Feature Industrial Cleaning
An uncertain future for nPB? A
cleaning solvent that has been in widespread use in industrial markets for many years is under threat. In December 2012 the European Chemicals Agency (ECHA) listed npropyl bromide – more commonly known as nPB - as a substance of very high concern (SVHC) and is now reviewing its future use. Depending on the outcome of the ECHA review, users may be required to reduce their fluid consumption volumes further or replace their existing nPB fluid within the time period that will be specified. nPB is already a solvent classed as a ‘carcinogenic, mutagenic or reproduc- tive toxin (CMR) and the Solvent Emissions Directive 1999-13-EC (SED) restricts consumption to below one tonne per annum.
The SED requires that substances or preparations containing volatile organic compounds (VOCs) classified as CMRs be replaced as far as possible by less harmful substances or prepara- tions within the shortest time feasible. As a result, more organisations are looking at alternatives to nPB.
Precision cleaning
nPB is used in a broad range of indus- trial applications which include preci- sion cleaning and solder flux residue removal in electronic parts manufac- turing. It was first introduced in the mid-1990s as a less toxic alternative to hydrochlorofluorocarbon solvents. The main driver was a move toward reducing the use of ozone-depleting substances. At that time there was insufficient information available to allow an accurate characterisation of its toxicity. However, based on various studies conducted over the past 10 years the original 200ppm eight-hour time weighted average exposure guideline for nPB has been gradually downgraded. Today the exposure guideline has been established by the American Conference of Governmental Industrial Hygienists (ACGIH) at 10ppm. Furthermore, the California OSHA has a proposal to set the exposure guideline at 5ppm – a concentration that may be unachiev- able in vapour degreasing operations. So, regardless of the ECHA’s review,
nPB’s future does not look positive. Readers may be asking why this mat- ters right now: can they not wait until the outcome of all this? That is an option but a risky one. The process of
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researching, evaluating, testing and trialling alternatives takes time. For companies handling precision compo- nents there is too much at stake to take quick decisions not backed by thorough due diligence.
Looking at the alternatives Safer alternatives to nPB-based degreasing include aqueous and semi- aqueous processes. One benefit of these processes is that they have a rela- tively safe health and environmental
“The reality is that users may not be given any choice but to seek alternatives so it makes sense to start looking at the available options sooner rather than later”
profile (although large volumes of contaminated liquids still need to be safely disposed of). However, the cleaning quality may not be sufficient for many applica- tions, particularly where precision components are involved. In addition, the process can be difficult to maintain and drying can be time-consuming with the risk of water stains. The typi-
nPB is used in precision cleaning and solder flux residue removal in electronic parts manufacturing
A cleaning solvent which has been widely used in industry for many years has been listed as a substance of high concern and as such its future use is under review. Alexej Dens of 3M UK looks at the alternatives
cally high energy and waste water dis- posal costs are further disadvantages. Alternatives for metal degreasing include HFC-4310mee and HFC- 365mfc-based cleaners. These have favourable properties to enable effi- cient cleaning and are low in toxicity but have relatively high Global Warming Potential (GWP) figures which mean that under environmental legislation they are more likely to be considered for restrictions in the years to come. Under the requirements of (EC) No. 842/2006 operators are required to be certified as competent for systems using hydrochlorofluoro- carbon (HFC)fluids.
A further option that more compa- nies are looking at is the use of hydro- fluoro ethers (HFEs).
These tick a number of boxes: they aren’t classified as CMR solvents (so there is no risk of falling foul of that legislation should it become more strict in the future); they have zero- ozone depletion potential and low GWP; and some HFE-based mixtures can be used as ‘drop-in’ replacements to nPB so there is generally no need to replace existing cleaning equipment.
Rapid drying time Importantly, HFEs – which are already deployed in many large operations worldwide – do not compromise on quality of cleaning. Drying time is rapid and removal of residue is effi- cient. Any disadvantages? In some instances, there may be a need to upgrade or replace existing equipment to ensure that low consumption levels are achieved. The initial investment may be higher but there is anecdotal evidence that once in place, less clean- ing fluid is needed compared to other solvents, particularly in open top cleaning tanks.
While replacing nPB does require time, effort and potentially invest- ment, there are viable alternatives and ones which ultimately can lead to improvements in cleaning processes, as well as addressing health and safety concerns. The reality is that users may not be given any choice but to seek alternatives so it makes sense to start looking at the available options sooner rather than later.
3m UK T: +44(0)8705 360036
www.3m.co.uk/novec
NOVEMBER/DECEMBER 2013 Factory Equipment
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