"Remarkbly enough, few employees were ill at that time."
Nothing remarkable about it. TCE has been used industrially for over a
century in often terrible conditions of operator exposure. Very few
cases of disease appeared; those that did were mainly hepatic lesions in
heavy drinkers/smokers. Under normal conditions of industrial use, the
stuff is relatively harmless.
I wouldn't stick my arm in it though: transdermal absorption can be
quite high.
Brian
Inge wrote:
> Once upon the time..we had an open 500 liters cleaning bath for
> degreasing machined parts. There was a vapour evacuating tube above, but
> that was all. The operator lowered the parts into the tank and let it be
> there for a few minutes at + degrees (don't remember how much). A
> propeller caused the TCE to flow around the details. It happened that
> someone lost the grip of the lifting tool and the metal thing hit the
> vehicle's bottom. What to do? Quickly put full arm lengt into the bath
> and get the component, and rinse skin in water. Remarkbly enough, few
> employees were ill at that time. Not that I recommend a return to such
> madness, just a fading away memory. Alcohol is accepted limitlessly in
> every home, but not a few centiliters of TCE. Even more mad.
>
> There is more for the future purists to wow about....Just wait and see
> when the first side effects of Viagra will appear..that cacaphony will
> override TCE noise
> Not a very logical thread, maybe because the glass of Famous Grouse I
> just had....
>
> Thanks for the good lesson about Titanium. Made me even more observant
> on the case of phase displacements and built up "squamous" (isn't there
> a professional word?) superficial phenomenons. On the q how to determin
> the cleanliness, I think of simply boil the part in water and see if any
> fatty debris flows to the surface. If someone got a better idea, you
> are welcome to share with me.
>
> To end this mail, I add something I didn't know before. A friend of mine
> is from Iran and he speaks little farsi (old persian). I mentioned
> something about chemistry and he asked " do you know what or where the
> word chemistry comes from ?" No, I said. "It's farsi 'chemi' which
> means gold. 'Al-chemi' means 'make-gold' . The later all know, but how
> many knew that chemist was old persian language?
>
> Inge
>
>
> ----- Original Message ----- From: "Brian Ellis" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, March 30, 2009 4:40 PM
> Subject: Re: [TN] Titanium
>
>
> Titanium is a funny metal. Fabricated items, such as snob-value watch
> cases, are often sintered into a rough shape before machining, rather
> than cast, as would be gold. This is because casting is very expensive
> as it is done in a vacuum (hot Ti burns on O2 and N2 long before its
> melting point!!!). Ti is extremely difficult to machine, whether
> sintered or derived from a casting, but sintered is the worst. The tool
> must be really perfectly ground without wear and the Ti must be really
> well cooled (pumped cutting oil systems such as for steel or non-ferrous
> metals are often insufficient). This is because there is a phase change
> induced by pressure at temps above ambient, locally softening the metal
> crystal-by-crystal and this causes the metal to deform onto the tool and
> gall. This often 'snowballs' by minor galling inducing ever-increasing
> deformation. I don't know all the ins and outs of Ti galling but I have
> observed it as a severe problem in practice (in a former life, I
> designed a part for working in HCl that had to be turned from bar; the
> turner had hell's own job!).
>
> I mention this because your "squamous" surface may be due to galling,
> especially if the part is sintered, rather than cast.
>
> As for TCE, I knew one of the guys who was behind the ban in Sweden. At
> the time, I had long and heated discussions with him that he was making
> a BIG mistake. I never was a fan of halogenated solvents but I always
> admitted there were some applications for which they were indispensable.
> The idiocy started in E Germany where a factory's employees had an
> abnormal number of cancer cases ascribed to TCE. No epidemiological
> study was made or confounding factors determined. It later transpired
> that the TCE was stabilised with epichlorohydrin, a known carcinogen but
> it was too late, Germany had already decreed TCE was a known carcinogen
> in humans (MAK1) with a PEL of (I think) 1 ppm. For some reason, they
> never wanted to correct this error, despite serious studies to the
> contrary, and some other countries followed suit. FYI, perc, which is
> potentially more toxic than TCE, is classed as MAK3 in Germany with a
> PEL of 25 ppm. Carbon tetrachloride, which is KNOWN to be a lot more
> toxic than TCE, is also classed as MAK3 with a PEL of 10 ppm. It simply
> makes no sense whatsoever. I think you will find Germany's stupid
> classification of TCE will reach REACH, if it hasn't already done so. To
> get back to my Swedish colleague, he argued that all applications using
> TCE could be replaced by aqueous cleaning methods. Memories of these
> arguments still make me squirm; you simply could not have a scientific
> discussion based on fact, he had a political point to make. At one
> point, in a committee meeting with ~20 persons present, he was shot down
> in flames by the consensus and he simply stormed out of the room,
> slamming the door (this was c. 1989, when we were desperately trying to
> promote all known means of cleaning using relatively safe non-ozone
> depleting solvents, such as TCE, in preference to 1,1,1-TCA).
