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The 5Cs of choosing between solvent and aqueous processes

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When evaluating which process best meets the needs of a particular situation, the following five factors – the ‘5Cs’ – are a useful starting point:

1 Cleaning effectiveness

Aqueous processes are often ineffective for cleaning intricate components, such as those with fine or blind bores. Because of their low surface tension characteristics, new generation solvents can penetrate into the hard-to-reach areas of these components for superior cleaning.

2 Cost effectiveness

To understand cost of ownership of cleaning processes and chemistries, a range of factors need to be considered. These include the cost of storage and monitoring of more hazardous agents such as nPB and Trike, the higher energy consumption and footprint of aqueous processes and the contribution of cleaning process speed to overall productivity.

3 Compliance

Care needs to be taken with a number of restricted solvents. Perchloroethylene (PERC) and Methylene Chloride (MECL) are classed as CMRs (carcinogenic, mutagenic or reproductive toxins) by the Solvent Emissions Directive 1999-13-EC. This requires substitution in the shortest possible time. Both require vapour extraction and consume high volumes of solvent.

Now a candidate for Annex XIV of REACH as a ‘Substance of Very High Concern’ (SVHC), n-Propyl Bromide (nPB) also requires the earliest possible substitution. US hygienists’ body, the ACGIH, has lowered its recommended threshold limit value for nPB from 10 ppm to just 0.1 ppm, amid concerns over health risks.

4 Consumption

Aqueous–based processes involve longer wash times, increased mechanical energy, and often a drying phase. These factors can more than double their energy consumption when compared with new-generation solvent-based cleaning processes.

Unlike solvent-based cleaning processes, aqueous processes use large amounts of water, which needs to be deionised before use. In addition, contaminated waste water needs to be disposed of, adding to costs and indirect environmental impacts.

5 Compatibility

Compatibility of cleaning agents with the components to be cleaned, whether metals, elastomers or plastics, is vital to prevent damage to component surfaces.

Some component materials are susceptible to water damage or flash rusting, which may render aqueous cleaning processes unsuitable.

We will be happy to advise you on which component cleaning systems or chemistries, whether solvent or aqueous, are best suited to your requirements. For more information please call us on 01506 443058.

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