The VAQUA process offers many benefits for surface peening

Citation

(1998), "The VAQUA process offers many benefits for surface peening", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 4. https://doi.org/10.1108/aeat.1998.12770daf.007

The VAQUA process offers many benefits for surface peening

The VAQUA process offers many benefits for surface peening

Keywords Abrasive developments, Surface preparation, Wet blasting

The VAQUA wet blast process is now accepted throughout industry as a fast and environmentally friendly method for cleaning, surface preparation and shot peening. The considerable benefits of VAQUA processing has for many years been specified in the international aerospace industry for peening applications. Mike Beirns, aerospace applications engineer at Abrasive Developments, explains the process.

Abrasive Developments Ltd has, for over 50 years, been developing and refining the traditional "blast cleaning" process into a controlled surface treatment technique known as VAQUA ­ a process which is now widely accepted throughout the world as a versatile efficient and economical metal cleaning and finishing process. The process is used extensively by the international aerospace industry for manufacturing, repair and overhaul of lifed engine components.

Shot peening using glass bead media and the VAQUA wet process is widely used to produce compressive forces at the surface of a component. The presence of compressive forces will reduce the initiation of micro cracking and opportunities for premature fatigue failure.

At the heart of the process is a specially designed pump which is capable of delivering a steady flow of abrasive media and water onto the surface of the component. This mixture contains 20 to 30 per cent of solid matter in the form of a medium which, when accelerated by compressed air, produces a gentle but extremely dense blast stream.

Considerable process benefits are achieved by the process when compared to conventional dry shot peening which produces a rougher surface condition for similar peening intensities.

VAQUA wet peening has the advantage of using water as a means to propel the spherical peening media to the surface of a component but at the moment of impact, the water acts as a barrier. This thin film of water reduces the degree of surface deformation but allows transmission of compressive forces into the component.

As a result, a smoother surface profile is achieved which enhances component performance in service. The range of aeroparts benefiting from VAQUA wet peening is gradually increasing as new generation wide cord fan blades for high bypass engines and compressor blades within the engine core are introduced.

Midlands, UK-based surface treatment equipment manufacturer Abrasive Developments has introduced a range of standard and custom built VAQUA wet peening equipment aimed at satisfying current specifications with many installations operating successfully throughout Europe and on the Pacific Rim.

Considerable design and development resources have been allocated to the design of VAQUA equipment with particular emphasis being placed on flexibility. As a result the equipment offered is unique ­ it is claimed that it is the first of its type capable of processing a wide range of fan blades and compressor blades in the one machine. Large fan blades for gas turbines including the Rolls-Royce family of civil engines such as Trent, RB211 and V2500 can be processed with trials on other engines currently being carried out.

Additionally, many processing specifications can be achieved including: GE, P&W, Allied Signal, Snecma and Rolls-Royce. Abrasive Developments is also sensitive to the ever-changing demands of the market and is currently developing approvals with OEMs for a ceramic peening media, thus further increasing the flexibility of VAQUA equipment.

Aerospace processing specifications often demand automatic machine operation and classification of media together with in-line media condition monitoring. VAQUA machines are designed to allow this (Plate 6). Additionally secondary software maintains media volumes to ensure that full process cycles can be completed which are of prime concern when processing lifed compressor parts.

Owing to the nature of the shot peening process and extended hours of machine operation slight variations in equipment performance can occur. VAQUA machines offer reporting features which highlight machinery drift from preprogrammed set points and issue warning of potential failures. These reporting features aid equipment performance and form an important part of machine maintenance as dictated by OEM specifications.

Plate 6 Typical VAQUA wet peening machine for fan blade peening

Automatic monitoring systems provide an accurate report on machine function and condition, ensuring maximum operating efficiency is consistently achieved.

Considerable financial benefits with a single machine installation include:

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  reduced media costs;

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  reduced utility costs;

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  cost reduction in subcontract processing;

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  reduction in space occupied ­ one machine has a reduced footprint compared with multi-plant;

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  reduced servicing cost of equipment;

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  reduced tooling costs as polyurethane fixing is durable and long lasting compared to metal fixtures;

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  payback time is reduced as a wide variety of parts can be produced through one machine.

The full scope of machine flexibility is best demonstrated by the rapid changeover achieved for processing of wide cord fan blades to smaller, high pressure compressor blades. Modular tooling and fixturing is used extensively to aid accurate location and masking of parts and allows a wide choice of components to be processed within one fixture.

Accurate masking of compressor parts is essential to a successful shot peening operation as poorly produced masking can result in lengthy remedial work and in extreme circumstances scrapping of parts produced out of tolerance.

Polyurethane masking which facilitates rapid part change over and high throughput of components is used extensively as a part of ADL's design philosophy. The concept of using polyurethane as an accurate mask and location device has the advantage of reducing operator error and increases speed of machine loading within a production environment.

The company has designed and manufactured a large number of polyurethane masks and fixtures and has built up a pool of standard designs.

Manufacturing and repair of aerospace components requires considerable financial control with lead times and inventory being reduced to the lowest order of cost. Abrasive Developments say they recognised the need to support its customers in this activity and have set up stocking policies for shot peening and abrasive media to suit individual needs. As the UK's largest stockist of consumable media Abrasive Developments holds consignment stock as part of a programme of customer support.

A "one-stop-shop" philosophy includes supplying capital equipment and all associated media, production tooling/fixturing, spares, service support and training on a global scale.

Abrasive Developments is a member of Unicorn International plc, one of the world's leading manufacturers of high-quality superabrasives, bonded abrasives and coated abrasives for a wide range of precision engineering applications.

For further details contact Abrasive Devlopments Ltd. Tel: +44 (0) 1564 792231; E-mail: vaqua@waverider.co.uk