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topic 22256

Alternate to Trichloro Ethylene (TCE)


A discussion started in 2003 but continuing through 2019

2003

Q. In our company, in India, we are serious in replacing TCE at the earliest. In the March 2002 issue of Metal Finishing, I noted that nPropyl Bromide(nPB) can be used as alternate. Even though our objective was to replace TCE fully, nPB being inflammable with low flash point , to start with we were inclined to try with 50:50 mixture of TCE and nPB. Mixing of both were good and the performance was also good in metal cleaning. But there is one concern on WEL,( Worker Exposure Limit.) We have a figure of WEL for TCE as between 90 to100 ppm.The same in nPB as supplied by a manufacturer is only 10 ppm. But we do not have an apparatus to measure,WEL of the mixture of TCE & nPB.

I request help in the following points.

1. Is the use of TCE &nPB; mixture in conventional degreasers acceptable?These degreasers are operated normally in top open condition and have condensing coils in the top zone to condense the vapours.

2. Any safe limit prescribed for WEL,internationally?

3. Any apparatus available for finding out WEL

Thanks for any expert advice on this issue.

Rangaswamy Srinivasan
brakes - Chennai, Tamil Nadu, India


2003

A. Using TCE (trichloroethylene) is not a good idea as it has been identified as a possible carcinogen (i.e., may cause cancer). It was originally favoured as a replacement for the more harmful trichloroethane, which was banned under the Montreal Protocol in 1989.

The Montreal Protocol tried to ban all ozone depleters as it will result in an increase in exposure to harmful UV radiation and an increase in cancers associated with exposure to the sun etc. Unfortunately some national governments have not seen it worth their while to preserve the Earth, so I suspect they must originate from another planet.

Nevertheless, trichloroethylene has now been identified as also being a possible carcinogen and it too is being phased out, albeit voluntarily. There are numerous substitutes that may be suitable, but unfortunately both trichloroethane and trichloroethylene are extremely good at degreasing parts! One possible substitute is n propyl bromide (nPrB or 1-bromo propane), but this has a disadvantage that it is a very strong irritant to the mucous membranes and the skin - consequently it has a very low exposure limit of 25 ppm TWA. However, it does not appear to be a carcinogen nor an ozone depleter. Many other degreasers are available, but it is more of a "horses-for-courses" scenario. There are numerous aqueous based systems around that may or may not use ultrasonics, or you can use solid CO2. It all depends on what you want to clean and what the contaminant is. To combine TCE with nPrB doesn't solve any of the problems of the materials, in fact it compounds them and makes things worse because you are using two very unpleasant materials instead of one! nPrB is overall better than TCE, but you still need to take special precautions. I would suggest you look for a totally different cleaning system, such as an aqueous or semi-aqueous one, or even CO2. The problem with the internet is that what is available in one country may not be available in another, so I suggest you discuss your problem with a reputable, global, chemical supply house.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


2003

thumbs up sign Now, Trevor...

It's not that some governments don't want to save the earth. It's the usual issue that people define fairness according to different perspectives, the old issue of whose ox is being gored.

Millions of Americans have each paid many hundreds of dollars to retrofit their automobile air conditioners because we can no longer re-charge them with ozone-depleting substances ... while most of the world faces no such restrictions. Americans have accepted that we can no longer replace an old refrigerator or freezer until we first pay a specialist a substantial fee to come out and recover the freon, and then stand in queues at city hall for stickers and forms swearing to and documenting that removal ... although few other countries do anything even remotely similar.

But yes, we resist a protocol that says that if our child suffers an asthma attack and is clutching desperately for a breath, that s/he may only relieve the suffocation by inhaling powders and hoping that some of the powder will get to their lungs rather than it all stick to the wet inside of their mouth). Our afflicted children aren't permitted even a milligram of freon in an inhaler, while the later-developing countries remain free to squander ozone-depleting substances, washing their automobile parts in open buckets of it out in the street.

One point of view is that the Montreal protocol did not so much say that CFCs are bad, as that America's businesses should be closed down so other countries could manufacture CFCs instead. While I admit to engaging in a slight bit of hyperbole, I invite all readers to simply read the Montreal protocol (it's on the internet, and only about 6 pages long), and form your own opinion about how much I am exaggerating. Probably the main reason that America hesitated to sign the Kyoto protocol was because of what the Montreal protocol taught us: that such resolutions are usually as much about bashing America as reducing pollution. When will there be some international agreements proposed that aren't prefaced with essentially: 'Whereas Americans, being selfish & ignorant oafs, ...'

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2003

A. Dear friend,

While I debate the comments on the carcinogenic nature of TCE, I would like to emphasise the benefits and "cost" of TCE in comparison to any other means of cleaning. Perhaps, aqueous cleaning is an option, but it has a lot of limitations. We recommend aqueous cleaning in a variety of fields, but at times it is not the best solution if "cleaning" is not proper.

I give below a few facts:

Trichloroethylene has never been considered to be ozone-depleting and is not mentioned in any annex of the Montreal Protocol nor its amendments and is never likely to be. In 1999, 78,842 tonnes of TCE were known to have been used in W. Europe for solvents applications In 2003, the US production of TCE is expected to top 100,000 tonnes. If TCE were forbidden, then neither country would use so much. 2000 World production of TCE is estimated at about 500,000 tonnes.

However, I can guide better if I know the process and your consumption pattern. Just to inform you in a non-commercial way, we speak from experience. Meanwhile, don't waste your time in finding formulas in cookery books for mixing various solvents, its better if you go for God gifted products and try not to be inventive as it just might be more harmful to your workers.

Jatin Aggarwal
- New Delhi, India



April 27, 2012

Q. I am working with a piston rings manufacturing unit and we are using TCE for washing and drying of rings. Kindly let us know if there is an alternative to using TCE as solvent.

Mayank Lahariya
- Mumbai, India



Is low volume usage of TCE harmful to employees?

September 23, 2019

Q. Our use of TCE is about 20 liters per month and one liter at a time, The use is for cleaning oiled bushes before brazing. I want to know:
1. Whether such a low quantity use is harmful to the handling personnel
2. If so,what is the alternate?

gopalan arunachalam
Vacuum Heat treatment - Bangalore,India


September 24, 2019

A. Hi Gopalan,

We are not toxicologists here, so any argument on toxicity will be from available literature, rather than from expertise knowledge...hence treat any comment with a little caution.

TCE is classified as a carcinogen, which means it may cause cancer in humans. Cancer causing agents tend not to cause cancer after a single exposure, but over multiple exposures over longer periods of time, sometimes into 10s of years.

TCE is also narcotic and an asphyxiant, so must not be used in enclosed condition. There will be a national occupational exposure limit that must not exceed.

So, yes, TCE can be harmful, but it does depend on how you use it and how you protect your workers from exposure.

There are all sorts of processes that could potentially replace TCE, from simple solvents such as iso propyl alcohol and acetone, to aqueous solutions, to mixtures such as Vertrel or Novec HFEs, to more complex alcohols used in special kit. Whatever you do, you must comply with your country's laws on these chemicals.

Brian Terry
Aerospace - Yeovil, Somerset, UK

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