>
> Would it be possible to use TCE in a zero-emissions machine? (Virtually
> 0 ppm in the workshop at all times, certainly less than 1 ppm.) Surely
> that cannot be forbidden? It would also ensure compliance with the EU
> VOC Directive.
>
> Brian
>
>
>
> Hernefjord Ingemar wrote:
>> I reckon that some mineral oils seem to be very bullheaded. We had let
>> parts pass aceton and etanol and some other cleanings, and to our
>> surprise, after electron beam vacuum welding the two (cleaned)parts
>> together, small and yellowish fatty things appeared on the liquid
>> surface when the finished part was recleaned after the welding. This
>> was done by dipping the flasklike part in a degreasing tank.
>> Evidently, mineral oil was still hidden in the titanium surface after
>> machining, despite it looked clean and left no debris when you rubbed
>> with a white cloth. In a high magnification microscope you can see a
>> lot of microscopic damages, void or what to call the rude surface.
>> Just unlike steel and other metals. Whatever machining parameters or
>> tools, it seeems as titanium is "squamous" after the drilling,
>> milling etc.
>> TRI...hmm...was cast out here twenty years ago...chemo textile
>> cleaning is allowed to be done with perchloroethylene, which I find
>> remarkable. The later is not better in a environmental point of view.
>> Inge
>>
>> PS. VIGON 200 = 11-12 (pH)
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
>> Sent: måndag 30 mars 2009 13:04
>> To: [log in to unmask]
>> Subject: Re: [TN] Titanium
>>
>> I'm not sure that Vigon will be satisfactory for removing mineral oil
>> residues and their additives, as these will not saponify in the
>> amines. You will need something with the pH exceeding 12-13 and with
>> stronger tensio-active components.
>>
>> I'll shock you by suggesting a trichloroethylene blend in a
>> zero-emissions cleaning machine with a vapour phase final. I don't
>> care what people say, it is a damned good low-cost solvent, used
>> sensibly it is perfectly safe, it is non-carcinogenic to humans (it is
>> carcinogenic to rodents in high doses, but their metabolism of the
>> substance is
>> different) AND IT WORKS!!! (If needed, I have details of
>> epidemiological studies with cohorts of tens of thousands supporting
>> my statements.)
>>
>> In the unlikely event that this alone would be insufficient for your
>> needs, then consider an aqueous solution, depending on the residue
>> analysis after TCE.
>>
>> Brian
>>
>> This alone would probably be sufficient and low-cost
>>
>> Hernefjord Ingemar wrote:
>>> The tests will show. If one or two steps can be left, of course very
>>> good. On the other hand, the cost for these units is so high, that
>>> some dollars saving is negligible. Unlike the normal production when
>>> cents are hunted for.
>>> The alcaline bath will possibly be superseded by our Vigon 200 tunnel
>>> cleaner. /Inge
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
>>> Sent: måndag 30 mars 2009 11:28
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Titanium
>>>
>>> Ingmar:
>>> The process you suggest probably will work, but I suspect it is
>>> overkill. I suspect that the alkaline cleaner will be enough on its own.
>>>
>>> Good luck.
>>> Rudy Sedlak
>>>
>>> --- On Sun, 3/29/09, Hernefjord Ingemar
>>> <[log in to unmask]> wrote:
>>>
>>> From: Hernefjord Ingemar <[log in to unmask]>
>>> Subject: Re: [TN] Titanium
>>> To: [log in to unmask]
>>> Date: Sunday, March 29, 2009, 11:58 PM
>>>
>>> Thank you, Rudy&Steve.
>>>
>>> It seems as a suitable treatment would be this one:
>>> a)Solvent degrease, followed by
>>> b)Alcaline bath, followed by
>>> c)DI ultrasonic bath, followed by
>>> d)Micropowder blast, followed by
>>> e)HNO3 dip, followed by
>>> f)DI ultrasonic bath.
>>>
>>> We will try this today already. We do not like HF, so that kind of
>>> process is skipped. Our problem is not primarily to remove the oxide,
>>> but to ascertain that all threading/cutting oil is gone, also that
>>> the numerous micro pores are emptied from their content.
>>>
>>> /Inge
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
>>> Sent: lördag 28 mars 2009 20:19
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Titanium
>>>
>>> Although Titanium lightly alloyed is used in some joint replacements,
>>> it may well be more commonly known for its use as Nitinol, a
>>> Nickel/Titanium alloy, which has weird "memory" properties. Nitinol
>>> is one of the more common stent materials.
>>>
>>> Cleaning Titanium is quite difficult, particularly if it is heavily
>>> oxidized, as the common "cleaning" agent, (Hydrofluoric Acid) attacks
>>> Titanium vigorously, and then to frost the cake, this causes Hydrogen
>>> embrittlement.
>>>
>>> Not everyone/everywhere is as "enlightened" as we like to think we
>>> are, and yes, there is still choro-ethanes still in use in cleaning
>>> (Think "dry cleaning" clothes).
>>>
>>> There are proprietary cleaners which purport to get around these
>>> issues. If interested, contact me off Technet.
>>>
>>> Rudy Sedlak
>>> RD Chemical Company
>>>
>>>
>>>
>>>
>>>
>>>
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