre bag filters. It was selected because of its suitability for chromated aerospace coatings and its ability to capture more than 99.9 per cent of particles measuring 3 microns and above. Using sensing probes, differential photohelic gauges and variable frequency fan motors, exhaust air volumes are automatically adjusted as filters load up with paint overspray. When spraying is completed, an operator activates the purge and cure modes on the control panel. The system then automatically removes paint fumes, de-energises the spray guns and re-sets the air-make-up unit to deliver 90 per cent return air during the cure cycle. Cure temperature is adjustable up to 40¡C. A PLC-based system with a touch-screen controls all functions of the spray booths and provides information about the main components. The stripping booth and paint booths all incorporate comprehensive safety features, such as over-temperature protection, automatic shut-down if specific parts of the equipment fail, emergency stop systems, door interlocks, fire detection systems, emergency lighting, drench showers and eye washes. They have been designed for a life of at least 25 years, and steelwork has been treated to protect it from corrosion by the sea air. In addition to the stripping booth and spray booths, Hodge Clemco and GFS also supplied two paint mixing rooms and provided full operator training.

Past News Items