The problems associated with solvent cleaning and degreasing of metal parts within industry are widely acknowledged. Moreover, as regulations such as COSHH and SED become ever more stringent, the restrictions relating to solvent use and the risks presented both for users and companies alike will unavoidably increase.

A snapshot of the obligations and regulations to emerge in recent times illustrates this point all too clearly. Take, for example, Trichloroethane 1.1.1. Banned from October 2000 because it contributed to the hole in the ozone layer, its 'safe' replacement - Trichloroethylene - was itself re-classified in 2002 to a category 2 carcinogen (risk phrase R45 - may cause cancer) despite previous assurances from suppliers. Now more recently the Solvent Emissions Regulations, introduced in 2004, require the replacement of Trichloroethylene in the 'shortest possible time' or compliance with new stringent emission limits by 31 October 2007 in applications where replacement is not possible and the consumption of solvent exceeds one ton per annum. These controls also apply to other volatile organic compounds (VOC's) including Perchloroethylene (risk phrase R40 - risk of irreversible effects). (References: HSE Information sheet No. 34, Defra Guidance Note AQ9(04))

Of course, throughout this time, other 'safe' alternatives have been brought to the table such as, for example, 'drop in' replacement N-Propyl Bromide. Despite significant promotion, this too was subject to an HSE Chemical Hazard Alert Notice due to the potential risk of damage to the nervous system and adverse affects on fertility. Overall, it is a scenario that means, not only is there increasing regulatory pressure, but also that the choice today of alternative 'safe' solvents is itself now very limited. With associated high costs, there clearly needs to be a very good technical reason for manufacturers to go down the solvent route.

The solvent issue is just one instance of a growing trend towards dramatically greater and broader control of the use of chemicals in industry. Everybody involved in engineering must stay abreast of an increasing number of guidelines, regulations and documentation - much of which directly affects those involved in component cleaning processes.

The industry has taken steps to address these very serious concerns - the development and promotion of 'enclosed' solvent degreasing equipment being one example. Designed to safeguard users from these risks, it scarcely addresses, however, the difficulties faced by service or maintenance engineers who still need to enter the system and risk exposure during routine or breakdown work. Solvent being brought to site in caskets reminiscent of those used for handling nuclear waste and carrying the 'skull & crossbones' and 'toxic' warning signs can only help to focus attention at site.

But if there exists an argument that says exposure of employees to these serious health risks is partly due to the absence of a genuinely 'safe' alternative, it is one which has now been ripped apart by a manufacturing company in Tewkesbury.

MecWash Systems has been at the forefront of component cleaning technology for more than a decade and each of its stand alone systems - all based on the use of aqueous solutions - are highly regarded for their performance and environmental benefits. The company points to a long list of familiar names amongst its client base including TRW, Delphi, Cosworth and JCB. In all cases, products and components are held securely - either in baskets, plastic containers or purpose-designed fixtures, depending on size and complexity - and then subjected to the optimum combination of flood and spray washing, rinsing, hot air and vacuum drying. Where specific requirements dictate, dedicated component jetting and ultrasonics can also play a part.

Now the organisation has taken a major leap forward with its latest introduction - an Aqueous Vapour Degreasing system - which, quite simply, provides an alternative to solvent degreasing that, remarkably, uses nothing more threatening than water. The MecWash AVD system is a new self-contained, stand alone unit which also cleans and degreases components held within a single rotating, oscillating or static drum but, here, by reproducing the benefits of a solvent degreaser. Within the chamber, components are subjected to a three step process comprising immersion, a vapour phase and evaporation which not only requires relatively low energy consumption and produces no waste water but also keeps chemical costs low and, of course, uses no harmful solvents.

Paul Young is Sales Director at MecWash Systems and describes the sequence that has been shown to produce extremely high quality results -

"Parts are front-loaded via a roller conveyor or load table and are held securely in metal mesh perforated baskets or containers," he says. "They are then immersed in an aqueous solution which is used at elevated temperatures, comparable to Trike, before being subjected to a vapour phase using distilled aqueous solution to produce a high quality surface finish.

"Extraction drying then takes place which benefits from a fast process time due to the high temperature flash off. A specially designed condensation process captures the steam, re-uses its energy for drying and recycles the recovered water. Subject to the tenacity of the soils being removed," he points out, "the entire process can take less than five minutes with all parts exiting in a clean and dry condition."

Operation at such elevated temperatures produces a high level of thermal energy that in turn softens and breaks down soils that would normally be resistant to aqueous cleaning. This same process reduces the viscosity and surface tension of the solution which helps to achieve penetration of small diameter holes - with the cleaning and drying results therefore achieved much more quickly.

"The aqueous solution is also dosed with a very low percentage of a specially developed high temperature surfactant and inhibitor," continues Paul Young, "which aids 'surface wetting' and cleaning performance. A further benefit of using an aqueous solution over solvents, of course, is the ability to impart a rust inhibitor to give corrosion protection for ferrous parts. This is of particular note where components are destined for storage rather than immediate onward assembly."

For both large and small engineering businesses, the new MecWash AVD System provides a highly versatile and safe cleaning and degreasing solution which, at a stroke, eliminates both current concerns regarding solvents and confronts pending solvent legislation head on. The absence of chemical hazards is enhanced by the removal of the need for special transport, storage, handling and waste disposal issues to be addressed - commonplace with solvents - and the virtual elimination of trade effluent considerations. This is achieved because the aqueous solution is continuously distilled and recycled with only concentrated oils and metal swarf removed from the system.

Improved cleaning performance due to the ability to spray and agitate the solution - not advisable when using volatile solvents - is also a key factor whilst the system is sufficiently versatile to handle both ferrous and non-ferrous components.

"It also requires lower capital cost compared to 'enclosed' solvent systems," adds Paul Young, "whilst the benefits arising from its compact machine footprint, simple controls and low maintenance requirements need little further explanation."

MecWash is supplying a choice of AVD system sizes to suit most customer requirements - the standard AVD 400 has a process chamber measuring 400mm x 400mm x 600mm. Across the range, the only service connections that are required are for electricity, air and water.

The system is seen as complementary to existing MecWash units, enabling the company to broaden the suitability of its technology to a wider range of users than ever before - building on its track record which comprises more than 300 installations world-wide. The MecWash name, believes Paul Young, has become synonymous with quality, reliability and performance using aqueous, environmentally friendly technology. Now, with the benefit of this pedigree, the company has, at a stroke, taken the component cleaning industry to a new stage. By effectively re-writing the rule book, it has eliminated the need for solvent emission monitoring records to be kept to meet legislation compliance requirements and, markedly more importantly, has removed health and safety risks to employees whilst eliminating consequent liability insurance.

"We believe the new AVD system knocks the solvent propaganda machine out of the water," concludes Paul Young - reflecting not just the benefits of the company's aqueous-based technology, but also the impact the new system is set to make across the engineering industry.