Media stripping facility install
Media stripping facility install
Keywords USF Vacu-Blast, DARA, Coatings, Removal, Aircraft, Peening
USF Vacu-Blast International, part of the USF Surface Preparation Group, has supplied a "whole aircraft" plastic media stripping (PMS) facility to the Defence Aviation Repair Agency (DARA), Fleetlands, Portsmouth, UK (Plate 3). This follows the proven operation of similar PMS facilities at Royal Air Force St Athan in South Wales and at RAF Kinloss in Scotland.
Plate 3 USF Vacu-Blast plastic media stripping facility installed at DARA, Fleetlands, UK
DARA undertakes work for all three UK services – the Royal Navy, the Army and the Royal Air Force – and the facility is used for the controlled stripping of paint and other surface coatings from complete helicopter fuselages, mainly from Sea King, Gazelle, Lynx, Chinook and pending approval on the new Merlin (EH101) aircraft, during regular repair, overhaul and re-paint operations. The facility, which supersedes chemical stripping, is also used to remove coatings from critical mechanical parts prior to non-destructive testing.
According to USF Vacu-Blast, the PMS process can be controlled closely to remove coatings selectively layer by layer, when required, and does not damage delicate substrates such as anodised surfaces. It also claims inherent health and safety and environmental benefits, since no potentially hazardous chemicals or liquid effluent are involved.
Housed in a new surface finishing complex at the Fleetlands site, the PMS enclosure measures 23 metres long x 7 metres wide x 8.5 metres high and incorporates the "Waffle-Floor"TM pneumatic blast media recovery system, a USF Vacu-Blast invention.
The Waffle-Floor system utilises a constant downdraught of air which continuously directs used blast media, dust and debris through a heavy duty floor grille into a series of under-floor "mini-hoppers". These are connected to a common duct through which the material is conveyed pneumatically to the generator-reclaimer. This automatically recycles reusable blast media to the blast nozzle, thereby minimising media consumption. Degraded material and debris are directed into the dust collector for safe disposal as dry waste.
Because there are no moving parts, the system is said to be virtually maintenance-free and the floor design removes the need for pre-loading with non-recoverable blast media. The under-floor hoppers and ductwork are automatically purged free of blast media, which allows the media grade to be changed easily. The constant downdraught of air has the advantage of enhancing operator visibility.
In the case of the Fleetlands facility, the Waffle-Floor grid sections and connecting ductwork are incorporated into the existing concrete floor of the hangar and can withstand a load of 5,000kg, transmitted through an aircraft jack with an 8-inch diameter footprint.
Other features claimed of the facility include high-integrity media/debris separation to ensure that only good quality plastic media is recycled and process consistency maintained, in-process monitoring of media flow, and the use of acoustic construction techniques to minimise noise levels. The enclosure incorporates heating and cooling for the comfort of operators, and all processing parameters are controllable from an external console situated by an observation window.
Although the USF Vacu-Blast facility uses high-quality thermoplastic acrylic abrasive media, the design of the blast generator and recovery system allows for the possible future use of an alternative starch-based media which has different flow characteristics.
The facility was supplied by USF Vacu-Blast as a turnkey installation,including site preparation, operator and maintenance training and commissioning.
USF Vacu-Blast also reports that it has recently supplied a special automatic precision peening machine to the Italian company, Sicamb SpA, specifically for the fatigue life improvement of the wheels and associated wheel components fitted to the new Eurofighter "Typhoon" aircraft. Sicamb manufactures these aluminium alloy and steel parts as workshare partners of Dunlop Aviation.
Based on Vacu-Blast's proven "Ventus AXT" design and controlled by a PLC based system, the machine has a 1,500mm x 1,400mm x 1,200mm high processing enclosure and incorporates an array of four peening nozzles fitted to a two-axis roof-mounted blast nozzle manipulator. Components are attached to special fixtures on a variable speed powered turntable, which rolls in and out of the enclosure to facilitate manual loading and unloading. The maximum component processing envelope is 700mm in diameter by 700mm high.
The new machine can handle both steel shot and glass beads, depending on the type of part to be processed, and is equipped with the latest in-cycle magnetic media separation and classification system. This is said to ensure total segregation between the two types of peening media used and guarantees that only the highest grade media is recycled to the nozzles via the generator-reclaimer,thereby maintaining optimum process integrity and repeatability.
Further details are available from USF Vacu-Blast International, USF Surface Preparation Group. Tel: +44 (0)1753 526511; Fax: +44 (0)1753 538093; E-mail info@vacu-blast.co.uk
